In: Civil Engineering
The following laboratory tests are performed
a- Setting time test of cement paste samples
b- Compressive Strength of mortar cubes
c- What cement component (C2S, C3S etc.) plays most important role in each of the tests and why?
d- Which cement type will give you best and worst results for each of the tests? For compressive strength assume that it was run 3 days after casting
For a and b what are the significance and use of each of these tests
a- Setting time test is performed to check the initial and final setting time of cement paste. It is essential to find out the initial and final setting time as it will lead us to that we have to use the admixture or not, such as accelerator or retarder.
We don't want that cement sets during the transportation time before placing it or sets too slowly to affect our project time.
So get to know about the initial time which shows hydration and hardening has started and final setting time, which shows cement has lost is plasticity.
b- compression test is performed to test the grade of cement and to get ensured that it will perform in resisting stresses as it should when used.
c- C2S and C3S don't play much roles in setting time of cement, but C3A and C4AF play a vital role in setting time of cement. They come first in reaction with water in the process of hydration. It does affect the setting time of cement. The reaction of C3A is very aggressive, while hydration as more would increase the quantity of C3A more fastly the cement would harden. That's why gypsum is added to delay the reaction of C3A with water to resist instant hardening.
C2S and C3S paly role in strengthing of cement.
C3S contributes to the strength development in the early weeks
C2S contributes to strength development after the early weeks till the year.
d- cement contains more amount of C2A, and C3A compare with normally will give the worst results in a run of 3 days.
cement contains more amount od C3S and regulated amount of C3A will provide best results in a compressive test run in 3 days