Question

The capillary porosity and Gel/Space ratio of a cement paste (mixture of cement and water) one year after mixing are 0.30 and 0.66. Determine the degree of hydration and w/c ratio initially used to make the cement paste.

Answer 1

The degree of hydration is 0.8571 or 85.71% while value of w/c is 0.608

Step-by-step explanation:

As per given data Capillary porosity=P_c=0.3

Gel/Space ratio of the cement paste is given as gs= 0.66.

Also

`P_c=w/c-0.36 \alpha`

Here

• Pc is the capillary porosity which is given as 0.3
• w/ is the ratio which is to be calculated
• α is the degree of hydration which is also to be calculated.

Now

`w/c=0.3+0.36 \alpha`

Now the Gel/Space ratio is

`gs=(V_gp)/(V_g+V_p)`

Here

• V_gp is the volume of gel inclusive of pores which is given as 0.68 α

• V_g+V_p is the total volume of gel and the capillary pores which is given as 0.32+w/c

`gs=(V_gp)/(V_g+V_p)\\0.66=(0.68 \alpha)/(0.32 \alpha +w/c)\\0.66=(0.68 \alpha)/(0.32 \alpha +0.3+0.36\alpha)\\0.66=(0.68 \alpha)/(0.68 \alpha +0.3)\\\alpha=0.8571\\\alpha=85.71\%`

So the degree of hydration is 0.8571 or 85.71%.

Putting value of α in equation of w/c as

`w/c=0.3+0.36 \alpha\\w/c=0.3+0.36* 0.8571\\w/c=0.608`

the value of w/c ratio is 0.608.