Utilization of the circulating fluidized bed combustion ash in autoclaved aerated concrete: Effect of superplasticizer

Abstract

This paper aims to solve the problem of high water absorption in the use of circulating fluidized bed combustion ash. Meanwhile, the feasibility of using the circulating fluidized bed combustion ash to prepare autoclaved aerated concrete was studied. The circulating fluidized bed combustion ash autoclaved aerated concrete samples with different water consumption and different dosages of water reducing agent were prepared. The rheological properties and gas-foaming results of the slurry, the compressive strength, the dry density, specific strength, pore structure and hydration products of the products were analyzed. The results show that the incorporation of polycarboxylate superplasticizers has a positive effect on the rheological properties of the slurry, the gas generation, and the physical properties of the sample. Its water reducing effect not only can improve the rheological properties of the slurry to match the gas generation rate of the aluminum powder, but also optimize the pore structure to reduce the number of harmful pores (less than 50 nm) and improve the strength of the product. Because a large number of uneven macropores are introduced, the high water consumption is unfavorable to the compressive strength of the product to a certain extent. However, too low water consumption would hinder cement hydration to produce C-S-H gel and reduce the formation of tobermorite. It is noticed that the reasonable combination of water consumption and water reducing agent can improve the strength of aerated concrete products without significantly changing the bulk density of the sample. This paper provides a theoretical basis for use of other high-water-demand solid wastes similar to circulating fluidized bed fly ash in the preparation of autoclaved aerated concrete.