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>> Tony: That's my name.
My name is Tony Kojundik.
Just call me Tony, that's fine.
We'll be cool.
I know you guys don't have a real dedicated background in
concrete, that you guys are in construction management and that
you cover a lot of different aspects so if there's some
things I get into in concrete that you don't understand,
stop me.
But I'm going to try to keep things that you as construction
managers are going to run into out there in the concept that's
behind it and the logic behind it and those type things.
We're talking about high performance concrete and at the
start I am going to show you a little video here as kind of an
introduction to high performance concrete.
You may recognize some of the people.
>> Video: World News Tonight with Peter Jennings continues.
Now Solutions.
There are several ways to dramatize tonight solutions.
We could tell you that the horizontal asphalt
infrastructure anomaly is a curse for millions of American
drivers at this time of year, that would be potholes
for most of us.
We could tell you that fifty-two and a half billion dollars a
year goes to highway construction and maintenance,
not to mention all the other money to repair the bridges and
the other pieces of the nation's infrastructure.
It is safe to say, we think, that if the ancient Romans were
watching tonight, they would be asking 'what took you so long'?
Here's ABC's Jack Smith.
>>Jack Smith: Roads and pavements.
Bridges and support columns.
All of what's called America's infrastructure is slowly
crumbling because what it's made of does not last.
This is ordinary concrete and this is what happens to it after
years of punishment.
It falls apart.
Most of the concrete in the nation's highway and bridges has
a life of just 30 years.
What's the solution?
I am standing on it.
Brand new stuff called high performance concrete.
This is a sample.
Engineers say this will last, not twenty or thirty years, but
one hundred years, maybe longer.
This is what America's roads and bridges could be
made of in the future.
Engineers in the New York State Department of Transportation
discovered how to make it two and a half years ago.
>> Engineer: We were surprised when we actually did all the
calculations, and got the test results back and said 'my
goodness, this really is going to work.'
>> Jack: Researchers stumbled on the formula after the clean air
act forced power plants to reduce pollution.
Huge quantities of the industrial waste called fly ash
began piling up, collected from smoke stacks.
First used as a filler in cement, it turned out to be a
key ingredient in strengthening it.
>> Engineer: So this is one-quarter industrial waste.
But it makes the cement many times tougher.
That's right.
>> Jack: High performance concrete is seventy four percent
cement, twenty percent fly ash, and six percent micro silica,
another type of ash.
All mixed with water.
When it dries, ordinary cement is actually porous, not solid,
that is how salt and water get in.
But the fly ash and micro silica are ten times to a hundred times
finer than talcum powder, and professor Ken Holver of Cornell
has found they literally fill in the microscopic holes in cement
and demonstrates it with colored tennis balls.
>> Prof. Ken Holver: The next thing I would want to do,
if I wanted to
densify this box, is get some mid-size particles and take
those mid-size ones, and try and get them into the box.
>> Engineer: They fill in all the smaller voids in between the
cement particles and we just have a
very, very, dense material.
>> Jack: More waterproof?
>> Engineer: Correct.
>> Jack: Stronger?
>> Engineer: Yep.
>> Jack Lasts longer.
>> Engineer: Yes.
>> Jack: The new concrete is three times more water
resistant, twenty times less likely to form cracks, and in
pressure tests,
>> Voice of engineer: 9060 PSI
>> Jack: has proven almost twenty percent stronger than
regular concrete However, modern scientists were not the first to
make high performance concrete.
The ancient Romans were, mixing volcanic ash with their cement
to make it far tougher.
[Car horn honking] It is one of the reasons the Coliseum and
other Roman buildings have lasted so long.
>> Engineer Paul St. John We really literally re-invented
what our ancestors two thousand, three hundred years ago had
already done.
>> Jack: At least 11 states are following New York's lead.
High Performance concrete is more expensive than ordinary
concrete, but because it is easier to lay down, it costs
about the same to use.
Engineers say not only could it be an answer to much of
America's infrastructure problems, but it could
revolutionize all construction.
Jack Smith, ABC News, Albany NY >> Tony: That video was actually
recorded February 11, 97, so six years ago.
They showed a map that only had a few states that have used high
performance concrete on their bridges.
As of last year, all fifty states have used high
performance concrete on the bridges one way, shape, or form
or another.
New York and Ohio were probably the first two guys to come on
board full stream, where the fellow at New York, Don
Streeter, was saying that they only come up with it back two
years before 97, which would have been 95.
Reality is they did their first overlays and
bridges in the mid-80's.
Likewise, Ohio and then they looked at them, they watched
them, the monitored them, they tested them, they looked at them
for another five, ten years until they really got the data
back which what he was talking about.
We looked at the numbers and they're really
going to work out.
They know they are going to get extra life
out of these structures.
And those two examples New York and Ohio they've been using high
performance concrete, that type of mix design that Streetor
talked about there, since 97 on all of their structures.
There's probably a thousand in both states that have been
built, both overlays, and new and I say that because every
state is different.
What happens in Illinois doesn't necessarily transfer to what
happens in Indiana, and likewise New York doesn't affect what
happens in Pennsylvania, my home state.
I am ashamed to say that our state has four what I could call
high performance concrete bridges.
And we've got New York and Ohio right next to us
that has thousands.
You know the technology just doesn't transfer, which is part
of what we do with the Silica Fume association.
As you see in the manuals that you have, the book is published
by the FS, the SFA, and the Federal Highway Administration.
We have a contract with the FHWA to help them provide technology
transfer to the various states since the states don't talk to
one another, the Feds have to effectively try and take the,
you have to take the technology to you know Moses, you know
you've got to take the mountain to Moses,
instead of the other way around.
If you work for IDOT you only travel within Illinois.
You don't go to Michigan.
We don't have any roads in Michigan.
Why would you go to Michigan, even though there's a technical
conference in Michigan that you may learn something from, you
don't go there so the technology has to be taken out.
Which is what we help the FHWA do The federal government has
cut back so much on their field people that now they've reached
out to industry like ourselves to help them with
the technology transfer.
We don't want people to reinvent the wheel.
We don't there's no need for a state to put down a bridge deck
and watch it for next five to ten years.
Yes, the Federal Highway Administration, as we will see
here, recognizes the benefits of using high performance concrete
versus how we built the interstate system
the first time.
You saw some numbers on there of 52 billion dollars.
That was '97 dollars.
The last contract, the last congress authorization for funds
was three hundred eighteen billion dollars for all
transportation systems.
I think like a hundred billion of that was for bridges.
But today we are going to talk about high performance
concrete in particular.
Let me see if we can bring all this up here.
Thanks.
Straighten out the projector if you would.
What is high performance concrete?
One of the performances we think of is the strength.
High strength.
Easy to measure.
You make cylinders, you cure them for 28 days, you test them
in a laboratory, you know how strong the concrete gets.
Normal concrete sidewalk concrete, highway concrete, 4000
psi at 28 days.
That's how long it takes the concrete to change from the mud
in order to get hard and develop some strengths.
You see a lot of high strength concrete on high-rise buildings.
This is 311 South Wacker.
When it was built, it was the tallest concrete building
in the world.
There has since some other ones.
They use high strength concrete in the columns of the buildings,
If you think about it, it stands to reason, if you were to make
this column out of 4000 PSI to support this weight, the column
would become very large, to support that mass of weight on
there, the dead weight.
If you make this column 12,000 PSI with a higher modulas of
elasticity the column can become a lot smaller.
Not less is the columns smaller, and you're using less steel, but
now if you've got you've got twenty of these columns going up
through the whole building top to bottom and you save thirty
five percent square footage on every column times twenty?
They lease the building based on square footage, so if you can
reduce that column size, if there was no column, Donald
Trump would love it, because then he could rent out
the whole floor.
So the idea is to make the columns as small as possible,
with the highest strength as possible, and then it gives the
owner something more to to rent, to lease out, and make more
money off of it.
High strength in Chicago twelve thousand right now Trump tower
is going in at sixteen thousand PSI concrete.
They have a modulas of elasticity, they actually didn't
require strength, they required a certain modulas of elasticity
out of the concrete, so that the building
would stay rigid enough.
They have an equation, where if you live on the top floors, you
can't feel the building sway, I think it is like one time in
thirty years, that you should be able to feel the building sway.
And they go from that measurement back to how strong
the concrete has to be in order to keep the building that rigid
in the two hundred mile an hour winds that they get in Chicago
sometimes at those elevations.
So its a crazy calculation, but they are up around 6.6 million
modulas of elasticity, which is really high.
That's just one property of high performance concrete.
The FHWA says that high performance concrete is a
concrete in which certain characteristics are developed
for particular application and environment.
And the operative words there in the sentences being certain
characteristics; concrete can have a lot
of different characteristics.
High strength is one.
Right now, in the construction industry one of the big things
in concrete is art concrete, stenciled concrete.
You have some pavements out here that are stenciled to make it
look like bricks.
It is actually concrete they threw in colors on it, they'll
have the drive areas to look like specialized stones, with
colors on it.
That's actually a high performance concrete.
They are doing something other than making a gray
slab on the floor.
They are getting either; they are getting something out of
that concrete.
Here is a list of what the FHWA says are some
of the HPC characteristics.
It can be ease of placement.
Have you ever heard of self-consolidating concrete?
SCC?
That's the probably the latest thing in the last five or six
years in the concrete industry.
They've got certain chemicals, and silica fume can be used for
for that application.
But they are able to make a concrete that flows like water.
But it doesn't separate from the aggregate.
The aggregate and the mortar, and everything moves in unison.
So, you know, normally, anybody work with concrete?
By hand, actually wheel barrowing it and putting it in
or what type of work?
Actual finishing?
Ok you know how heavy it is to pull the concrete around?
You know it's backbreaking work to do.
SCC concrete, particularly in a pre-cast plant, where they are
filling up concrete in forms, or even in houses, where they are
filling up basement walls.
SCC concrete, they can place it at one end of the form and let
it flow like water to the other end of the form, and the
aggregate will stay with the leading edge of the flow.
In a precast plant they've cut labor, you know, probably eighty
percent in the last six years, They don't have to vibrate the
beams and they get much better finishes on their concrete.
But that is just one area that would be a
characteristic for performance.
Early age strength.
If we wanted the fast track, if we wanted
to rebuild an intersection.
We wanted to get on it and off it in four hours time.
You can do that.
There is concrete that you can tweak that characteristic and
make it happen.
The idea here is to make engineers think when we talk
about performance to have them begin to think that there's more
that you can do to concrete, besides just achieve strength.
Strength is just where everybody's head has been for
the last hundred years or so.
You know, if a little is good, a lot has to be better.
But there are other things that make concrete fail,
not just strength.
