Question

Explain why an increase in water-to-cement ratio for a fixed amount of cement results in lower concrete strength.

Answer 1

Water is an essential material for concrete construction. The water cement ratio is the ratio of the weight of water to the weight of cement used in a concrete mix and has an important influence on the quality of concrete produced. As per IS 10262(2009), the water-cement ratio for concrete mix ranges from 0.4 to 0.7. A lower water-cement ratio leads to higher strength and durability , but may make the mix more difficult to place. Too much water will result in segregation of the sand and aggregate components from the cement paste. Also, water that is not consumed by the hydration reaction may leave concrete as it hardens, resulting in microscopic pores (bleeding) that will reduce final strength of concrete. A mix with too much water will experience more shrinkage as excess water leaves, resulting in internal cracks and visible fractures (particularly around inside corners), which again will reduce the final strength.