Properties of cellular lightweight rubber wood fly ash geopolymer mortar containing cement

Abstract

The rubber wood fly ash (RWFA) was a by-product of heat energy production in Songkhla, Thailand. This research aims to investigate the possibility of using the RWFA and cement (PC) to produce a sustainable starting material. The PC was used to enhance the properties of cellular lightweight rubber wood fly ash geopolymer mortar containing cement (CLRWFAG-PC). The Na2SiO3:NaOH ratio was set at 70:30 with the NaOH concentrations of 8 molar. The sand (S):RWFA:PC ratios were 50:50:0, 50:45:5, 50:40:10, 50:35:15, 50:30:20, 50:25:25, and 50:20:30, and foam contents were 0 %, 1 %, 3 %, and 5 %. The unit weight and compressive strength of the CLRWFAG-PC samples were measured after 7, 28, 60, and 90 days of curing, while the thermal conductivity and microstructure were determined after a 28-day curing period. The unit weight decreased as RWFA content and foam content increased. The sample at S:RWFA:PC ratio of 50:50:0 and foam content of 5 % had the lowest unit weight, which was 11.27 kN/m3. The maximum 90-day compressive strength of the CLRWFAG-PC samples with an S:RWFA:PC ratio of 50:25:25 and foam content of 0 % was 39.12 MPa. The results indicate that decreasing PC content and increasing foam content reduced 28-day thermal conductivity due to increased porosity and reduced unit weight. SEM/EDX images reveal that adding PC to CLRWFAG samples improved unit weight and compressive strength while increasing foam content rose porosity and voids, reducing unit weight and compressive strength. The findings and observations from this investigation will further our understanding of the properties and hybridization mechanism of CLRWFAG-PC samples.

Keywords

• Rubber wood fly ash
• Cement
• Cellular lightweight mortar
• Geopolymer