this video is sponsored by bespoke post in January of 2023 the western coast of the
United States was hit with some really severe storms one after another and it has left some
pretty severe weather for a state like California that's notoriously in drought you think that'd be
a good thing but if you look around here this is what happens when you have too much rain typical
mitigation strategy is to to Port the water and to get it into a storm drain and to get it out to the
ocean right that's a that's a quick fix but the problem in San Diego is it's raining right now but
from March to November we might not get another drop of rain we have heavy heavy snowfall in the
mountains and there's even been loss of life and children missing it's been a huge problem
and it got me thinking about something I saw about seven years ago on a story about thirsty concrete
or concrete that could let water through to avoid things like this but seven years later I've heard
nothing about it so what happened where's the Thirsty concrete if it was the answer to flooding
why aren't we using it that's what we're talking about today I'm Ricky and this is two-bit da Vinci
one of the main culprits for flooding is concrete pavement asphalt and other impervious ground cover
that doesn't let water soak back through in fact a study that I was just reading about recently says
that for every one percent of the land you cover in an impervious cover like concrete you increase
the risk of flooding by 3.3 percent so if you look at any major city we've paved paradise and
put up a parking lot and that has some major ramifications because like everything else in
science and engineering water management is a question of equilibrium so we have water that
we use all summer and we have evaporation from the Sun hitting the Earth and plants and trees
and roots and we have a system and then in the winter when the rains come that water
should return to the Earth but if we cover more and more of our world in concrete this is what
happens runoff where water doesn't drain it just runs right over and down into storm drains now
the first thing we can do is a storm drain it is a type of pervious ground cover and it actually
does a pretty good job but the problem is all that water still isn't returning to the Earth
instead it runs out into the sea where we don't harness it and to the point about equilibrium
what happens when we lose water all summer and we're not putting it back eventually the water
level just continues to fall and eventually the end result is desertification and this is San
Diego we don't want to see that happen so what can we do in the case of water unfortunately
it's a bit of an unstable equilibrium and what I mean by that is picture a rock on the top of
a hill versus a rock on the bottom of the valley on the top of a hill if you don't move it it could
be in equilibrium and steady but any disturbance in either direction will cause that rock to run
away and go further and further and further down the valley in contrast a stable equilibrium would
be a rock in the valley either way you push it it'll return to a level state so as we run off
more water it poses two problems first we're not capturing that water back but the second
problem is that the soil becomes hardened as the Sun beats down on it and that top layer of
clay soils and other types of ground cover will almost become like Concrete where it gets harder
and harder if you've ever seen deserts that have scars with cracks that have formed from loss of
moisture in the soil that kills vegetation it kills plants and trees that dig roots to kind
of mix up the soil hardens it out and it makes it even harder for water to seep back in as a result
it just sits on top and eventually floods away and doesn't return to the Earth so that is why
water management is Central to good urban planning because without it we'll eventually run further
and further into debt and lose our water supply under us but it's not so simple first a quick
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and you for supporting the show okay this is your typical concrete and asphalt it is made
to be waterproof as you can see from these puddles and obviously standing water is bad for a lot of
things mold bacteria Cheetos and everything else so the idea behind a porous or thirsty concrete
is the opposite of this imagine you can have the strength and stability of a concrete foundation
without this water retaining component here's how thirsty concrete works traditional concrete
is made up of four ingredients cement The Binding agent that holds it all together rocks sand and
water if you get up close and look at this you'll see it's very very tight and that's
because the rocks are porous there's a lot of gaps and voids but the sand fills that in so to
get water to actually seep through just get rid of the sand thirsty concrete can drain between
80 and 720 liters per minute of water per square meter which is so impressive that can almost feel
like an optical illusion we've grown accustomed to concrete being so waterproof for so long in
fact when I watched those YouTube videos that went viral on thirsty concrete about seven years ago my
first thought was this is a trick like how does this work because it just feels wrong so unlike
many of the ultra high tech Solutions we cover here on this channel that cost way more money
than the traditional approach this is actually pretty simple just concrete minus the sand and
