High Performance Concrete (INT2253, Spring 2006) - Full


Uploaded by WafeekWahby on 09.04.2012

Transcript:
[no dialogue].
Good morning everyone my name is Tony Kojundic.
You all can grab my business card there K-O-J-U-N-D-I-C.
Just call me Tony please--with the Silica Fume Association.
Our association actually sponsored here today by the
Federal Highway Administration.
As you can see in your booklet that you guys picked up there.
The book was the silica fume user manual.
was published by both the SFA and the FHWA,
Federal Highway Administration.
Part of the effort is what they call technology transfer,
sharing what's been done in concrete technology over the
last 30 years or so trying to expedite the learning curve
of the next generation of you guys coming up
through the ranks.
Before we get started I want to play a little tape here to give
you a little background here.
You know which button to push, thank you.
[Unclear dialogue].
♪ [music playing] ♪♪
>> male voice over: World news tonight
with Peter Jennings continues.
Now solutions.
>> Peter Jennings: There are several ways
to dramatize tonight's solution.
We could tell you that a horizontal asphalt
infrastructure anomally is a curse for millions of American
drivers at this time of year that would be pot holes
to most of us.
We could tell you that $52.5 billion a year goes to highway
construction and maintenance not to mention all the other
money to repair the bridges and other pieces
of the nations infrastructure.
It is safe to say that if we think 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 of what its made of does not last.
>> Jack Smith: This is ordinary concrete and
this is what happens to it after years of punishment
it falls apart.
Most of the concrete in the nations highways and bridges
has a life of just 30 years.
What's the solution?
I'm standing on it brand new stuff called
high performance concrete.
This is a sample, engineers say this will not last 20 or
30 years but 100 years and maybe longer.
This is what America's roads and bridges could be
made of in the future.
Engineers at the New York State Department of Transportation
discovered how to make it two and a half years ago.
>> Don Streeter: 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 Smith: Researchers stumbled upon the
formula after the Clean Air Act forced power plants
to reduce pollution.
Huge quantities of industrial waste called fly ash began
piling up and collected from smoke stakes.
First used as filler in cement turned out to be the key
ingredient for strengthening it.
So this is one-quarter industrial waste?
But it makes the cement many times tougher?
>> male speaker: That's right.
>> Jack Smith: High performance concrete is 74%
cement and 20% fly ash and 6% micro-silica another type of
ash all mixed with water.
When it dries ordinary cement is actually porous not solid
that's how salt and water get in.
But the fly ash in micro-silica is 10 to 100 times
finer than talcum powder powder.
Professor Ken Holger of Cornell has found they literally
fill in the microscopic holes in cement and demonstrates it
with colored tennis balls.
>> Professor Ken Holger: The next thing I would want to
do if I want to densify this box is get some midsized particles.
And take those midsized ones and try and get them into the box.
>> Don Streeter: They fill in all the smaller voids
inbetween the cement particles and we just have a very,
very dense material.
>> Jack Smith: More waterproof?
>> Don Streeter: Correct.
>> Jack: Stronger.
>> Don: Yes.
>> Jack: Last longer?
>> Don: Yes.
>> Jack: The new concrete is 3 times more
water resistant, 20 times less likely to form cracks,
and in pressure tests has proven almost 20%
stronger then 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.
It's one of the reasons the Coliseum and other
roman buildings have lasted so long.
>> Paul St John: We really literally reinvented
what our ancestors 2,300 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's easier to lie down
costs about the same to use.
Engineers say not only can it be an answer to much
of Americas infrastructure problems but it could
revolutionize all construction.
Jack Smith ABC news Albany, New York.
>> Tony: They use the term micro-silica
in that video and that just another term for silica fume,
which is the group we are here talking about as you
know from news cast, most news cast are writtem to
an eleventh grade level.
So that was the introduction to high performance concrete as
ABC News conveyed it back in February 11, 1997,
nine years ago.
So that map they showed of the nine states or eight states
that have used high performance concrete right now
that map is complete.
Every state has used high performance concrete
on their bridges.
We'll talk a lot about what Illinois does on their bridges
here and what they have done down here on interstate 70 and
up along 294, and in Chicago.
As part of the presentation but that's kind of the background,
the idea is that even though this was invented two and a
half years before they shot this video so that would've been
95, reality is Ohio put down their first bridge in
84 with silica fume concrete.
New York did their first bridge in 1986.
The State DOT's have a way of studying things for a
long time before they flip a switch and go with it for
full specifications.
So they look at this material in place for a number of
years before they went ahead and switched over and started
doing all their bridges with high performance concrete.
New York and Ohio are two examples that since 1997,
every one of their structures having to do with a bridge has
been built with high performance concrete.
The mix design that they showed you there, those compositions.
Illinois, every state is a little bit different in
their learning curve.
Some states, to give you an example, I'm from Pennsylvania
and sorry to say I think we only have four bridges that I
would consider high performance concrete by design.
Where you go to Ohio and New York and they probably have
thousands already in place and that's what this whole
idea of technology transfer is we don't want people to have
to reinvent the wheel.
We already know how to do this, the technology is already in
place we need to get it out there in our industry and
construction industry and begin using it.
The problem is that most of the technology that we use in
the construction industry is 30 to 50 years old.
We still place concrete the way they did our fathers
and forefathers before us still placed concrete.
But as you saw on that one video there, the one fellow mentioned
about the Romans and the idea that we are going back to that
technology and that's where we'll try and start.
[No dialogue].
When people think of high performance concrete a lot of
times they think of strength.
If a little bit is good then a lot must be better and in a
lot of cases that would be good.
If you are doing a high raise building this is 311.
This building next to the Sears Tower in Chicago is 311
South Wacker...they used high strength concrete as the
columns in this building.
This is some 12, 14,000 psi concrete.
Six million modulus of elasticity runs from the
foundation all the way to the top of the building here.
The idea of using high strength concrete, if you were to design
the building with 4,000 psi columns, the columns would be
very large to support all that weight.
If you could make the concrete stronger and stiffer then you
could use a lot less columns to support that same dead load.
well if you're Trump and you're leasing it at what a couple
thousand a square foot, that extra square foot that you save
by reducing that column size on every floor more then pays for
any cost differential for high performance concrete,
in this case high strength concrete.
I mentioned Trump because that's his next
big building going up in Chicago.
It has 12,000 6.6 million modulus of elasticity
high-strength silica fume concrete all the way.
I think it's 80 stories right now but they keep
changing the elevation.
They keep that stuff secret.
But what is high performance?
We talked about high strength, high performance.
In the past, concrete was just concrete and as they said,
it failed within about 30 years.
The FHWA describes high-performance concrete as a
concrete in which certain characteristics are developed
for a particular application and environment.
The operative words in that sentence
are certain characteristics.
Strength is just one characteristic of concrete.
There are a lot of other characteristics and some of
those characteristics may be these types of things that we
can make concrete very easily to place.
Has anybody heard of self-consolidating concrete?
They call is SCC.
This is concrete that you really don't place or finish it flows
like water and all the aggregate in the concrete moves with it.
In a precast yard, it's literally in the last five
years, it's literally revolutionized the way that
they do precast concrete in the yard.
Before they had vibraters and laborers and people striking
off the I-beams and gurders and those types of things now
they pour this concrete in at one end of the form and it runs
all of the way down to the other end of the form
and they are done.
There's no vibration, there's no noise, there's no laborers
climbing all over the place.
And that's only in the last five or ten years.
That's a high performance concrete.
This compaction without segregation,
that would be the same thing.
Concrete that would flow into place and move without
the aggregate separating from the mortar.
That's what segregation is when everything falls apart.
You want things to stay together homogeneously.
It could be fast tracking.
You may want the strength to happen very early
or long term properties.
Maybe you are building a structure like a highway
or an airport that has 75 or 100 year design life
to it or a building.
How long is a design life for a high rise building?
A couple hundred years I don't know.
Permeability or density.
Density could be both heavy weight...light weight
concrete depending on what your goal is If you are doing a
nuclear shielding at a hospital or something, you may have
some pretty heavy concrete.
