An assessment of microcracks in the interfacial transition zone of recycled concrete aggregates cured by CO2. (10th March 2020)

• Record Type: Journal Article
• Authors: Li, Yang; Fu, Tenghuan; Wang, Ruijun; Li, Yan
• Is Part Of: Construction & building materials. Volume 236(2020)
• Publication Date: 2020-03-10
• Subjects: Recycled concrete aggregate -- Carbonation -- Scanning electron microscopy -- Interfacial transition zone -- Mechanical property; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2019.117543
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: CO2 curing enhanced the physical properties of RCA. Long CO2 curing time and small RCA particles resulted in a small microcrack width in the ITZ. The morphology of the ITZ was observed during CO2 curing of RCA. A clear relationship between the mechanical properties of RAC and the Wc at the ITZ of CO2 treated RCA was observed. Abstract: The effect of carbonation on the properties of recycled concrete aggregate (RCA) was investigated in this study. RCAs with diameters of 10–20, 20–30 and 30–40 mm were carbonised for 0, 7, 14 and 28 days. Scanning electron microscopy was used to measure the average microcrack width (Wc ) in the interfacial transition zone (ITZ) of the aggregate and mortar in RCA, and the dependencies amongst Wc in the ITZ area and the mechanical properties of recycled aggregate concrete (RAC) were assessed. Experimental results show that carbonation treatment modifies the ITZ microstructure. Wc rapidly and slowly decreases during the early and later stages of CO2 curing, respectively. Wc of ITZ after 28 days of CO2 curing corresponds to 14.1–16.9% of that without CO2 curing. The small aggregate and large specific surface area can facilitate the absorption of additional CO2 by using RCA during carbonation and accelerate the decrease in Wc . Moreover, the mechanical properties of RAC (e.g. compressive strength and modulus of elasticity) increase with the decrease in Wc .