Experimental Study on the Physical Properties and Freeze-Thaw Resistance of Rice Straw-Mortar Composites

With the increasing demand for the resource utilization of agricultural waste and the development of sustainable building materials, rice straw-mortar composites have attracted considerable attention owing to their renewability and environmental friendliness. In this study, a three-factor and three-level regression analysis experiment was carried out using Design-Expert software to obtain the optimal physical properties and mix ratio of rice straw-mortar composite materials. With an optimal mix ratio of 15% gypsum, 20 mm straw length, and 15% straw content, the composite achieved a compressive strength of 3.06 MPa, a dry density of 1.340 g·cm^-3, and a water absorption of 20.8%. A freeze-thaw cycling test of 15 cycles from -20 °C to 20 °C resulted in a strength loss of 32.2-47.2%, a mass loss of 2.1-4.5%, and water absorption of 21.8-37.2%. The results suggest that rice straw-mortar composites may be suitable for non-load-bearing wall applications under freeze-thaw exposure conditions.