The effect of allowing concrete to dry before it has fully cured

Abstract

Summary This report gives the results of experiments done to find the effect upon strength of curing concrete in an absolutely or partially dry state. It is normal practice to keep concrete wet for four or five days after placing. For example on page 85 of “Specification 1952” is stated that: “It is important that concrete should be kept damp for as long a period as practicable. This can be achieved by sprinkling, covering with damp sacks or any similar method, and, except in the case of high alumina cements, is considerably assisted by leaving damp shuttering in position as long as possible. If concrete is allowed to dry out at an early age the strength and permeability will be impaired and the shrinkage increased.” The results of the present experiments show, however, that as far as strength is concerned the curing can be done at any time. Thus if the concrete is allowed to become dry for a period and is then re-wetted, it will continue to increase in strength as though the dry period had never existed. The experimental work was done in two parts, the first to find the eflect of curing concrete in absolutely dry air, and the second in ordinary room atmosphere.