Use of a Water-Repellent Admixture to Improve Concrete Performance

Abstract

In recent years, especially in Japan, various types of chemical admixtures have been developed, with emphasis on making highly durable concrete and on developing the highly flowable concrete for labor-saving. In this paper, one kind of water-repellent admixture incorporating highly reactive silica powder, denoted as WRP, was examined to confirm its effect on various concrete properties. The concept is not only to prevent water penetration due to water repellency provided by the siloxane compound but also to compensate for the hindered hydration due to its adsorption to cement particles by the use of the highly reactive pozzolanic material. The efficacy of the admixture was confirmed as to its ability reducing the water permeability with little lowering of mechanical properties dependent on the dosage of WRP. From the tests for carbonation, drying shrinkage, resistance to freezing and thawing and the air-void systems, the effect of WRP was confirmed as satisfactory for those properties.