Chemical design of lightweight aggregate to prevent adhesion at bloating activation temperature

Abstract

The purpose of this study is to control the viscous behavior of lightweight aggregates through the chemical design of a lightweight aggregates material in order to solve the problem of the adhesion of lightweight aggregates by viscous behavior in the bloating activation temperature range of lightweight aggregates. In order to induce a reduction of Fe2O3 inside the aggregates, Fe2O3 and carbon were added to acid clay so as to produce aggregate. The particle density and the water absorption rate of the aggregates were measured, the cross-section was observed with an optical microscope, and the distribution of hematite of the lightweight aggregates was confirmed by a 3D CT analysis. Pilot scale rotary kiln experiments were performed. The optimal additive contents for the production of lightweight aggregates using acid clay were 8–13 wt% of Fe2O3 and 2–3 wt% of carbon. The addition of additives decreased the bloating activation temperature, and viscous behavior was promoted in the core portion of the aggregates, resulting in a difference in the melting point between the shell and the core. As a result, the occurrence of adhesion at the aggregates surface was suppressed.