In this case, we are looking at a stilling basin of a dam that
will show a little video on here that the concrete obviously was
eroded away by abrasion erosion.
That needs a concrete that has extra toughness.
That's a performance that can be improved.
If you are making containment vessels for
low-level radio active.
This is Hanford Nuclear Site in Richland Washington.
Twelve foot thick slab or walls of concrete here.
They are worried about heat of hydration.
When concrete gets hard, or changing from a wet state to a
hard state, it generates heats as part
of the chemical reaction.
And then that big mass of concrete in big thick walls like
that, concrete can get pretty hot.
If you have a core differential temperature from inside of that
slab to the outside of the slab that's greater than thirty six
degrees F, it will crack.
Well, obviously they don't want this to crack.
Because it's supposed to last a couple hundred years, containing
radioactive materials, so they want it to be volume stable and
low heat of hydration.
They don't want it to generate a lot of heat.
They want the concrete still to get hard and last a couple
hundred years, but they don't want it to hit a hundred sixty
degrees when the outside environment is fifty.
So there's things they can do to the concrete to make that work.
It's not just driveway concrete.
or to make longer life.
That's where the FWHA spends most of their focus on, how we
get our bridges, as we heard in the video, to last longer.
The last inventory in 2005 said we had just short of six hundred
thousand bridges in the United States, these aren't culverts.
I am trying to think of the definition.
They had a certain length that would actually make it a bridge.
It's not just culverts over the little creeks.
Its a physical bridge.
Of those five hundred ninety five thousand, there's about
twenty-eight percent that are rated deficient.
Deficient either because they are under capacity, structurally
deficient, falling down, this bridge right here
is in that category.
There's a lot of eerie bridges like that in Pennsylvania, not
just at Erie.
But in Illinois, we are down to eighteen percent.
The national average is twenty-eight percent, so
Illinois has done a great job in the last ten years of cutting
that number down, because the original number, this thing was
up around 240,000 ten years ago.
A lot of states have done a good job of knocking the number down
and Illinois is one of them.
Illinois has been using high performance concrete, the first
overlay was placed here in 1986.
State Route 4 crossing I-55 {unclear dialogue}
is the overlay.
It is still in place, they only expected the overlay to last
about ten years and we are up to what since 86, twenty years.
So they have doubled the life out of that overlay.
An overlay was put on the bridge because the bridge was rated as
deficient.
Most of the bridges failed because of chloride attacked
through the surface of the bridge, getting into the
concrete, which acts like a sponge, sucks up the water,
sucks up the chlorides.
Once you get enough chlorides in the concrete, at the layer where
the steel is, that {unclear dialogue} corrosion is actually
an electric chemical reaction, that you need an electrolyte to
carry the current through the concrete, and its the chlorides,
the negatively charged chlorides, in the concrete that
act as that current.
We are a little bit beyond ourselves here, but the idea of
an overlay is to repair to get extra life out of a bridge that
they would normally have torn down to put up a new one.
So in Illinois' case, they got twice the life out of it instead
of having to tear it down and start over again.
We see a lot on parking garages, not just bridge decks, but
parking garages are probably even more frightening because
most of their decks are very, very thin.
Most of their decks have post-tensioning cable in it.
The cables are all under tension and they are jackhammering out
concrete because of corrosion and failure.
This happens to be underneath the Amoco building in Chicago,
which, if you, it's one of the three tallest
buildings in Chicago.
It's like 105 stories and we are six stories underground
hammering out the foundation.
What's wrong with this picture?
We are taking out the foundation of a one hundred five-story
building above us.
So, this was made with conventional concrete.
The chlorides were brought in by cars, driving on the highways,
they park underground in the warm building, the moisture and
everything falls off the vehicles, they are underneath
the building, there's no way for them to come out,
they are there forever.
They get into the concrete whatever gets deposited there,
stays there.
So parking garages under buildings are notorious for this
type of problem just because they are trapped.
Whatever get in there doesn't get out.
Outside parking garages uh, yeah >> Student: Did you say six
stories underground??
>> Tony: Yes, I think it is actually like eight or ten.
no no no That's cool.
But what does service life mean on something like a parking deck
or a bridge?
This is a famous way of depicting it from Professor
Tuutti, back in '82.
Chloride acts as, or concrete acts as a sponge, that's this
initiation period here, where it is allowing chlorides and
carbonation to actually penetrate and get into the
concrete.
There's no corrosion happening at that point in time.
It takes a certain amount of electrolyte in the concrete to
start corrosion.
That's where we see the corrosion starts here, and then
as it corrodes, when steel corrodes, it effervesces and
swells, it swells to four times its normal size.
And although concrete is real strong under compression, it is
real weak under tension, and the expansion of rusting steel is a
lot of force when it swells up to four times its size, that
causes the concrete to break.
Once the concrete breaks, more water gets in, more corrosion,
freeze-thaw, you get potholes happen very quickly.
That's the propagation period.
The one bridge that had the sign of Erie pointing to it,
obviously, was in this part of the structure, or was in the
part of the equation of its service life, way beyond the
initiation phase.
But when do you pull the plug on a bridge?
When do you say it is done?
Well, that one is done.
That happened a month ago, about 20 miles from my house, crossing
Interstate 70.
Luckily no one was hurt.
Imagine that no one was hurt on this.
The bridge was forty years old, the reinforcement was completely
rusted through.
It's on the shoulder, you know, so all the salts and all the
waters and everything are going to run to the side of the edge
of the bridge, where the gutters are.
That's where the salts and everything got in, they lost all
the steel there.
There was no traffic on it at all, it fell down under its own
weight.
This building was rated deficient.
It was scheduled to be repaired, well, it is now, but there's two
other bridges that were made all at the same on either side of
this one, PNDOT has since shut down both of those, and I think
last week they actually blew up this one.
So, I mean, you know, some states learn by taking it out of
service before this happens, sometimes the end of service
life is, can be pretty dramatic.
>> Dr. Wahby: [Unclear dialogue] >> Tony: Without the steel in
the concrete, concrete is very brittle.
It will break like a pencil.
That is why you have reinforcing steel in concrete.
Steel is real good in tension.
Concrete is real bad in tension, so if you put those two
together, you got the good, you know, you've got them both
working together.
But obviously the steel in this case is completely corroded
through, so that it was acting like a pencil.
Just the weight of the bridge itself, the concrete couldn't
carry it without the steel.
>> Dr. Wahby: [Unclear dialogue] >> Tony: Yeah.
Yeah, it was five in the morning when it went down.
This happens in parking garages all the time.
Bridges are more catastrophic because of their potential, but
Minneapolis is famous for having parking garages fall down for
the exact same reason.
But the salts just corrode through the reinforcing steel
and there is nothing left holding up the structure, other
than the concrete pretzel, and the pretzel snaps.
>> Student: [Unclear dialogue]
>> Tony: Yeah, Interstate 70.
Just south of Pittsburgh.
How do we make high performance concrete?
Well, concrete, real simple, is two ingredients.
It's glue and it's the aggregate.
The aggregate is the sand and the rock.
Normally that is something that happens locally, that you are
going to get out of the ground locally, and normally it's the
best material that you have in your concrete.
If you think real pragmatically, about what happens with
concrete, people complain about A.) it cracks.
It has carbonation, it has conductants, it takes in
chlorides, it scales, it has creep, it has [unclear dialogue]
all these things happen to the mortar.
Except for alkali silica reaction, which could happen
from your aggregate, but that is something we know
how to take care of.
That's normally the aggregate's the best thing you have.
So, you know, you are dealing with mortar here, and you are
dealing with aggregate, those are the two things you are going
to put in concrete, these cause you a lot of problems if you
don't do it right.
This is the good stuff in the concrete, so real pragmatically,
I want to use more aggregate and I want to use the least amount
of cement that I have.
I want to make it the best glue that I can possibly make it, but
I don't want to use a lot of it, because a lot of it gets
me into trouble.
That statement alone, that I just made to you, is almost one
hundred eighty degrees different than what everybody thought in
the last fifty years in the concrete industry.
You got a problem with your concrete, put more cement in it.
No.
If you add water to these three things, slag, portland cement,
class C fly ash, they hydrate.
What that means is they react.
Chemically, they react with the water,
and become something different.
Like baking a cake, you put flour and milk together and
sugar, and you bake it, it becomes something different.
Well, likewise, when you put cement with water together, the
cement starts reacting with the water, and it starts growing
crystals, and the crystals interact, and that is what makes
the strength.
Slag does the same thing; class C fly ash does the same thing
also.
They hydrate.
Silica fume, I wish I had a class F fly ash picture here,
but I don't, but if you add those two things to water, all
you've made is dirty water.
They don't hydrate.
But if you remember that video, the fellow in New York was
talking about this Roman Technology where they used the
ash from Vesuvius, what they actually did, was they ground it
up with the local limestone from Pozzolana Italy, and when they
put those two things together, this silica, which is in F ash
and silica fume reacts with lime, and actually makes
concrete, actually get hard.
It get hard pretty good, too, if you think of the Appian Way, and
the Coliseum, and all these other buildings that are still
up there.
So, we've got a technology here, this Pozzolana chemistry, and
that is really what it is called, it is called Pozzolanic
chemistry now, this idea of lime reacting with silica, morpha
silica, that been around for a couple thousand years.
Portland cement was patented in 1824.
Less than two hundred years ago.
So we only have two hundred years of history of working with
cement, this type of cement.
It's called portland cement because the color resembled the
rocks that they found on the Isle of Portland, which is an
island off of England.
It has nothing to do with Maine, or Oregon, it has to do with
that island.
But if we put these materials together, we can have some good
things happen.
If we combine this portland cement chemistry with this
pozzolanic chemistry, we can make a really good glue for our
concretes, even though all those materials look like powders,
there are some differences in those materials.
Slag, fly ash, two different types of cement.
They are basically have the same particle size distribution, if
you look at the D50, fifty percent of the particles, the
D50 is probably about what, twelve microns, thirteen
microns, somewhere out there ten to twelve micron, the D50 of
silica fume, ends up being about .1 micron.
Very, very fine material.
A hundred times finer than cement grains.
What it is, is he's asleep, I was going to throw it to him,
here you go.
That's actually silica fume.
That's a full container of silica fume.
If you think of the word silica fume 'fume' in latin means
....anybody??
Ehhh close.
No, fumata in the restaurant bathroom.
no fumata.
No smoke.
Fume' is smoke in Latin, or French, Italian, and it actually
is silica smoke.
That's captured smoke.
You can open up the container and look at it, that's fine.
It won't jump out.
It won't float away.
If you throw it in the air, half of it will probably stay in the
air, but, that the materials as its captured, the smoke weighs
about eight pounds a cubic foot.
