Question

1. Two-inch mortar cubes were fabricated using three mixes (A, B, and C) with the same mix proportions. However, the characteristics of class C fly ash used in the mix are different, as shown in the following table. The fabricated samples were exposed to the same curing conditions (i.e. temperature and humidity) until the compressive strength was evaluated.

Mortar mix	Weight of fly ash in the mix (g)	Specific gravity	Median particle size (µm)	Specific surface area (cm2/g)
A	100	2.01	21.2	2120
B	100	2.45	4.9	5700
C	100	3.14	15.0	3600

State the mortar mix that will yield the highest 7-day compressive strength. Justify your answer.

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Answer 1

Mortar Mix-A will give highest compressive strength. Beacause Class-C Fly ash has the property to gain high compressive strength at later stage of the curing so it will not get high initial strength. So Mortar-A mix contains less Specific gravity than B & C and have less specific surface area also. That's why it will get higher early strength than others.