Experimental Study Of PVA Fiber Reinforced Iron Ore Tailings Sand Concrete

Iron ore tailings belongs to mineral waste.Large quantities of tailings will not only waste land,but also cause environmental pollution.Moreover,most tailings ponds are located near operations or construction,and too high accumulation will bring danger to construction personnel.Therefore,in view of the principle of green,economical,environmental protection and sustainable development,adopting iron tail ore as fine aggregate to replace natural river sand and machine-made sand to prepare concrete not only helps to alleviate the shortage of natural river sand resources,but also helps to realize the recycling of iron tail ore and environmental protection,and encourages the efficient flow of resources.In this paper,based on the above analysis,on the basis of the above analysis,the basic mechanical properties of the concrete with different substitution rates were studied(0%,30%,40%,50%,60%,70%,80%,90%,100%)and different PVA fiber content(0%,0.1%,0.2%,0.3%).The main research results are as follows:(1)By optimizing the mix ratio of PVA fiber iron tail sand concrete,the concrete with workability meeting the requirements was prepared.With the increase of fiber content and iron tail sand replacement rate,the fluidity,cohesiveness and the water retention of the concrete mixture decreased significantly.The slump initially increases and then decreases as the rate of replacement of iron ore tailings sand increases,and the best replacement rate is30%.It showed a decreasing trend with increasing fiber content,and the higher the content,the larger the decrease in amplitude.(2)The compressive test results show that the specimens with 0% and 0.1% PVA content all show brittle failure,and the final failure form is typical vertical cone.When the PVA content is 0.2% and 0.3%,the specimen has good integrity when it is damaged.Under the same fiber content,the compressive failure forms of different iron tailing sand replacement rates are basically similar.The compressive strength initially decreases and then increases with increasing PVA fibre content,and is lower than that of regular concrete.A maximum compressive strength of 0.3%PVA is achieved.With the increase of the replacement ratio of iron ore tailings,the strength of the concrete is first increased and then reduced.When the replacement ratio is 30%,the maximum strength is reached.(3)Based on the results of the split tensile test,brittle failure occurs in specimens with0% and 0.1% PVA contents,and specimens fail along a major crack and break in half.The failure mode of the When the fiber content is 0.2% and 0.3%,showing that the centre of the specimen is an amain crack,and there are several fine vertical cracks surrounding it,but the two ends are still connected,and some integrity is retained during the failure.For the same fiber content,the replacement rate of the iron ore tailing sand has no effect on the fracture tensile failure mode.With the increase of fibre content,the splitting tensile strength is increased,and the maximal strength is reached when the content of 0.3% is increased.With the increase of the replacement rate of iron ore tailings,the fracture toughness is firstly increased and then decreased.(4)The bending test results show that: The specimen without fiber and 0.1% fiber content is brittle failure,and the failure process of the specimen is short,and the failure is in two halves along the main crack.When the fiber content is 0.2% and 0.3%,the failure form is a main crack,with small cracks attached to the periphery,and certain integrity is maintained during failure.Along with the increase of fiber content,the crack width on the sample is reduced gradually and no longer passes through the crack.With the increase of the fibre content,the width of the crack on the surface of the sample will decrease gradually.As the PVA content is increased,the bending strength of concrete was first reduced and then increased,and the optimal content was 0.3%.With the increase of the replacement ratio of iron ore tailings,the bending strength increases and then decreases,and the strength reaches its peak when the replacement ratio is 30%.(5)The bond slip test results show that the bond property of iron tailings concrete and reinforcement is affected by the following factors: Reinforcement diameter > replacement rate > anchorage length > fiber content.A two-stage expression is used to describe the bond slip constitutive model of PVA fiber iron tail sand concrete,and the formula for calculating bond stress and slip is proposed.The predicted results of the model match well with the simulated and experimental values of ABAQUS.