fillers there are a couple limitations to Thirsty concrete for one it's not as strong as you can
imagine the more void you introduce and thirsty concrete has around 30 voids meaning the Rocks
like the area in between have voids that take up about 30 percent of their volume and as a result
there's less surface area for that cement to bind to and it's not as strong so for that reason odds
are you're gonna have to go with a thicker slab of thirsty concrete like if you wanted
a four inch slab of pavement you might need six or seven or eight inches of thirsty concrete you
stood the water benefits with a little bit more extra strength Plus in the future you might even
need some rebar or other reinforcing materials to really strengthen and give you that long lasting
finish now to keep thirsty concrete working effectively it also requires a little bit of
Maintenance and cleaning up like street sweepers otherwise loose debris and sand and dirt and dust
will just fill in the top layers and hinder its ability to seep water through so to answer our
original question if this stuff is so great why isn't it everywhere well the answer is it's a tool
not a solution it would be like buying your spouse a brand new kitchen versus buying your spouse a
table saw and a bunch of sheets of plywood if we think of thirsty concrete as an end-all be-all
yeah it's not going to work but as a tool it has some really interesting potential for the future
of Urban Design and development future roads built with thirsty concrete sitting atop Stone aggregate
reservoirs could absorb water and hold it below the road surface this wouldn't just mitigate
floods but dramatically reduce the chances of hydroplaning where your car's tires lose contact
with the road when traveling fast enough to lift off the ground on a pocket of water this is why
we have deep grooves on road tires it's not for dry conditions in fact grooves reduce the contact
patch and reduce the grip on dry roads but in wet roads and wet conditions they can be a lifesaver
giving surface water channels to travel along while still making contact with the ground these
under a reservoirs could slowly seep water back into the ground and also be built with overflows
where excess water can drain out to storm drains or holding ponds and if you're thinking this is
just a pipe dream for warmer climates like San Diego where it never reaches freezing temperatures
you're not alone most people I've talked to have all voice concerns of freezing and thirsty
concrete and if you have any insights about this please leave us comments below where we can
all learn together but generally speaking water freezing on roads is a problem because water gets
under areas with cracks then as the water freezes it expands and has nowhere really else to go so it
places high levels of pressure on the road surface and results in breaking up of the concrete thirsty
concrete with 20 to 30 percent void spaces might actually allow for enough of the collected water
to expand when it freezes to move without adding the pressure on the road the Minnesota Department
of Transportation actually did a study over three years from 2008 to 2011 where they tested various
forms of thirsty concrete with severe Winters this is a great data point their goals were
to test for storm water management freeze thaw durability traffic noise reduction and general
longevity they pour different concrete cells instrumented with thermocouple strain gauges and
water Watermark sensors to record the resulting performance not too surprisingly the deflection
or movement up and down was higher in the Thirsty concrete than traditional concrete but as long as
the roads hold up this isn't necessarily a bad thing in fact one pretty surprising result from
the study is that thirsty concrete roads actually absorb more sound and are quieter thirsty concrete
also is found to reduce the number of freeze thaw cycles and generally held up about as well as
traditional concrete thirsty concrete even reduces the subsurface temperatures in the summertime and
increases the subsurface temperatures in the winter time both good things but it's not all
good news the study found that traditional street sweepers were largely ineffective as
they just agitated the surface dust further into the pores reducing all the benefits of thirsty
concrete they found that vacuuming the roads twice a year resulted in the best performance
and this maintenance needs to happen soon after the construction to prevent irreversible clogging
so now on top of everything else municipalities have to do they need to pull out their dysons and
vacuum their roads twice a year the makeup of the road layer is as follows a seven inch thick layer
of pervious concrete four inches of railroad ballast Rock and finally eight inches of a
gap graded base this is construction aggregate 1-5 made up of a mixture of rocks one two to
four inches in size and size 5 rocks which are about one inch or less in size after three years
there was some surface cracks along the path of Tire travel in cell 89 that was previous
concrete on top of clay soil and again this is a possible problem for thirsty concrete because as
you mentioned the bond between the Rocks without the sand aggregate in between is reduced further
testing will be required to figure out exactly what causes this and how best to remediate it but
the biggest issue this research found is how uneven the drainage rates were for different
