Mechanical Properties and Hydration Mechanism of Alkali-Activated Feldspathic Sandstone Composite Cementitious Materials

This study aims to lower sediment control costs in the Yellow River Basin and enhance the resource utilization of Pisha sandstone. Pisha sandstone was treated by mechanical ball milling and high temperature calcination. Through alkali excitation technology, Pisha sandstone and mineral powder were compounded to develop alkali-activated Pisha sandstone composite cementitious material. The effect of Pisha sandstone content on the mechanical properties of Pisha sandstone composites was studied. The changes of hydration products and microstructure were analyzed utilizing a microscopic test, and the corresponding hydration mechanism was revealed. As the content increases, the material’s mechanical properties progressively decline. When the mass fraction of feldspathic sandstone reaches 33%, the 28-day flexural strength and compressive strength of feldspathic sandstone composite cementitious material are 10.26 MPa and 61.2 MPa, respectively. When the content of Pisha sandstone is too high, the hydration products of the sample are less, and there are more unhydrated mineral particles. The combination of particles and hydration products is weak, resulting in a loose structure.