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.

Abstract

The volume changes of cement-based composites are significantly exhibited during the hardening process. Initial phases of the hardening are complemented by the expansion due to the heat evolution that is subsequently alternated by the shrinkage. Both could cause the crack initiation causing significant loss of the durability and service-life shortage. The present paper focuses on the experimental investigation of the surface treatment of fresh concrete, which is applied to prevent sudden loss of the moisture during a hardening process, especially during the concrete highway construction. The technology of concrete highway production is extremely costs demanding, but its efficiency is determined by the longer lifespan in comparison with the asphalt pavement. However, negative impacts of the drying shrinkage could significantly reduce the durability. The efficiency of used treatment was investigated in terms of restrained shrinkage tests, water adsorption and mechanical testing. In addition, there were studied two types of conventional Portland cement. Performed program confirmed great sense of the curing on the concrete durability; in addition, there was well illustrated the efficiency of the utilization of blended binder systems in the paper.

Abstract

The purpose of this study was to clarify the internal change of concrete structures during drying. Therefore, we used X-ray CT to investigate water content and volume changes inside cement paste specimens during drying. Changes in the CT image intensities and measurements on the images indicated water content and volume changes, including local changes detected with digital volume correlation. Next steps will be to understand the link between volume changes and the local water content.