Kind: captions
Language: en
I am about to get buried in concrete and
while that's happening I'm going to
explain everything you need to know
about this substance so the first thing
that I want to clear up is the
difference between cement and concrete
cuz people often mix these up okay
cement is like the glue it's the Matrix
of stuff oh there I feel it okay that
feels good now concrete is cement plus
aggregate so plus gravel and sand and
this is filling up really rather quickly
cement is the most important man-made
substance on the planet we use more of
it than any other substance apart from
water every year 500 kg of cement are
created for every man woman and child on
Earth and that amount of cement can make
two cubic met of conrete which is about
two of these big fish bowls this video
was sponsored by Ren I don't think
people realize just how important
concrete is so here's another way to
think about it every year we make a
certain weight of goods out of copper
more out of aluminum and then you have
glass asphalt lime iron is a big one for
all the steel and then there's ceramic
and wood but by far the solid product we
make the most of is cementitious
material essentially cement we use as
much of it as we do all other materials
combined and it's easy to see why
concrete is liquid rock you can pour it
into any shape you like it's strong and
durable and inexpensive and it is so
easy to produce that people have been
making a version of it for thousands of
years to make primitive cement the key
ingredient is limestone which is
basically calcium carbonate if you heat
it up to around 1,000°
that drives off CO2 out of the rock
leaving calcium oxide which is also
known as quick lime now if you grind up
the calcium oxide and mix it with water
you get an exothermic reaction that
creates calcium hydroxide which you can
pour into a mold and over a time it will
absorb CO2 from the atmosphere turning
back into calcium carbonate as the water
evaporates now that's a pretty good
primitive cement it's the first way that
people ever made cement but there are
several drawbacks to it I mean for one
thing you can't make the molds very big
because otherwise CO2 can't penetrate
all of the material and Harden it plus
it's not going to work underwater where
there is no CO2 to harden your
mixture the Romans discovered the
solution to these problems they added
volcanic ash called paalana to the
crushed Limestone before heating it up
and they discovered this cement was much
stronger and much more durable they used
it to create the larg larest
unreinforced concrete dome in the world
the pantheon which has stood for 2,000
years and they built concrete peers into
the sea which hardened underwater some
of which are still standing
today I did not expect it to feel this
heavy like it's already like really
weighing down my feet and making me
slightly concerned about um being able
to get out what I can tell you is that
concrete is about three times as dense
as water are you able to lift a leg I
just want to make sure that you're not
going to have like some suction sh I'm
going to try to lift the leg just to see
how bad it's going to be what I like is
having my feet on the bottom and I'm not
sure I can get them back down there
after I lift it up but oh boy okay so
that was like I'm going to try to
lifting this leg pretty
slowly and I was able to lift it so at
least up to this point I am able to get
out my fear is that the concrete is so
dense that when it gets up around my
chest it may apply a lot of pressure
making it hard to breathe it's like
being in a Tren having a cave in on you
cave in your lungs so you could breathe
cuz once they contract and the weight
gets against your
lungs that's going to be hard have you
thought about that well now that you
mention it but we do have oxygen on hand
just in case earlier I practiced how I
could get out of the bowl if I'm in
trouble do you feel that's okay that's
no problems okay great
so how did Roman concrete Harden
underwater and in thick slabs that CO2
couldn't possibly
penetrate there is a claim that it was
Superior to Modern concrete so was it
for centuries the Roman recipe was lost
it was only discovered in a book in a
Swiss Monastery in the 1400s and since
then Architects scientists and Engineers
have been experimenting with different
cement recipes to try to achieve the
best result now it turns out that that
Incredible strength durability and
ability to set underwater of the Roman
cement that came from the pusala that
volcanic ash that was added and nearly
2,000 years later people discovered that
adding clay or Shale to the Limestone
before it was crushed and heated
produced the same effect and the reason
is that all of these materials contain
silica and silica totally changes the
chemistry of the C
it means that it doesn't need to dry in
