Shrinkage of concrete exposed to hot and arid climate

A long-term investigation into the drying shrinkage of concrete exposed to natural weather conditions in Kuwait was undertaken. Fifty-two concrete mixes were prepared, and prisms were made and exposed to natural weather after a 28-day period of laboratory curing (water and/or air curing)., Parameters investigated included water-to-cement ratio, type of cement, type of admixture and dosage, type of pozzolanic material, water curing period, and type of curing aid and special coating. The admixtures included normal and high range water reducers, and retarders. No adjustment was made on the initial concrete mix proportions when an admixture was added. Drying shrinkage measurements up to a maximum age of 726 days are reported. The results indicated that the drying shrinkage of concretes made with the various admixtures fell within a narrow band, indicating that no particular admixture had a severe negative effect on the concrete. However, the effect of admixture dosage needs further study. Also, the inclusion of either silica fume or pulverized fuel ash, or the use of white cement in the concrete, resulted in a lower drying shrinkage. However, there was no specific pattern for the drying shrinkage results when the water-to-cement was varied. Finally, some of the curing compounds/aids and special coatings used were more effective than others in reducing the drying shrinkage.