Preparation and mechanical properties of magnesium-cemented straw composites

Abstract

Magnesium-cemented straw composites (MCSC), as an environmentally friendly and energy-conserving material, have an enormous potential to achieve favorable properties, especially for bending strength. In this study, rice straw powder, fly ash, and magnesia cement (MC) were mixed to prepare MCSC. An optimization formula for composites was found to promote the bending strength by 490% from 0.28 MPa (empty sample) to 13.89 MPa (composites). From the variance results, the molar ratio of MgO/MgCl2 (M value) and addition of rice straw (As) noticeably impacted the compressive and bending strengths. The optimum schemes were:10% (weight ratio) for rice straw, 10% for fly ash (Af), 5 for M value, 12 to 15 for H value (the molar ratio of H2O/MgCl2), 20-mesh of straw powder (Ms), and 28 days for the curing time (T). Considering the different use of MCSC, if the weight vector was 0.7 (compressive strength) and 0.3 (bending strength), the optimized formula was M5H25Ms20T15daysAs10%Af10%. If the weight vector was 0.3 (compressive strength) and 0.7 (bending strength), the optimized formula was M5H10Ms20T3daysAs10%Af10%.