Experimental Investigation on Concrete Using Corn Stalk and Magnesium Phosphate Cement under Compaction Forming Technology

Agricultural by-products are increasingly used in the production of bio-based concrete. Compaction forming technology was used in this study to develop a sustainable biocomposite made from corn stalk (CS) and magnesium phosphate cement (MPC). The goal was to experimentally evaluate the effect of forming pressure (FP), CS content, and fly ash (FA) content on the apparent density, compressive strength, and thermal conductivity of CS-MPC biocomposite (CMB). Furthermore, the microstructure changes of typical CMB samples were analyzed by conducting scanning electron microscopy (SEM) tests. The results indicated that the apparent density and thermal conductivity of CMB were less influenced by the FP, while the compressive strength can be effectively improved by increasing FP. The increase of CS content from 25% to 45% led to a 47% reduction in thermal conductivity and a significant decrease of compressive strength. The inclusion of FA had little influence on the apparent density, but resulted in 9.48% reduction in thermal conductivity by adding 20% FA. The optimum FA content of 10% was recommended as MPC admixture, which can increase compressive strength of CMB by 4.17%. The linear empirical model for predicting thermal conductivity by apparent density was established. The microstructure changes inside CMB showed the bonding properties between MPC and CS, and the corresponding micromechanisms were analyzed. The findings provide a basic theory for using CMB as thermal insulation material in buildings.