order to harden in fact the water
becomes an integral part of that
hardened concrete so that it actually
achieves maximum strength when it sets
underwater so this is the compressive
cylinder curing room we're required to
maintain the concrete samples in 100%
humidity so we've chose to submerge them
in water in a lime bath every time
concrete suppliers pour concrete on a
job site they cast sample cylinders of
the material so they can later test it
to ensure it has the strength required
so we actually intercept a little bit of
the concrete going into whatever
structure they're pouring a slab a wall
will'll intercept it into a wheelbarrow
take the wheelbarrow over to our testing
station and start casting these
compressive cylinders every day we're
breaking these cylinders checking it for
strength you can see these have been
broken today this strength increases
over time so samples are tested at 7 14
and 28 days when the concrete is said to
have reached full strength so what we do
is we list the date that there will be
placed in the compression machine on top
of every cylinder in reality it will
continue strengthening after
that samples are placed in a hydraulic
press and then the pressure is increased
on them until they fail all right ready
yeah let's start loading sure we want to
maintain around 30 PSI per second and
it's important to load at that rate yeah
you don't want to shock it you don't
want to shock it by applying too much
load too fast this middle number is
showing us our strength pound in pounds
per square inch and then the top number
the big number is showing us the force
of pounds we're applying what are we
going to get up to like 7,000 PSI 10,000
10,000 so this is going to be really
strong very strong okay yeah it's always
fun when we get something over
10,000 like a free show bang it'll shake
this room and these are reinforced
concrete
walls it's amazingly just like you can't
see anything happening even under all
that pressure it's still holding I know
right it's oh here it goes start it goes
11,000
mhm over 11,000
now oh
yeah a lot haven't you you didn't even
budge at all that's my favorite part
yeah that's cool let's see I like that
like the strongest Concrete in the world
well the strongest Concrete in the world
is going to be like a lab only thing in
a competition was above 100,000 PSI
today virtually all concrete is made
with a cement formulation discovered in
the 1840s it's known as Portland cement
but the name is really just a marketing
term you know they claimed that the gray
color of the cement would resemble these
very desirable rocks which were quered
near the Town of Portland England but
the Portland cement was made by crushing
up Limestone and then mixing it with a
certain percentage of shale or clay to
provide the silicates and that was all
ground up into a fine powder and put in
a kiln and heated to very high
temperatures and what comes out are
these nodules that are really hard
they're called clinker now it's
suspected that cement Chemists in the
past may have produced clinker by
accident when they overcooked their lime
mixtures but since this clinker is so
hard to grind down they just considered
it waste but if you do grind it down the
cement that it produces is far superior
to basically any other chemistry we've
discovered which is why it is so
commonly used today now there are lots
of compounds inside Portland cement the
most common one is tricalcium
silicate I'm now feeling incredibly
buoyant like I am now floating in
concrete which is pretty ridiculous cuz
most of my body is out of the material
but because it's three times as dense as
water you can float just up to your
waist this is totally unexpected I did
not expect to be able to like float in
concrete my feet are off the floor
that's where my feet are my feet are
here and my shoulders are up and I'm
just being pushed up out of
this once you have the cement powder the
other things you need to make concrete
are the Aggregates Sand and Gravel
these are blasted out of a
quarry then they're ground up to be
particular sizes there are very strict
requirements about the sizes and shapes
of the aggregate which is going to get
poured into the concrete because of
course that will affect the strength of
the concrete that results yeah this is a
just a a well-graded concrete sand the
most well-rounded material helps the
contractor as far as their finish
ability goes yeah you know when they're
running that trial over that slab they
want to rounded particle not a jagged
crushed particle do you really want like
a spherical sand a rounded yeah
spherical sand like a a river stone like
a river sand designers on the Strip want
to pour concrete elevated they want to
lighten up the load of the deck we'll
incorporate some lightweight aggregate
in place of this normal
weight 38 size typical concrete will
