Abstract—This study investigates the potential of using crushed concrete as aggregates to produce green and sustainable concrete. Crushed concrete was sieved to powder fine recycled aggregate (PFRA) less than 80 µm and coarse recycled aggregates (CRA). Physical, mechanical, and microstructural properties for PFRA and CRA were evaluated. The effect of the additional rates of PFRA and CRA on strength development of recycled aggregate concrete (RAC) was investigated. Additionally, the characteristics of interfacial transition zone (ITZ) between cement paste and recycled aggregate were also examined. Results show that concrete mixtures made with 100% of CRA and 40% PFRA exhibited similar performance to that of the control mixture prepared with 100% natural aggregate (NA) and 40% natural pozzolan (NP). Moreover, concrete mixture incorporating recycled aggregate exhibited a slightly higher later compressive strength than that of the concrete with NA. This was confirmed by the very dense microstructure for concrete mixture incorporating recycled concrete aggregates compared to that of conventional concrete mixture. Keywords—Compressive strength, recycled concrete aggregates, microstructure, interfacial transition zone, powder fine recycled aggregate. I. INTRODUCTION EPARING and reusing concrete from construction- demolished waste (CDW) is paving the way towards sustainable construction [1]. The huge increase in CDW volume is the main challenge facing construction industry [2]. Significant efforts are being made to find ways to reuse these huge amounts of CDW. The use of recycled concrete as aggregates in new concrete mixtures helps conserving natural resources, decreasing production energy and reducing the amount of waste deposited in landfills [3], [4], which maximizes the economic benefits of S. Boudali and S. Poncet are with the Mechanical Engineering Department at Université de Sherbrooke, Sherbrooke, QC, Canada (e-mail: sara.boudali@USherbrooke.ca, Sebastien.Poncet@USherbrooke.ca). A. M. Soliman (Assistant Professor) is with the department of Building, Civil and Environmental Engineering at Concordia University Montreal, Montréal, QC, Canada (e-mail: ahmed.soliman@concordia.ca). B. Abdulsalam (Postdoctoral fellow) is with the department of Civil and Environment Engineering, at Western University, London, Ontario, Canada (e-mail: babdulsa@uwo.ca). K. Ayed (Associate Professor) is with the department of Civil Engineering, laboratory LABMAT-EPO at National Polytechnic of Oran, Oran, Algeria (e- mail: ayeddzkada@gmail.com). D. E. Kerdal (Professor) is with the Civil Engineering in the department of Civil Engineering, laboratory LM2SC-USTOMB at University of Sciences and technology of Oran Mohamed Boudiaf Oran, Algeria (e-mail: djkerdal@yahoo.fr). CDW [5]. RAC can be incorporated in producing new concrete mixtures (i.e. recycled concrete aggregate concrete (RCAC)) [6], [7]. Concrete made with RA has different characteristics from those of conventional concrete [8], [9]. Depending on the properties of the RA, RCAC strength grade can vary from normal and up to high strength concrete [10]. The properties of RA vary widely due to its different sources and many possible compositions of the original concrete [9]. Moreover, previous research showed that the addition of CRA to concrete does not have an adverse effect on its performance [11]. Conversely, the addition of PFRA as a replacement for cement was found to increase concrete compressive strength significantly [12]. Moreover, the surfaces of RA are wrapped by old cement paste. Hence, the ITZ of RCAC is more complicated than that in NA concrete [13]. Characteristics of the ITZ will depend mainly on the properties of the RCAC such as flowability and strength [12]-[14]. However, information on concrete using PFRA and CRA is still insufficient. Detailed information about characteristics of concrete using RA is needed before its wider implementation in today’s construction. The present study aims to examine the influence of mechanical and morphology of PFRA and CRA on strength and microstructure development of RCAC. II. MATERIALS AND TESTING PROCEDURE A. Materials Ordinary Portland cement CEM II 42.5 B with a specific gravity of 3.16 kg/m 3 and specific surface area of 3519 cm 2 /g according to European Standard EN 197 [15] was used in all mixtures. NP extracted from Bouhamidi deposit in the Beni- Saf region (North- West of Algeria) was used in this study as a mineral admixture. After drying at 105 °C to eliminate free water, CRAs were produced after crushing of waste concrete from the Laboratory of West Algeria Public Works with an average compressive strength of 40 MPa [12]. For PFRA, waste concrete samples were crushed to less than 80 µm, resulting in a specific surface area of 300 m 2 /kg. This very fine recycled aggregate powder was essentially composed of silica and alumina (more than 60%). The particle size distributions for RCP and cement are shown in Fig. 1. Table I presents the properties of binders. Both natural and recycled gravels with two size ranging 0.12-0.20 in. (3-5 mm) and 0.39-0.59 in. (5- 15 mm) were used as coarse aggregates. Table II lists the Microstructural Properties of the Interfacial Transition Zone and Strength Development of Concrete Incorporating Recycled Concrete Aggregate S. Boudali, A. M. Soliman, B. Abdulsalam, K. Ayed, D. E. Kerdal, S. Poncet S World Academy of Science, Engineering and Technology International Journal of Civil, Environmental, Structural, Construction and Architectural Engineering Vol:11, No:8, 2017 966 International Scholarly and Scientific Research & Innovation 11(8) 2017 scholar.waset.org/1999.3/10007637 International Science Index, Structural and Construction Engineering Vol:11, No:8, 2017 waset.org/Publication/10007637