Study On The Performance Of Steel Fiber And Nano Silicon Modified Geopolymer Pervious Concrete Based Solid Waste

As a special kind of concrete with connected pore structure,pervious concrete has become one of the most effective technical means to construct ecological "sponge city" because of its functions such as water permeability,air permeability,sound absorption and noise reduction.However,Portland cement is the main cementing material used to prepare pervious concrete at present,which has some problems such as non-renewable and high energy consumption in the production process.Therefore,in the current scarcity of natural resources,it is particularly important to find a kind of green and energy-saving cementitious material with both cement characteristics.To solve the above problems,in this paper,coal gangue and household waste incineration furnace slag ball grinding into micro powder through physical excitation,respectively combined with slag as the precursor of geopolymer reaction instead of cement to prepare coal gangue slag base and incinerator slag base geopolymer pervious concrete,and on this basis the use of steel fiber and nano SiO2 modified and enhanced two kinds of geopolymer pervious concrete.By studying the mechanical properties,water permeability,frost resistance and pore structure of the aforesaid geopolymer pervious concrete,the following results have been obtained:(1)Firstly,the compressive strength,pervious performance and pore structure of pervious concrete under different vibration times are studied,and the optimal vibration time of pervious concrete is determined to be 15s.Then,orthogonal test was used to determine the benchmark mix ratio of polypermeable concrete in slag base with three factors of bone glue ratio,alkali equivalent and sodium silicate modulus.The optimal parameters were determined as bone glue ratio 4:1,alkali equivalent 6%and sodium silicate modulus 1.4 by range analysis.(2)Secondly,in order to explore the influence of solid waste based micro-powder on geopolymer pervious concrete,coal gangue and incineration slag were substituted for(0%,10%,20%,30%,40%,50%)slag to prepare geopolymer pervious concrete,and its performance was studied.The results show that the mechanical properties and frost resistance of pervious concrete from coal gangue slag base and incinerator slag base decrease with the increase of the replacement rate of coal gangue and incinerator slag.The porosity increases with the increase of substitution ratio.The permeability coefficient decreases gradually with the change of slurry fluidity.When the replacement rate of coal gangue is 30%-40%and the replacement rate of incinerator slag is 20%-30%,the pore diameter distribution of geopolymer permeable concrete is relatively concentrated and uniform.Under the premise that all the properties meet the specifications,the maximum replacement rate of coal gangue and incinerator slag is recommended to be 30%and 20%respectively.At this time,the 28d compressive strength,tensile strength and flexural strength of polypermeable concrete of gangue and slag base are 20.6MPa,3.74MPa and 3.2MPa,respectively.The porosity is 17.84%and the permeability coefficient is 2.66mm/s.The 28d compressive strength,tensile strength and flexural strength of the polypermeable concrete in the incinerator slag-slag base are 23.4MPa,4.26MPa and 4.2MPa,respectively.The porosity is 16.78%and the permeability coefficient is 1.98mm/s.(3)Then,in order to improve the problems of low toughness and high brittleness of polypermeable concrete in solid waste base,steel fiber is used to toughen the polypermeable concrete in coal gangue-slag base and incineration slag-slag base.The effects of different volume contents of steel fiber(0%,0.5%,1%,1.5%,2%)on the performance of geopolymer permeable concrete was studied.The results show that the effects of steel fiber on the mechanical properties,water permeability and frost resistance of the two types of geopolymer pervious concrete are consistent:the mechanical properties first increase and then decrease with the increase of steel fiber content.The water permeability and frost resistance first decrease and then increase with the increase of the dosage.The effect of steel fiber on pore structure is only slight.After comprehensive analysis,the optimal volume content of steel fiber for both types of ground polymer pervious concrete is determined to be 1%.At this time,the 28d compressive strength,tensile strength and flexural strength of polypermeable concrete of gangue and slag base are 23.2MPa,3.99MPa and 3.5MPa,respectively.The porosity is 16.95%and the permeability coefficient is 2.28mm/s.The 28d compressive strength,tensile strength and flexural strength of the polypermeable concrete in the incinerator slag-slag base are 26.6MPa,4.66MPa and 4.6MPa,respectively.The porosity is 16.03%and the permeability coefficient is 1.78mm/s.(4)Finally,on the basis of toughening steel fiber,nano SiO2 was used to further modify two kinds of geopolymer pervious concrete,and the influence of different mixing amounts of nano SiO2(0%,1%,2%,3%)on its performance was studied.The results show that with the increase of nano SiO2 content,the mechanical properties of the two types of geopolymer pervious concrete first increase and then decrease.There is no change in water permeability.The frost resistance decreased first and then increased.The addition of nano SiO2 has no effect on the macroscopic pore structure.Comprehensive analysis shows that the performance of the two types of ground polymer permeable concrete reaches the best when the nano SiO2 content is 1%.At this time,the 28d compressive strength,splitting tensile strength and flexural strength of polypermeable concrete in gangue and slag base are 25.5MPa,4.11MPa and 3.9MPa,respectively.The porosity is 15.62%and the permeability coefficient is 2.03mm/s.The 28d compressive strength,splitting tensile strength and flexural strength of the geopolymer pervious concrete in the incinerator slag-slag base are 27.2MPa,4.81MPa and 4.9MPa,respectively.The porosity is 15.19%and the permeability coefficient is 1.59mm/s.