Early age cracking and capillary pressure controlled concrete curing

Due to the evaporation of water at fresh concrete surfaces, a capillary pressure is built up in the pore system of the material leading to shrinkage deformations, i.e., to the so-called capillary or plastic shrinkage, and possibly to cracking. By influencing the capillary pressure build-up, the risk of cracking in the very early age, i.e., within the first few hours after casting, may be reduced significantly. A method of controlled concrete curing is proposed. It is based on in situ measurements of the capillary pressure by using wireless sensors. If the measured pressure reaches a previously defined threshold value, the concrete surface is rewetted. Experimental and numerical results concerning the physical behavior of drying suspensions are presented and observations made during on-site capillary pressure measurements are discussed.