Correct Answer - Option 2 : Decreases
Effect of the strength of concrete:
Increase in fineness of cement
- The fineness of cement affects hydration rate, and in turn, the strength. Increasing fineness causes an increased rate of hydration, high strength, and high heat generation. By increase in fineness we get more surface area due which we get better paste which led to dense bonding and better packing which results into increase in strength.
Increase in water cement ratio
- Fluidity of concrete increases with water content because addition of water enhance intre-particle lubrication. At site it is normal practice to increase the water content to make the concrete workable which lowers the strength.
Decrease in curing time
- The purpose of curing is to ensure that the concrete does not dry out prematurely, but retains moisture so that it will build up strength and gain durability and resistance to wear. The concrete should be kept continuously damp for at least 7 days to achieve satisfactory curing.
- When concrete is not cured properly, its durability, strength and abrasive resistance are affected. When the surface of the concrete is not kept moist within the first 24 hours after the casting, the evaporation from the exposed horizontal surface results in plastic shrinkage cracks and a weak and dusty surface.
Decrease in size of aggregate
- It is interesting to note that in lean mixes larger aggregate gives the highest strength while in rich mixes it is the smaller aggregate which yields higher strength.