Properties of sustainable cellular concrete prepared with environment-friendly capsule aggregates

Abstract

This study introduced novel environment-friendly capsule aggregates (CAs) with core-shell structures by encapsulating sodium alginate beads (SABs) with a fly ash shell. Two types of CAs with different particle sizes were synthesized by adjusting the SAB size. Cellular concretes with different densities were further fabricated by these lightweight aggregates. The effects of CAs on the density, flow value, setting time, compressive strength, and modulus of elasticity of the concrete were studied. The microstructure and evolution mechanism of CAs in the cementitious matrix were also discussed. The results demonstrated that the CAs shell has the capacity to protect the SAB in the core from damage during the mixing process. The alginate core can achieve a density reduction of 25% for cellular concrete from fresh to dry condition. The function of CAs not only effectively lightens the weight of concrete with the alginate dehydration, but also provides internal curing for the cementitious matrix to reduce its autogenous shrinkage. The results indicated that it is feasible to use CAs for the production of the lightweight concrete to achieve goal densities of 1200, 1400 and 1600 kg/m3, with corresponding compressive strengths and modulus of elastic ranging from 11.5 to 28.3 MPa and 9.5–18.3 GPa, respectively.