Recycled Sand and Aggregates for Structural Concrete: Toward the Industrial Production of High-Quality Recycled Materials with Low Water Absorption

Abstract

Concrete recycling to produce aggregates is crucial in reducing the demand for virgin materials in the construction industry, particularly for the most widely used building material—concrete. A potential solution to enhance the quality of recycled aggregates involves the removal of the adhered cement paste from their surfaces. In this study, samples of industrial demolished concrete were selectively separated into recycled sands and aggregates while removing the hydrated cement paste. The recycled materials were characterized to assess their suitability for structural concrete production. The behavior and underlying mechanisms of recycled sands and aggregates proved to be identical, irrespective of their size. Water absorption emerged as a key parameter for evaluating the purity and quality of these materials. The statistical analysis revealed that when the water absorption of recycled aggregates and sand falls below 5%, the compressive strength may, at most, decrease by 15% (97.5% confidence) at any replacement level. Consequently, they can entirely replace virgin materials without a significant negative impact on fresh or hardened concrete properties at a constant cement content. Concrete samples with recycled materials had comparable workability, strength, and durability characteristics to references with virgin materials. The production of high-quality recycled aggregates and sand can facilitate complete concrete recycling and hence significantly contribute to virgin materials preservation, thus making concrete more sustainable.

Advancements in Green Materials for Concrete in South East Asia: A Mini Review

“…In stage 1 of the experiment, different percentages, from 0% to 100%, of RCA concrete were tested by using it in the construction of Samwoh's Eco-Green Building. The final results showed that the compressive strength for low and medium concentrations remained consistent, whereas there was some increase in strength when the percentage of RCA concrete increased [23]. The success of the RCA concrete results could be used to expand building codes to permit the implementation of RCA concrete in the construction industry.…”

A contribution to the study of mortars prepared with recycled sand

“…This is certainly due to the fact that the hardened cement paste which adheres to the aggregates is porous and its density is lower than that of natural sands and aggregates. For this reason, it was found that the density of the recycled material gradually decreased as the bonded cement content increased (Skocek et al, 2024).…”