Effects of micro silica on the compressive strength and absorption characteristics of olive biomass ash-based geopolymer

Abstract

The use of alkali-activated biomass ash binders is one of the strategies being adopted to produce environmentally friendly concrete. The work presented in this paper is a comparative investigation of the compressive strength and sorptivity performance of olive biomass ash (OBA)-based alkali-activated binders. Micro silica was incorporated into the OBA/kaolin-based binder at replacement levels of 0, 5, 10, 15, and 20 wt %. Mortar specimens were prepared and cured at ambient and an elevated temperature of 60 °C for 24 h. Test results showed that the incorporation of micro silica at a 10 % replacement level led to an increase in compressive strength by 25 % for specimens cured at ambient temperature. However, the addition of 20 % micro silica lowered the compressive strength of the specimens cured at 60 °C by more than 35 %. It was also found that curing geopolymer specimens at elevated temperatures increased the sorptivity by more than 100 % compared to specimens cured at ambient temperature. The incorporation of 10 wt % micro-silica was found to further reduce the sorptivity by 25 % for ambient temperature-cured specimens. X-ray diffraction tests and scanning electron microscopy (SEM) observations were conducted on paste samples to understand the microstructural changes before and after the incorporation of micro silica.

Keywords

• Olive biomass ash
• Alkali-activated
• Elevated temperature
• Sorptivity
• Micro silica