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Influence of recycled concrete aggregate enhancement methods on the change of microstructure of ITZs in recycled aggregate concrete
Graphical abstract Display Omitted
Highlights The BSE-IA and EDS analysis were employed for characterize the ITZs of RAC. Aggregate enhancements could take obviously strengthening effect on ITZs. Soaking RCA in CEM-SF slurries had a better improvement effect on ITZs. The Ca/Si atomic ratio of ITZs was reduced after enhancement of RCA.
Abstract Recycled concrete aggregate (RCA) enhancement is an important method to improve the performance of recycled aggregate concrete (RAC). However, the quantitative studies on the change of microstructure of interfacial transition zones (ITZs) were few and far, especially after enhancement of RCA with different methods. This paper investigated the influence of carbonation enhancement (carbonation time, soaking in CH saturated solution and then carbonation) and chemical enhancement (respectively soaking in Na2SiO3 saturated solution and cement-silica fume (CEM-SF) slurries) of RCA on the change of microstructure of ITZs (including the ITZ between old aggregate-new paste (ITZ1) and ITZ between old paste-new paste (ITZ2)) in RAC. The porosity, the un-hydrated cement particles (UH) content, the volume fraction of hydration products (VFHP) in ITZs and the width of ITZs were obtained by backscattered electron imaging analysis (BSE-IA) and energy dispersive spectrometer (EDS) analysis. Results showed that the carbonation enhancement of RCA could not effectively strengthen ITZ1. However, soaking RCA in Na2SiO3 saturated solution and CEM-SF slurries could decrease the porosity and the UH content, develop the VFHP, and reduce the width of ITZ1, then strengthening ITZ1. Both carbonation and chemical enhancement could take obviously improvement on ITZ2. Additional calcium sources could be added to RCA by soaking in CH saturated solution, improving the effect of carbonation enhancement of RCA. Soaking in CEM-SF slurries had a better improvement effect on ITZs. After RCA was soaked in CEM-SF slurries, the porosity in ITZ1 and ITZ2 decreased by 36.8% and 44.0%, the UH content of ITZ1 and ITZ2 decreased by 22.6% and 53.6%, the VFHP of ITZ1 and ITZ2 increased by 22.6% and 20.9%, and the width of ITZ1 and ITZ2 decreased by 42.9% and 50%. EDS analysis showed that the Ca/Si atomic ratio of ITZs was reduced after RCA enhancement, which generated more hydration products and then decreased the porosity and the width of ITZs.
Influence of recycled concrete aggregate enhancement methods on the change of microstructure of ITZs in recycled aggregate concrete
Graphical abstract Display Omitted
Highlights The BSE-IA and EDS analysis were employed for characterize the ITZs of RAC. Aggregate enhancements could take obviously strengthening effect on ITZs. Soaking RCA in CEM-SF slurries had a better improvement effect on ITZs. The Ca/Si atomic ratio of ITZs was reduced after enhancement of RCA.
Abstract Recycled concrete aggregate (RCA) enhancement is an important method to improve the performance of recycled aggregate concrete (RAC). However, the quantitative studies on the change of microstructure of interfacial transition zones (ITZs) were few and far, especially after enhancement of RCA with different methods. This paper investigated the influence of carbonation enhancement (carbonation time, soaking in CH saturated solution and then carbonation) and chemical enhancement (respectively soaking in Na2SiO3 saturated solution and cement-silica fume (CEM-SF) slurries) of RCA on the change of microstructure of ITZs (including the ITZ between old aggregate-new paste (ITZ1) and ITZ between old paste-new paste (ITZ2)) in RAC. The porosity, the un-hydrated cement particles (UH) content, the volume fraction of hydration products (VFHP) in ITZs and the width of ITZs were obtained by backscattered electron imaging analysis (BSE-IA) and energy dispersive spectrometer (EDS) analysis. Results showed that the carbonation enhancement of RCA could not effectively strengthen ITZ1. However, soaking RCA in Na2SiO3 saturated solution and CEM-SF slurries could decrease the porosity and the UH content, develop the VFHP, and reduce the width of ITZ1, then strengthening ITZ1. Both carbonation and chemical enhancement could take obviously improvement on ITZ2. Additional calcium sources could be added to RCA by soaking in CH saturated solution, improving the effect of carbonation enhancement of RCA. Soaking in CEM-SF slurries had a better improvement effect on ITZs. After RCA was soaked in CEM-SF slurries, the porosity in ITZ1 and ITZ2 decreased by 36.8% and 44.0%, the UH content of ITZ1 and ITZ2 decreased by 22.6% and 53.6%, the VFHP of ITZ1 and ITZ2 increased by 22.6% and 20.9%, and the width of ITZ1 and ITZ2 decreased by 42.9% and 50%. EDS analysis showed that the Ca/Si atomic ratio of ITZs was reduced after RCA enhancement, which generated more hydration products and then decreased the porosity and the width of ITZs.
Influence of recycled concrete aggregate enhancement methods on the change of microstructure of ITZs in recycled aggregate concrete
Liu, Jian (Autor:in) / Ma, Kunlin (Autor:in) / Shen, Jingtao (Autor:in) / Zhu, Jianbin (Autor:in) / Long, Guangcheng (Autor:in) / Xie, Youjun (Autor:in) / Liu, Baoju (Autor:in)
16.02.2023
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
Aggregate enhancement , Recycled concrete aggregate (RCA) , Recycled aggregate concrete (RAC) , Interfacial transition zone (ITZ) , Backscattered electron imaging analysis (BSE-IA) , RCA , Recycled concrete aggregate , RAC , Recycled aggregate concrete , ITZ , Interfacial transition zone , ITZ<inf>1</inf>(OA-NP) , Interfacial transition zone between old aggregate-new paste , ITZ<inf>2</inf>(OP-NP) , Interfacial transition zone between old paste-new paste , ITZ<inf>3</inf>(OA-OP) , Interfacial transition zone between old aggregate-old paste , CH , Calcium hydroxide , CEM-SF slurries , Cement-silica fume slurries , C-S-H , Calcium silicate hydrate , UH , Un-hydrated cement particles , VFHP , Volume fraction of hydration products , BSE-IA , Backscattered electron imaging analysis , EDS , Energy dispersive spectrometer , SP , Polycarboxylic acid superplasticizer , SEM , Scanning electron microscopy , E-SEM , Environmental-scanning electron microscopy , BSE , Backscattered electron , IPP , Image-Pro Plus
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