Sustainable production of recycled concrete aggregates by lime treatment and mechanical abrasion for M40 grade concrete. (25th January 2021)

• Record Type: Journal Article
• Authors: Prasad, Deepak; Pandey, Arunabh; Kumar, Brind
• Is Part Of: Construction & building materials. Volume 268(2021)
• Publication Date: 2021-01-25
• Subjects: ASTM American Society for Testing and Materials -- C&D Construction and Demolition -- CC Control Concrete -- CWA Coefficient of Water Absorption -- FA Fine Aggregate -- HRCA Hammer crushed Recycled Concrete Aggregates -- IRC Indian Road Congress -- IS Indian Standard -- ITZ Interfacial Transition Zone -- LMRC Concrete containing Lime & Mechanically treated Recycled Concrete aggregate -- LMRCA Lime & Mechanically treated Recycled Concrete Aggregate -- MRC Concrete containing Mechanically treated Recycled Concrete aggregate -- MRCA Mechanically treated Recycled Concrete Aggregate -- N Normality -- NA Natural Aggregate -- OL Ordinary Light -- PPC Portland Pozzolana Cement -- RAC Recycled Aggregate Concrete -- RCA Recycled Concrete Aggregate -- RCW Recycled Ceramic Waste -- rpm revolutions per minute -- RWA Rate of Water Absorption -- SEM Scanning Electron Microscope -- w/c water to cement ratio -- XRD X-Ray Diffraction; Recycled concrete aggregate -- Lime treatment -- Mechanical abrasion -- Recycled aggregate concrete -- Compressive strength -- Flexural strength -- Water absorption -- XRD -- SEM -- Petrography; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2020.121119
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: 5 min grinding of hammer crushed concrete is more effective than 3 or 8 min. Lime and mechanical treatment of RCA is more effective than mechanical treatment alone. 30% substitution of natural aggregate by RCA is optimal for M40 grade concrete. The dependency of LMRC properties on normality of lime solution is more than on duration of lime treatment. LMRC has higher strength and lower water absorption as compared to MRC. Abstract: Apart from aiding the environment, exploitation of recycled concrete aggregate (RCA) as a potential substitute for natural aggregates (NA) contributes to a framework of sustainable development as well as helps in maintaining an ecological balance by avoiding fast depletion of natural resources of aggregates. Therefore, in this investigation, the effects of mechanical beneficiation and lime treatment of coarse RCA on various properties of concrete were studied. The demolished concrete was crushed by hammer in size range of 25–4.75 mm, followed by grinding for 3, 5 and 8 min. It was found that 5 min of grinding was more effective based on the degree of success in the optimum removal of adhered mortar. Further, RCA ground for 5 min (MRCA) was graded into two different nominal sizes of 20 mm and 10 mm as per IS 383. Subsequently, MRCA was immersed in a lime solution of concentration varying from 1 N to 2.5 N for 3 and 7 days. These aggregates were termed as 'LMRCA'. MRCA and LMRCA were used for partial replacement of coarse NA in M40 grade concrete at the rate of 10% up to 40% by weight. Various tests like compressive and flexural strength test and water absorption tests were performed. It was found that up to 30% NA can be replaced by MRCA or LMRCA in recycled aggregate concrete. But, the concrete admixed with LMRCA showed better properties than the concrete admixed with MRCA. Moreover, these experimental results were verified by employing microstructural and mineralogical analysis. In concrete admixed with LMRCA, the normality of lime solution was more dominant than the duration of LMRCA immersion in a lime solution. Also, the improvement in strength and water absorption of concrete admixed with LMRCA was proportional to the normality of lime solution.