Mix proportion optimization for cement-based absorbent materials mixed with EP and SAP: Performance and microstructure

To achieve the organic combination of rainwater resource recycling and urban construction, this study innovatively prepares a dry cement-based water absorbing material (DCWAM) using superabsorbent polymers (SAP) and expanded perlite (EP). A systematic study based on response surface methodology focuses on mechanical properties, water absorption properties, and deformation properties to achieve optimization of DCWAM mix proportions. Moreover, the influence of SAP and EP on the microstructure characteristics of DCWAM is revealed through SEM and XRD analysis. Experimental results show that with the addition of SAP and EP, the flexural strength initially increases and then decreases, while the compressive strength shows a decreasing trend. After water absorption, the above properties decrease by 50.67% and 46.03%, respectively, resulting from the accelerated internal crack development caused by the water absorption expansion of SAP and EP. The addition of EP increases the water absorption rate of DCWAM, slows down the development of cracks under external forces, and improves deformation performance. For SAP, the early water absorption rate is reduced, but it can achieve more sustainable water absorption, thereby improving the final water absorption rate. When 0.3% SAP and 17.5% EP are added, the water absorption rate reaches its maximum, which is 38.4% of its own weight, about 20 times that of ordinary cement paste.