Study on untreated and alkali treated rice straw reinforced geopolymer composites

In this study, plant fibre reinforced geopolymer composites were prepared using industrial waste slag and agricultural residue rice straw. The properties of the untreated and alkali treated rice straw reinforced geopolymer composites were investigated. The bending strength, water absorption thickness swelling rate and water absorption of the composite materials were evaluated. The results show that both the untreated and alkali treated rice straw can significantly improve the bending strength of the geopolymer; however, the alkali treated rice straw exhibited a higher enhancement effect. At a curing time of 28 days, the bending strength of the alkali treated rice straw reinforced geopolymer composites (ATRSRGC) with 10% fibre content reached 13.6 MPa, which exceeds the requirement specified by the China National Standard “Cement Bonded Particleboard” for superior product (≥10 MPa). The water absorption thickness swelling rate and water absorption of these two composite materials increased with the increase in the fibre content. However, with the increase in the water immersion time, their water absorption thickness swelling rate and water absorption showed different changes. We found that the ATRSRGC had a higher water absorption thickness swelling rate than the untreated rice straw reinforced geopolymer composites (UTRSRGC), indicating that high water absorption thickness swelling rate should be considered if the alkali treated rice straw is used for the production of particleboards. Infrared spectroscopy analysis shows that the rice straw and geopolymer were physically combined. Furthermore, scanning electron microscopy analysis results show that the geopolymer matrix bonded with the alkali treated rice straw better than the untreated rice straw. •Geopolymer composites were prepared from industrial waste slag and agricultural residues rice straw.•Binding effect of alkali treated rice straw with geopolymer is better than untreated rice straw.•The prepared geopolymer composites have potential to be used as particleboards.