Water weighs sixty-two point four.
This weighs eight.
That's captured smoke, literally.
The plants used to look like this in your, obviously this is
taken out of the users manual that you have in front of you, I
should probably say something about the user's manual first.
That's written for producers and practitioners of concrete.
It's written for ready-mix producers,
it's written for contractors.
It's not an engineering document.
It's a real how-to.
The first couple chapters deal with the background, like this
is actually in chapter one.
What is silica fume, where it comes from?
All those things we are going to cover here real quickly.
Latter parts of the book, chapter 6 deals with mixed
designs and proportioning.
Chapter 8 deals with contractor issues of placing and finishing,
so it's all written to FHWA wanted to document.
We have enough engineering documents on
high performance concrete.
We needed something to take from that industry back to the people
who actually have to build with it, and teach those people how
to build with high performance concrete.
That's what this manual's dedicated to.
I think it is perfect for what you guys are headed for.
>> Dr. Wahby: [Unclear dialogue] >> Tony: You will have
dirty water.
{Laughs}
>> Dr. Wahby: [Unclear dialogue] >> Tony: You can actually mix it
in with water.
The one video that we will see on the dam
that is being repaired.
The way of introducing that into the concrete was actually
in a liquid form.
Where they suspended the silica fume in 50/50 in liquid vs.
trying to handle it in the dry form.
That was before they figured out how to handle material that
light in a dry form.
What they found was and I thought this was pretty unique
too, they put that material in a big silo, about 6 stories high,
and blow a lot air, very low pressure, but about 700 cfm of
air through the bottom of this silo, to the extent that that
top of the silo looked down on the top of it, it looked like
the whole thing is boiling.
Just all kind of air coming up through the silo.
What happens is, is when the air goes through this column of
silica fume, it causes those little particles to collide, and
because of Vander wall's forces, the attractions of fine
particles, they actually start sticking together.
And so we can actually increase the bulk density of the silica
fume, from eight pounds per cubic foot, up to about forty.
And once it get up to forty, then they can haul it around,
and put it in trucks, and blow it into silos, and treat it like
silic, or treat it like cement, and fly ash, and treat it like
any other material, and handle it.
Can't handle it when it's eight pounds a cubic foot.
But when you get it up to about forty, you can
handle it that way.
But it's I think it's strange, because normally, if you if even
like flour or something, if you want to fluff it or make it
lighter, you blow air into it, right and it fluffs everything
back up again, just like shaking that up in the container, you
fluff it all up again.
But if you do that long enough, if you fluff it long enough, it
starts getting heavier.
I, which I think, is a neat trick but anyhow.
This is a schematic of the plant that produces silica fume.
What they are doing at point A is they are putting in quartz,
big rocks, about the size of your fists, almost pure white,
quartz, coal, wood chips, coke, and they ignite it all in a open
arc electric furnace.
The electrodes anywhere from twenty-four to
thirty megawatt electrodes.
You walk into a furnace building I swear you can feel the stray
electrical current in the air, its so powerful.
What they are doing is they are melting the quartz and they are
melting the quartz to extract silicon.
Element number fourteen on the periodic chart.
Si That's a chunk of it here that we'll pass around.
The only thing you make out of silicon is silicones.
Dow-Corning and GE, they take that element and run it through
their reactors and turn it into silicones.
Bathtub caulkings, is what everybody comes to mind, glues,
used in dashboard, used in plastics, it's used in shaving
cream, it's used in deodorants, its used in cereal boxes, fake
***, it's used in anything that has silicone in it, it
starts out as that rock, that element right there.
Element number fourteen.
That's what comes out of the bottom of the furnace
after it's tapped.
The smoke as you saw used to go up the stack fifty years ago,
now they pull it down with fans, and run it through
a series of filters.
After it comes out of the filters, it weighs, what you
have in that container.
The densification silos that I talked about happen afterwards.
But that's pretty much where it is produced.
This is what it looks like coming out of the ladle.
The hot silicon metal is poured into chills, that's exactly what
it does and these big flat slabs is chilled.
Then they drop it on the ground and it shatters like glass.
That's starts the crushing process.
They crush it to that size and they'll take it even further.
They'll take it from that size all the way down to ten microns
in size, which is, you know, pretty damn fine.
They use that in ceramics.
This is actually, as I said, the silicon metal coming off,
or the silicon.
This is the silica fume, or the silicon fume'
going up the stack.
As it comes off the silicon, it's all gas.
SIO gas.
When it hits about 600 F or excuse me 600 C it combines with
another oxygen, and forms an SiO2 solid.
So you get this precipitation from a vapor to a solid like a
formation of a rain droplet, is how the material ends up being
so fine.
Remember how we said it was 100 times finer than cement grains.
It's its captured smoke, is what it comes down to.
>> Dr. Wahby: [Unclear dialogue] >> Tony: Yeah, that's a question
that always comes up because of the name silica, and maybe these
next couple slides show it better.
This is another example of trying to give a perspective of
what we are talking about here.
If this if a cement grain, one little piece of powder of cement
were the size of the Washington monument, silica fume would be
the size of a six-foot guy.
That's the difference in size.
On a typical mix, if you are using, and they normally use
five, ten percent silica fume cement replacement, if you are
using that much, the number they calculated number is about two
million pieces of silica fume for every cement grain.
Which I think is what it says down here.
No, must be the next one.
When this material is formed into a solid from this vapor,
this is a real close-up of what the material looks like.
Little glassy spheres.
I had somebody look at this some researcher looked at this and
they didn't know what it was.
They were calling these, what did they call them?
Oh they called them death stars.
[Laughter] Because of the, you know,
obviously the way it is formed.
But because there are amorphous, amorphous means non-crystalline
and crystalline silica is what produces silicosis.
Crystalline silica is what you'll find in the beach, the
sand, the dust that is blowing off the beach since you are
getting ready for spring break here.
Don't lay on the beach too much, you'll get silicosis.
How's that?
But that's crystalline silica.
Crystalline silica, when you fine powder you breathe in,
it'll get hung up in your aortal, and in your lung sacs,
and that's the start of silicosis.
With this material, round is considered respirable.
You breathe in you breathe it out, it doesn't get hung up in
your lungs.
It's one of the cleanest things in a ready mix yard.
The safest thing.
People don't think so, because it has the name silica, but they
keep thinking its crystalline silica
and it produces silicosis.
You have to tell them all the time you use silica in your
plant, in your sands all the time.
You put sands in your concrete all the time.
Sand doesn't react with cement water, does it?
You can cut open concrete ten years later, look under a
microscope, the sand is still there.
You put silica fume in with cement, seven days later, you
cut it open, look at it under a microscope, you won't find any
of the silica fume, because it's reacted.
Amorphous silica reacts, crystalline silica does not.
There, even though there's silica in the title, they are
two separate materials.
This is another shot of trying to show you the
particle packing theory.
Dr. Hover on the video was talking about fitting this
little balls between other balls, and this is the shot of
actually a cement grain.
One cement grain here and one cement grain here, one micron
scale and that's silicon fume particles mixed in within.
I always used the example of, if you can visualize filling up a
barrel full of baseballs.
You can only get those baseballs so close together, and you have
void spaces between all the baseballs.
Capillary pores in concrete, just like regular concrete.
If you mix bb - Yes {laughter}
>> Student: {Unclear dialogue} just on a relative scale, how
big would water molecules be or
chloride molecules [unclear dialogue]
>> Tony: In the chlorides' case, its in the dissolved state in
water and really you are talking about
>> Student [Unclear dialogue]
>> Tony: Yeah. Yeah. Yeah. Right. Right.
Because you put something between those baseballs.
Otherwise you know, you could pour water
through it pretty easily.
Just physically blocking the pores.
That's what the ceramic people do in the
particle packing theory.
Their theory is if they get all the particle graded just so,
then if you squeeze them altogether, there's no room.
It's one hundred percent dense.
That's why you get some little ceramic parts put in your hand,
you know their, they're this size and they weigh 3 pounds.
You know, they are just so densely packed
together of particles.
And that's what we are trying to do with concrete.
If you think about it, that's what we do on
the aggregate side.
We start off with big aggregate, we mix in the gradation of
aggregates, and then the gradation of sands, so that when
you put all those things together, they fit together very
nicely, so that you can use very little cement.
Very little glue.
So all we are doing now, instead of grading the aggregate, we are
grading the powders, we are grading the mortars, we are
finding something to fit in that finest fraction
between the cement grains.
But you still will have some permeability.
Yes, yes, Yeah it's not waterproofing.
It's not waterproofing.
Your example, you are still getting a little bit through.
Less permeable though, compared to if you did nothing.
And
>> Student: Gradation [unclear dialogue]
>> Tony: What's the difference?
>> Dr. Wahby: [Unclear dialogue] >> Tony: No, the rock that you
have, the silicon the elemental silicon is just Si.
The silica fume is SiO2 amorphous, so there's not no,
no, they are not, they are two different animals.
They are two different animals.
The silicon that you have there as it comes out of the furnaces
is about three nines pure.
99.9% pure.
If you want to make, you know, silicon chips or protovoltake
cells, or something like that, you've got to push up to five or
six 9's pure.
They'll take that rock, and do further things to it to drive
out more of the impurities, so that they can make silicon chips
and wafers and those type things.
But it all starts out as that material. Yeah.
It all starts out as that material.
The fume is the waste material.
You know that's the pollution that used to float in the
atmosphere and people used to have to sweep off their steps.
As they're saying here, the common thought was before the
use of pozzolanic materials for particle packing, that the best
you could do was to lower the water cement ratio.
Use the least amount of, lower water, cement ratio.
You have lower permeable concrete.
So that was always the trend, if you wanted low permeable
concrete, you made low water cement ratio concrete.
And what the next slide shows is that is not necessarily the
case, but there is ways.
It is the case you do get a lower permeable concrete, the
three five is pretty low, but by adding a portion of silica fume
or replacing the cement with even seven percent silica fume,
you can get somewhere around sixty to eighty percent
reduction in permeability.
Even at a real low water cement ratio of concrete.
All those different values there, 120D, those are all
different permeability tests, that people run on concrete, and
this is just a way of comparing all these
different test methods.
Showing, more or less shows the same thing,
the same type of trends.
So it takes very little of this particle packing to get the
biggest impact, as you see you have a point of diminishing
return here at about seven percent.
From here on out is a cement replacement, you are only
producing strength.
If strength is your goal on a high-rise building, it may be up
there at that dosage.
If you are dealing with parking garage, or bridge deck, you
probably don't need strength, you are looking for this though,
you are looking for a reduction in permeability to keep the
chlorides out, or a loading dock or an industrial floor, or a
chemical plant, or a sewage treatment plant, or anywhere
where you have an aggressive chemical that is going to get
into the concrete.
