关键词: 铁尾矿, 煤矸石, 抗压强度, 孔结构, 水化进程

Abstract: In order to realize the reuse of iron tailings，coal gangue and other solid wastes，reduce the dosage of cement in concrete，and ease of iron tailings as concrete admixture solely against the negative impact of the compressive strength，composite admixture was prepared with the iron tailings，coal gangue and fly ash.The influence of dosing and ratio of composite admixtures on the compressive strength and microstructure of concrete were investigated.The results indicated: ①The addition of composite admixture reduces the compressive strength of concrete.When the contents of composite admixture was 20%，it has little influence on the compressive strength at the later stage，and the compressive strength at 28 d ages could reach 421 MPa，reaching the standard of C40 concrete.When the contents of composite admixture was 30%，the maximum compressive strength reached 384 MPa at 28 d ages.② The activity of iron tailings is low，which degrades the compressive properties of concrete as the sole admixtures，but it has the filling effect and dispersive effect.Both fly ash and coal gangue have certain pozzolanic properties.Fly ash has higher activity and ball effect and its contribution to the compressive strength of concrete is higher than coal gangue.The synergistic effect of iron tailings，fly ash and coal gangue alleviates the deterioration of concrete compressive property caused by iron tailings as the sole admixtures，and the optimal admixture mass ratio is 1∶2∶2.③ The composite admixture with 20% contents promotes cement hydration near the interface transition zone，but degrades the overall pore structure.The composite admixture with 30% contents optimizes the pore structure of concrete，obviously reduces the porosity rate of the interface transition zone，but has a negative effect on cement hydration.The results showed that the composite admixtures change the porosity rate and hydration process of the interfacial transition zone，and the balance of the pore structure and hydration process of the interfacial transition zone is the key to improve the macroscopic strength of concrete.

Key words: iron tailings, coal gangue, compressive strength, pore structure, hydration process