| Geopolymer ecological concrete is made of a geopolymer gel material and coarse aggregate.It has a concrete structure with pores inside.It has the characteristics of air permeability and water retention,which can make plant roots enter the concrete,realize the perfect combination between concrete and green vegetation,and then achieve the purpose of soil consolidation and slope protection,slope treatment and landscape greening.In the experiment,metakaolin and alkali activators were used to prepare geopolymer gel materials to replace traditional Portland cement.Four factors and four levels of orthogonal experiments were designed to determine the optimum mixing ratio of geopolymer ecological concrete materials by designing different alkali activator modulus and concentration,alkali activator solute and metakaolin ratio,coarse aggregate and geopolymer gel material ratios.Based on this,the effects of different coarse aggregate gradations on the performance of geopolymer ecological concrete were studied.The physical and mechanical properties,resistance to water erosion,resistance to dry-wet cycle-sulfate erosion and plant growth were tested.The main research contents of this paper are as follows:(1)The influence of geopolymer gel parameters on the preparation process and mechanical properties of eco-concrete was studied.The compressive strength and splitting tensile strength of geopolymer eco-concrete were related to the increase and decrease of the alkali activator modulus.Higher alkali activator concentration and coarse aggregate to geopolymer gel material ratio,higher aggregate to geopolymer gel ratio are not conducive to the development of ecological concrete strength.The geopolymer ecological concrete is prepared when the mass ratio of geopolymer gel material to coarse aggregate is 1:5,the concentration of alkali activator is 40%,the modulus is 1.3,and the mass ratio of alkali activator solute(sodium silicate+sodium hydroxide)to metakaolin is 0.3 has higher strength and water permeability.(2)Through the experimental study of different coarse aggregate gradation specimens,the influence of aggregate gradation on aggregate surface area,aggregate specific surface area,porosity and permeability coefficient,and the coating thickness of geopolymer gel on different aggregate gradations are obtained.The stress-strain curve of geopolymer ecological concrete specimen under uniaxial compression is obtained,and the peak strain,elastic modulus and energy absorption capacity of the specimen are obtained.The normalized stress-strain formula model of geopolymer ecological concrete with parameters a and b is proposed.At the same time,the splitting tensile strength and flexural strength were carried out to obtain the tensile mechanical properties of the specimens under different aggregate gradations.(3)In order to obtain the optimal aggregate gradation of geopolymer ecological concrete,the experimental study of dry-wet-sulfate erosion resistance and the test of apparent damage,mass loss and strength loss of specimens under water erosion resistance were carried out.By obtaining two groups of optimal gradation specimens,the relationship between plant height,germination rate and relative water content of leaves under different porosity under the same nutrient matrix conditions was discussed.The difference between the actual porosity and the plane porosity of geopolymer ecological concrete was studied.The microstructure of the interfacial transition zone formed by geopolymer gel and aggregate was observed,and the mechanism of geopolymer gel was further analyzed. |
