Experimental Study On Mix Proportion Of Pervious Concrete Pavement Slab And Design Of Composite Structure Form

With the development of ‘sponge city',more and more attention has been paid to pervious concrete.Pervious concrete has the advantages of protecting and replenishing groundwater resources,improving driving environment,adjusting surface temperature and humidity and alleviating urban waterlogging.The special porous structure of pervious concrete not only provides excellent performance,but also affects its physical and mechanical properties and antifreeze durability.At the same time,due to the porous nature of traditional pervious concrete pavement,there are many problems such as easy blockage,difficult maintenance and poor durability.It is of great significance to study the relationship between the proportion factors of pervious concrete and the physical and mechanical properties and the frost resistance and durability of pervious concrete,and to change the traditional pavement form of pervious concrete.In this paper,the effects of water-binder ratio,aggregate particle size,slag content and silica fume content on the porosity,permeability coefficient,compressive strength,flexural strength and freeze-resistance durability of pervious concrete were studied by using the orthogonal test of three levels and four factors.By changing the main factors affecting the performance of pervious concrete,adding SR-Enhancer and changing the target porosity,the mixture ratio was optimized.Pervious concrete pore structure is the main factors affecting its performance,but it is lack of the complexity of the pore structure better description method.This study adopts the specimen slice image processing method for flat face structure research.The analysis of the test results show that the method of image plane porosity and volume method of effective pore volume consistent,confirmed the feasibility of the method of image.Image method can better statistical pore and pore size distribution,and the number of internal porosity of the pervious concrete characteristics is of great significance.From the structural form of innovation,changing the traditional form of pervious concrete pavement,the development and design of a new form of pavement can overcome from the structure of pervious concrete easy to block,not easy to clean,not easy to maintain and other shortcomings.The experimental results show that:(1)Among the four influencing factors of water-binder ratio,aggregate particle size,slag content and silica fume content,water-binder ratio is the main significant factor affecting the physical and mechanical properties and frost resistance and durability of pervious concrete in the early and late stages.Aggregate particle size is the main factor affecting the average equivalent pore size inside the pervious concrete.The larger the aggregate particle size is,the larger the internal void will be.When slag content is 15% and silica fume content is 5%,pervious concrete has better physical and mechanical properties and anti-freeze durability.(2)According to the relationship between the pore structure characteristics such as plane porosity and equivalent pore diameter of pervious concrete and the pervious performance and strength performance of pervious concrete,the increase of the proportion of small pore diameter will increase the strength and decrease the pervious performance of pervious concrete;When the proportion of large pore diameter increases and the pore diameter distribution is concentrated,the strength increases and the permeability increases.(3)With the increase of curing age,on the one hand,slag and silica fume react with calcium hydroxide produced by hydration of cement,and at the same time promote the hydration of tricalcium silicate and dicalcium silicate,so that the diffraction peaks of tricalcium silicate,dicalcium silicate and calcium hydroxide are significantly reduced.The content of alkali in pervious concrete can be reduced by adding slag and silica fume,and the durability of pervious concrete can be improved.(4)Proposed a modular design of waterproof concrete road slab that pervious concrete combined with high strength of ordinary concrete.The combination of implementation were separable design to reduce urban water accumulation to avoid the happening of flood by changing upper plate,and avoid the disadvantages of traditional pervious concrete pavement such as easily blocked,difficult maintenance,promptly eliminate seeper;The lower plate adopts high strength ordinary concrete and bears the upper load,which solves the disadvantage of low strength of traditional pervious concrete pavement.The combination of pervious concrete upper board and ordinary concrete with mineral admixtures reduces the cost compared with other pervious concrete paving and road cover.