Study On Properties Of The Ecological Slag Based Geopolymer Pervious Concrete

Pervious concrete has a certain bearing capacity,at the same time,its unique porous structure can make the road surface runoff rapidly infiltrate,can alleviate the urban waterlogging,supplement the groundwater,and has a certain effect of filtration and purification of runoff sewage.Geopolymer is a new green material with energy conservation and environmental protection.It can save resources and reduce carbon dioxide emissions to alleviate the "greenhouse effect" by replacing cement with geopolymer.Based on coordinating the contradiction between the mechanical properties,water permeability and purification property of pervious concrete,a kind of ecological slag based geopolymer pervious concrete material is developed to promote the application of pervious concrete in the construction of sponge city.In this paper,the comprehensive effects of the content of alkali activator,basalt fiber and diatomite on the mechanical properties,water permeability and water purification of the slag based geopolymer pervious concrete are studied by orthogonal experiment analysis and grey relational theory.The results show that the diatomite content has the most significant influence on the mechanical properties,water permeability and water purification of the slag based geopolymer pervious concrete among three factors.And the contents of alkali activator and basalt fiber significantly affect the mechanical properties of the slag based geopolymer pervious concrete,but they have little influence on the water permeability and water purification of the slag based geopolymer pervious concrete.It is illustrated that the strength of geopolymer paste is much higher than that of cement paste by mechanical property experiment of paste.Furthermore,the analytical results of orthogonal experiment and field emission scanning electron microscopy(FESEM)show that the appropriate amount of alkali activator can improve the degree of hydration reaction with aluminosilicate material and the strength of the slag based geopolymer pervious concrete;and the appropriate amount of basalt fiber can significantly improve the mechanical properties of the slag based geopolymer pervious concrete;and adding diatomite has adverse effects on the mechanical properties and permeable properties of the slag based geopolymer pervious concrete.The effects of the content of alkali activator,basalt fiber and diatomite on the purification characteristics of the slag based geopolymer pervious concrete were studied.The experimental results show that the slag based geopolymer pervious concrete itself has a certain purification effect on runoff sewage,adding diatomite can greatly improve the water purification characteristics of pervious concrete,while the content of alkali activator and basalt fiber have no significant effect on the removal rate of pollutants.Based on the comprehensive balance of the mechanical properties,water permeability and water purification characteristics of the composite modified slag based geopolymer pervious concrete,the optimal content of alkali activator,basalt fiber and diatomite is recommended: the content of alkali activator is 17%,the content of basalt fiber is 0.9%,and the content of diatomite is 5.8%,which provides a reference for the engineering application of the ecological slag based geopolymer pervious concrete in sponge city construction.