In the quest for sustainable construction practices, a groundbreaking study led by Thamires Alves da Silveira from the Federal University of Pelotas in Brazil has shed new light on the potential of construction and demolition waste (CDW) as a viable partial replacement for natural aggregates in concrete. Published in the journal *Waste* (which translates to *Waste* in English), the research delves into the mechanical performance and durability of concretes incorporating varying proportions of recycled coarse aggregate derived from CDW.
The study, which explored replacement levels ranging from 0% to 100%, is particularly notable for its examination of intermediate replacement levels—20%, 25%, 45%, 50%, and 65%—areas that have been less explored in previous research. This refined approach allows for a more nuanced understanding of performance thresholds, offering valuable insights for practical applications.
Da Silveira and her team evaluated several key parameters, including fresh-state slump, axial compressive strength at 7 and 28 days, water absorption, sorptivity, and chloride ion penetration depth after 90 days of immersion in a 3.5% NaCl solution. The results are promising: up to 50% CDW content, the concrete maintained slump, characteristic strength, and chloride penetration within the limits for moderate exposure conditions, as per ABNT: NBR 6118 standards. “This indicates that, with careful mix design, we can significantly reduce the environmental impact of concrete production without compromising its structural integrity,” da Silveira noted.
However, the study also highlighted some challenges. Water absorption doubled from 4.5% (0% CDW) to 9.5% (100% CDW), reflecting the higher porosity and adhered mortar on the recycled aggregate. This necessitates adjustments to the water–cement ratio and SSD pre-conditioning to preserve workability and minimize sorptivity. Concretes with more than 65% CDW exhibited chloride penetration depths exceeding 15 mm, potentially compromising durability without additional mitigation.
The implications for the construction industry are substantial. As the demand for sustainable building materials grows, this research provides a roadmap for incorporating CDW into concrete mixes, reducing the environmental footprint of construction projects. “The judicious incorporation of CDW, combined with optimized mix design practices and the use of supplementary cementitious materials (SCMs), demonstrates technical viability for reducing environmental impacts without significantly impairing the structural performance or service life of the concrete,” da Silveira explained.
For the energy sector, which often requires durable and sustainable construction materials for infrastructure projects, this research offers a compelling alternative. By leveraging CDW, companies can not only reduce their carbon footprint but also potentially lower material costs, making it a win-win for both the environment and the bottom line.
As the construction industry continues to evolve, this study underscores the importance of innovation and sustainability. It paves the way for future developments in the field, encouraging further exploration of recycled materials and optimized mix designs. The findings published in *Waste* serve as a testament to the potential of CDW, offering a glimpse into a more sustainable future for construction.