Research On The Influence Of Groove Shape On The Performance Of New-type Permeable Concrete Paving Brick

Permeable Concrete Paving Brick(PCPB),as a new sustainable pavement material,has been widely applied to various occasions for the construction of urbanization because of its excellent environmental and economic benefits.PCPB is commonly made up of mono-sized coarse and fine aggregate,cement and a small amount of admixtures for improving its strength.It is characterized by outstanding air permeability and water permeability with certain strength,as well as wear resistance,sound absorption and noise reduction.However,recent studies have shown that the permeability of traditional PCPB is not well reflected in practical applications,because the water permeability coefficient,an indicator that represents the water permeability of PCPB,will decrease with the increase of its service time.Therefore,some scholars have carried out research on the new-type PCPB.The new-type PCPB is characterized by the presence of holes or grooves in the brick,through which rainwater can quickly infiltrate,not only to assist the brick to permeate water but also to alleviate the decrease in permeability caused by blockages.For the new-type PCPB,its strength will be reduced due to the existence of holes or grooves.In addition,the water permeability and durability of the new-type PCPB have not been determined,so in-depth research on the performance of the new PCPB is needed.This paper is based on the research project "Research and Application of Ecological Green Permeable Paving Materials in Severe Cold Areas" of Jilin Provincial Science and Technology Department.The orthogonal experimental design method was applied to investigate the effect of the mix ratio parameters of PCPB on its mechanical properties and water permeability.The large-scale general finite element analysis software ANSYS was employed to model the PCPB,and the factors affecting the finite element calculation results were analyzed by the single parameter change method.The influence of groove shape on the mechanical properties of PCPB is analyzed through finite element calculation and compressive strength test,and the influence of groove shape on the long-term water permeability and frost resistance of the new-type PCPB is analyzed through simulated plugging test and freeze-thaw cycle test.The weight of each performance index of PCPB is obtained based on the entropy method,and the influence of groove shape on the comprehensive performance of PCPB is analyzed.The main conclusions obtained are as follows:(1)The effects of sand rate,silica fume content and alkali activator dosage on the compressive strength,splitting tensile strength and permeability coefficient of PCPB were analyzed by the orthogonal experimental design method.The results show that sand rate is the most important factor affecting the strength and permeability of PCPB.The incorporation of silica fume will improve the strength of PCPB without affecting its permeability.The addition of alkali activator will improve both the strength and permeability of PCPB.The optimal sand ratio,silica fume content,and alkali activator dosage are 5%,10% and 4% respectively.(2)The effects of the concrete constitutive relation,failure criterion,mesh size and convergence tolerance on the PCPB finite element ultimate load value were investigated by the single parameter change method.The results show that when the elastoplastic MISO model is selected for the constitutive relation of concrete,the crushing option is turned off in the failure criterion,the mesh size is 10 mm,and the convergence tolerance is 0.5%,the simulated value is the closest to the real value.(3)The influence of groove shape on PCPB strength is analyzed through ANSYS simulation and indoor compressive strength test.The results show that the calculated results obtained by setting appropriate modeling parameters are close to the measured values.The semi-circular groove PCPB has the highest compressive strength.(4)The loss rate of water permeability coefficient of PCPB with semi-circular grooves is much lower than that of PCPB without grooves,indicating that reserved grooves can improve the long-term water permeability of PCPB.The grooves will slightly reduce the frost resistance of PCPB.The calculation results of the entropy method show that the long-term water permeability of the new-type PCPB is more important than the frost resistance and mechanical properties,which should be paid more attention during the long-term service.The semi-circular groove is the optimal groove shape of the new PCPB,which has more high strength,best long-term water permeability and better frost resistance.