Study On Sulfate Resistance And Modification Of Pervious Concrete

Pervious concrete plays an important role in the construction of sponge city.Good water permeability makes it have the advantages of water permeability,road environment improvement and water resource recycling.However,this property is also one of the important reasons for its low strength and poor resistance to external erosion.Sulfate erosion is one of the most common and harmful erosion environments in China,especially permeable concrete structures in saline soil and coastal areas,which are more seriously damaged due to the coupling effect of dry-wet cycle and sulfate.Therefore,the study on the resistance of pervious concrete to sulfate attack under the action of dry-wet cycle is beneficial to the development and application of pervious concrete in saline soil and coastal areas.In this paper,starting from the coupling effect of pervious concrete subjected to wetting and drying cycles and sodium sulfate erosion,four different admixtures were selected to study the influence of admixtures on the basic mechanical properties and sodium sulfate erosion resistance of pervious concrete through orthogonal test.The porosity,permeability coefficient,compressive strength,quality and other parameters of pervious concrete were determined by referring to relevant specifications.Combined with the characteristics of the actual environment,the specimen adopts the way of natural drying,and evaluates the corrosion resistance of the specimen by the loss rate of compressive strength,mass loss rate,porosity loss rate and permeability coefficient loss rate.The influence of various factors on its performance is systematically studied.The main research content of this paper is as follows:（1）The basic performance of pervious concrete is studied by changing different material composition.Using range and variance analysis method,the basic mechanical properties of pervious concrete are analyzed,and the influencing sequence of factors and the optimal dosage of the basic mechanical properties of pervious concrete are obtained,and the functional relationship between porosity,permeability coefficient and compressive strength is established.The results show that the basalt fiber has good compatibility with the cementitious material and can enhance the compactness.Mineral admixtures consume Ca（OH）₂to produce C-S-H gel with higher strength,which can improve the compressive strength of pervious concrete.（2）The corrosion resistance of pervious concrete to sodium sulfate under dry and wet cycle was studied by changing different material composition.It is found that sodium sulfate erosion before 20 dry-wet cycles has positive effects on strength loss rate and mass loss rate of pervious concrete,and negative effects on permeability coefficient loss rate and porosity loss rate.However,after 20 dry-wet cycles,the strength loss rate and mass loss rate of pervious concrete gradually decreased,while the permeability coefficient loss rate and porosity loss rate gradually increased.The range variance analysis was used to obtain the influence sequence of each performance index of pervious concrete and the optimal dosage of each component material for every 10 dry-wet cycles.Finally,the best material composition of pervious concrete resisting sodium sulfate erosion was obtained through comprehensive analysis.（3）Microstructure and influence mechanism analysis.SEM and EDS were used to analyze the microstructure changes of pervious concrete under the action of dry-wet cycle and sulfate coupling.It was found that the erosion mechanism of pervious concrete under the action of dry-wet cycle and sulfate coupling includes chemical erosion and physical erosion.Appropriate mineral admixture and basalt fiber can improve the corrosion resistance of pervious concrete to sodium sulfate.Reduce the corrosion of sodium sulfate on pervious concrete.