Low heat of hydration and mass concrete structures
with real thick walls.
This happens to be a combination of both.
These are real thick walls out at the Hanford
Nuclear Site in Richland, Washington.
They are utilizing both low heat of hydration and
long term properties.
Obviously, they are storing nuclear waste in there
they're be in there for a couple hundred years, so they're
trying to keep that alive.
This last website is actually a place for more information on
bridges, part of the FHWA presentation that we do.
But how do we make high performance concrete?
This is all the cementitious materials
that we put in concrete.
Cementitious materials mean that when you add water to them they
hydrate, they react chemically.
The cement and water together become something different.
The concrete doesn't dry out.
The water is actually used in a chemical reaction and we will
talk a little more about that chemical reaction.
These three powders, Portland cement, slag, and fly ash class
C, if you add water to those guys they will
hydrate, they will get hard.
They're cementitious silica fume or micro silica and if I had
class F fly ash, if I had another pile of that, if you add
water to these two guys, all you'll get is dirty water.
They don't hydrate.
They don't hydrate at all.
But if you go all the way back to that first video, said where
the guy said we stole stuff from the Romans.
That's what the Romans actually used to build the
Appian Way and the Colosseum and their old structures that we
still go over there and visit.
They used actually the Vesuvius ash which is pretty close to
silica fume with ground up local limestone pulverized and
that's what they made their concrete out of.
It was so popular that they called it after the city where
they got the ash from the city in Italy is called Pasalana.
So this chemistry, this type of chemistry here was silica fume
and this F ash is reacting with lime
is called Pasalanic chemistry.
That has been around for 2,000 years.
This chemistry, this Portland cement chemistry,
is hydration of water.
Portland cement was patented in 1824 in England.
It's called Portland because the cement actually resembled the
rocks on the Isle of Portland.
It has nothing to do with Maine or Oregon, it's because it
resembled these rocks off this island in the UK when they
first came up with this product.
So this chemistry here this technology has only been around
for less then 200 years.
What we're doing here with high performance concrete is we're
combining these two chemistries.
We're combining this 200 year old chemistry with this 2,000
year old chemistry over here.
I'll show you how all of that works.
A little bit about cement hydration I wont bore you to
much because this isn't a chemistry class.
But real straight forward, if we take cement or reactive class C
fly ash or slag and add water to it, it produces what's called
a calcium silcade hydrate gel, CSH.
That's actually the glue of the chemical reaction when this
goes forward this is the glue that holds everything together.
The cement hydrates and grows crystals.
The crystals interlock and they get real
strong on a micro scale.
That's only about 65% efficient in producing this glue.
The other 25% or 35% goes to producing calcium hydroxide,
calcium in lime.
That's a good thing.
About 35% of that goes to producing lime
and then some heat.
Well what happens if we add a Pozzolan to it
using that Roman technology.
If we have the same cementitious materials together with water in
this case we would combine our Pozzolan material either silica
fume or F ash.
What happens is this material reacts with the calcium
hydroxide and converts it into more CSH gel.
So it acts as a catalyst if you will of making this chemical
reaction more efficient in producing the glue.
And less efficient in producing this calcium hydroxide.
In concrete you hear guys talk about free lime, my concrete
floor is dusting, if you look at mortar on some of the buildings,
I haven't looked at the building around here.
But if you look at mortar on the sides of buildings
you can see white leaching out of the side, running down the
side of nice pretty bricks on homes that they have spent
millions of dollars on and they've got this stain leaching
down the side of their bricks.
That's just calcium hydroxide breaking down, that's the free
lime coming out its a real weak crystal and when it comes out of
the cement it's the reason why floors dust, it's the
reason why mortar leaches.
Pozzolans will tie that up and convert it into more of the glue
that holds everything together, so normally when you would add
Pozzolans to concrete, first thing that's going to happen
is you are going to get really strong because you're
making more glue.
So you've got to balance out all of this chemistry.
But that's what happens on a chemical stand point.
This is a little chart showing the effect of adding silica
fumes or micro sillica content and the reduction in the calcium
hydroxide you probably have to get about 28% of silica fumes to
eliminate all of it if you really wanted to,
most people don't.
What is silica fume and how is it produced?
Silica fume the name, silica and fume, its Latin for smoke.
No fumar, no smoking.
Its smoke, it's silica smoke its actually the smoke that's
given off of [unclear dialogue] furnishes where 50 years
ago at least in this
country use to go in the atmosphere.
This is silica fume.
It is full, its a full container,
it feels like it is empty.
It's captured smoke.
It won't come out, you can take it off,
it's fine, it's just real light.
It probably has a bulk density of eight pounds in a cubic foot.
So a cubic foot is...what's water?
What's the cubic foot of water weight?
60 some?
62.4 pounds.
So this silica fume, it weighs about eight in that container.
That's actually captured smoke, in the past it used to go
out of this stack here what they do now is they pull it down the
stack with fans, and run it through filters and when it
comes out of this filtering system that's the material
that comes directly out of the filter.
It's so light in that condition that you really cant use it the
people that produce this material for concrete they
actually densify that material up to about 40 pounds per cubic
foot, so that it can be handled in trucks and thrown around like
cement and handled nomadically.
That's the original material I wanted to show you
the lightness of that material.
I wont throw this but this is actually the silica, the SI that
comes out of the bottom of the reaction.
They take quarts coal, wood chips, and coke and smelt it all
into this open narpalipic furnishand they are trying to
get the SI the silica out of those quarts.
That's what they're tapping out of here, and that's the
element I'm passing around here, that's element number 14.
I think, element number 14 on the periodic chart Si.
The smoke as it goes up the stake is gas an SiO gas, and it
combines as it cools somewhere around 600 C, it combines with
another oxygen and forms a solid.
But because it's going from a vapor to a solid its like a
formation of a rain droplet.
These things are perfectly round and smooth and its a
condensation of that vapor so you end up with an SiO2
amorphous powder which is what the silica
fume is in that container.
This is a shot of what the furnish looks like as they're
tapping the silicon metal Si comes out about 1300 to 1400 C.
They pour it into big chills and it gets hard, a chill is exactly
what it does it chills the material until it gets hard and
then they drop it on the floor and it scatters like glass and
they start the crushing process.
They'll crush it to that size and they will crush it all the
way down to 10 micron for use in some ceramics and glasses and
those types of things.
What's silicon used for?
Silicones, probably 80% of the market buy that elemental
material take it [unclear audio] and turn it into silicones.
Bathtub caulking you think that are automatically but the
deodorant, shaving cream, dashboards, cereal boxed, fake
hooters all those things start out at silicone, that also
started out as that piece of metal that's going around
before they turn it into silicones,
that's how it all starts.
And this is actually the silica fume that goes up the stack.
This is a shot of silica fume particles magnified.
But to show their roundness amorphous,
amorphus means non-crystalline,
and they are obviously non-crystalline if
they're is amorphous.
The amorphousness, the roundness is what makes them reactive.
You can put crystalline silica in with cement and water and it
doesn't react as a pozzolan.
Sand is crystalline and silica you mix that with concrete and
it still stays sand.
You mix this stuff with cement and water and in seven days time
its all calcium silicade hydrade, it's no longer silica
fume it's reacted.
The amorphousness of the silica fume, of the silica particle
which makes it reactive, it's also the amorphous nature which
makes it non-hazardous.
When people will hear silica, the first question we get is all
silicosis, its hazardous, guys don't want to touch, don't
breath that stuff it will kill you, you have kids.
It's not this is probably the safest stuff at a readymix plant
because it is amorphous and it's consider a
nuisance dust, it's respirable.
Respirable is in the category of cigarette smoke.
You breathe it in, you breath it out.
Crystalline silica because of its angularity when you breath
it in, it gets hung up in your [unclear audio] and your lungs
and those types of things and
that's what produces silicosis.
Really laying on the beach on a windy day is probably the worst
place to be for crystalline silica.
A little comparison here and this is
out of the users manual here.
The users manual was put together for practitioners.
It's not an engineering document, it's written for ready
mix producers and written for contractors, it's written for
people who actually have to make this concrete and
build stuff out of it.
