Production of lightweight cementless binders using supplementary cementitious materials to replace autoclaved aerated concrete blocks

Abstract

Recently, the application of sustainable cementitious materials to improve the efficiency of buildings has become of great importance as part of carbon neutrality. This study aims to develop lightweight cementitious binders made of supplementary cementitious materials and various additives to replace autoclaved aerated concrete blocks. To this end, the mechanical properties of 36 cementless binders using fly ash (FA), fly ash cenosphere (FAC), and ground granulated blast-furnace slag were assessed. The FA or FAC activated with Ca(OH)2 and Na2CO3 binders, which showed a density of 637.6–1576.3 kg/m3 and a compressive strength of 7.4–65.0 MPa, were selected as representative samples, and their microstructure and thermal performance were further characterized. The results showed that FAC acted as a filler and precursor, occupying space in the binder, and reacting partially with activators simultaneously. In particular, increasing FAC content increased the porosity of the hardened matrix, remarkably reducing the weight of the binders. In addition, the thermal conductivity of the binders was significantly reduced to 0.25–0.27 W/m·K, which increased their thermal efficiency. This lightweight, thermally efficient cementless binder is expected to be applied to commercially available blocks.