Mechanical Property and Microstructure of Nano-SiO2 Recycled Fine Aggregate Concrete
The demand for infrastructure construction has been increasing,and a large number of waste facilities need to be updated and replaced,resulting in an increasing production of waste concrete.Simultaneously,the construction industry is facing an increasingly severe problem of natural resource scarcity.The sand and gravel aggregates preparation from waste concrete has become one of the key solutions to this problem.However,the performance of recycled concrete prepared from such sand and gravel aggregates is generally poor,and cannot replace the natural concrete for engineering construction.To solve these problems,the study used recycled fine aggregate(RFA)with different mass substitution rates to replace natural fine aggregate(NFA)of equal mass to prepare recycled fine aggregate concrete(RFAC),and modified it with nano-SiO2 at dosages of 0,1%,2%,and 3%to replace cement.The influence of RFA and nano-SiO2 substitution rates on the mechanical properties and microstructure of RFAC was studied for improving RFAC's performance and making it superior to natural concrete for engineering construction.The result indicates that with the addition of RFA,the compressive strength,splitting tensile strength,and flexural strength of RFAC significantly reduce compared with natural aggregate concrete(NAC).When the substitution rate of RFA is 100%,the compressive strength,splitting tensile strength,and flexural strength at 28-day reduce by 20.6%,26.1%,and 19.1%respectively compared with NAC.With the addition of nano-SiO2,the compressive strength,splitting tensile strength,and flexural strength of RFAC are significantly improved compared with RFAC without nano-SiO2.The improvement amplitude gradually increases with the increase of nano-SiO2 content.When the content of nano-SiO2 is 3%,the compressive strength,splitting tensile strength,and flexural strength of RFAC at 28-day with different RFA substitution rates increase by 23.4%-30.7%,31.3%-39.7%,and 26.8%-35.3%respectively compared with NAC.Meanwhile,nano-SiO2 can promote the cement hydration reaction,reduce the content of C3 S and Ca(OH)2,promote the formation of C—S—H,act as the crystal nuclei to fill pores,repair the weak interface transition zones inside RFAC,improve the compactness of RFAC matrix,and enhance the mechanical properties of RFAC.
road engineeringrecycled fine aggregate concreteexperimental analysismicrostructurenano-SiO2
NETL
NSTL
万方数据
