High Quality Low-Density Artificial Aggregate Related to Starting Materials and Heating Conditions -Development of high quality artificial low density aggregate (1st report)-

Artificial low density aggregate (LDA) is mainly used in lightweight concrete. The use of highly efficient LDA is a convenient way to realize a high efficient lightweight concrete, because aggregate occupies 70 % of the volume in concrete. However since emphasis have mainly been placed in the production cost of LDA in the past, high quality LDA has yet been produced.The purpose of this investigation is to improve the properties of LDA so that it has higher strength and lower water absorption, which in turn will expand its application. The LDA properties such as glass content, grain size of raw material, additional quantity of expanding agent, and heating pattern and the relationship between each property are studied. The results are;(1) As Nambu et al. (1993) reported that when the glass content of starting material is increased, LDA strength is increased while water absorption is decreased.(2) Finer the grain size of starting material, higher the strength and lower the water absorption of LDA.(3) Grain size of SiC (Yakushima-Denko Corp.,CF-4000), as expanding agent, of less than 1μm is effective for the expansion of LDA.(4) LDA made from perlite with around 90% glass content has double the compressive strength while only having one tenth of the former LDA.(5) Decrease of expanding agent addition stabilizes the quality of LDA, because temperature influence becomes small.