Study On The Effect And Mechanism Of Iron Tailings Powder In Silicate Gel System

In recent years,admixtures have been appliedd widely in modern concrete with the development of water reducer agent.The shortage of conventional admixture is very obvious;On the other hand,a huge amount of solid waste output and accumulation cause serious ecological and environmental pressure,non active admixtures such as stone powder and tailings powder have drawn industry's attention as mineral admixtures used in concrete.This paper studies the effect and mechanism of iron tailings powder in silicate gel system.It focuses on the fluidity and rheological property of paste,strength of hardening body,hydration degree and pore structure.Results showed that the effect of iron tailings powder on silicate gel system is superposition of dilution effect,accelerate effect and filling effect;Iron tailings powder does not significantly affect the fluidity of cement paste when its content is lower than 20%,Shear thinning behavior gets more obviously with iron tailings powder content increases within a certain range;Strength decreased with the increase of iron tailings powder content,while the late strength of mortar and concrete is higher than that of blank group with low content of iron tailings powder;The influence of strength factor was lower than that of content,namely,iron tailings powder can play a positive role on strength,especially for low water binder ratio;The role of iron tailings powder in paste,mortar and concrete is not same,at the late period of hydration,the positive effect on mortar and concrete is greater than that on paste;The strength can be improved with finer iron tailings powder,especially in the later hydration period;A certain amount of iron tailings powder can promote hydration degree of composite material;The hydration degree decreases with the finer iron tailings powder.Iron tailings powder can refine pore structure and increase compactness of hardening body.Chloride ion test showed that the impermeability grade of concrete is medium at the age of 28 and 270 days,the chloride permeability of concrete is great with 20% iron tailings powder,while reducing water binder ratio can reduce the porosity ratio and improve the impermeability of concrete with a large amount of iron tailings powder.Mercury injection test showed that adding iron tailings powder can decrease most probable aperturethe at the age of 3 and 270 days,especially for the number of harmful hole whose size is larger than 50nm;Increasing the specific surface area of iron tailings powder can refine pore structure better,when the dosage of fine iron tailings powder is lower than 20%,the filling effect is great.At the age of 90 and 270 days,SEM test on microstructure can come to conclusion that appropriate dosage of iron tailings powder can increase composite paste density;Increasing the specific surface area of iron tailings powder can play filling effect more significantly.