Because all concrete is a sponge.
>> Student: You are looking for durability >>Tony: Yes, they
have, there's, at one count and it is a couple years old
already, but there were two hundred different companies in
the United States that sold chemicals for sealing concrete.
Everything from Thompson's water seal, to some pretty
sophisticated stuff that 3M makes.
But there's two hundred different people that make
chemicals to seal the surface of concrete to make it last longer.
If any worked, you know, wouldn't it put
somebody out of business?
But what happened is they all fail in time.
They all traffic off.
They all fail either because of wheel traffic, because of UV
traffic or freeze/thaw or something.
And they are all superficial treatments, where what we are
talking about here is actually making the concrete.
You are making the concrete, when you have a chance to do
right the first time, you can make it real low impermeable
from the get-go.
That's longer life, that's exactly
what they are trying to do.
One way of looking at this is a life-cycle model.
This Life-365 model is software that was we helped pay for with
Grace and Master Builders.
It's actually an ACI document.
ACI365 is the committee that deals with
predicting service life.
And what this model has or allows you to do, is build the
structure and put it in various parts of the United States.
Build it with different types of concrete, turn the crank and it
will tell you how long it will last and how much it cost to
last that long.
Show you how that works.
Real basically, it gives you a procedure where you can design
the deck, in this case I used the example of the
Illinois Toll Way 294.
They have eight-inch thick slabs.
They have four percent steel, the volume of steel
is four percent.
They've got two inches of clear cover over their concrete.
What this model allows you to do, is build a couple different
cases, I tried to keep it simple, and just use the base
case and the high-performance concrete that they are using.
You can have thirty different cases, if you wanted.
The model knows the surface chloride chemistry for in this
case, Chicago, I didn't have one for Charleston.
Nearest other place I think was Springfield, so I picked on
Chicago, instead.
But it also has the temperature history per year, so it knows
how much salt if going to hit that bridge.
In this case, we said we wanted our bridges to
last for fifty years.
And in this particular case, that wasn't designed life.
The one video we saw in New York, they said the original
interstate system, when they started it in 1956, and the
average bridge lasted thirty-five years.
Which was great, when they started building the interstate
system, they didn't have 18-wheelers.
You know they didn't have 80,000-pound trucks running down
the highway.
We are pushing over a 100,000 now and they didn't have as many
that were on the highway.
And they probably had maybe two percent of the 18-wheelers back
then in 1956.
You didn't have the highways to carry them, so the highways you
had were the winding two lane roads.
You didn't put the big trucks on them because
they weren't feasible.
So there wasn't any 18-wheelers back then.
So they have those bridges, even though then they tried to design
them with as much safety factors they could put
into these bridges.
The guys that design the interstate system, they had no,
they had some idea of what impact it was going to have on
our economy, but it was only about half of the impact that it
actually had on our economy.
And now we know that if we do it right now, now we have a second
chance to redo our bridges, we have a chance to make them last
fifty, sixty, seventy-five years.
They won't last forever, but they'll last more than what we
got out of them the first time.
This is what this model tries to show here.
The basic mix design water cement ratio, we actually can
put in some dollars in the case to see what the model looks like
when we run the test.
A yard of concrete up in Chicago, that's probably light,
it's probably closer to a hundred and a half, hundred and
fifty, but I put a hundred and twenty bucks.
The model knows for this water cement ratio concrete, there's a
certain deficiency excuse me, a certain diffusion coefficient
built into that concrete, there's a certain permeability.
That's the permeability number.
It takes a certain amount of chloride concentration at the
steel two pounds per cubic yard to start corrosion, so we've got
to get two pounds of salt per cubic yard down to the steel, in
order to start corrosion.
We are going to put an epoxy coated bar or an epoxy coating
on our steel to try and make the steel from corroding.
It's an electric chemical reaction.
All epoxy coating is, is rubber coating this wire.
You are coating the steel with a layer of nonconductive material
to try and keep electrical current from hitting that rebar,
that steel, that's all it does.
It doesn't, it'll still start corroding when you get to two
pounds per cubic yard of chlorides, but it'll corrode at
a much slower rate.
Gray steel, without epoxy coating will have a propagation
of only about six years before the structure is you know really
falling apart bad.
But epoxy bars will buy you about twenty years of life, in
that propagation part of the model, we had the initiation
part in the propagation part, is buying us extra time in that
propagation part.
The high performance concrete, we use the same water cement
ratio little bit extra higher cost, we put silica fume and fly
ash in it, had a big effect on the diffusion coefficient.
We're still going to corrode at the same amount of chlorides, if
we can get them in there.
And we are using epoxy bars, as I said this is what they are
actually doing up at 294.
We turned the crank on this model; it says the base case is
going to achieve our two pounds of chloride in six years, eight
years, of normal use.
Normal use in that area is I used to have a bag of six pounds
of salt per square foot per winter.
That's how much the DOT figures they actually throw on the 294
bridges, in the course of the whole winter.
Six pounds of salt end up on one every square foot of bridge that
they have on 294 over the course of winter.
That's a lot.
In the case of the high performance concrete, to get
that same point two factor we are out here twenty some years,
twenty-four years plus.
If we turned the crank on this, and they are actually running
the economic model, we see that going in place the initial cost,
the high performance is a little bit expensive, according to our
model, but easily if we have a corrosion, it's not going to
happen until twenty seven years versus seven years.
And we put epoxy on top of it, we are going to last the forty
seven years before we have to repair that bridge, versus, half
as much, versus twenty seven.
According to this particular model.
We could tweak it, we could do other things, we could make this
bridge last a hundred years, we could use more cover, we could
toughen up the mix, we could do various things for it.
In this case the goal was fifty years,
which is what they achieved.
That's what they wanted to afford.
They are not worried so much about this thing lasting a
hundred years.
This is in Chicago.
They know they are going to over capacity it before they get the
fifty years.
They just want it to last that long so that it
doesn't fall down.
They'd rather it be obsolete because of capacity, not able to
carry all the vehicles that they are going to be driving around
up there in fifty years, but to have it last without repairs.
Ok on this?
Makes sense?
A little bit?
In the manual here, we said this manual ,as you all can read, is
not for engineers.
It is for contractors and the people in the field that are
actually doing the work.
Silica fume and this type of technology, you know, we have
heard it said that it has been around for a couple thousand
years, and it's been in this country since the mid-seventies.
I've been doing it since the early eighties but there's still
a large group in the construction industry that
hasn't really embraced high performance yet, and sorry to
say, it's the people that actually have to do the work.
The engineers, and the designers, and the owners, and
the FHWA, and the DOT, and everybody else, they know what
this can do.
As they said nine years ago, we know the numbers work, the
models work, now we have to get people to do the right things.
It's a little bit different than regular concrete.
We've seen some of the differences, here in particle
packing, and those type aspects.
What does that mean to the constructor, what does that mean
to a ready-mixer.
What does he have to do differently with the way he's
been doing business for the last thirty years, how does that
change his life?
That's all covered in this manual.
That's a real how-to.
It's written to that audience.
It tells you how to set up your batch plants.
If you are proportioning concrete, there's a very long,
elaborate formal engineering way of doing mix designs or if you
have a good mix design, that you know has already worked, use
that as a starting point and just tweak it into your own.
Again technology transferred.
Don't start, you know don't reinvent the wheel, if you know
you already have structures in this case, table six two in the
manual is actually two pages worth of mix designs that across
the top here gives you where it was used.
A high rise building, columns, another high rise building, a
bridge mix in New York DOT, it's actually the mix that was on the
on the video.
A shot creed mix.
You want a shot a silica mix shot creed, here's the starting
point of a mix design.
The Hanford Nuclear site, low heat of hydration, those mix
designs, there's parking garages,
and a couple other mixes.
Those are all starting points so that you don't have to reinvent
the wheel.
Because this is an FHWA publication, that table is all
in kg/cu m but if you go to the back of the book in the
appendix, all the tables are in lb/cu yd.
They are all in our language.
>> Dr. Wahby: [Unclear dialogue] >> Tony: The mix designs? Yes.
>> Dr. Wahby: [Unclear dialogue] >> Tony: These are mix designs
that have been published in technical papers.
All of these structures that are listed here have all been you
know documented and discussed and studied, so yes the mix
designs are all in public domain.
They are only starting points, because you have to incorporate
your own aggregates, and your own aggregates, the sands, are
going to be different, the limestones, or gravels are going
to be different.
You have to tweak your mix design for
your own materials anyhow.
These are just starting points so that we don't have to start
over from those very laborious engineering practices of coming
up with the mix design.
We already have good ones, let's just start with these
and just tweak them.
And how we tweak them is they have the book goes through a
step-by-step procedure.
I think there are six different steps here of how to take one of
those mix designs and turn it into your own.
Again I said it is written, it is real practical.
Producing it at a ready-mix plant.
There's a chapter on chapter seven in here setting up silos
to handle silica fume is a little bit different.
We saw the material's obviously lighter, we found out there was
another property to the material that is pretty unique.
[Coughs] It has an electrical charge.
Most [unclear dialogue] more of an magnetic charge.
That happens to be at the opposite end of the
spectrum as steel.
So, when you, if these pipes, you know, from blowing from a
truck, and blowing it into a silo, blowing it through these
small confined spaces, we found that if you blow it threw steel,
it has a tendency to want to stick to the walls.
Just from this magnetic attraction, and once it starts
sticking, it just builds up on there.
But they found that by using rubber, rubber and silica fume
are at the same end of the magnetic spectrum, so it's like
two negative poles repelling each other.
And when you blow it through rubber all day long, and it
never packs up on it.
So one of the little tricks here of setting up a plant for
handling this material is the guys have to get rid of their
steel pipes.
The rubber works better.
The material's also used in bags.
Some of these bags are actually repulpable, which is what they
are doing here that allow you to just dump the whole bag into the
concrete truck.
The paper's designed to actually shred up with the aggregate to
beat it up and actually dissolve back into cellulose fibers -
doesn't dissolve - it re-pulps.
The aggregate beats the paper back into its cellulose fibers.
It doesn't work on all mixes, if you are dealing with over-lay
mixes where the aggregate is real small, half inch aggregate,
pea gravel, number eights those type things.
The aggregates' probably not impacting the paper enough to
really do the shredding, so the manual goes into great detail of
what mix design these bags can be thrown in on.
There are some mix designs where we are doing overlays, where you
may have to dump the contents into the back of the mixer, but
it comes in bag form, it comes in bulk form.
The major work that is going up on in Chicago, and all the
high-rise buildings, they'll work with it out of silos.
The Interstate 70 here as it crosses the border from Indiana
into Illinois those bridges were all repaired with this concrete
in '03, '02, that was actually done with bags.
