Development of Combination-Type Self-Compacting Concrete and Evaluation Test Methods

More than ten years have elapsed since Self-Compacting Concrete (abbreviated as SCC), which does not require consolidation, made its appearance. SCC has been applied in many construction projects, including ultra-large structures. To achieve excellent self-compactability in heavily reinforced areas, SCC should deform well under its own weight without segregation of ingredients. Therefore, research on SCC had been focused on improving both deformability and resistance to segregation. However, there was still no standard test for evaluating self-compactability and resistance to segregation of SCC. The authors developed evaluation test methods for simple application in the manufacturing stage and at construction sites. At present, these evaluation test methods are recommended as standard test methods in Japan Society of Civil Engineers specifications. At the time, it was still difficult to produce SCC of constant quality at ordinary ready-mixed concrete plants because facilities and quality control of materials had not reached the required level. For improved manufacturing and handling, an SCC with a viscosity agent (β-1,3-Glucan) was developed. It is possible to reduce quality fluctuations in a fresh state for commonly available materials and production facilities. At present, this type of SCC is defined as "Combination-type" in a recommendation of the Japan Society of Civil Engineers. This paper summarizes these evaluation test methods and introduces a Combination-type SCC developed to facilitate production and handling.