Study On Feasibility And Mechanical Properties Of Replacing Sand For Construction With Iron Tailings

The implementation of the national "double carbon" strategy has made the clean utilization of secondary resources and metallurgical waste an urgent need for the modern metallurgical industry.Tailings are the largest proportion of waste after metallurgical beneficiation extraction,which the highest percentage of these is iron tailings.Due to the lack of effective treatment means,the accumulation of iron tailings not only occupies a lot of land resources but also causes pollution to the environment easily.Meanwhile,concrete and cement mortar are important construction materials in the field of engineering,and natural river sand or mechanism sand is its important raw material.Natural river sand is depleting due to long-term mining,and mechanism sand is expensive,so there is an urgent need to find an alternative source of sand.Iron tailings have the potential to replace construction sand in the preparation of mortar and concrete,as their main composition and physical form are similar to the natural river sand.Which can not only reduce the production cost,but also realize the waste utilization of iron tailings,responding to the call of comprehensive promotion of "double carbon" strategy,with great potential social,economic and environmental benefits.The feasibility of using iron tailings as construction materials was verified through the tests of mineral composition,chemical composition,ionic composition,particle gradation and other basic properties determination.Based on the test results,the optimum watercement ratio of 0.45 was determined,and the preliminary design of iron tailings mortar and concrete ratio was carried out;secondly,the substitution mechanism of iron tailings was studied in terms of hydration activity and microstructure,and the strength of its internal effect was compared,and the mechanism of the effect of inactive iron tailings in the preparation of construction materials was initially summarized;finally,the effect of different amounts of iron tailings and different ages on the preparation of construction materials was investigated through experiments.The practical effects of different iron tailings admixture and different ages on mortar,aggregate-mortar interface and concrete were investigated.The main conclusions obtained are as follows:(1)The chemical and physical composition of iron tailings is similar to that of construction sand and meets the requirements of construction sand specifications,so it can be used as a potential sand source in mortar and concrete.(2)Iron tailings mixed into the mortar can reduce the number and volume of pores,making the pore size distribution more concentrated,showing a physical filling effect,while the impact on the hydration activity inside the mortar is small.The effect of "physical effect" of iron tailings itself is stronger than "chemical effect".(3)The incorporation of iron tailings will improve the mechanical properties of mortar and concrete,and improve the properties of the aggregate-mortar interface,and a series of tests have shown that iron tailings can be used as sand for construction.(4)This paper concludes that the optimal substitution gradient of iron tailings should be between 25% and 50%,and in practice,the substitution rate needs to be controlled;a too high substitution rate will inhibit the development of the strength of the building material.