So I think that this group here.
Right, yeah, good.
The beginning parts you still see in chapter two here,
we're still talking about what is silica fume and the sizes.
We're showing cement grains on the left panel and silica fumes
or micro silica particles.
They are about 100 times finer then cement grains.
Cement grains you grind from a rock down to a powder where the
silica fume is a vapor that's condensed.
To put it in more layman's terms, we compare it
to the Washington Monument.
If the cement grain was the size of the Washington Monument the
silica fume particle would only be the size of a six-foot guy.
We show the crystallanity of the cement particle versus the
amorphous silica fume powder.
And again that shot.
What happens in concrete though?
Think about the cement grains regardless of how small they are
you can only get them so close together.
It's like filling a barrel full of baseballs you can only
get them so close together and you have that void spaces
between all of those baseballs.
What happens is in comparing cement grains and silica fumes
if we mix baseballs up with bee bees you can see what's going
to happen we will fill up all those void spaces between those
cement grains which is really what we're
doing with the silica fume.
But now we are filling them up with
another cementitious material.
It's going to react with cement water hydrations, so we're
going to close off the capillary
pore with cementitious material.
So we end up with low permeable concretes, concretes that will
suck in less deleterious chemicals.
Industrial floors, lactic acids, beer plants, slaughter houses,
bridge decks, parking garages, Indianapolis airport has a 6000
car parking garage that starts next month.
Its also a silica fume concrete for this reason that they want
that structure to have a 75 year design life.
You get one chance to do it right.
You can put as many chemicals as you want on the surface of that
concrete and they all wear out over time or you do it right the
first time and make it low permeable to start with.
Get your longevity or your life longness from
that way, that technology.
This is probably the first use of silica fume
in the United States.
The US Core of Engineers, and the Bureau of Reclamation use
silica fume on all of their water ways for abrasion erosion.
Water carries aggregates, big rocks that will tumble and break
away concrete and what they found is that by making a very
high strength concrete they use silica fume to get pretty high
strengths they are able to make the
concrete very abrasive resistant.
Can I switch videos here?
We've got another one here on this project that I think is
coming up next.
[no dialogue].
This is structure is actually on the video that we're going to
get ready to play here.
This was done back in 1983.
A little bit of updated history cause the video will tell you
everything about the construction but..it was built
I think in 1966 or 1967 and was repaired
every 6 years until 1983.
So it was repaired twice.
And this is the result of...they lost a foot of concrete
that abrated away, and they're actually in danger
of losing they're whole steeling basin.
So they put 13,000 PSI concrete on here as abrasion erosion
resistance, and that was done in 1983 and we're
now up to 23 years.
They use to send divers down every year and inspect it.
Actually measure the wear and do all of those good technical
things and they just say this is a waste.
It's up to 23 years and we are happy with it, so they don't
even go down there and look at it anymore.
It's still in place so they've gotten four times the
life out of it.
Their goal was to get twice the life out of it and they're up
to four times now.
Yeah go ahead and start it up.
You can cover that please.
♪ [music playing--no dialogue] ♪♪.
>> video male voice-over: Elbord Technology Company
presents the story of [unclear dialogue] micro
silica additives and the concrete used to repair the
Kinzua Dam's stilling basin.
This ultra high strength loads concrete was used to repair the
stilling basin at the Kinzua Dam here in the Allegheny Valley in
Pennsylvania in October and November in 1983.
Hi, I'm Mark Luther.
I'm a project engineer for Elbord Technology Company.
We are working on this project.
It's repair of the stilling basin of the Kinzua Dam.
>> video male voiceover: The US Army Core of
Engineers is the federal agency responsible
for maintaining the nation's water ways, the Kinzua Dam and
it's stilling basin is one of 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 a river or other body of water.
If there were no stilling basins, the energy from the high
velocity water would simple 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 204 feet wide
by 180 feet long with 5 foot thick slabs of concrete.
It was originally placed in an 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 have 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 lead a contract to
repair the entire slab with one foot minimum overlay of low
slump steel fiber reinforced concrete.
The very best concrete known for this type of repair work.
Nine years later in 1982, underwater inspections by
divers show that in some places the one foot overlay of steel
fiber reinforced concrete had been worn away and as much as
two feet of the original slab was also gone.
And then over here you see the worst damage, this is where the
greatest ports from the upper [unclear audio]
number two occur.
This is where the water impacts and swirls around and the energy
is stilled 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 then that.
Well as you can see he fellow with the Philadelphia rod there,
I don't know if you can see how deep he is there.
I would say were he is standing there is over two
feet deep right now.
What they are doing is taking elevations using that rod and
the level behind us here to determine where the level of
this concrete is now so they can determine what they need to do.
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, Mississippi.
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 to have an abrasion erosion resistance
suited for the Kinzua repairs.
Through the use of micro silica additives, it was possibly to
obtain strength and denseness that made concrete far more
resistant to abrasion then any concrete produced in the
United States before.
It has long been known that the strength of concrete would
increase dramatically if we were able to fill it's pores
with a cementitious binder.
Concrete with emsac additives achieves its extreme resistance
to abrasion through its 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 satisfactorially 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 as ten inches, giving a flowing
consistence 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 pounds per square inch at seven days and
over 17,000 pounds per square inch at 90 days.
In its specification for the Kinzua Dam stilling basin
rehabilitation, the US Army Corps of Engineers required the
concrete to attain compressive strength of 10,000 psi at seven
days and 12,500 PSI days at 28 days.
Slump was required to be from seven to ten inches.
The contractor is Casey Company of Pittsburg, Pennsylvania.
The concrete was produced by Harman Brothers Ready Mix
concrete company in Warren, Pennsylvania.
I can't think of anywhere else in the United States today where
they are pumping ten inch concrete and getting 16,000 psi
unconfined compression results in 28 days.
That's what we're doing here.
That's one sample we have received.
The average is closer to 13,000 psi in 28 days, but you have to
keep in mind this is flowing concrete.
Typically, it is a ten-inch slump.
This is Harman Brothers Concrete Plant where the 2,000 cubic
yards of micro silica concrete will be made for the dam.
This site 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 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.
Here is Elborg's 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.
[No dialogue].
The concrete will discharge into the remix hopper of
the concrete pumping machine.
[No dialogue].
From there, the concrete is then transported down to the formwork
where the concrete is placed into the slabs and there it is
put into place.
This is just one way to transport concrete.
They have 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 remix hopper is, samples are taken from the
concrete and these samples are tested to make sure the concrete
has the proper consistency.
♪ [music playing] ♪
The concrete had maintained its ability to flow and to level its
self after eight miles of trucking from
the ready mixed station.
♪ [music playing]. ♪
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 again we expect our materials to last
twice as long as anything that has been used so far.
We saw in that video they were using a liquid grey, real thick
liquid that they were pouring in.
They called it the emsac additive.
That was actually the silica fume in water.
That's one of the ways in introducing this into concrete
instead of handling it in a dry form to actually suspend it in
water then just handle it in the water form and that's what
they used in this project 23 years ago.
No not yet.
Before we move on any questions on what we've seen.
Any body work with concrete?
Yet?
Not yet?
What's that?
You have done a few things with it, like what?
>> male speaker: Foundations.
>> Tony: Okay placing it, out
there pumping it, by hand?
You've got to do that.
You've got to work with concrete by hand to appreciate the
advantage of pumps.
Concrete is what 4,000 pounds per cubic yard roughly, so two
tons of concrete per yard and a truck will show up with ten
yards you got a lot of weight and you've got a lot
of material to move.
You better either have a lot of people or good
equipment to do it.
Since you all are going to go out in the field here shortly
and work in the construction industry this next little
segment that we have here is actually...we call it
construction site investigation.
This is our version of CSI.
We all get to be detectives on a project and figure out
what went wrong.
But before we do that, we're going to split up into groups
here into like five person groups and if you want to take a
break and grab some cookies or something here before we break
up into groups we can do that now.
if you all want to.
Yes, no?
No?
Yeah take a break really stand up grab a cookie
get a drink of water.
[No dialogue].