weigh 150 lb per cubic foot normal
weight this gets us about 110 lb per
cubic foot
the Aggregates are haul to the concrete
plant in big trucks all right I'm going
to release the
[Music]
rock where they're
dumped and then they travel on big
conveyor belts up into storage piles
these get loaded into big Hoppers and
then weighed out and poured into the
trucks the control operator is going to
Open this gate drop material into this
Hopper down into the mixer truck
below this is where the batch operators
controlling the
plant right here in front of our batch
operator William is the actual recipe
that he's going to dispense into the
concrete mixer each line represents a
different component in the concrete that
top one there is a 3/4 Rock we have an
intermediate 38 rock below it there's
your Sam over here in this column he's
targeting for instance 3/4 Rock he wants
to hit 13,000 lb of material for that
load the computer is going to try to hit
13,42 lb of 3/4
Rock so everything's everything up right
now now if he goes out of Tolerance and
he overshoots a Target it's going to
change to red a red color up here on
this screen we're actually showing the
holding Hopper this material he's
weighing is directly above the mixer
truck that just pulled under the
plant what about the water William being
orange yeah we're a little under on that
but we can always add a little water
yeah we cannot take it
away all right I'm going to take a look
inside the truck
here that's what it looks like down
inside a cement truck so I was
interested to see what would be the
difference in strength between pure
cement cement with sand and cement with
sand and gravel like the typical
concrete mix that they would make so I
had them make up these special cylinders
and test them in the hydraulic press you
might think that since pure cement has
the most glue it would be the strongest
cement's the the magic right the glue so
if we lessen or lower the amount of
cement per unit volume we're going to
have less strength but when we tested
the pure cement cylinder it fractured a
lot as the load was
applied is that it no let's let it keep
going it can take some more pressure
what 8,000 PSI now it
failed now cement plus
sand
9,163 PSI edit the prediction my
prediction was based on the strength it
was 2 weeks ago which we we have here we
got 14 days of 6,600 so you know reason
would be it probably break another
thousand PSI above that but it
definitely gained a lot and finally
cement plus sand and gravel this is the
normal concrete
mix is that it no part of
it
whoa okay so that's it that's
it so it did fail at
8,300 mhm okay I was surprised to see
that all the cylinders broke under about
the same pressure thing to me really
interesting that you could have all of
that cement right but you don't get
appreciably stronger than like this or
that cement is the most expensive part
of concrete so if you can get away with
reducing it down to 30% in the mix and
still get the same strength
characteristics well then you should
definitely do that the other thing that
was interesting was pure cement seemed
to flake and Chip more as it was loaded
so it seemed like adding the aggregate
actually helped helped the sample cohere
and stay together even under all that
load so was Roman concrete Superior to
Modern concrete well the answer is no in
short I mean there were some surprising
advantages that Roman concrete had for
example it was actually less well mixed
than modern concrete so there were
little blocks of undissolved calcium
oxide or quick lime that remained inside
Roman concrete and then what happened is
when the concrete cracked and water got
in there it would dissolve that calcium
oxide forming calcium hydroxide and then
you would get the new growth of calcium
carbonate so Roman concrete was actually
self-healing that's kind of a
fascinating Advantage but I would say by
and large you know when we look back at
the Roman structures we only see the
ones that have survived to this day so
there is a Survivor bias and finally
there's the issue of cost we could make
very strong ret that could last an
incredibly long time but we choose not
to because it's just cheaper and we
don't expect our buildings to last that
long before the concrete goes out on
site they have to make sure it's the
right consistency for the customer not
too dry and not too runny this can be
adjusted with water but you don't really
want to do that cuz that can also affect
the strength so here they use modern
chemicals like super plasticizers up
here on the top left you have our
dispensing units for all our chemical ad
mixtures and that's what they're adding
now of super plasticizer it makes the
concrete easier to work and spread
around without really changing the water
content very much to check that the
consistency is right they perform
something called a slump test or spread
