Study On The Performance Of PVA-ECC With Tailings Sand

With the rapid development of the country’s economy and the improvement of the degree of industrialization,the scale of gold production is increasing,and the tailings output is increasing year by year.However,our country’s current utilization rate is low in tailings resources.The gold tailings that fail to get timely,effective handling and utilization will take up a large amount of land resources,causing geological disasters,serious pollution ecological environments,and even harm people’s health.Engineered Cementitious Composites(ECC)have excellent properties such as high tensile strain and high tensile strength,which can effectively respond to engineering problems such as high brittleness,easy cracking,and cracking or failure of ordinary concrete materials.At present,scholars have carried out related research on ECC with the iron tailings,but there is little research on the application of gold tailings in ECC,Based on this,the paper will use domestic CAS-FT701 PVA fiber to replace REC-15 PVA fiber,and replace quartz sand with gold tailing sand with similar particle size and composition to prepare green,low-cost PVA-ECC materials,and carry out corresponding performance study.The main research contents are as follows:(1)Research on microscopic mechanical properties.According to the ECC design theory,carried out the matrix fracture toughness test and the single-slit tensile test,and study the fracture properties of the matrix and fiber bridging properties of the ECC with different fiber types,fiber content,and tailings sand substitution rate,and then analy the micromechanical performance index σpeak/σa and Jb’/Jtip of ECC.(2)Study on fracture toughness of matrix and fiber bridging.Through the four-point bending test of the thin plate and the compressive strength test of the cube,study the flexural and compressive properties of ECC,and explore the regression relationship between the ECC bending absorption energy and the micro-mechanical property index,and further analyze the curved toughness and distribution law of bottom surface cracks of the ECC with 2.0%fiber.(3)Capillary water absorption study.Based on the capillary water absorption test results and the capillary absorption theory of parallel tube porous media materials,analyze the influence of fiber content,tailings sand content,crack width,standard curing time and other factors on the water absorption coefficient of ECC.Constructe the water absorption height model and water distribution calculation model of ECC,revealing the moisture distribution law of ECC.(4)Research on freeze-thaw cycles durability performance.Analyze the changes of surface morphology and the development of internal cracks after freeze-thaw cycles of ECC with different mix ratios;analyze and evaluate the anti-freeze performance of ECC by taking the mass loss rate and relative dynamic elastic modulus as the anti-freezing performance indicators.Reveal the change of compressive strength and loss rate of ECC after freezing cycle.Using ultrasonic non-destructive testing technology to test the thickness of the damage layer of the ECC after the different freeze-thaw cycles,and established a predictive model of the thickness of the damage layer with high precision.In addition,study the capillary water absorption performance of ECC after the freeze-thaw cycle.