That last video on the abrasion erosion, the mechanism that the
Corps found of the reason why higher strength concrete is more
abrasive erosion resistance.
Same thing on industrial floors too and loading docks and coal
tipples and any place where you have truck traffic and scraping
and those kind of things.
What happens is if you take a concrete as a
combination of two ingredients.
It's the mortar and the aggregates and what happens is
the aggregates are normally a lot stronger then the mortar.
What happens is the mortar abrades away first, the weak
link in the system, abrades away first until it lost all of the
bond that holds the aggregate in place.
Then the aggregate freezes up and it becomes free.
But it's the weak link that wears out first and what they
found making higher strength concrete more abrasive
resistance in this case 13,000 to 14,000
psi concrete, is they were making
the mortar as strong as the aggregate so that when it
abrades that everything abrades at the same rate.
If everything abrades at the same rate you really don't
loose the aggregate which is most of the mass.
When you lose most of that mass then you're losing a lot
of your structure.
So that's how they've overcome abrasion erosion is by making
both parts of the system virtually equal strength.
There's no sense in throwing a high abrasive resistant
material, if you do industrial floors, the old technology was
to throw on a shake hardener they called it.
The finishers would throw on a real hard rock on the surface
and try and work it into the surface with their blades as
they finish the concrete.
Well that's fine the rocks were abrasion resistant but
you're still burying it in 4,000 psi mortar and that's the
stuff that's going to--it's the weak link.
It's going to fail first, not the strongest link and once the
weak link fails, then everything else starts to fail
in the system.
So the whole idea is to make a system that doesn have any
weak links which is what the Corps of Engineer does.
They say dams, waterways, southern Illinois here near
Paducah, they're doing the lock and dam there across the Ohio.
All of that under water concrete is silica fume concrete
[unclear audio] any waterways.
This next little segments here on our crime construction site
investigation, part of the handout the two pages that you
all took from up here are talking about
this Hetch Hetchy water system.
We are going to learn a little bit about California sitting
here in Eastern Illinois.
anybody been to Yosemite, California?
Go out there at least once in your life.
Can you move thatbook please?
This is a map of the area that we're going to
be talking about here.
The handouts, this bay area water system.
What they do is they capture the water in the sierras from the
snowmelt to feed all of the populations of people
Along the coast.
California basically a desert.
Once you get off the mountain range right here on this side or
this side which is Death Valley and Nevada and
there's nothing out there.
It's basically a desert and the only way they can support all of
those people is to collect every bit of water in the mountains.
I think there are only three rivers in California that
actually flow freely to the ocean.
That's something up state up here where they still have a lot
of salmon and steelhead and things like that run so they
still keep those open for some reasons.
But otherwise every other river in California is captured for
its water whether it's for irrigation or for people.
This is part of the system here.
The bay area water system operate in Yosemite Valley which
this is a shot of one of the monuments in Yosemite valley.
It's actually called half dome.
A little background information on Yosemite.
John Mueller on the right through his efforts and without
anybody in Congress actually seeing Yosemite, Congress
made it a national park.
The very first or second, no the first national park.
(male speaker).
I think I'm related to him.
>> Tony: Really?
One of my heroes.
His grandson is still real active in the sierra club and
things like that.
>> Unknown Student: Really?
My uncle is somehow related to him, like through...because my
last name is Mueller too.
>> Tony: Really?
Wow.
Wow.
Wow.
What's that?
>> male speaker:
He's on the California court.
>> Tony: I've climbed his mountain
named after him.
Anyway his efforts in law being in Congress and everything they
made this piece of land a national park then Teddy
Roosevelt went out there to show him around.
But Mueller was very active in trying to keep this wilderness,
wilderness and in 1913 the bay area people
decided that they needed water.
This was a good place for water so they created
this Hetch Hetchy Dam.
Which Hetch Hetchy is a reservoir, Hetch Hetchy is
actually the title of that paper that I handed out to you.
It's actually a canyon a couple miles north of this
valley we are looking at here.
They literally dammed up that whole valley and
filled it up with water.
There's one right next to it in Yosemite Valley that people
from all over the world go and visit.
I's a natural park.
It's the place you have to go there at least once in your life
and it will take your breath away as that photograph shows.
But if you go a little north of here the exact same
valley is damed up and full of water.
Mueller fought so hard to stop this in 1913 that after they
passed the law to dam it up, he died two months later.
Losing that battle, losing the Hetch Hetchy battle.
Anyhow to give you some perspective of what
the valley looks like.
This is El Capitan one of the mountains where
people climb it and I.
This is actually the Petronas Towers super imposed on it.
That's the tallest reinforced building in the world.
It's in Singapore, three quarters of a kilometer high,
something like that, 120 stories.
Sean Connery and Catherine Zeta-Jones, that one movie with
the cat that walked between up here, that's the building.
That's super imposed on this rock 4,000 feet one rock from
bottom to top you stand back and it's your whole field of vision.
So it's a pretty impressive place.
And you can see on this map that this is the valley where El
Capitan and Half Dome, this is the valley here that is in place
that we showed pictures of.
This is the Hetch Hetchy Valley up here and you can see it's all
blue, it's all dam that dams up the water.
They need that water though.
They have got 4 million people I think that the water system in
the paper says that they capture.
To give you some idea of the snow.
This is a shot last June, this is a shot last week or two weeks
ago, this is a shot last March, the same shot.
What do they get 20 to 30 feet of snow?
It all melted, this was March 19 last year and this is June 30
last year same shot so snow was what up to here.
They capture all of that nothing goes to the ocean this is what
they live off of and this is what Hecth Hetchy
looks like full.
They dammed up and filled it up with water.
Can you imagine this being another 2,000 feet lower?
I don't know how many years of water they
have stored in Hetch Hetchy.
It's a great place to keep water because it's so large the down
side to it is it's up so high.
It's 8,000 feet up, only so much water and snow lands
up here and can get into here.
Most of the snow is from there on down so what they do is they
literally capture the water in lower reservoirs and pump the
water back up the mountain into Hetch Hetchy.
Cause it's such a large reservoirs they've got so much
big area there where they can't capture the water so they pump
the water from lower reservoirs that capture it back up into
this major reservoir here.
One of the projects we are going to work on here is actually a
pump station at Cherry Lake.
Cherry Lake is this lake here you can see these little tunnel
shafts this is all pumping water back up hill.
Cherry Lake is here and this little tunnel right here
is our project.
So we are up in the Sierras in the middle of nowhere
having to do a construction job.
You'll go to these places if you're lucky.
The whole system from Hetch Hetchy as you see here is 200
miles long, 60 miles of tunnels, 5 different pump stations,
treatment plants and reservoirs supporting all of
these people all the way up, that's the water system
from that particular reservoir.
The designers out there at the bay area transit system one have
to repair this pump station and you only want to do it once
at least within a couple generations.
So they want a 100 year design life, 200 year design life.
They want to do it once and not have to come back to it if
they can get away with it.
So they go back and find out all this Corps of Engineer stuff on
abrasion erosion and how to make life long concrete and they find
out that silica fume is a good way to make this
type of concrete.
So they go to their users manual and they find on chapter 6 here,
we have a selection of mixed designs.
Starting points instead of, again, we talked about
technology transfer instead of starting over from scratch.
Other people have already done it.
They start off with a good idea and make it your own.
Adjust it, tweak it, and make it what you are going to do.
So we know we need a very high strength concrete.
We go to our tables here and we find that there's a couple
high strength concretes here and they both are high-rise
buildings, but that's okay.
We are looking for the strength in this particular case.
Come up with a mixed design here this is all in metrics, the
appandix...that's because it's FHWA.
It has to be in metrics.
The appendix in the book, though, is all in
pounds per cubic foot.
All in English units, our units.
So they use this as a starting point and say we need to make a
mixed design that in order to reach this design life for the
bureau, they wanted about 10,000 psi.
This manual will take you through step-by-step of taking
that original mixed design and adjusting it
into your mixed design.
And what they do here is you keep that mortar fraction of
that mixed design and I won't go through step-by-step here, well
I guess we do.