parts of the Thirsty concrete this is because of building a traditional road is like building a
mass-produced economy car at least currently a thirsty road is more like a hand-built bespoke
Rolls-Royce because there are so many variables in how large the rocks are when they come together
there is greater variability in these cement bonding and the resulting drainage and strength
this means that it's generally harder to get an even and reliable product that can withstand the
test of time now while you do want water to seep into the ground wherever possible there are some
really key exceptions like for example this is a huge problem you don't want pools of water
saturated back into the ground near Bridges and the pilings and the footings for this bridge
here are going to potentially be destabilized so while yes we do we do need to find areas
where we want water to seep back into the ground buildings and other critical infrastructure are
not one of them thirsty concrete is incredibly promising but we'll need to start experimenting
with it at smaller less trafficked areas like the minnesotans did to come up with better
methodology for producing it this is like anything in engineering and construction and hopefully it
does happen and this concept isn't abandoned so now looking back at that viral video from seven
years ago it leaves me with as many questions as it does answers what was the composition of
the aggregate base was the amount of water used just enough to fill the stone Reservoir below
before completely filling it and overflowing was there actually a holistic drainage system
in place to carry this water out to storage ponds how much traffic did the road see and
what care was taken to maintain it and vacuum up surface dirt hopefully after this video you
can see something like this with equal parts wonder and curiosity and a healthy skepticism
and appreciation for all the challenges that lie just under the surface now if you're wondering
what you can do personally to help with this where you live how about rain capture off your
roof check with your municipality if that's legal I have heard from some viewers that it's illegal
in some places it's hard to explain but it has to do with runoff and capturing water back into
rivers and stuff but for me where I live on a hill if we had a couple hundred gallons of rain
capture we could keep that water from running off and flooding Fashion Valley like we showed here
earlier in the video and then we could use that water plant and irrigate our crops in the spring
and summer time for a few months at least reducing the burden of extra water that we would need to
consume the bottom line is while we have taken great strides in Water Management in building
and Urban Development we still have a long way to go storm drains are great for preventing floods
but can cause our runaway effect and drying out of topsoil as we mentioned all of life is in an
equilibrium and the case of water if you pave more of the ground that runoff means the water
is not going back into the ground and if we keep pumping water out it's just a matter of
time before these effects have prolonged impacts more and more dry conditions mean less plants less
plants means less roots that can kind of break up the dirt and increase the water saturation levels
it's a runaway effect and this is literally why we make this channel we love modern civilization
it's amazing roads to wherever you want to go and cars power plants right homes and power delivery
batteries but all this stuff has an impact on our environment and the question really is how
do we get clever about handling it and when it comes to water thirsty concrete is super
interesting but clearly more needs to be done we need to build a city where thirsty concrete is
at the foundation of Road design or parking lock development but what if that road that we showed
earlier was designed to flood that way nothing else Upstream if it does that is a part of Urban
Design we need all this water to have a place to go and like we've always talked about it all comes
down to the rate of things most light rains are fine right we have enough storm drain systems in
place to handle light rains but when you have a three-day storm or multiple storms back to back
to back that can overload pretty much everything that's where dams have to open doors to release
water and all those other Downstream effects a lot of this stuff is systematic and holistic it
doesn't just get solved by one road or one trench or one reservoir it takes a rethinking and this is
something I think is going to happen in the coming years because at some point something's got to
give water is becoming a scarce commodity and we just got a free gift of trillions and trillions
of tons of gallons of water and we're literally sending it right back to the ocean that doesn't
feel very good I think we can do better we must do better and I think we will thirsty concrete yes
not much has happened it's been really quiet for seven years but I'm not ready to give up on it yet
I think it has a place in the future so as more studies or more projects use it come out we'll
cover those in the future all right if you like this video thank you so much don't forget to hit
like subscribe comment engage with us we're here let us know what we can make next and if you like
this video I think you like this one as well until next week I'm Ricky and this is stupid DaVinci