Concrete with Shirasu aggregates for sustainability: a review on research progress and application in Japan

This paper presents a critical review of the main research progress and application of Shirasu concretes in Japan recently. As a kind of pyroclastic-flow deposits, Shirasu aggregate was considered as one kind of nonstandard aggregates for modern concrete industries because it usually has a low density and a high water content rate, and also contains a large amount of fine powder on its surface. However, with the considerations that Shirasu has a high level of pozzolanic activity and can be available widely and easily in Japan, many studies had been performed in Japan in the last two decades. The key concerns in the paper focus on the basic fresh properties of Shirasu raw material, the mix design, and the basic material properties of Shirasu concretes. Based on this review, several recommendations were provided for future works. Through the review, Shirasu concrete considered as a construction material could present accepted material properties compared with traditional concrete, including basic fresh and mechanical, and durability properties. It was suggested to apply concrete structures with careful concerns and recommended to structures under several special environments. Using this aggregate, several kinds of high-performance concrete also could be produced.