These are the specifications--in this case, this is for a bridge
deck but just to give you an example of the
step-by-step--these were the specks that you had to meet on
the mixed design.
Instead of going to a high rise building, they picked out a
specification, a DOT bridge deck in Colorado.
They looked at all the cementitious components first
whether it's high strength or a bridge deck, it's the same steps
that we go through.
They took the materials, the cementitious materials for that
high performance concrete and added your own local
aggregates to it.
Your own aggregates have their own specific graveties, they
have their own volume.
So you have to match that up.
The cements, silica fume, and fly ash, their specific
gravities are pretty much universal
across the whole country.
They don't change but your local aggregates will.
So you add your local aggregates in to
balance out your proportions.
I won't go through the details because you guys don't
need to do that.
But when you go to a laboratory and actually make this concrete
there's an ASTM specification, it's called C192 that is very
precise on how you make concrete in the laboratory.
Well, the problem is C192 was writing back in 1965 before any
of this technology came around in the early 1970s.
Following C192 in the laboratory you may not get the high
performance that you are looking for out of the concrete.
So the manual goes into detail here if you are going to make
high performance concrete in the laboratory, these are the steps
to go through.
It's a little bit different.
Really it involves longer mixing.
Laboratory mixers aren't real efficient compared to big truck
mixers where you have 40,000 pounds of material tumbling
around and mixing.
Lab mixers are relatively small and there's not
a lot of energy in there.
So, there's a lot more mixing here compared
to the ASTM test method.
But the mix design specifications for 100 years the
water bureau said they wanted 10,000 psi in 56 days.
That's the age of the concrete because this concrete was
going to be exposed to freeze at least for the first year
before it was submerged back under water.
The concrete to be air entrained.
It's where they actually put in, literally, soap bubbles into the
concrete making very, very tiny small bubbles to give the water
in the concrete, the moisture that's left over in the gel...
when the water freezes, it expands 9%.
What this air entrainment does is it gives it a place for that
freezing water to expand to without breaking the concrete.
Any concrete exposed to freeze-thaw conditions whether
it's driveways, sidewalks, curbs.
If it's outside, it's probably going to
be air entrained concrete.
The guys in the laboratory gave your construction crew
the mixed design.
Their laboratory mix, they achieved the specifications.
They were able to achieve 11,000 psi out of this concrete in 56
days and had 5% air.
So this is what you know is going to be made on your job
site and this is what the mixed design looks like.
They put in 700 pounds per cubic yard of cement.
Because of the location of this, we couldn't bring the materials
to make, we couldn't bring in the fly ash and the slags and
those types of things you would use.
So we just went with one pozzolan material, in this case,
was a silica fume.
Water-cement ratio has anybody ever heard that concept,
water-cement ratio?
The lower the water cement ratio normally
the higher the strength.
Typical concretes in the driveway will be 0.45
maybe 0.5 water-cement ratio.
That's really what it is, it is the amount of water to the
cementitious materials which in this case is these two combined.
So we'd be looking at the
cementitious factor would be 780.
The water would be 250 pounds of water, something
like that using that ratio.
They incorporated the local materieals both from California.
Caltrans approved limestone, Sacramento's sand.
Air Entraining add mixture was the product called Microair.
They used a water reducer to make this concrete.
They were delivering a slump at least in the laboratory they
were delivering a slump of six inches which is fine
that's something we can work with.
It's something we can move around by hand.
Cause we are not going to do this with pumps and stuff.
When we take it out to the pump station the guys call into to
you and they say we got a problem.
Our high strength concrete is setting up too quickly.
Setting up means I can't get on it, I'm trying to place
it and I can't move it.
It's getting hard already.
We're taling about within 30 minutes after bunching, this
stuff can't be pumped and they can't move it into this
pump station, they can't pump it through there and it's
starting to set up is all you know.
This is what you know about the project site,
it's called Cherry Lake.
You're about 6,000 feet in the Sierra's
in the late September.
All the materials because of the
remoteness--remember you're on the edge of a national park
so there's no quarries or roads.
You're probably an hour and a half away from nothing.
So all the materials have to be trucked in the site.
The structures going to be under water for life so we need that
6% air entrained for freeze thaw exposure here.
Our goal or your goal here over the next little period is to
try and figure out what happened to that concrete.
Try to figure out what could have possibly
happened to that concrete.
When they made it in the laboratory, it was a six-inch
slump and had flow to it and moisture to it.
When they made it out in the field it was drying up.
They made it and it was wet and within a matter of 15
minutes, boom, it was gone.
It was dried up, they couldn't move it. It was like a block
mix real, dry to the hand.
You couldn't even make a ball out of it.
It was drying up that quickly.
You go on the site and this is what you find the dam's been
lowered down, the waters all exposed or the
rocks all exposed.
That's the pump station that's going to be built.
The tunnel leads back up into Hetch Hetchy.
You can see the tunnel here.
This is one part of the construction site.
Most of your crew lives on site because of the remoteness.
That's another location, another shot of the pump station,
some of the material around there.
That's your batch plant.
We've got a couple little trucks here.
One batch plant, they trucked in the materials,
the limestone, and the sand.
Everything is all right there.
You can't use the water from here though because that's
potable water so you actually have to truck in your own
water from there too.
Some national park, another shot of the batch plant.
A couple different shots of the batch plant
showing its isolation.
The pump station is actually right here behind these
rocks where the construction is.
They're talking about trucking this material from here to
here and they can't get it out of the truck.
They made it in one place and they can't get it out of
the truck in the other place.
They got the mixed design here they know it works, your on
the site, there's no help, and you have to come up with an
answer of what happened?
Why's this stuff drying out?
There's a trick to how you do this.
Anybody ever knows how you come up with the right idea.
You come up with a lot of ideas and somewhere in those a lot
of ideas will be the right idea.
So what we are going to do here in the next five, ten minutes
or so we have enough people to break up into
at least three groups.
You know five or six in a group in the back, in the center,
up front, and the idea is to try and come up with as many ideas.
Nothing is far-fetched, nothingis off the table.
What could possibly have made that concrete dry up in
10 minutes, 15 minutes?
Where do we start on this?
Count off six in the back.
>> male speaker: Maybe the temperature?
>> Tony: Put it down, everything counts.
The idea here in the next 10 minutes to see if you can come
up with at least 10 to 15 different things that
could have gone wrong.
Everything counts, in the group I want you to work together
in a group to talk this over.
Somebody make notes because we are going to talk about some
of these ideas that we come up with here.
But the whole idea of this exercise here is again to come
up with the right idea and come up with a lot of ideas.
Everything counts from sabotage to you make it up.
Four or five in the back.
You guys know each other man, get together.
Three groups.
Why don't you guys move over here?
You five and then you two over here will work with those guys.
Yeah, there you go.
[No dialogue].
No bad idea at this point.
No off the wall idea at this point.
The only way to come up with the right one is to come up with a
lot of them.
[No dialogue].
You actually watch this happen to.
In this set up here this is the example that they did
right before your eyes.
You watched them batch the concrete and watched them truck
it over to the pump.
The guys got to rack it out of the shoot by hand and it
dried up that quickly.
They actually made the concrete in front of your eyes and
showed you the phenomenon of it drying up.
They weren't lying.
[No dialogue].
>> male speaker: [unclear audio].
No because they couldn't make concrete out of it
they couldn't do anything with it.
It literally dried up.
Dried up to the point where i say it's like a brick mix,
you couldn't pump it you couldn't do anything with it.
It was drying up right before their eyes.
>> male speaker: [unclear audio].
Normally the mixed accordance to ACI had workability of
an hour and a half.
>> male speaker: [unclear audio].
To less then 30 minutes.
In the laboratory they were able to keep the properties for an
hour and a half slowly losing though.
As the concrete begins to set up but in this case
it was very quick.
Very quick.
>>male speaker: [unclear dialogue].
The lab that did the mix design?
In Sacramento, so they used
all the local materials that was all checked.
>> male speaker: [unclear audio].
Oh Yeah.
[Unclear dialogue].
They're not able to place it.
Everything up to this point is fine.
[No dialogue].
Just a lot of ideas.
