Study on the Practical Use of Urea to Reduce Drying Shrinkage of Concrete by Spraying Urea Solution under Cold Environment

Abstract

Concrete cracking caused by drying shrinkage adversely affects the durability of a structure. The results of past research has shown that drying shrinkage can be reduced by adding urea as an admixture to the concrete. However, mixing various admixtures at the factory increases the costs for equipment and labor. To reduce drying shrinkage more easily and inexpensively, the urea solution can be applied to the concrete surface by soaking or brushing. However, urea solutions are not suitable for use in cold weather because urea in solution crystallizes at low temperatures. This study attempted to solve this problem by mixing antifreeze, which resists freezing, with a urea solution. It was found that the crystallization temperature of urea can be lowered by mixing the urea solution the antifreeze. Furthermore, it was confirmed that the antifreeze/urea solution reduced drying shrinkage for both mortar and concrete.

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