Preparation of glass shell fly ash-clay based lightweight aggregate with low water absorption by using sodium carbonate solution as binder

Abstract

Fly ash-clay based lightweight aggregates with low density and low water absorption were prepared using sodium carbonate solution as binder and coke particles as pore-forming agent. The addition of 60 wt% coke particles to the initial formula of only fly ash and clay could form the porous structure and effectively lower the apparent density. The apparent density, water absorption and strength of the aggregates at different conditions including mass concentration and sintering temperature were tested. It was found that the mass concentration 10 wt% of the sodium carbonate solution was the best concentration to form the completely glassy shell at 1220 °C. And the glassy shell could significantly lower the water absorption from 22.97% to 8.84%. Then the glassy shell aggregates with low density (1.22 g/cm3 apparent density), 8.84% water absorption and particle strength (4.25 MPa) were obtained. All the properties meet the national standards of GB/T 17431. Therefore, using sodium carbonate solution to replace water as the binder by spraying in the forming process is a simple and applicable way to lower the water absorption of aggregates in the industrial production of lightweight aggregates. At the same time, the production of aggregates using solid waste fly ash as a raw material can effectively reduce production costs.