Study On The Method And Properties Of Geopolymers Prepared By Engineered Sediment

As the proportion of urbanization in China increases year by year,more and more infrastructure projects begin to be constructed,which brings some problems,such as the large amount of waste soil generated by underground excavation,and the carbon emission caused by the heavy consumption of cement,etc.At present,the existing engineering sediments are mostly handled by means of external transport and landfill,and a few are reused by means of comprehensive utilization.However,there are some defects such as low utilization rate,secondary waste generation and narrow application range.In this paper,gepolymers were prepared by mechanical and calcined activation treatment of engineering sediments and alkali excitation.This method is simple and can be used in large amount without adding cement.The prepared geopolymer cementitious materials not only have good mechanical properties and working properties,but also have the advantages of cost saving and carbon emission reduction.The main research contents of this paper are as follows:In this study,the particle size of engineering sediment was treated to below 0.03 mm by mechanical means,and the treated residuum was calcined at 600-900℃.By means of XRD,TG-DSC,FTIR,the material composition and micro morphology of calcined residue were analyzed to explore the mechanism of action of mechanical treatment and calcined activation treatment engineering sediment.The optimum calcining temperature of engineering soil was selected by the compressive strength of sediment geopolymers at corresponding calcining temperature.The results show that calcination can transform kaolin in the engineering sediments into active metakaolin by dehydroxylation.Metakaolin polycondensation with alkali solution forms a three-dimensional network structure,which is the main contribution to the strength of sediments geopolymer.When the calcination temperature is 800℃,the activation effect of engineering sediment is the best,the strength of the prepared geopolymer is the highest,the compressive strength of 28 days can reach 44.3 MPa.The effects of different water-solid ratio,alkali content and sodium silicate modulus on the physical properties,environmental and economic benefits of sediment gepolymer were investigated.In this study,engineering sediment activated by the optimal calcining temperature was used as raw material.Firstly,mechanical properties,setting time and fluidity of sediments geopolymers under different water-solid ratio,alkali content and water glass modulus were tested,and LCA analysis was conducted to analyze their energy consumption,preparation cost and CO2 emission under the whole life cycle.Then,based on the above six indexes,the performance and benefit of residual land polymers were evaluated comprehensively,and the optimal design proportion interval of residual land polymers was determined.This part of research results for the subsequent mortar and concrete mix design experiment to provide a theoretical basis for the practical application of sediments geopolymers.Based on the optimum mixing ratio interval of sediments geopolymers,mortar and concrete prepared by using sediments geopolymers as cementing materials were studied in this paper.Firstly,the effects of different water-solid ratio and solid-sand ratio on mechanical properties and flow properties of sediment geopolymer mortar were studied.Then,the selection range of concrete water-solid ratio is determined on the basis of mortar,and the influence of different water-solid ratio and unit water consumption on the compressive strength and workability of sediment geopolymer concrete is studied.The last reference to the design of the Portland cement concrete method to establish the water-solid ratio of sediment geopolymer concrete and compressive strength,the unit water use and slump of the linear regression equation,and puts forward a set of calculation formula of the surrounding the based on strength and slump in sediment geopolymer concrete mixture ratio design method,provides the basis for the application of the sediment geopolymer in concrete.