Because bridges use a little bit less volume of concrete than the
high-rise would.
So it comes in, it comes in different forms, but the manual
will go into detail step by step of how to do it right.
>> Tony: Some of the sexy applications for silica fume
concrete, and this is under construction right now, this is
actually an artists' rendition of the Hoover Dam, and a bridge
that they are building below the Hoover dam.
I don't know if anybody has ever taken a tour.
Anybody every taken a tour of the Hoover dam?
Outside Vegas?
There you go.
This, this road comes down State Route 92 and weaves it way back
up this side.
Goes right across the top of the dam.
And the visitor's center is over here and the parking garage is
here and people are on this highway and the tour lets out
here and people are on this highway.
There are eighteen-wheelers that cross this.
It's like driving eighteen-wheelers through recess
in a schoolyard.
I mean there's people all over this bridge all day long, taking
a tour, and they've got to snake down this canyon and across it
and back up the other side at about fifteen mile an hour, plus
now the 9/11 terrorists threat, the idea is to get all that
traffic off the bridge, not just for safety reasons, but for
terrorists reasons.
This bridge has been designed for thirty years, after 9/11 it
is being built real quick.
The columns in that bridge, another artists rendition, the
box beam here and the and the concrete going up to the this is
going to be a steel bridge here with asphalt decking, but all of
the concrete here is all silica fume concrete, all 10,000 psi,
actually 12,000 psi silica fume concrete.
This is another artist's rendition of it.
They've gone to great lengths to because of where it is, and
because it is going to be photographed quite a bit to try
and make it blend into the surroundings as
much as they could.
That's probably over-exaggerated.
The web site here is pretty cool.
You can actually drive across this bridge on the website.
What the surrounding is going to look like.
You know, it's a 3-D model of what the bridge driving across
will look like.
I need to start the other tape, if we may.
Questions. Anything.
[Video sound - water rushing]
>> Video: El Born Technology Company presents the story of
EMSAC micro silica additives and the concrete used to repair the
Kinzua dam's stilling basin.
This Ultra-high strength flowing concrete was used to repair the
stilling basin at the Kinzua dam here in the Allegheny Valley in
northern Pennsylvania, in October and November 1983.
>> Mark: Hi I'm Mark Luther and I am the project engineer for El
Born Technology Company we are working on this project, its
repair of a stilling basin of Kinzua dam.
>> Video: The US Army Corps of Engineers is the federal agency
responsible for maintaining the nations waterways.
The Kinzua dam and its stilling basin
is one its responsibilities.
A stilling basin is exactly what its name implies.
It stills the water that flows out of the dam before it reaches
the main channel of the river or other body of water.
If there were no stilling basin, the energy from the high
velocity water, would simply gouge out great holes in the
riverbed and its banks, and possibly endanger the stability
of the dam.
At Kinzua, the stilling basin is a large area about two hundred
four feet wide by one hundred eighty feet long with five foot
thick slabs of concrete.
It was originally placed in operation in 1966 and was made
of good quality concrete, with six inch sized aggregates.
By 1973, the combination of high-velocity water flow and the
presence of debris in the basin had eroded the concrete surface,
and caused general erosion, with holes as much
as three feet deep.
That same year, the US Army Corps of Engineers, let a
contract to repair the entire slab with a one-foot minimum
overlay of low-slump steel fiber reinforced concrete, the very
best concrete then known for this type of repair work.
Nine years later, in 1982, underwater inspections by divers
showed that in some places, the one-foot overlay of steel fiber
reinforced concrete had been worn away and as much as two
foot of the original slab was also gone.
>> Mark: And the over here you see the worst damage.
This is where the greatest force from the upper slew scape slew
scape #2 occurs.
This is where the water impacts, and swirls around and the energy
is killed.
And as you can see, it has really done a number on the
concrete here.
Some of these holes are two and a half to three feet deep, if
not more than that.
As well as you can see, the fellow with the Philadelphia rod
there, I don't know if you can see how deep he is there, but I
would say where he's standing right there is over two feet
deep right now.
And what they are doing is taking elevations using that rod
and the level behind us there to determine where the level of
this concrete is now, so they can determine what they
need to do.
>> Video: In order to more effectively repair the Kinzua
dam stilling basin, the corps of engineers initiated extensive
abrasion erosion testing at its Waterways Experiment Station in
Vicksburg, MS. It wanted to determine which materials are
able to stand up to high velocity water, often containing
rocks and boulders from the riverbed.
Lab tests of concrete produced with EMSAC micro silica
additives found it to have an abrasion erosion resistance
suited for the Kinzua repairs.
Through the use of EMSAC micro silica additives, it was
possible to obtain a strength and denseness that made concrete
far more resistant to abrasion than any concrete produced in
the United States before.
It has long been known that the strength of concrete will
increase dramatically if we were able to fill its pores with a
cementitious binder.
Concrete is EMSAC additives achieved its extreme resistance
to abrasion through it ultra high strength and virtual
impermeability.
With EMSAC additive, it is possible to create these
properties and still maintain a flowing
and self-leveling concrete.
But first the Corps of Engineers required field tests at its
Neville Island facility in Pittsburg, using a ready-mix
concrete plant operation, to prove this concrete could be
produced and placed satisfactorily under normal day
to day working conditions.
Three different concrete mixes with three different blends of
EMSAC additives were batched and shipped from a transit mix plant
in the Pittsburg area.
The concrete was rapidly placed and finished.
Slumps were as high a ten inches, giving a flowing
consistency for easy handling and placement.
Membrane curing compound was applied immediately after the
final finishing operation.
At Neville Island, concrete containing EMSAC additives
tested over 10,000 psi at seven days, and
over 17,000 psi at ninety days.
In its specification for the Kinzua dam stilling basin
rehabilitation, the US Army Corps of Engineers required the
concrete to obtain compressive strength of 10,000 psi at seven
days and 12,500 psi at twenty-eight days.
Slump was required to be from seven to ten inches.
The contractor is KC Company of Pittsburg, PA.
The concrete was produced by Harmon Brothers Ready-mix
Concrete Company in Warren PA.
>> Mark: I can't think of anywhere else in the United
States today, where they are pumping ten inch concrete, and
getting 16,000 psi on confined compression tests results in
twenty-eight days.
That's what we are doing here.
That's one sample we have received, the average is closer
to 13,000 psi in twenty-eight days.
But you have to keep in mind, this is flowing concrete.
Typically it's a ten-inch slump.
This is Harmon Brothers concrete plant
where the 2,000 cu. yds.
of micro silica concrete will be made for the dam.
This sight is about eight miles from the dam.
Behind me is the plant where the concrete will be made.
One of the advantages of EMSAC concrete is that you can make it
in an ordinary concrete plant, which this is.
No special modifications were made to this plant to enable us
to make a very high strength concrete.
>> Video: Here is El Borns mobile dispensing unit, used for
batching EMSAC into the truck mixer preloaded with concrete.
The EMSAC and the concrete were mixed in the truck before the
truck left for the dam.
The concrete will discharge into the remix hopper of the concrete
pumping machine.
From there, the concrete is transported down to the formwork
where the concrete is placed into the slabs, and there it is
put in place.
This is just one way to transport concrete.
They had thought about using buckets.
They decided on this job to go with the pump because they get
better control and it goes a little faster.
Our particular concrete seems to pump very well.
Where the re-mix hopper is, samples are taken from the
concrete and these samples are tested to make sure the concrete
has the proper consistency.
The concrete had maintained its ability to flow and to level
itself after eight miles of trucking from the
ready mix station.
The curing compound is put on to seal the water into the concrete
so we get efficient hydration.
After the concrete has been put in place, the basin will again
be filled with water and we expect our materials to last
twice as long as anything that has been used so far.
>> Tony: That dam, if you followed the timeline for the
structure, it was built in '66, it lasted for six years, and
then they put steel fiber reinforced
concrete in for repair.
The steel fiber reinforced concrete then lasted nine years,
up until 1982.
In 1983 they went down and did this repair in 1983.
The divers have gone down, they used to go down pretty
regularly, but they've even stopped going down now.
They are up to twenty-three years now.
They expected, you heard them say they expected it to last
twice as long.
They were hoping to get ten years, twenty years, and they
are already up to twenty-three and they don't even go down and
look at it anymore.
It is just performing that well.
What they found is the mechanism for failure in most abrasion
erosion, or in most abrasion, is that even with wheel traffic, is
what happens is the weak link of the concrete breaks down first.
And normally the weak link of the concrete is the mortar, is
the glue, is the cement part that holds everything in place.
And after you lost enough of that that bond, then the
aggregate comes free.
And the aggregates comes free and it gets ground in and more
stuff loose, so its really the loss of the weak link first that
causes the abrasion erosion, because then everything happens
after that.
The idea of making the mortar stronger is to make it so that
there is no weak link.
Make the mortar as strong as the aggregate so that everything
abrades at the same rate.
You see a lot of industrial floors, that in the past, they
used to place a normal concrete and the contractor would come
out and throw a shake, they call it a shake, you throw a hard
aggregate on the floor.
Sometimes they were actually iron aggregates and actually try
and work that into the concrete surface for more abrasion
resistant surface.
And that's all well and good, you put a really a abrasive
resistant aggregate in a 4,000 psi mortar, the mortar breaks
down first, the aggregate comes free, you've got, you know, you
haven't changed the weak link, you've made your better material
better, but you haven't changed the weak link, and that's what
fails first, and that what the Core of Engineers and the Bureau
of Rec and everything they do now on locks and dams.
Paducah KY has a lock and dam, a super lock that they are putting
in down there now.
It is a six-year construction project.
All the underwater concrete will be silica fume concrete, because
you only want to do it once.
You don't want to come back in twenty years and do any repairs.
You want to do it one time and walk away from it.
>> Dr. Wahby: [unclear dialogue] >> Tony: For repair?
>> Dr. Wahby: [Unclear dialogue] >> Tony: When was that done?
>> Dr. Wahby: [unclear dialogue] >> Tony: ok see this, since 83?
The Bureau of Rec and the Corps of Engineers have switched over
to this technology.
That would have been a preceding technology.
Questions? Sure.
Thanks man. We talked about high strength in high rises and
columns on bridges as one high performance concrete.
In Seattle, all the high-rise building since 86 that used to
be all steel, and since 86 on they are all concrete.
Now what they do in Seattle I think is pretty,
is pretty ingenious.
I don't have any slides on it, but if you think about that last
slide we showed of reinforced concrete, this is what you
typically see.
Is that out of focus for you?
No, ok, it is for me.
Typically you see the steel inside the concrete inside the
form, because concrete is good in compression, but not real
good in tensile.
