Hello and welcome back.
The hydration process refers to the chemical process that takes place between the cement and the water.
Now we've got a little more chemistry to look at today but this will be the last time for a while.
Don't worry.
This one is very important and at the end of this you'll be able to define the hydration process.
If you're unsure of anything and give this lecture another watch and let's try and get this one to really
sink in so we know that c 3 Yes and c to us provide the majority of the concrete strength and that water
H2O is added to start the chemical process writing these out we get the following two chemical reactions
first of which is C three x plus six H2O water which becomes C three years to age three and three CIA
O H two and c is three plus four H2O which becomes C three s to age three and C.A. O H two.
The important part being that we have calcium silicate hydrate C3 s to age and calcium hydroxide S.A.
O H two.
But for now we'll focus purely on the calcium silicate hydrate CSA H for short these serious H is the
gel is where the concrete gets its ability to hold everything together and a strong matrix form the
CSA takes the form of tiny rose that grows out of bone and hydrated cement particle and joins to over
cement particle rods to effectively fused together to give us the strength really the more cement particles
hydrate the more CSA forms and the stronger the concrete will get it's a fine line though the mix needs
enough water to completely hydrate and do the hydration process but too much water will actually weaken
the concrete the hydration process is naturally very quick and if left as it is it would set too quickly
for us to be able to actually cast workable concrete we need time between the cement being mixed with
the water and the concrete being in its final position ready to go and this is where gypsum comes in
gypsum access the -- to slow the hydration process down to give us enough time to get the concrete
to site cast it in place vibrate and finish if necessary you may hear people talking about green concrete
the initial set of the final set.
These are all stages of the hardening process.
Once placed the concrete is still workable and can be moved around with relative ease and this is when
it will undergo its initial set and then become unworkable although unworkable is slightly fairly weak.
Now all at this stage we would call this concrete green.
From there it moves into its final set which is the longer process of hardening which can continue for
over five years after the concrete is cast.
To make sure the concrete is able to successfully go through its initial and final set we need to make
sure there is enough water as we know the cement paste can only form in water filled spaces.
This is why curing the act of keeping the concrete moist after casting is very very important.
This seems like the perfect time to introduce admixture as mineral and mixtures to be precise.