Experimental Study On Engineering Characteristics Of Geopolymer Recycled Concrete Road Base

With the rapid development of urbanization in China and the rapid economic development,a large number of concrete structures will be demolished or transformed,resulting in a huge amount of abandoned concrete,the recycling of waste concrete has become a problem to be solved in the engineering field.Geopolymer material is a new environmental cementitious material.it can not only solve the treatment of waste concrete,but also reduce the exploitation of natural stone,the use of cement and the emission of air pollutants,which has obvious environmental,economic and social benefits.Based on the basic principle of geopolymer,the geopolymer cementitious materials were prepared by waste concrete powder and fly ash.Through the geopolymer cementitious material and the waste concrete aggregate preparation of geopolymer recycled concrete,and use this concrete as a road base material.The main research contents include the preparation of geopolymer cementitious materials and geopolymer recycled concrete,the engineering properties of geopolymer recycled concrete and the study on the mechanical properties of geopolymer recycled concrete base.Through the study of the above content,the geopolymer recycled concrete can be used as a road base material.The main findings are as follows:(1)The results of physical and mechanical properties of recycled aggregate show that the pavement performance of recycled aggregate of abandoned concrete basically meet the requirements of semi-rigid base materials of high-grade highway.(2)Through the orthogonal test to determine the best proportion of geopolymer cementitious material composition,the results show that the influence of three factors on unconfined compressive strength of geopolymer cementitious material is:the quality ratio of waste concrete powder and fly ash(CP:FA),sodium hydroxide solution,water glass modulus.The optimum mix ratio of geopolymer cementitious material in the area is CP:FA = 70:30,NaOH solution concentration =18 mol/l,sodium silicate modulus is 1.5.(3)The mechanical properties and pavement performance of geopolymer recycled concrete show that the unconfined compressive strength,splitting strength,unconfined compression modulus,water stability and drying shrinkage of geopolymer recycled concrete meet the relevant specifications.Compared with the cement recycled concrete,the mechanical properties of geopolymer recycled concrete are weaker than that of cement recycled concrete under the same amount of cementitious material.The water stability properties of both are basically consistent.The drying shrinkage property of geopolymer recycled concrete is better than that of cement recycled concrete.(4)Using the BISAR3.0 and HPDS2011 program,the mechanical calculation of the geopolymer recycled concrete base layer with different geopolymer cementitious materials was checked,the results meet the specification requirements.Through orthogonal test,the pavement structure is designed and analyzed,and the orthogonal scheme is calculated by the BISAR3.0 and HPDS2011 program,the optimal combination of each structure is obtained through calculation analysis.