Abstract: To enhance the performance of cement mortar modified with iron tailings, a specific proportion of α-hemihydrate gypsum was incorporated into the mortar to prepare test specimens. The effects of α-hemihydrate gypsum content and iron tailings content on the fluidity, drying shrinkage, mechanical properties, and durability of cement mortar were investigated. The hydration mechanism was examined through mineral composition and microscopic image analysis. The findings indicate that the addition of α-hemihydrate gypsum significantly increases the slump index and reduces drying shrinkage rate in the mortar. When the replacement ratio reaches 15%, the compressive strength, flexural strength, and durability of the mortar doped with α-hemihydrate gypsum achieve optimal conditions. The chemical activity of α-hemihydrate gypsum promotes secondary hydration, subsequently enhancing the density and various indicators of the mortar. The test results serve as a valuable reference for modifying environmentally friendly, low-carbon, and high-performance cement mortar.

Key words: cement mortar, iron tailings, α-hemihydrate gypsum, slump, strength, durability, microstructure