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Q: Which of the following sentences is INCORRECT in the case of mortar?
  • A. Even a small percentage of mica, if present, considerably lowers the tensile strength and adversely affects the compressive strength
  • B. There is a gain of compressive strength by the replacement of less than 25% of cement by hydrated lime
  • C. Cement lime mortars are helpful in autogenously healing of cracks
  • D. It requires about twice as much cement to produce mortar of a given strength when fine sand is used as it does with coarse sand
Correct Answer: Option B - Mortar– • There is a loss of compressive strength by the replacement of less than 25% of cement by hydrated lime. • The density and strength of mortars made of the same class of aggregate decrease as the proportion of fine aggregate is increased. • When the percentage of mixing water is increased beyond that required to form a placeable mix, the density and strength of mortar reduces. The proportionate effect is greatest at the early ages.
B. Mortar– • There is a loss of compressive strength by the replacement of less than 25% of cement by hydrated lime. • The density and strength of mortars made of the same class of aggregate decrease as the proportion of fine aggregate is increased. • When the percentage of mixing water is increased beyond that required to form a placeable mix, the density and strength of mortar reduces. The proportionate effect is greatest at the early ages.

Explanations:

Mortar– • There is a loss of compressive strength by the replacement of less than 25% of cement by hydrated lime. • The density and strength of mortars made of the same class of aggregate decrease as the proportion of fine aggregate is increased. • When the percentage of mixing water is increased beyond that required to form a placeable mix, the density and strength of mortar reduces. The proportionate effect is greatest at the early ages.