TITLE:
Recycled Concrete Aggregates: Review Physical, Mechanical, and Durability Characterisation and Comparison with Natural Aggregates
AUTHORS:
Babacar Diouf
KEYWORDS:
Recycled Concrete Aggregates, Sustainable Concrete, Physical-Mechanical Properties, Durability, Circular Economy, Construction and Demolition Waste, Alkali-Silica Reaction
JOURNAL NAME:
Open Journal of Civil Engineering,
Vol.16 No.2,
June
18,
2026
ABSTRACT: The progressive depletion of natural aggregate resources and the growing generation of construction and demolition waste (CDW) have intensified global interest in recycled concrete aggregates (RCA) as a sustainable substitute for natural aggregates (NA) in concrete production. This review synthesises quantitative data from more than fifty peer-reviewed studies published between 2012 and 2024, focusing on the physical, mechanical, and durability properties of RCA-based concrete (RAC) compared with natural aggregate concrete (NAC). Key findings indicate that RCA exhibits significantly lower apparent density (1.91 - 2.70 g/cm3, average 2.32 g/cm3) and substantially higher water absorption (2% - 15%) than NA (0.5% - 2%). Los Angeles abrasion values for RCA (20% - 45%) are systematically higher than those for NA (15% - 30%), reflecting increased friability attributable to adhered cement mortar (20% - 56% by mass). The compressive strength of RAC at 28 days is reduced by 2.6% - 43% relative to NAC, depending on the replacement ratio, while the modulus of elasticity decreases by up to 30%. In-service durability indicators, carbonation depth, chloride penetration, and freeze-thaw resistance are likewise adversely affected with increasing RCA content. Pretreatment methods, including accelerated carbonation, thermal treatment, and polymer impregnation, substantially improve RCA quality. The use of supplementary cementitious materials (SCMs), particularly ternary blends of Portland cement, Class F fly ash, and metakaolin or silica fume, is the most effective strategy for controlling alkali-silica reactivity (ASR) in RAC and improving overall durability. These consolidated data provide a robust basis for the development of harmonised normative specifications and circular-economy construction practices.