Remember it is volume at this point.
>> male speaker: [unclear dialogue].
>> Tony Kojundic: The right one will be in there.
I guarantee it.
The right one will be in there if you generate at least 10
to 15, you'll get the right one.
[No dialogue].
Where did the water go?
We know that cement water really doesn't react that quickly.
Cement water takes some time for that chemical reaction like
baking a cake, it takes a while.
It takes some hours for it to start reacting.
So we know it's really not hydrating that quickly.
So something else is happening to the water.
Something else is making it dry up.
We've got middle of California in September
where it never rains.
So water is critical to everything,
but where did it go?
Surface dry, truck dry?
>> male speaker: [unclear dialogue].
>> Tony Kojundic: When they made it, it looked wet.
By the time they trucked it over to that site, you can see they
had to drag it out of the chute.
They couldn't even get it out of the chute.
It was drying up that much.
To them, it looked like it was setting up.
To them, it looked like it was flash setting.
The guys on site, they don't know any better,
they're just making concrete.
It looked like concrete over there.
A hundred yards later, it looks like it's setting up to me.
But we know that cement water doesn't react that fast.
Not unless you have really some super excellerators
to kick it off that quickly.
I don't know.
Did some people throw some excellerator in there?
Somebody threw in a jar of salt or something in there
to make it set up quicker.
I don't know.
>> male speaker: [unclear audio].
>> Tony Kojundic: And silica fume and air.
That mix design that was.
Yeah, I'll put that back up there.
That was the, pretty straightforward.
Cement, silica fume, sand, gravel, air, water reducers, had
the slump, got our strength.
Everything was fine in the lab.
Never made it in the field.
Never made the concrete in the field.
This is the first, your first attempt.
That's why you're called in.
[No dialogue].
Anybody have 10 ideas yet?
[No dialogue].
There you go.
In your groups, pick out the...
now through your collection, pick the three that you
think are the better ideas.
As a group, you should all have the roughly the same one's.
If you have more than 10, begin to try and go
through and figure out your best 3, which ones you
think maybe most likely.
[No dialogue].
They could just be your favorite ones.
>> male speaker: [unclear audio].
>> Tony Kojundic: Yes, when you do lab mixes,
special project lab mixes, they normally bag up the
materials that are going to be used on the project and
give them to the laboratory and use exactly the same materials.
>> male speaker: [unclear audio].
>> Tony Kojundic: Potable water.
No, it wouldn't be water from the same place
but it would be drinkable water.
It's not supposed to be, but that could have been
one of the ones down there.
When they do those mixed designs in the lab, they'll bring,
they'll fly the aggregate in, fly the sand
in, cement, everything.
Even the air entrained and water reducers and chemicals.
They'll make a true lab mix, but that's the big step
between what we call lab crete and filled crete.
In the lab, it was great.
Now you're in the field.
Now you have to make a real high performance concrete that's
going to last for 100 years in the middle of nowhere and
now all of a sudden it's not working the same way.
What happened?
What's going on?
That's what we're trying to come up with here.
You guys got your favorite three?
What is your least favorite three?
Mark those.
[No dialogue].
Got your least favorite three with your most favorite three?
We need a spokesman, now, from our groups.
Are you ready?
Let's just do this real democratically.
To pick a spokesman for each group, on the count
of three, each group point to the spokesman.
Point to the person in your group you want to be spokesman
on the count of three.
Ready, one, two, three.
Who's got the most fingers?
Alright, the guy that got the most fingers, he
gets to pick the spokesman.
How's that?
The guy that get's the most fingers gets to
pick the spokesman.
Alright, you pick a spokesman then.
Who wants to go first, in the back.
What's your top three?
Hang on, we've got to write these down somewhere.
We've got to keep track of these.
What do you got?
>> male speaker: [unclear audio].
>> Tony Kojundic: Okay, humidity?
>> male speaker: [unclear audio].
>> Tony Kojundic: What was the last one?
>> male speaker: [unclear audio].
>> Tony Kojundic: Okay, next group.
>> male speaker: We had a lot of the same
but truck contamination.
The truck that was bringing the material in.
[No dialogue].
Human error maybe while they were mixing it.
[No dialogue].
>> male speaker: [unclear audio].
>> Tony Kojundic: No, temperature in
the atmosphere.
Last group.
>> male speaker: [unclear audio].
>> Tony Kojundic: Chemical contamination.
Okay.
A, what was your worst idea?
>> male speaker: [unclear audio].
>> Tony Kojundic: Inadequate mixing?
That's a pretty good idea, not the worst.
No one urinated in your concrete or anything?
That's a good one, good idea.
>> male speaker: I guess the local aggregate,
not the right material because you're not
taking any local aggregates.
>> Tony Kojundic: A mix up in materials
that was your least favorite one.
Okay yeah cause the laboratory would have checked that.
What's yours?
>> male speaker: [unclear audio].
>> Tony Kojundic: Those are all good ones too.
Okay, yeah.
>> male speaker: Sabotage.
>> Tony Kojundic: That happens.
Where's the light, which light?
Concrete, this concrete that we made was drying up.
We don't really think it was contamination cause we actually
saw them make a truck.
They duplicated what they can make in front of your eyes.
They more of less duplicated the same phenomenon
that it was drying up.
Where'd the water go?
We don't think it's a cement water reaction, we think there's
something else that's going on here.
You guys had all talked about temperature and elevation in the
atmosphere and humidity.
You're there your, skirting around the issues.
You probably just don't know the materials well enough
and that's why we are doing this today so you will know the
materials well enough.
But your all touching on the issues right here.
When you make concrete--you guys have maybe
done this camping at a fireplace.
You ever get rocks soak them in water then throw them in the
fireplace and watch them explode?
Poof.
Rocks will come flying out of there.
What happens is that rock you threw in a bucket
of water it sucked up water.
When you threw it into the fire, all that water changed into
steam very quickly and exploded that rock like popcorn.
It exploded that rock.
Well, all of these rocks in concrete hold water.
All of these rocks here and all of that sand holds water.
They call it absorbed water.
Most rock will hold in this case probably about 2%
of its weight in water.
In other words if you put, if you..in an oven, you dry out
rocks, you put them in a bucket of water you let
them soak over night.
You dry them off so they are surface dry and you weigh them
they are going to be 2% heavier then they were the day before.
In a case of sand, Wafeek, what, 12% or 14%?
Sand can actually hold up a lot of water not on the surface,
this is inside the material like a sponge,
it's actually sucking up water.
It's the reason why the rock blows up when you throw it in
the fire, all that steam is trying to escape very quickly
out of that rock so it pops.
The give away in this particular case was when this guy you can
see the front end loader here picking up his aggregate,
he picked up his aggregate and dumped it into that bucket
and a cloud of dust came off the aggregate that
completely covered the whole back side of his tow
motor of his front end loader.
If it's dusty, the aggregate can't be wet.
Right?
Because if the aggregate is wet, it's not going to be dusty.
You guys had said humidity,
temperature, elevation, atmosphere.
All of these this are conclusive in that part of California.
You're all on the issue they are all conducive to drying.
That's why we are capturing the water out there, there is
not water this is California.
That's why we dam up all of the rivers.
To capture all the water so their aggregates were,
they call it saturated surface dry.
If you put those aggregates and let them suck up there full
absorption of water and take them out and dry the sheen
off the aggregate.
Just let it lay out there so the sheen evaporates.
That's considered saturated aggregate surface dry.
The aggregate is fully saturated so the aggregate doesn't
know whether it's getting water from rain or purposely
putting water or whether it's sucking the water
out of the concrete.
It's physics this is going to take water.
It needs to absorb so much water.
So when they were making concrete here with
this bone-dry aggregate because it's dusting
all over the place.
That was the tip off that they are working with aggregate
that was below SSD.
When they made the concrete, the aggregate literally sucked
the water out of the concrete.
In that 10 to 15 minutes, 25 minutes it took to drive
that hundred yards, the aggregate sucked up the water
so much that there was no water left in the concrete.
It was all inside the aggregate or trying to get inside
of the aggregate.
You with me on that?
Does that make sense?
