Study On The Properties Of Polyvinyl Alcohol Fiber And Mineral Admixture Pervious Concrete

Pervious concrete is an important material of construction of "sponge city",which has the advantages of water permeability,breathability,sound absorption and noise reduction,water purification,inhibition of urban "heat island effect" and improvement of soil ecological environment,etc,but it still has problems such as low strength,insufficient toughness and durability.Therefore,in this paper,high-strength and high-elastic mold polyvinyl alcohol fiber,silica ash and mineral powder reinforcement materials are added to pervious concrete to improve the mechanical properties and brittleness characteristics of pervious concrete,and the performance mechanism of polyvinyl alcohol fiber,silica ash and mineral powder reinforced pervious concrete is revealed by combination with scanning electron microscopy,failure morphology,folding ratio and tensile ratio,and the splitting tensile strength model and conversion relationship between the strength of pervious concrete are established,in order to provide reference for expanding the application of pervious concrete engineering.The main research results of this paper are as follows:(1)The target porosity,water cement ratio and the amount of silica ash has significant effect on the mechanical properties and water permeability of perviois concrete.The amount of mineral powder has significant effect on the compressive strength of pervious concrete,but the influence of flexural strength,splitting tensile strength,effective porosity and water permeability coefficient is not obvious.The addition of silica ash and mineral powder in pervious concrete can improve the microstructure of its interface weak area,thereby improving the compressive strength of pervious concrete,and the optimal content of silica ash and mineral powder is 8% and 5%,respectively,compared with the control group without silica ash and mineral powder,the compressive strength is increased by 13.6% and 8.1%.(2)The influence of polyvinyl alcohol fiber with different length and content on the mechanical properties of pervious concrete is different.When the compressive strength and flexural strength has the maximum value,the optimal length and optimal content of fiber are 12 mm and 0.15%,respectively,and the compressive strength and flexural strength are increased by 18.7% and 26.5% respectively compared with the undoped fiber control group.When the fiber length is 12 mm and the content is 0.1%,the splitting tensile strength reaches the peak,the splitting tensile strength are increased by 27.3% compared with the undoped fiber control group.and the mechanical properties of pervious concrete are reduced if the amount is too much,polyvinyl alcohol fiber has little effect on the porosity and permeability coefficient of pervious concrete.Polyvinyl alcohol fiber improves its failure and brittleness characteristics by increasing the folding and tensile ratio of pervious concrete.(3)The relative error between the calculated value and the measured value of the established splitting tensile strength prediction model is within 6%.The conversion empirical formula between compressive strength,flexural strength and splitting tensile strength of pervious concrete is preliminarily obtained.(4)The comprehensive properties of pervious concrete are optimized,The compressive strength values of pervious concrete when mixed with 8% silica ash,5% mineral powder and 0.1% and 0.15% polyvinyl alcohol fiber test group are 26.7MPa and 27.3MPa,flexural strength is 4.6MPa and 4.5MPa,and splitting tensile strength is 4.5MPa and 4.5MPa,which are higher than the strength of the control group without fiber and silica ash,mineral powder and the three reinforcing materials when they are doped,and the maximum growth rates of compressive strength,flexural strength and splitting tensile strength reaches 34.5%,35.3%,36.4%respectively.SEM electron microscopy scanning results show that the internal doping of silica ash and mineral powder increase the compactness and pore structure of pervious concrete,and the polyvinyl alcohol fiber forms a fiber mesh network structure with tensile effect in the concrete matrix,so that the polyvinyl alcohol fiber,silica ash and mineral powder synergistically improve the comprehensive properties of pervious concrete.