| With the development of urbanization,there are more and more concrete pavements,and the hardened concrete pavements make a large amount of heat concentrated in the city,which leads to the "heat island effect".When it rains,if the rainwater can’t be effectively discharged from the road surface through the drainage system,it will generate water,which will bring inconvenience to pedestrians and driving.Permeable concrete can make the rainwater on the road surface flow to the ground quickly,effectively replenish the groundwater,and alleviate the urban heat island effect.However,when the permeable concrete is applied in practical projects,there will be some problems such as insufficient strength,insufficient toughness and easy cracking.As a kind of fiber with high elastic modulus and high tensile strength,carbon fiber can play the role of crack resistance and bridging cracks after being added into permeable concrete,which can improve the performance of concrete,but at the same time,there are some problems such as being difficult to disperse in matrix and unclear content.Therefore,in this paper,firstly,the mechanism of fiber reinforcement with permeable concrete as matrix is studied.Aiming at the problem that carbon fiber is difficult to disperse,the dispersibility of carbon fiber in dispersant and matrix was studied by experimental research.On this basis,the influence of the length and content of carbon fiber on the mechanical properties and permeability of permeable concrete is explored,and the optimal mix ratio of carbon fiber reinforced permeable concrete is obtained,which provides technical basis for the concrete construction of carbon fiber reinforced permeable concrete.The main research results are as follows:(1)Analyze and study the reinforcement mechanism of fiber.The critical length of fiber in pervious concrete consists of the length across the gap and the anchorage length at both ends.The equivalent aperture of pervious concrete made of coarse aggregate with 5-10 mm particle size is 3mm,and the critical length of carbon fiber in pervious concrete is 9mm;.If the carbon fibers are evenly distributed in the concrete matrix,3/4 of the carbon fibers have different degrees of reinforcing and crack resistance.(2)By studying the dispersion of carbon fiber,it is found that polycarboxylate superplasticizer can improve the dispersion of carbon fiber in permeable concrete,and the dispersion is the best when the concentration of polycarboxylate solution is 1.5%.(3)In order to explore the effect of carbon fiber in strengthening crack resistance and toughening in permeable concrete,a two-factor multi-level test was adopted,and it was found that the compressive strength,flexural strength and fracture toughness of permeable concrete could be increased by 40.4%,73.7% and 114% at the highest,while the permeability decreased to some extent,but it still met the engineering requirements.The length,volume content of carbon fiber and the interaction between them all have influence on the performance of permeable concrete.(4)Based on the analysis of entropy weighting method,it can be seen that under the premise of 0.3 water-binder ratio and 18% target porosity,the optimal mixing ratio of carbon fiber reinforced permeable concrete is 12 mm in length and 0.6% in volume.The strength of permeable concrete prepared according to this mixture ratio can reach 35 MPa,and the flexural strength is increased by 65.38%.This mixture ratio can provide reference for practical engineering application. |