That was actually the root cause.
The coarse aggregate and the fine aggregate, the
coarse aggregate had about 1.8% absorption.
On both we figured the ash was there also, or the sand was
there also, the fine aggregate.
Combined those materials were 2800 pounds worth of
material and 1.8% absorption.
They told us we were roughly lacking 42 pounds of water
which is roughly 8.3 gallons of water.
Which in a yard of concrete rule of thumb, one gallon equals
one inch of slump.
So if we were making a six-inch slump of concrete at the
batch plant and we lost all this absorption, we went from six
inch down to a one-inch slump and that's why they
couldn't get it out of the truck.
The aggregates sucked up the water out of the concrete
and made it so they couldn't do it, they
couldn't place it.
They were able to place it then,
pump it into place.
The red fugitive dye on the surface is actually a
curing compound to seal in the water so it fully hydrates.
And that was there corrective action was they batched all the
aggregates first in those trucks and added the water to
those aggregates for 15 minutes.
Let them mix inside of the truck and let all of the or at least
try to stabilize its initial draw on then made concrete
on top of it.
And they were able to make the 10,000 psi and pump it and
do all the good stuff they had to do on site.
Questions?
>> male speaker: [unclear audio].
>> Tony Kojundic: In most cases, well no, in most cases that's
the first thing on a construction site that is not
allowed is adding water to concrete.
It's what everybody wants to do because it's the easiest
thing to do is to add more water to it.
You add more water to it and you change that water
cement ratio when you do that and that's the number one
thing that effects strength and performance is by adding more
water to it.
You're making it weaker the more water you add.
So no, they didn't add water.
They knew it was suppose to work, they had to mix designs
and they knew it worked in the laboratory.
Now they just had to duplicate it in the field.
The whole point here though is even though we are talking
about high performance concrete and real exotic and in far
away places, it's real basic fundamentals.
It's physics.
The rock has to satisfy its water demand.
It all starts there.
You can't make concrete unless the aggregate is at SSD.
I've seen it in Bloomington, I've seen it in
Indianapolis, I've seen it in Troy, Illinois.
I'm thinking of areas around here where people are trying to
make concrete but with aggregates that is below SSD.
They wonder why they can't control the concrete.
In the mean time, the concrete is constantly changing
because the aggregate is sucking up the water.
Rule number one, a real fundamental, the aggregates
have to be fully satisfied with their water demand in order
to make concrete.
If they're below SSD, you will see this stuff happening and
when stuff like this happens on a job site, it's real easy to
sit in a classroom and nice peacefully discuss what's going
on at the job site.
There's a little bit more tension that happens when you
are trying to think through these things and
sometimes walk away.
Walk away and go think.
Walk away and go watch them batch the concrete.
Go watch them do it again, and see this cloud of dust come
over top of the front end loader and you know the light
bulb goes off over your head.
It's dry, it's bone dry.
That's the answer.
You go home or go for a hike.
On deck placements something you find with high
performance concretes are that they're very low
in bleed water.
For those of you that have ever worked with concrete before,
there's a certain amount of water in conventional concrete
that's really not needed for hydration.
What happens is, as concrete is placed, all the material
tends to settle a little bit in place and it forces the
excess water up through the capillary pores to the surface.
It's called bleed water.
Typically on concrete, you don't finish that bleed
water into the concrete.
You have to let it evaporate.
If you finish it into the concrete too early, you trap
that water into the concrete and then when it freeze thaws in
this area the side walk or someone's driveway will peal
off in the very first winter and you get the
trouble phone calls.
Ninety-nine percent of the time it's because they sealed the
bleed water into the concrete, conventional concrete you
have to let that bleed water come up and evaporate.
With high performance concrete, particularly with silica fume
remember we don't have these bleed water channels,
we don't have these capillary pores
The silica fume is those little bee bees have filled in
between all of those baseballs so there is no capillary
pores, there is not bleed water.
And for finishers out on site it's a little bit different
because there is not bleed water.
They don't have to wait to finish it and because they had
been doing the same thing forever and ever you know 30,
50 years I've been finishing the concrete the same way and I'm
not going to finish it anyway different.
It's different you're not making a 1950 concrete, we're
making 2000 high performance concrete that's going to
last two to three times longer then it did before.
One of it's properties is there's no bleed water, even in
a fresh state it's very low in permeability.
You've closed off all of those capillary pores.
So the placement techniques get a little bit different.
What this little video here that we will play is actually the
Chicago Skyway looking west or actually north right now.
Gary, Indiana is behind us.
The bridge decks there were just repaired in 2003
with high performance concrete.
This is a video showing there placement techniques that
are a little bit different than what most people think
of with concrete, with bleed water.
In this case, they're finishing and placing and doing all of
this and having it cured within 15 minutes after placement.
We saw in that one video at Kenzua Dam where they
were placing the concrete and spraying it with curing
compound right behind it, that white pigmented curing
compound on top.
In this case, they're going to cure it but they're going to
cure it with a wet mats, wet burlap, wet cotton mats, they're
going to actually lay on the concrete.
The idea is to keep the water thats in the concrete in the
concrete so that it hydrates the cement.
If in a condition like this where we have direct sunlight
and wind blowing, low humidities, the same thing that
we saw happen on the aggregates in the Sierras would happen
to the fresh concrete.
The evaporation on the surface would be so great that the
concrete would start to crack.
It would start to dry out like a lake bed before it had a
chance to get hard.
It's going to take a couple hours for that to set up
and the chemical reaction to happen.
So this is what the video looks like on a
placement of a bridge.
[No dialogue].
They've learned to control cracking on bridges by
staggering the placement of the reinforcement over top
of one another.
You can see how they are staggered here.
Engineers like to draw things nice on a blueprint
what have you.
But reality those bars above one another cause a stress
riser and can cause cracking so they stagger the top
and bottom mats.
Here's the concrete being delivered to site.
It will be pumped on to the bridge deck.
That's probably a seven and a half inch slump.
Concrete being pumped onto site.
Note what's on the bottom of this hose.
You never let concrete free fall out of a hose.
They have a little S here on the bottom so the
pump literally has to pump it out.
If it free falls directly out of the hose and smacks
against the deck most cases you would lose a lot of
air entrainment those little air bubbles that you purposely
freeze thaw get collapsed.
Then you don't have good concrete for freeze thaw.
So that's why they put that little S underneath there
it makes you pump it out.
You can see the guys are only finishing outside the rails.
You can see the wet cotton mats are being placed on very
close behind the bridge paver.
I actually on a job site these rails.
I actually like to put the rails out of the pavement area If you
only need hand finishers for what's outside the rails will
make nothing outside the rails, put the rails
outside the structure.
Put the rails on top of this parapet here and on the other
parapet so there is nothing here for the
hand finishers to finish.
See all of those guys working outside the rails?
And they're going to do that
all the way back because they have to pull these rails
out and there going in hand finishing.
Why?
You got extra labor there.
The machine does wonderful job inside the rails.
Well make it so that the rails are the whole thing.
You can save a lot of labor in this case.
They eventually did this but as you see that had three extra
guys on both side just to finish one foot on concrete.
I mean it's crazy.
>> male speaker: [unclear dialogue]
>> Tony Kojundic: Hose?
More so for air, to keep the air in the concrete.
When they got too far ahead they actually stopped
their placement and let the guys on the wet
burlap here catch up.
Without bleed water on this concrete you don't want it to
surface dry so they got it protected under water and you
can see them spraying the water on the surface.
They try to keep the placement of the concrete very close
here for the same reason.
Everything, they call it fast track construction.
The concrete goes down, the bridge paver paves it,
the curing is right behind it and every body goes home.
The next thing that is going to happen is the paving
guys are going to be smart enough, you see they've got a
paver that has rollers and a pan drag and a wet burlap drag
The next thing they need to invent is the wet burlap being
placed automatically behind the paver.
So as the paver goes down the bridge, everything
gets done completely.
There's even less labor out there if you do it right.
There's a lot of potential out there to use as the one
video said from New York, this concrete actually gets
placed easier because there's no bleed water.
