Effects of lime content on properties of autoclaved aerated concrete made from circulating fluidized bed ash

Abstract

In order to reduce the cement consumption during the production of autoclaved aerated concrete (AAC) made from circulating fluidized bed ash (CFBA), this paper investigated the effects of lime replacements for cement on gas-forming volume, bulk density, water absorption and compressive strength of AAC. The results show that the volume of gas formed in AAC during the pre-curing stage decreased as the lime content increased from 3 wt% to 22 wt%. After autoclaving cured for 7 h, the bulk density and water absorption of AAC increased with increasing the lime content. The compressive strength of AAC gradually increased from 3.0 MPa to 3.6 MPa as the lime content increased to 16 wt%. More defined tobermorite crystals formed as the lime content increases to 19 wt%, contributing much to the strength enhancement of AAC, whereas the lime content beyond 16 wt% adversely affected the microstructure of AAC.

Keywords

• Autoclaved aerated concrete
• Circulating fluidized bed ash
• Lime content
• Strength
• Hydration products