Study On The Influence Of Rheological Properties Of Polymer Cement Slurry On Pervious Concrete

The performance of pervious concrete has a direct impact on the service life of municipal engineering such as roads.Ordinary pervious concrete often has poor mechanical properties,and the coordination between mechanical properties and pervious properties is poor.Polymer and mineral admixtures are usually used to improve the quantity and strength of slurry,so as to improve the performance of pervious concrete.However,in addition to the quantity and strength of the slurry,the rheological properties of the slurry mixed with polymer are also one of the important factors affecting the mechanics and permeability of pervious concrete.In this paper,polyacrylate（PAE）emulsion,silica fume,water reducing agent and thickening agent cellulose ether（HPMC）were selected to organically relate the rheological properties of polymer cement slurry with its composition,the amount of slurry and the relationship between bone glue ratio.The fluidity and plastic viscosity of cement slurry were measured by using the test method of cement slurry fluidity and rheometer,and the influence law of rheological properties of cement slurry was explored.The results show that the rheological properties of the slurry are affected by the ratio of cement to cement,the ratio of water to cement,the amount of additives water reducing agent,thickening agent（HPMC）and the replacement rate of silica fume.When the polymer cement-cement ratio,water-cement ratio and wollastonite replacement rate are constant,the amount of water reducing agent mainly affects the fluidity of polymer cement slurry,and the amount of HPMC mainly affects the plastic viscosity of polymer cement slurry.The influence of the fluidity and plastic viscosity of polymer cement slurry on the bond strength,coating thickness and anti-spalling ability of the slurry was explored,and the corresponding relationship between the mechanical properties and water permeability of polymer pervious concrete was established.The results show that when the polymer slurry fluidity is about 185mm and the plastic viscosity is about 1.05Pa·s,the drawing bond strength of polymer slurry is about 3.3MPa,the coating thickness is about 0.76～0.90mm,the slurry distribution is uniform,the average standard deviation is between 0.10～0.12,and the polymer slurry has strong anti-spalling ability.The delamination index is only 6.8～12.8,and the performance of pervious concrete is improved.Based on the optimum parameters of rheological properties of cement slurry,the influence mechanism of PAE emulsion cement ratio,water cement ratio and silica fume replacement rate on slurry bond strength was discussed,and the corresponding relationship with mechanical properties of pervious concrete was established.The results show that the optimal mixing ratio of slurry is 6%PAE emulsion cement ratio,0.25 water-cement ratio and10%wollastonite replacement rate.In this case,the bond strength of slurry is 1.69MPa,and the compressive strength and flexural strength of pervious concrete reach the maximum38.8MPa and 5.1MPa,respectively.With fixed forming method,the optimum parameters of rheological properties of polymer cement slurry and the optimum mix ratio of slurry were selected to analyze the influence of bone glue ratio on the porosity of pervious concrete.The results show that when the bone glue ratio is 3.5,the increase of porosity and water permeability coefficient is the largest,which increases by 21%and 31.3%,respectively.At this time,the porosity is 17.6%and the water permeability coefficient is 2.36mm/s.The optimal parameter of bone glue ratio is proposed as 0.35.The hydration process of polymer cement slurry and the microstructure of polymer pervious concrete were analyzed by XRD and SEM.The results show that the polymer slurry prepared under the optimal parameters of rheological properties,slurry mix ratio and bone glue ratio has better comprehensive properties,and the characteristic peak of cement Ca（OH）₂mixed with polymer emulsion and silica fume decreases,indicating that the hydration products of the mixed PAE emulsion and silica fume have chemical reactions with cement.The content of Ca（OH）₂in the cement decreases and the pervious concrete becomes more dense..