New Trends in the Development of Chemical Admixtures in Japan

Abstract

This paper describes the history and new trends in the development of chemical admixtures in Japan. PC (polycarboxylic acid)-based agents are the main products in the superplasticizer market. A low-stickiness type PC-based superplasticizer has been developed based on the conventional PC-based superplasticizer. The flowing speed of concrete with low stickiness type PC-based superplasticizer is faster than that with the conventional PC-based superplasticizer. By addition of a new viscosity agent consisting of a mix of anionic and cationic surface active agents, the three dimensional reticulation structures is formed in fresh cement paste and the viscosity of the cement paste can be increased and segregation can be prevented. The hydration of cement in sludge water is controlled by addition of a set-retarder, and the specific surface area of cement does not increase while a large amount of unreacted alite remains in the sludge water. Recycling of concrete at ready mixed concrete plants is possible without adversely influencing the properties of concrete when sludge water with the set-retarder containing gluconate salt is used. The slurry type and powder type calcium aluminate based accelerator (CA) and calciumsulfoaluminate based accelerator (CSA) for shotcrete have been developed. In the case of CA, the final setting time of the mortar is accelerated by increasing the dosage. By adding of CSA, both the initial and final setting times of mortar are shortened with increased dosages.