Stripping of aggregate from mortar in waste concrete heated by microwave:Mechanisms of differential-temperature stress and vapor expansion pressure  

作　　者：Yanping Sheng Xiao Huan Peizhen Hu Liangliang Li Ahmed Abdulakeem Zhoujing Ye Linbing Wang Yanping Yin 

机构地区：[1]School of Materials Science and Engineering,Chang'an University,Xi'an 710064,China [2]Engineering Research Center of Transportation Materials,Ministry of Education,Chang'an University,Xi'an 710064,China [3]National Center for Materials Service Safety,University of Science and Technology Beijing,Beijing 100083,China [4]School of Environmental,Civil,Agricultural and Mechanical Engineering,College of Engineering,University of Georgia,Athens,GA 30602,USA

出　　处：《Journal of Traffic and Transportation Engineering(English Edition)》2024年第3期538-558,共21页交通运输工程学报（英文版）

基　　金：the financial support from the open project funds for National Major Science and Technology Infrastructure of Materials Service Safety Assessment Facilities,China(MSAF-2020-106);the National Natural Science Foundation of China(No.51808051)。

摘　　要：Microwave heating,which is used for pre-treatment of concrete before it is comminuted,stands as a strong candidate for selective liberation of multiphase materials like concrete.This paper is concerned with the selective liberation of concrete's raw constituents(particularly aggregate)for recycling by considering the water content of concrete as a parameter of microwave heating for the first time.The deterioration law of the concrete's performance was characterized by the variation in the splitting tensile strength and relative dynamic modulus after heating by microwave at different water contents.Besides,tests were conducted to evaluate the performance of the interface transition zone(ITZ)between aggregate and mortar as well as to investigate the reasons for the stripping behavior of aggregate-mortar,which included the interface tensile strength test,temperature measurement,and porosity test.The deterioration law of splitting tensile strength and relative dynamic modulus revealed that the performance of concrete was subject to different degrees of damage depending on the water content.Furthermore,experimental results showed that interface bonding strength between aggregate and mortar was dramatically impaired,and a large temperature difference was generated between the aggregate and mortar during microwave heating.Meanwhile,the permeable pores increased considerably even when the specimens were dried.In the presence of water,the intactness of ITZ between aggregate and mortar was destroyed by microwave heating,and its performance was significantly lowered,which led to the occurrence of stripping behavior between aggregate and mortar.This was reaffirmed by the microstructure presented by scanning electron microscopy.Thus,the newly developed microwave pretreatment improved by providing appropriate water contents for concrete corresponding to different strength grades is a promising method for recycling aggregate from waste concrete.

关 键 词：Waste concrete Recycled aggregate Microwave heating Stripping behavior Differential-temperature stress Vapor expansion pressure 

分 类 号：U414[交通运输工程—道路与铁道工程]