Preparation and Properties of Alkali-activated Diatomite/Bauxite Cementitious Materials

Alkali-activated materials (AAMs)have become a key research focus in the field of novel building materials due to their low carbon emissions and excellent mechanical properties. In this study, diatomite and bauxite were used as raw materials to systematically investigate the effect of different calcination temperatures on the activation of diatomite, as well as the impact of various diatomite content, water-to-binder ratio, alkali equivalent, and activator modulus on the mechanical properties and microstructure of alkali-activated diatomite/bauxite cementitious materials. The results indicate that diatomite exhibited optimal pozzolanic activity after calcination at 600 ℃ for 2 h. In the alkali-activated system, the material shows the highest compressive and flexural strength when the diatomite-to-bauxite ratio is 4 ∶ 6, the water-to-binder ratio is 0. 4, the alkali equivalent is 6%, and the activator modulus is 1. 0. The orthogonal test analysis reveals that the mechanical strength of the cementitious materials decreases with the increase of water-to-binder ratio and follows a trend of first increase and then decrease with diatomite content, alkali equivalent, and modulus. XRD and SEM analyses demonstrate that the crystallinity of mullite and N-A-S-H gel in the material is high, significantly enhancing the matrix’s density, reducing crack formation, and improving the mechanical properties of the material. These findings provide theoretical support for the development and application of alkali-activated diatomite/bauxite cementitious materials.