T1-3: Microstructural Location of Hydration Products

Question 1

Describe the reference microstructure

Answer 1

Inner products are in the originally cement particles-occupied space

Outer products are in the originally water-filled space

Question 2

In early age microstructural development, what are the time frames for:

a) the dormant (or induction) period

b) setting

c) hardening

Answer 2

a) 0.1 hours to ~4 hours

b) ~4 hours to 12 hours

c) 12 hours to 28 days

Question 3

Describe the trends for the relative amounts of the following products (in early age microstructural development):

a) CH
b) C-S-H
c) AFm
d) AFt

What has the highest amount of product?

Answer 3

C-S-H has the highest relative amount

Question 4

Describe the schematic diagram for a section of an unhydrated polymineralic cement grain

Answer 4

NB. C3A = tricalcium aluminate, CS3 = tricalcium silicate

Question 5

Describe the cement hydration reaction after 10 minutes

Answer 5

Question 6

Describe the cement hydration reaction after 10 hours

Answer 6

The paste sets, max. rate of heat evolution

Question 7

Describe the cement hydration reaction after 18 hours

Answer 7

Secondary hydration of C3A produces long needles of AFt

Question 8

Describe the cement hydration reaction after 1 to 3 days

Answer 8

AFm formed

Question 9

Describe the cement hydration reaction after 14 days

Answer 9

Reaction product becomes very slow