Just the opposite, steel is real good in tensile, but it is not
real good in bending and flexual so you combine those two
properties together, you get a good column.
What they've done in Seattle, is instead of putting the steel
inside, they have hollow form work, hollow tubes, round tubes,
eight foot diameter, no steel inside whatsoever that go up
through, you can see a couple tower cranes here.
That they literally pump the concrete into the bottom of
these steel forms, fill up the steel form, they'll be one floor
in height, and they put another one on top of it, so they'll be
eight to twelve feet high, they fill all the concrete up.
The forms stay in place.
So you've got this concrete column that is
jacketed in steel.
And you are going to put pressure on that concrete, and
that's great because the concrete is great in
compression, but like a ball, if you press it, it wants to
squeeze, and that's what happens when you break a cylinder.
Did you ever break a concrete cylinder?
Ok when you squeeze a concrete cylinder, what happens is if it
fails right, you've got a cone on top of a cone.
You've got a cone on top of a freshtrom.
What happens is this this part in between blows out like a
rubber ball, when you squeeze it down,
this stuff expands and blows out.
Well, you put a steel jacket around that cylinder, how much
weight can you push on that before that concrete breaks?
I don't know that it would, I don't know.
But that's how they are building their buildings.
And they are starting to do this in New York City now for obvious
reasons, but they've found that it is more economical.
They don't have to deal with all the rebar.
They don't have to deal with all that extra steel, these are stay
in place forms.
You put this form in, you fill it up with concrete,
it stays there.
You don't have to take it back out move it around put it in
other places, it's just like an assembly line.
The buildings just keep going up.
Every building that they have built in Seattle since that
time, has been built with this technology.
With filling up the steel casings.
I think that's a great way.
Let's look at a some High Performance
concrete mix designs.
Here's one that's used in piles in North Carolina.
Everything in their case, in the Carolinas they are getting all
their aggressive chemical attacks from the brackish water.
So everything that is underwater, the concrete piles
under water from here all the way up to the bottom of the
bridge deck is all high performance
silica fume concrete.
That is where they are going to get their chemical attack.
They don't get free style.
They don't throw any salt on the top here like you do,
like we do up North.
They get all theirs from down here.
So from here, from underwater all the way up to underneath
this girder here, from here on down is all
high performance concrete.
and this is the mix design that they used.
624 cement, some fly ash, Class F and silica fume, we are
talking about these two being pozzolan material.
Yeah sorry
>> Student: You guys still have to worry about all the sand and
salt coming off the water [unclear dialogue]
>> Tony: Yeah, but I think on the roadway, they are depending
on washing action from rain to wash that off, where whatever
hits this side here, what would spray and hit this may not get
washed off.
>> Student: [Unclear dialogue] that would be 365 days a year, I
mean, where we only put salt on 3 for months.
>> Tony: Excellent point.
Good point.
That's what they do.
In Florida, they stop about half way up.
They stop at twenty feet above the water.
I mean, it's the same. Why?
Every state is different.
They way they do things.
But that is a good point.
I know in parking garages, if you follow the American Concrete
Institute for designing concrete parking garages, they say
anything within I think it is a kilometer, or two kilometers of
the ocean, you should treat it as if it was you know, a parking
garage here, that has the same salt attack.
Well, what is the difference between a garage deck and a
bridge deck?
I mean, I am supporting what you are saying; they should use it
all the way up if they are this close to the water.
They do in the parking industry why don't you do it on bridges?
I don't know.
They are just slow in coming around.
But in this case in the Carolinas they take it
all the way up.
In Florida they actually stop here.
They were looking for strength, in this case, besides low
permeability, they were also looking for higher strength for
load bearing capabilities, so that's why they were pushing
this was typically twice as strong as typically you would
use if you were just looking for a lower permeable concrete.
Here's one from a New York DOT their actual mix 500 pounds of
cement, the same f-ash, some silica fume in there, and you
see they are only making 5,000 psi.
This permeability coulomb number is a rating of the permeability
of the concrete.
Little bit different in mixes.
You can see the goal.
The difference in the water cement ratio, lower for higher
strength, more cement and silica fume for higher strength.
If you are looking for permeability, you don't need
strength, so you can take a lot of cement out.
I seen the lowest cement factor I've seen in Colorado DOT
actually has a high performance mix design where they only use
390 pounds of cement per cubic yard, which if you go to Farrier
brothers over here it would probably blow their minds.
The probably don't have a mix design over here that has less
than 564, 564 pounds of cement in any of their mixes.
And they don't call it high performance, but yet, high
performance if you do it right, you mix the right materials
together, you don't need that.
And that's kind of the philosophy behind high
performance concrete.
Now that you've heard me talk for an hour or so, you all know
high performance concrete philosophy you all play poker
and everything else, tell me what that card is. Somebody
>> Student: Queen of Hearts
>> Tony: Yeah, it's the queen of hearts.
It's a queen of spades.
I can't look at it either.
I can say it without looking at it, but if I look at it I call
it a heart too, but it's not, its a queen of spades.
And that's kind of what we are talking about with high
performance concrete.
It's not the obvious.
It actually means, if you use the technology it actually means
use the least amount of cement possible.
Remember we talked about the good actor and bad actor in
concrete.
The aggregate is good, the mortar is bad.
You want to use more aggregate and less mortar, but you want to
make the mortar as good as you can possibly make it. Ok?
So using cement alone, only make it a certain a goodness, but if
you add pozzolans to it, then you can convert more of that
inefficient by-product of cement water hydration
into more cement.
What you get as you get as particle packing if you are
using silica fume and reduced permeability.
ASR control with f-ash and silica fume, if you use less
cement, you are able to use less water.
And it's the amount of water in concrete that
causes it to crack.
You only need a certain amount of water in a yard of concrete
to make concrete.
Roughly about thirty gallons of water.
If you ever see any mix design that has more than thirty
gallons of water per cubic yard, that extra water is only in
there to make the concrete crack.
heh heh And most people don't want their concrete to crack, so
you don't need that extra water.
So oneway to control cracking, is get rid of the water.
Well how do you get rid of the water, get rid of the cement, we
don't need all that cement in there anyhow.
So everything is kind of following in line.
Lower cement, lower heat of hydration.
When water and cement reacts together, that produces the heat
in the concrete and if you have a differential temperature, like
in those columns in New York, or in New York, in Chicago, those
columns when they cast them, they may get up to
160 degrees temperature.
If you have more than a 36-degree temperature difference
between internal concrete, and external, it will crack.
Thermal shock.
Just because of that temperature difference.
So what they do, is they do two things.
They try to make concrete that doesn't generate as much heat,
and then they keep insulation blankets wrapped around those
columns, so they can keep the heat in.
It's only the shock of the outside coolness that will cause
it to crack, and if you can keep it all warm, and let it go up
through it's heat of hydration, come back to ambient
temperatures, in a week time, you can take off those blankets,
and everything is fine.
It's come back down to ambient temperature, and you don't have
that thermal shock anymore.
But the idea of making concrete with low heat of hydration is
good to help reduce cracking.
Lower strength also helps to reduce cracking.
>> Dr. Wahby: [Unclear dialogue] >> Tony: Yes,
>> Dr. Wahby: [Unclear dialogue] >> Tony: In the case of the
precast industry, they want to turn their forms everyday.
So you are working on a 24-hour schedule.
If you are casting a beam, you know the size of this, you want
to cast it in a day, you want it to cook, and you want to be able
to take it out of that beam,
and do the exact same thing tomorrow.
And that beam has steel reinforcements, and post
tensioning steel, and you are going to pull that steel, and
you are going to make a structural member out of it, the
concrete has to achieve a certain strength before you can
do all of those things.
So, the idea of heating in a precast yard, is to try and get
those, we said one of the characteristics you could do on
high performance, is get early age strengths?
Precast would be that early age strength.
They want they want twenty-eight day strengths in one day, so
that they can turn that bed and make the same beam the next day,
whether its an I-beam or floors or something but in the case of
bridges or most other structures, it depends on the
structure you are building.
Heat of hydration comes into play when you are doing dams,
big containment vessels, columns, where you've got big
masses of concrete feet thick.
You know in the case of some of the dams, the Hoover dam is what
sixty feet two hundred feet thick at the base, something
some ungodly like that; I mean it is just,
the amount of thickness.
Well it's that mass of concrete that holds in the heat.
When they built the Hoover dam, you guys probably seen the video
on the discovery channel, they actually had pipes copper pipes,
running through the form work that they actually pumped
chilled water through, ice water, through the pipes.
They poured the concrete on top of all these pipes; the pipes
are still in place.
They poured all this concrete on there, as the concrete gets
hard, as the cement water hydrates,
it's a chemical reaction.
Well most chemical reactions do something, they give off a gas
or a heat or something, cement water happens to give off heat.
Well, if it is surrounded by all this other concrete, its a great
insulation, that stuff gets really, really hot, and if it
gets too hot, then it can crack.
You don't want cracks in a dam.
You know, it's to keep the water back, not to let
it come through slowly.
So they actually ran pipes through the mass concrete, and
ran cool water through it to try to control heat of hydration.
That was way before you know this type of technology, but it
is still done.
Chilled water through concrete in mass structures, dams, yeah
Bureau of Rec does quite a bit of that.
>> Tony: But the reason, one of the reasons why we can do this,
or how silica fume allows you to use the least amount of cement
possible, is you get a replacement factor for it.
Because of its size its fineness, and it chemical
reactivity, a small amount of it in this case we are talking
about a five to ten percent cement replacement, we can get
as much as four, five, six times replacement factor.
Which means if you take out one hundred pounds of cement, you
can put in roughly twenty pounds of silica fume, five to one
replacement, still get the same strength.
So you've gotten rid of some cement, gotten rid of all that
water, and you've put a material in that can particle pack and do
other things in the concrete so silica fume really helps then to
drive that cement factor lower and lower.
This happens to be the toll way, Illinois toll way mix on the
Chicago's skyway bridge that was done two years ago.
'03 This was actually their starting mix design with high
cement factor 665, some fly ash in there no silica fume, the
water, the gallons of water, this is the volume, absolute
volume that that mortar occupies.
And you see what they ended up doing when they switch over to a
high performance concrete?
They took out almost two hundred pounds of cement, fly ash here
is approximately the same, they used silica fume here at forty
pounds, and if you think about it, this forty pounds we said
that five to one cement replacement, they took out two
hundred pounds of cement and put in forty pounds here.
That's five to one, basically.
But when they did this, when they lowered the cementitious
materials, they are only 470, 570, 610, six hundred ten pounds
of cementitious materials on this water here is only a 4-0
water cement ratio, almost a 4-1 water cement ratio.
We talked about it before, low water cement ratios,
those type things.