test we're going to fill the cone to the
top nice and
level and we're going to pull that metal
cone off measure the distance it travels
on the board the concrete they're
pouring on me should have a spread of 27
in
we're going to measure it both sides
right on a 27 on that one and go this
way right on a 27 on that one so why is
it so important that you got the right
consistency of uh concrete you don't
want it too dry you want it wet enough
to flow and and fill up whatever
container you're trying to fill in this
case the sphere with you in it so the
question you're probably wondering is
how long can I stay in here before the
concrete hardens the usual answer is
about 4 hours without agitation and
that's why when you see concrete trucks
driving down the road that drum has to
be turning to keep the concrete agitated
and to prevent it from setting up but
what happens if the truck breaks down or
there's a traffic jam or something
breaks then at times concrete does
Harden inside the drum of these trucks
and that is a terrible outcome but there
is one thing you can do to slow the
concrete down from setting and that is
to add some regular
pop like Coke the sugars inside this
coke actually prevent the setting up
process from happening and that can buy
you a few hours so apparently these
truck drivers they drive around with a
few 2 L bottles of pop inside their cab
and so they can dump it in their load if
they have to to prevent it from setting
up so hopefully that means I'll get out
okay
too but how does concrete actually
Harden well you have the dry mixture of
gravel sand and cement powder and then
you add water the water starts
dissolving these cement powder grains so
ions enter solution and some of those
ions are calcium hydroxide so that's
what makes concrete a very basic
solution what do you see we're
approaching 12 11.8 so the pH of
concrete can get up to 12 or 13 the pH
of this is
11.8 and that's incredibly basic which
means if it's on your skin if it's on
your body it can be dissolving your skin
and cells being buried in concrete is
sort of like jumping in a vat of bleach
and that's why I'm actually wearing a
dry suit and some latex gloves yeah it's
not something you want to try at home so
do not try swimming in concrete so now
the ions are dissolved in the solution
and remember the most common compound in
cement is tricalcium silicate as it
reacts with the water crystals start to
form of calcium silicate hydrates plus
other hydrate minerals and all these
crystals grow and become interlocking
causing the concrete to harden note that
the water is essential to the formation
of these crystals so water is not
evaporating it's not drying out it's
actually becoming part of the solid
concrete material and that's why this
chemistry is called cement hydration is
also why freshly poured concrete should
be kept in as damp an environment as
possible Las Vegas is so dry they
frequently set up misters to spray
around new concrete to ensure the
humidity was high
enough one of the things I realized
while making this video is that
Limestone the core component of cement
and concrete well it comes from ancient
sea life limestone is formed from the
skeletons and shells of ancient sea
organisms that you know died millions of
years ago and then all of that got
compressed and now we use that to make
huge skyscrapers and you know overpasses
basically every huge piece of
infrastructure it's made with concrete
and so now when you look at a beautiful
city skyline what you're really seeing
is ancient marine life skyscrapers are
made of sea
shells skyscrapers are made
seashells skyscrapers are made of
[Music]
seashells yeah this is wild this is
hilarious I like I have no words I'm
like trying to push myself down into it
but it's like it pushes me up like I'm
pushing down into the concrete but it's
like B I'm getting pushed out of this
thing I'm just going to try to push
myself down in
here like that is it there is no you
cannot get buried in concrete okay I'm
doing my best right now to like sink
down and it is not happening but I'm
going to use my arms to to push myself
in
oh working against buoyancy this is hard
we were worried about getting me out but
like I can't stay in I'm going to try to
jump in here we
go that's it all right here we go one 2
3 that's
great that feels so good I like don't
want to get out this is uh so nice does
anyone got a time check this stuff is
not going to set up on me is
it so as we've seen concrete is one of
the most important materials in the
world it's made possible most of the
large scale infrastructure we rely on
but it also creates a lot of CO2 an
estimated 8% of the global total that is
more than the entire Aviation sector but
together we can do something about that
I would personally like to offset one
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watching