Behaviour and Residual Strength Prediction of Recycled Aggregates Concrete Exposed to Elevated Temperatures
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RESEARCH ARTICLE-CIVIL ENGINEERING
Behaviour and Residual Strength Prediction of Recycled Aggregates Concrete Exposed to Elevated Temperatures Asad‑ur‑Rehman Khan1 · Tariq Aziz1,2 · Shamsoon Fareed1 · Jianzhuang Xiao3 Received: 13 April 2020 / Accepted: 29 May 2020 © King Fahd University of Petroleum & Minerals 2020
Abstract Natural aggregates replaced partially or fully with recycled concrete aggregates (RCA) in preparing concrete has emerged as a sustainable construction technique and investigating the properties of such concrete has already been the focus of number of published studies. However, limited data are available for the case of recycled aggregate concrete (RAC) when it is exposed to extreme conditions like elevated temperatures resulting from accidental fires. In this study emphasis was, therefore, made to investigate residual properties of RAC in terms of compressive and tensile strengths, modulus of elasticity, Poisson’s ratio, and concrete mass loss of RAC subjected to elevated temperatures by conducting a detailed experimental investigation. For this purpose, concrete cylindrical specimens were cast having 0%, 30%, 50%, 70% and 100% RCA. These cylinders were then exposed to elevated temperatures ranging from 250 to 900 °C. Based on the experimental results, Elastic modulus and Poisson’s ratio were found to be significantly influenced for the specimens having percentages of recycled aggregates above 30% and when subjected to temperature elevation of above 500 °C. Overall, behaviour of RAC was more or less similar to natural aggregate concrete with a higher degree of deterioration. Furthermore, a residual strength factor (RSF) was also proposed to predict the residual strengths of RAC exposed to elevated temperatures which can be used effectively to estimate residual strengths of NAC and RAC when exposed to elevated temperatures. Keywords Construction waste · Recycled aggregate · Residual strength · Spalling · Mechanical properties · Elevated temperatures Abbreviations RCA Recycled concrete aggregates RAC Recycled aggregate concrete RSF Residual Strength Factor NCA Natural concrete aggregates NAC Natural aggregate concrete fc′ Concrete compressive strength DIC Digital image correlation SD Standard deviation wi Mass of the specimen before heat exposure ws Mass of the heat-exposed specimen after cooling C-S-H Calcium silicate hydrates * Asad‑ur‑Rehman Khan [email protected] 1
Department of Civil Engineering, NED University of Engineering and Technology, Karachi, Pakistan
2
Centre for Infrastructure Engineering, Western Sydney University, Penrith, NSW, Australia
3
Department of Structural Engineering, College of Civil Engineering, Tongji University, Shanghai, China
(σT) Residual compressive stress after exposure to high temperature (σ30) Residual compressive stress at room temperature (Nσ) Coefficient for decrease in the compressive strength ft Splitting tensile strength P The maximum applied load l The height of the specimen d The diameter of the of specimen
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