Normally lower means better, in this case, their old mix was a
lot lower water cement ratio than this mix was.
In essence, you would think this mix would not be as good,
following that technology, but what it shows was you are able
to use more aggregate, larger quantities of the good material
in your concrete, and strength wise, well permeability wise
first, the high performance is a lot less permeable, but strength
wise we see that the materials catch up at fifty, at fifty,
excuse me, at twenty-eight days.
That the strengths are basically the same.
At three days there's a little bit of lag here, but that's
actually good for cracking on a bridge deck.
When they ran this thing out to fifty-six days, this strength
went up to a over 6500, so they are actually talking about
taking more cement out of this because they don't need high
strength concrete on a bridge deck.
The bridge deck is designed for 4,000 psi, because when the
truck go over it, you want the bridge decks to do this, you
want it to bounce and flex.
If you make the deck too rigid, then it's not going to flex, so
they actually are talking about actually getting rid of more
cement out of this to make a lower strength concrete.
In the case of Colorado, when they asked their ready-mixers to
supply a mix design, most people will give you a minimum.
I want a 4,000 mix, I want a 5,000 mix, and you have to have
a percentage of strength higher than that.
In the case of Colorado, they say I want a mix design that is
between 5 and 6,000 psi, they cap you.
You actually make a mix design that hits that number.
They don't test you doing the project, but as you submit your
mix design for approvals for use on their structure, they make
you hit this category.
They know that extra strength is easy, but it brings a lot of
other bad things to performance, if you make too strong a deck.
They want to it get a low as permeable as they can, but they
also want it to be like regular concrete.
From a construction standpoint, we've got a couple things that
happen in concrete when we place it.
Now this is true for all concrete.
We have various conditions on the surface of the concrete that
cause drying.
Sunlight, wind, wind is probably the worst.
Humidity, moisture loss, there's always some type of evaporation
going on, just right here, right now.
In concrete, with regular concrete, that's probably a good
thing, because regular concrete when you place it, for you guys
that have worked with concrete before, you know when you place
it, when you strike it off, the first thing that happens is you
get a bleed water that comes to the surface.
You with me, the guys that work for concrete?
What happens is that bleed water, when you place that fresh
concrete, the concrete slowly settles, and as it settles,
there's excess water in there, we said anything over, I should
have stayed at that, anything over thirty gallons of water, is
all in there for cracking, you know you really don't need it to
make concrete, here's our thirty gallons of water, and the HPC
we've got an extra seven gallons of water in there, in the old
mix, it's just all going to end up in cracking, but that excess
water is not needed for hydration either.
So what happens is, as that concrete settles, this excess
water comes to the surface on conventional concrete, and you
have to let that water evaporate off the surface before you close
the surface and do your final texturing.
If you were to just place that concrete, conventional concrete,
and close the surface and start curing it, do everything that we
saw on that video, you would seal all that bleed water into
the concrete, and trap it under the surface, that's what a lot
of contractors get into trouble with when they do sidewalks and
people's driveways.
They place concrete and the very next winter, the whole top of
the concrete has scaled off and the owner is freaking because he
spent ten thousand dollars for concrete driveway that is
supposed to last for twenty years,
and it came off in one winter.
What happened is the contractor didn't let the bleed water come
up and evaporate.
He sealed that bleed water into the deck.
When the bleed water come up, it couldn't come up and evaporate,
so it made for a very weak surface in that concrete, and
when it went through freeze thaw, bam, you know when water
freezes it expand nine percent.
That expansion creates a real lot of tensile force in concrete
and we said concrete is not good at tensile so it fails in freeze
thaw very quickly.
That's conventional concrete, where there is some bleed water.
In the case of high performance concrete, this is where the
difference start to show up and we probably saw it in some of
the videos, is that the concrete looked gooey.
It looked sticky.
There wasn't a lot of no bleed water, you know because this
silica fume has filled up all the void spaces between those
baseballs with its BB's so there actually no excess capillary
pores for the water to migrate to the surface.
So on high performance concretes, normally there's no
bleed water.
Guys that finish concrete their whole life, you know this is the
only way they know who to finish it, you place it, you strike it
off, let the bleed water go, we come over, have a cup of coffee,
a sandwich, go back an hour later and finish the concrete.
Can't do that now.
High performance concrete doesn't have bleed water on the
surface, so if there's no bleed water on the surface to protect
the surface from drying, evaporation doesn't know that.
Evaporation is still drying the surface out.
Well, once, it dries out to a certain point, it cracks.
It's called plastic shrinkage cracks.
ACI says plastic shrinkage cracks, what is it by definition
it is cracking that occurs in the surface of fresh concrete
soon after it is placed or while it is still plastic.
Two key things; fresh concrete still plastic.
Fresh concrete means when the time the concrete comes down out
of the truck, it's fresh, it's moveable, it's plastic.
It only stays plastic for about three hours, until it sets.
The cement water hydration chemistry
makes it start getting hard.
So plastic shrinkage cracking only happens in that first
three-hour window.
If you can start developing strength in that concrete, you
won't have plastic shrinkage cracking, because it only
happens while it is still stiff and still fresh.
So we've got this three-hour window that we need to protect
the concrete from surface drying, but the concrete doesn't
bleed, so why do we have to wait for three hours?
If it doesn't bleed, lets just finish it sooner.
Well it's cured sooner.
If we can cure it in 10 minutes time, then who cares how long
plastic shrinkage may be in effect, we have it protected
from drying.
And that's kind of the way that the finishers have found.
This is a chart that is also found in a book looking at
finishing parking structures.
I am not going to spend time on this.
That'll take you through if you need it.
One of the ways to work with contractors, on placing high
performance concrete with silica fume without bleed water, is,
you know you, you and I we can stand here and be real didactic
and tell you information and you can understand it
and you can learn.
Some people can learn by see-do, like little kids, you show then
something, or follow me and you know they do it right away, ride
a bike, skiing, anything like that, they are good at see-do.
Contractors, you are not going to tell them how
to finish concrete.
and you are not going to show them, because they've been doing
this for thirty, fifty years, and they know how to do it.
Right?
Even though they may be doing it the way they do it with
conventional concrete, not for high performance concrete.
How do you get them to learn that?
And the way to do that is called guided discovery.
I'll let you discover what I wanted to tell you in the first
place, but I'll just guide you so that you discover what I
wanted to tell you.
You wouldn't have listened to me if I told you anyhow, so we'll
go out and do a test pour for never evers - it's people that
never, ever work - contractors that have never, ever worked
with high performance concrete before.
A lot of specifications will actually require a test pour.
And the engineer and the architect and the owner will
come out and actually stand around and [laughs] actually
stand around and watch the test pour, watch everything happen.
You know, watch the contractor do his thing.
What happens, is you, as the contractor is doing this test
pour, he see certain things, this is part of his guided
discovery.
He see that hey this concrete it's not as slumpy, even though
you said it was a seven inch slump here, this stuff kind of
sticks together, really well, it doesn't, it's not as slumpy as
what it normally should have been.
They pick up right away the fact that the concrete doesn't bleed.
You strike it off and there's, whoa, there's no sheen on the
surface of the concrete.
So, in various conditions, you actually leave part of the test
slab out let it go bad, it's a test slab.
Let them fail.
Let them see what happens if you don't do the right thing.
Another way for them to learn.
So then part of this test slab, we won't do anything to it,
we'll let them finish it they way they
would normally finish concrete.
Just so they can learn themselves what works
and what doesn't.
Once they learn that this has this plastic shrinkage cracking,
or potential, then they get in all these elaborate
evaporative protection schemes.
If you go to American Concrete Institute, they have a whole
list of different things you can do, from wind breaks, you know,
erecting a wind break to stop evaporation, wind screens, they
go into elaborate fogging, actually fogging, putting a mist
supposedly putting a mist in the surface trying to create a
higher humidity above the bridge deck, to stop you know to stop
this from happening.
You know, the evaporation from happening.
They go to great stretches of describing you know what to do
to try and stop evaporation.
Why, it's nature, you can't stop evaporation.
Deal with it.
And that's what we're talking about here.
Deal with it.
There's no bleed water.
You're, if you can place the concrete, you can close the
concrete surface, you don't have to worry about trapping any
bleed water, go ahead and do that.
You want to final texture, you want a broom texture, you want a
tine texture, fine, put it on and then begin your
curing right away.
Right behind it.
If you start curing right away, whether it a white pigmented
curing compound that we saw on the video, or whether it's
cotton mats, or wet burlap, start putting that on the
concrete right away, ten to fifteen minutes after it's been
placed, it's already under wet burlap, or it's already under
curing compound.
It's already done.
It's done, guys.
Go home, heh heh.
Contractors leave all your tools on the truck, all your hand
tools, all those extra tools for working the concrete, and
rubbing it, and making it look good.
They hate when I say this, and ready mixers love it, but the
concrete coming down the chute of that truck is as
good as it gets.
There's nothing the contractor can do to make it any better
from a durability standpoint, than taking it out of that truck
and doing whatever he has to do with it to build the structure,
and get away from it.
The more you work the surface, the lower durable
the concrete will be.
So, what we are talking about here is no delay in final
finishing and fast tracking.
If you have ever seen them pave a highway, they pave a highway
with very stiff concrete.
They slip form it.
They feed concrete out here, it is like play dough and a machine
walks along and the pavement comes out of the
back end of the machine.
Two hundred yards down the road, they'll have a curing train,
another bridge that comes across and they are spraying it with
curing compound and the finishes are all stretched out within
that two hundred yards.
Well, that's on a normal highway.
All we've done for bridge decks and with high performance
concrete is we've condensed that train, instead of being two
hundred yards long, we've condensed it down
to about thirty.
Where the concrete is placed, consolidated, surfaces closed,
textured, and curing begins, and everybody moves down the
pavement all at the same time.
>> Tony: You get down to the end of the pavement,
everybody goes home.
We don't have to stay around three hours and wait for the
bleed water to bleed and get out there and final finish it.
It's fast tracking, its this type.
Guys aren't used to that.
These finishers are used to being around there till 8:00 at
night finishing concrete that they should have been
off of at three.
But that's what they do.
It's a hard lesson for them to break.
You guys can be the change, the change demons.
Make things change.
I use this photograph because when you ask for a test pour,
this is what normally happens.
The ready-mix get a great slab in his yard, but this is a test
slab for a bridge deck.
And a couple things here.
These aren't the finishers; these are the superintendents
that are going to be there.
So these aren't the guys that are actually going to face you
know finish the concrete anyhow.
Secondly, this isn't the equipment.
They are not going to place the concrete on a bridge with a 2 x
4 they are going to use a big Bidwell paver
or sophisticated equipment.
All this stuff.
