Production of lightweight aggregates from bauxite tailings for the internal curing of high-strength mortars

Abstract

The pore structure of lightweight aggregates (LWA) has a direct influence on the performance and application of LWA. In this paper, bauxite tailings were used as the main raw materials for the production of LWA. CaF2 and CaCO3 were used as additives to modify the pore structure of LWA. The internal curing performance of pre-saturated LWA in high-strength mortars was studied. It was found that LWA made from 95% bauxite tailings and 5% silica fume had no expanding capacity despite SiO2/∑Fluxing ratio of 2.39. Its porous structure comes from the voids left by the dihydroxylation of clay minerals. CaF2 and CaCO3 increased the pore size of LWA and this effect became more obvious with the increase of CaF2 and CaCO3 content. LWA with a high water absorption could reduce the autogenous shrinkage of mortars most. LWA reduces the strength of mortars but using LWA with high water absorption can lower the negative effect on the compressive strength of mortars.