Relationship between the mechanical properties and carbonation of concretes with construction and demolition waste. (June 2022)

• Record Type: Journal Article
• Authors: da Silva, Sérgio Roberto; Cimadon, Felipe Nunes; Borges, Pietra Moraes; Schiavon, Jessica Zamboni; Possan, Edna; Andrade, Jairo José de Oliveira
• Is Part Of: Case studies in construction materials. Volume 16(2022)
• Publication Date: 2022-06
• Subjects: Construction and demolition waste -- Coarse recycled aggregate -- Physical-mechanical properties -- Microstructural analysis; Building materials -- Case studies -- Periodicals; 691.05
• DOI: 10.1016/j.cscm.2021.e00860
• Languages: English
• ISSNs: 2214-5095

Abstract

Abstract: The use of construction and demolition waste in the construction industry has been a constant issue for several years due to the amount of waste generated as well as the need to reduce the consumption of natural aggregates. This study has the aim of optimizing recycled aggregate from construction and demolition to verify its influence on the elastic modulus in structural concrete. For this, the substitution of coarse natural aggregate by coarse recycled aggregate was evaluated at replacement percentages of 0%, 25%, 50%, 75%, and 100% for concrete with different water/cement ratios (0.40, 0.50, and 0.60). With these criteria, macrostructural tests (compressive strength, splitting strength, porosity and water absorption), microstructural tests (scanning electron microscopy and X-ray microtomography), and accelerated carbonation were employed. The results showed that the mechanical and durability properties in relation to CO2 diffusion decreased as the substitution content of natural aggregate for recycled aggregate increased. The lower the a/c ratio, the denser the concrete and, consequently, the concrete properties are improved. Results showed that there are correlations between the mechanical properties and the carbonation of concrete with recycled aggregate. Through the proposed equations, it is possible to estimate elastic modulus from a given compressive strength at 28 days and with a w/c ratio ranging from 0.4 to 0.6. Based on the compressive strength and w/c ratio, it is possible to estimate the amount of substitution of natural aggregate needed in concretes for an expected elastic modulus. Highlights: Mechanical and durability properties were evaluated for application in structural concrete with recycled aggregates. Five levels of recycled aggregate replacement (0% 25% 50% 75% and 100%) were investigated. The increase in the replacement level of recycled aggregate decreases the concrete elastic modulus. A conceptual framework was developed to correlate the elastic modulus and other properties (compressive strength, carbonation depth and cement consumption). The framework can be useful to estimate the mechanical properties of concretes with recycled aggregates considering the fc and w/c ratio as input parameters.