There are not going to use a broom to texture it.
They are going to have it tied onto the Bidwell, but the only,
and they are not going to hand finish it.
So the only thing this is really accomplishing, is they are
seeing that there is no bleed water, you see there is no sheen
on this concrete, there is no water on the surface of this
concrete, so they are placing it, finishing it, texturing it,
curing it, go home.
Ten minutes.
If you do it right.
On a parking deck, this happens to be in Milwaukee airport.
This is slab on grade.
They use the slab on grade as a test pour, before they got up on
the decks, they figured if they were going to make a mistake, we
will do it on grade where we can yank it back out.
But you still, they used the bridge screed, they used the
paving screed, where that used to be over here, they are
bringing it over here now.
Right behind the screed, they are hitting it with the float,
to close the surface.
The float actually has a broom off the front of it, which I
think I have another video of, or a picture of.
And then spraying it with curing compound.
This white-pigmented curing compound is just that.
It forms a, it's a liquid that when it dries on the surface of
the concrete, it forms a film that you can actually kind of
pick off as a sheet, it almost forms like a rubbery film on the
surface of the concrete, to keep the moisture in the
concrete from evaporating.
This is another shot of a finishing of a parking deck.
Indianapolis airport is building a 6,000 car parking deck
starting next month.
Silica fume concrete is in the specifications.
All these videos and user manuals, and everything, the
local contractors are all going through right at this time to
learn this technique, where they place it, close the surface,
texture it, cure it.
They are pouring it off in strips.
You can see how they are going; you can see the individual
strips going across the deck.
Once they get down to the end of the deck, they are done.
Being finished and cured right here.
They never have to get back on this, - even though you can't
walk on this concrete, it is still considered fresh, where
old way of finishing you'd still get on this concrete and work it
later on, this stuff is still fresh, but it is done,
it is finished.
There is nothing left to do with it.
This is the yeah, here is the broom.
Actually invented a tool when we first started because of the
non-bleeding concrete here, you can see there is no shine on the
concrete, they use a tool which is called a Fresno.
It is a steel trowel.
A lot of guys that work with concrete, they use a lot of
wooden tools, wooden floats, bull floats, wooden floats.
Really good for consolidating aggregate and that type of
things with conventional concrete, but because this stuff
is real tacky, wood floats just kind of pull and
tug at the surface.
Instead of closing the surface, it'll actually rip the surface
back open again.
This concrete without the bleed water is very sticky.
It's cohesive and adhesive.
It'll stick to everything; it'll stick to itself.
So you start pulling it, it'll have a tendency to want
to rip apart.
So they have to close the surface and they do that with
this steel trowel, which works very well, and then they have to
put a texture on it.
Well, you know, if I am going to try to reach out there with the
broom, and put a broom texture on it, it's crazy, because you
can't balance it thirty feet out without it smacking
into the concrete.
This guy says I'll just attach, a contractor actually made this,
he just attached the broom off the front of his Fresno.
So when he actually pushes this tool out across the concrete,
this edge of the blade is in contact, everything is tilted
this way, this actually rides in the air as he is pushing the
bull float out across the deck, the broom rides in the air.
When he gets to its furthest point, he turns what's called a
hustler joint, right here, which changes the angle of the blade
from this angle to this angle, thereby lowering the broom onto
the deck and he pulls it back towards him.
He not only closes the surface, but he puts a texture
on at the same time.
Two steps in one.
Next guy sprays it with curing compound they go home.
Without the curing compound, without curing immediately, this
will crack.
That's like give me a piece of paper, and let me guarantee you
that it will crack now, so that I don't get the phone call.
If you don't cure it, it's going to crack.
Because there is no bleed water here.
I mean its physics, you know.
It's going to crack.
If you don't do the right steps.
Some of the things that they've found in the part of what's
doing the right steps is if you can, particularly on bridges,
they are placing them more at night.
Less traffic at night, it's safer at night without traffic
on the highways, but it's also a lower temperature at night.
And we talked about this temperature differential.
If you think about placing concrete in the morning, you
place concrete at 8:00 in the morning, it is probably going to
sit around for sixteen hours before it really
start gaining temperature.
So about twenty-four hours, about twenty-two hours, or so it
will be really peaking at temperature.
Well, twenty hours from 8:00 in the morning, is 4 in the
morning, so you're concrete is going to be getting is hottest
when it is the coldest outside.
It doesn't make sense.
You got, you know, you got the concrete gaining temperature at
the same time that your environment out
here is losing temperature.
If you place concrete at night, 6, 7, 8:00 at night, what
happens is, it starts getting hot at 3:00 in the afternoon,
4:00 in the afternoon, 5:00 in the afternoon, well that's fine,
that's the hot part of the day.
So everything climbs together.
It's not the fact that the concrete gets hot, It's this,
it's this, coefficient, and it's this, difference in temperatures
between the outside temperature and the concrete temperature
that will cause cracking.
So they place a lot of bridges at nighttime.
Lower temperatures at night
reduce temperature differentials.
They have a tendency to place it at the lowest slump possible.
If you place, slump is that on the video where they pulled that
cone up, and the concrete all fell, and they measured how much
slump that is.
When you have a very high slump concrete, and you are pouring it
over steel, what happens is sometimes is that concrete,
because it has so much flow, will have a tendency to start to
settle over the reinforcing bars, and the reinforcing bars
will act as stress risers, and actually cause the concrete to
crack as it settles around the reinforcing steel.
So you take some of the slump out of the concrete, and it can
support itself but lower slumps are better for reduced cracking.
This stuff you can't over vibrate it.
It won't segregate, and as we said before, early finishing was
better than excessive hand finishing.
All the curing practices that have been found to date has been
immediately cure it with water, at least for seven days, wet
burlap, those type structures.
When you are doing multiple bridges, multiple long spans,
bridges, normally what happens is if you have a single span
bridge, you know one column here, one column here, we are
going to cross the interstate in one continuous span, they'll
start pavement on this side, and just go in one complete motion
all the way until they are on the other side of the deck.
If you are doing viaducts, or like up on 294 in Chicago where
you have these long continuous spans, maybe a mile long, over,
not even over a river, over somebody's backyard, You know
just elevated, it's a bridge, but what you have, what happens
is you can't place those from one end to the other end
straight through.
Because as you are placing the concrete on the bridge, while
the concrete is still fresh, it has a lot of weight, it's liquid
almost, so it has a lot of weight on the surface and you're
deflecting that.
It doesn't have any strength bearing characteristics, because
it hasn't gotten hard yet.
So it can't support itself, so it adds a lot of weight to the
structure, so what happens is when you build multiple span
bridges, is you have to place all the positive
moment regions first.
You have to place all those regions over top of the columns
first, and then you come back the next day and you do the
negative moment regions, because of that weight loading.
If you were to do the one continuous pour straight
through, this extra weight on this third or fourth segment
would be cracking this concrete all the way back here just
because of the extra weight tilting the bridge, and this
concrete back here is not hard enough to support its
own weight yet.
So it's a little bit different construction practice when you
are doing excessively long bridges on placements.
If they have the technique worked out well, then this is
what it looks like in a snapshot.
The Bidwell paver is up here with the epoxy-coated bar, they
are putting a texture on this concrete here.
They are placing it in the evening, you can see by the
sunlight hours, and the wet burlap is probably
ten minutes maybe behind.
No bleed water.
I actually don't like this concrete, the guys they are
using an Astroturf drag.
A piece of Astroturf wrapped around a bull float.
And the guys this guy on the catwalk here just drug it across
this whole deck.
You can see there some rattiness that has been rolled
up on the surface?
They actually had polypropylene fibers in this concrete to try
and help with plastic shrinkage cracking.
I said there are a thousand one things you can do to control
plastic shrinkage cracking.
They really didn't need the plastic fibers if they are going
to cure it this quickly, but they still had it in there.
But what happens is that all those little fibers from the
AstroTurf grab onto the mortar, and the mortar is real sticky,
so it sticks to the fibers and it sticks to itself, so the more
you use it, the more mortar it pulls out off the concrete, and
the real rattier the surface becomes, But, the district
engineer in this particular case, they like it, this rough.
You drive your car across it, you can definitely tell there's
a different texture on the bridge that has got a whole
different sing to it.
This is some of what they do also.
I see engineers that go into great detail.
All the plastic shrinkage cracks, we've got to stop
plastic shrinkage cracking.
I have to fog the concrete.
I have to create this humidity.
So they go to great extents of putting in elaborate fogging
machines, and spending money.
It's wasted.
It's wasted.
First place, you are not supposed to spray the water down
directly onto the surface of the concrete.
It is supposed to be raising the humidity of the
air above the concrete.
You might as well just get a garden hose and spray
it on the concrete.
Secondly is, if they were prepared to put the curing on,
they don't have to texture this, they are going to come back and
saw cut it later, if the contractor was prepared to put
the wet burlap on this close to the paver,
what good is this doing?
He already has it under cure.
This is useless.
He has just spent all that extra money to do nothing.
If he did the right thing first, which is what he is doing, he
doesn't need the fogging machine.
Plus he is placing in the morning, but he's got the cure
on right away, so that is good.
People spend so much money on fogging.
It just doesn't, I mean, if you, if you can place it, and finish
it, and here again you can see it, the Bidwell's placing it,
this guy's texturing it, here is the wet burlap under there, it
is ten, fifteen minutes behind.
There is not a fire drill going on here, the guys aren't over
working, there's a, this is an easier job all around.
I don't like tools that stick to the surface.
We said that the wooden tools will stick and tug at the
surface of silica fume concrete.
Steel tools work best.
This is what a texture look like, people say well, if I put
a texture on, in the case you can see the Astroturf the green
up here, if I put a texture on here, when I lay this burlap on,
isn't it going to smash down all the texture?
And no, not really.
The guys that say that have never been out on a bridge deck,
because normally what happens is that he's got one end of the
burlap, and I have the other end here, we pick it up, we lay it
down on the deck, we don't drag it across the deck, we are not
dragging it across, we are laying it down across the deck,
so it's just the weight resting on the concrete.
Here is tined concrete that had wet burlap applied as was in the
other picture, literally minutes behind, wet burlap doesn't smash
the tines up.
Yes.
>> Student: [Unclear dialogue]
>> Tony: Good, I think we are close to the end anyhow.
>> Dr. Wahby: We see how rich [unclear dialogue] Any questions
for Tony: [applause]
>> Tony: Oh thanks.
If you need to reach me when you are out there working your jobs,
on anything that has to with concrete, it's my name
Tony@silicafume.org.
It's real easy.
Silicafume is all one word.
The other class took all my business cards, so I am sorry.
It's just my name: tony@silicafume.org o r g Thanks
guys have a great week.