You can fast track the direction and technology is slowly
catching up with new equipment all the time to take
advantage of that technology.
>> male speaker: [unclear dialogue]
>> Tony Kojundic: Well, with conventional concrete you
wouldn't finish this way.
You couldn't put the wet burlap on right away.
You'd have to let conventional concrete bleed and that
bleed water to come up otherwise you'd be trapping it
into the concrete.
But with this high performance concrete with silica
fume and there is no bleed water chapter eight in the manual
goes into great detail for contractors how to place
and finish silica fume concrete bridge decks and parking
garages which are the two biggest flat work
applications for it.
The whole thing is to fast track it, place it, finish it,
texture it, cure it, and go home.
Don't wait the three to five hours, you can
finish it a lot quicker.
The hard part is getting the guys that have been doing this
for 30 years to change.
That's where you guys are important
because you're the change.
You only know one way to do it.
You don't have 30 years of the wrong way of doing it.
A typical bridge deck then, when the placement is
really going efficiently looks like this.
You can see the placement machine up here
in the green steel.
They've drug an astroturf on a broom to give this texture,
real rough texture and the wet burlap.
You can see the proximity.
You can also see there's no bleed water,
there's no shininess on this concrete.
You can't walk on this.
This is still fresh.
There's no bleed water but it's done.
There's nothing better to do than put it
under wet burlap then go home.
Don't overwork it.
The hand tools that you see, the finishing tools, all those
extra tools for labors.
They're the worst things for concrete.
The concrete, very pragmatically, it's as good as
it gets coming down the chute of that truck.
There's nothing a contractor can do to make that concrete any
better from a durability stand point other than to do whatever
it is he has to build it and do it with the of effort possible.
If you have finishing machines to finish it, fine.
Put your rails out here so that the bridge machine can finish
all the way to where the parapet rebar are.
You don't have any laborers on the side to do it.
The machines doing everything for you.
Take advantage of all of those things.
This is a parking deck up in Milwaukee.
You can see the proximity of where they are placing it.
They're actually moving the screed from here.
You can see him walking it over to here.
But literally, 10 feet behind the screed, they've closed
the surface and texture it and spraying it
with a curing compound.
They are done.
They don't have to come back and work it again.
That's it.
Thanks guys.
[audience applause]
Any questions?
What did you learn about concrete today?
I have a question.
what'd you learn about concrete today?
Give me one thing that you learned.
[Unclear dialogue].
>> male speaker: The high performance concrete lasts 100
years compared to the old concrete that only lasts 20.
>> Tony Kojundic: There you go, if you design it for that.
If that's your property that you want.
If you want it to last that long versus SCC or fastrack.
There's other properties too,
that's just one property.
Long life is just one property, but yeah, that's a good one
for high performance. Anything?
>> male speaker: [unclear dialogue]
>> Tony Kojundic: Aggregate.
Excellent, that's rule number one.
You have to get the aggregates right.
It's most of the concrete.
It's the best thing you have in concrete.
The weakest thing, if you think about it, all the bad things
that happen to concrete, people talk about it scales, it
cracks, if effervesces, it carbonates, it has the
delayed ettringite formation, it has crete.
All of those thing happen to the mortar.
They don't happen to the aggregate.
All of those thing happen to the mortar.
So if your pragmatic, why use more mortar?
You wouldn't, you use the most aggregate you could use
possibly get into that concrete because
that's your best material.
It's also your cheapest material.
Use as much aggregate as you can possibly make then use the
least amount of cement that you can get away with to achieve
what you are trying to achieve.
But then use the pozzolans like the Romans did, use the
flyashes, silica fume, use slag, use all these other things to
make that cement even better than what it would've been
to begin with.
That's the next step that's happened over the last 25 years
in the concrete industry is combining this Roman technology
with Portland cement chemistries.
Good, what else?
Who else learned something today?
Anything?
>> male speaker: [unclear dialogue]
>> Tony Kojundic: Oh, there you go.
Good ones.
The second one you always get.
It's dark, it's dark material, it's black.
You know it looks like it's real nasty, it's called silica
I mean everybody's afraid.
Don't even touch that stuff get that stuff off you go over
there and wash it off.
You would be amazed what people say at a ready mix yard when
they see something new.
Everything that's in the yard is going to kill them.
It's not.
It is the least hazardous thing they're dealing with other
then their waters.
But you get that question all the time.
What else?
>>Male speaker: [unclear dialogue].
>> Tony Kojundic: Oh, that's more of a design.
>> male speaker: [unclear audio].
>> Tony Kojundic: In most cases, if at your job meetings.
You're at your job trailer, the structural engineer, the
architect, the owner's rep, everybody's going to be there on
the construction site.
That's when these issues come up.
What happens is, when you put rebars on a deck, the designers
have a tendency to want to make the picture look really nice
so they put all of their rebar real uniformly spaced and
right at top one another here.
What happens is when you place concrete with aggregate and sand
and everything else, is the concrete has a tendancy
to settle a little bit.
If it settles over top of these bars, if your aggregate
starts to settle like this, you can have what's called a
stress riser originating from the top of this bar.
The fact that you have both of these bars lined up on top
of one another kind of exacerbates that
situation from happening.
If you can and what that video is showing and this is some
of the new technology on bridge decks that you try to
elliminate cracking, is to stagger the bars.
There is no reason to have them directly on top of
one another than it looks nice on a picture.
In reality, it was causing some problems.
Stagger them if you can.
They also found that getting the bars closer together in the
top also helps control cracking but that's a
whole different technology.
Staggering, that's the reason for
separating it, to help control cracking.
The Interstate 70 down here that was repaired 2, 3 years ago,
those first 15 bridges from the Indiana border westward are
all silica fume concrete.
Prairie Materials made the concrete in Terre Haute and I
forget who the contractor was.
>> male speaker: [unclear audio].
>> Tony Kojundic: Is that who it was?
Okay, 2003, 2002, 2003, during the summer they did those.
>> male speaker: [unclear audio].
>> Tony Kojundic: Yeah, I think in the
design, they are already accounted for.
There's nothing extra that you have to account for by using
a lower permeable concrete.
If you were doing a concrete parking lot, you'd have to
account for all of that collection of water from that
parking lot and have to accomodate for drainage and
collection areas and those type things and that's one of the
big things against parking lots is because not only they're
radiant heat pick-up.
You know asphalt and concrete will suck up heat and make
environmental temperatures hotter but they also don't let
the water get into the soil and they all run off.
The newest technology that you're seeing in concrete,
particularly for parking lots is they call it pervious concrete
and it's exactly what it sounds like.
It's concrete but if you look at it, it literally looks
like a sponge.
You can actually see, not permeability or capillary pores,
you can see the openings.
You can see the pencil size openings through this concrete.
It's literally a hard sponge and the idea is so that
there is no run-off.
The water will go through the pavements and that's a real hot
topic right now.
You guys that are getting into the construction industry,
you'll definitely see pervious pavement in the
next five years, flat lots.
>> male speaker: How does it act in the
winter time when water gets inside them and freezes
[unclear audio].
>> Tony Kojundic: The freezing of water in
the winter time, all concrete always has humidity
in the concrete.
We've taken cores of concrete from Death Valley and looked at
the calcium silicate hydrate gel and that gel still
had 50% humidity in it.
So, there's always some humidity in the concrete and it's that
moisture that the air entrainment is used for freeze
thawing, it's that moisture that is always in the concrete.
It's not so much the external moisture that's getting into the
concrete, particularly with the high performance concretes.
It's the humidity that's in the concrete.
It doesn't go.
Anything extra is just extra.
It's just worse but there is always humidity in concrete.
The longer you leave it in water like this concrete that we
built up in the Sierras 20 years ago, it's been
under water for 20 years.
It's definitely stronger now than it was 20 years ago.
That hydration process, cement water reaction, it continues
almost forever as long as there is water around
to keep it going.
That's why the curing is done with the water and that's why
when you make concrete specimens, you put them in
water and that's all part of the chemistry.
Good.
Wafeek.
>> Wafeek: Do you have any other
questions, comments?
Thank you.
[audience applause].
[no dialogue].