Civil Engineering and Architecture 11(3): 1297-1305, 2023 http://www.hrpub.org DOI: 10.13189/cea.2023.110315 Effects of Pre-treatments on Microstructure and Mechanical Properties of Recycled Concrete Aggregates Shalaka Nirantar 1,* , Premanand Naktode 2 1 Faculty of Civil Engineering, N. K. Orchid College of Engineering & Technology, Solapur, 413002, India 2 Civil Engineering Faculty, Sandip University, Nashik, 422213, India Received November 12, 2022; Revised February 14, 2023; Accepted March 12, 2023 Cite This Paper in the Following Citation Styles (a): [1] Shalaka Nirantar, Premanand Naktode , "Effects of Pre-Treatments on Microstructure and Mechanical Properties of Recycled Concrete Aggregates," Civil Engineering and Architecture, Vol. 11, No. 3, pp. 1297 - 1305, 2023. DOI: 10.13189/cea.2023.110315. (b): Shalaka Nirantar, Premanand Naktode (2023). Effects of Pre-Treatments on Microstructure and Mechanical Properties of Recycled Concrete Aggregates. Civil Engineering and Architecture, 11(3), 1297 - 1305. DOI: 10.13189/cea.2023.110315. Copyright©2023 by authors, all rights reserved. Authors agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International License Abstract Deficiency of natural resources in construction industry is one of the major issues in today’s construction era. Another major problem, which not only construction industry, but the entire world is facing, is the management of construction and demolition (C&D) waste. Therefore, it becomes inevitable to recycle the C&D waste and to replace it partially with natural aggregate so as to reduce the strain on natural resources. Recycled concrete aggregates (RCAs) cannot be directly reused as it possesses poor quality in terms of physical and mechanical properties. The objective of this experimental work is to improve the properties of RCAs by using pretreatments such as mechanical abrasion, water soaking, acid soaking, and heating. It is found that using mechanical abrasion, weak acid soaking and moderate heating, the micro structure of the RCA is improved. Water absorption and porosity are improved by 20% and 17.75% respectively. Using pre-treated RCAs, with partial and complete replacement for natural aggregates, concrete cubes were cast and tested for evaluation of compressive, split tensile and flexural strengths. Compressive strength for 40% replacement is improved by 17.41% as compared with the M25 grade concrete made using natural aggregates. Also, replacement by 100% is possible and compressive strengths are comparable. Thus, using the pre-treatments, C&D waste utilization, reduction in consumption of natural aggregates (NA) is possible in medium grade applications leading to sustainable construction. Keywords Recycled Aggregates, Clung Mortar, C&D Waste, Treatments, Sustainable Construction 1. Introduction Aggregate is a key component in the building process. The aggregate market is projected to grow by 6.85% annually [1, 2] according to numerous studies. However, C&D waste is being produced in enormous quantities as a result of the demolition of old buildings to make way for new multi-story buildings. There was 1181 million tonnes of construction and demolition debris produced worldwide, a decade ago [3]. There are currently around 150 million tonnes of C&D garbage produced annually in India [4]. Disposal and management of construction and demolition debris are becoming increasingly difficult due to a lack of suitable disposal sites. The construction industry also faces a shortage of natural raw materials in the present day. The gap between the need for and the availability of natural aggregate is enormous. About 60 to 75% of concrete is made up of natural aggregate. "As a result, there is a rise in the manufacturing of aggregate made from natural stones, which could potentially disrupt ecological balance [5]. Many countries, including India, are experiencing a severe aggregate scarcity at the present time [6]. Thus, recycling C&D waste is one of the relevant and effective methods to alleviate pressure on waste management and advance the development of sustainable construction practices.