Experimental Study On Mechanical Properties And Damage Evolution Of Iron Tailed Sand Concrete At Low Temperature

With the continuous development of the construction industry,the exploitation of natural sand,the main material of concrete,is increasing year by year.The natural sand resources in China are in short supply,and the over exploitation of natural sand has caused serious damage to farmland and river channel.Iron tailing ore is the most abundant tailings resource at present,its composition is similar to that of natural sand,and it is an ideal substitute for natural sand.As a substitute of natural sand,the application of iron tailing in construction concrete has obvious advantages.It can not only solve the problem of resource shortage of natural sand for concrete,but also achieve the purpose of rational utilization of iron tailing and reducing environmental load.In this paper,iron tailed sand is used to replace natural sand in the preparation of concrete,and the influence of freeze-thaw cycle environment on the mechanical properties and damage evolution of iron tailed sand concrete is considered.(1)The orthogonal test method was used to study the preparation process of iron tailing sand concrete.The main factors affecting the strength of the material were determined as water cement ratio,replacement rate and sand rate.The influence of each factor on the strength decreased in turn.The optimum mix ratio of iron tailing sand concrete is 0.45 for water cement ratio,40 for replacement ratio and 38 for sand ratio.(2)Iron tailings can significantly change the frost resistance of concrete.With the increase of the replacement rate of natural sand,the frost resistance durability shows the characteristics of increasing first and then decreasing,and reaches the peak value at 40% replacement rate,and the corresponding mass loss rate of 100 freeze-thaw cycles decreases by 35% compared with that without replacement.(3)With the increase of freeze-thaw times,the damage and failure of concrete with iron tailing sand are mainly manifested as follows: the surface morphology is deteriorated,and the corresponding mass loss rate is up to 35%;the capillary water absorption coefficient is gradually increased,and the maximum value is 17.36;the compressive strength is linearly reduced,and the loss rate is up to 42.2%.(4)Through vic-3d technology to track the failure process of concrete with iron tailing under pressure,it can be found that the damage and failure experienced a local to overall evolution process,the initial crack occurred in the weak area of the sample edge,and gradually extended to the whole sample with the increase of load.The number of freeze-thaw cycles is the decisive factor for the development speed of concrete surface crack.(5)Scanning electron microscope was used to analyze the effect of freeze-thaw cycle on the micro structure of the section of iron tailed sand concrete.The results show that the replacement of natural sand with iron tailing sand can significantly improve the low temperature performance of concrete.