15 Years Later: Recycled Glass Paves Way for Sustainable Cities

Engineers in Hong Kong have successfully pioneered the use of recycled glass in concrete pavers for more than 15 years, addressing earlier concerns about cracking. Their extensive research confirmed that these pavers exhibit excellent performance, showing no internal cracking caused by alkali-silica reactions. This innovative approach significantly contributes to sustainable construction practices and effective waste management.

Discarded glass bottles, often a challenging recycling problem, were crushed and integrated into concrete mixes. The primary concern was the potential alkali-silica reaction (ASR) due to silica in glass, which could lead to concrete expansion and cracking over time. However, a 15-year evaluation of paving blocks installed around 2005 revealed their stability under real-world conditions.

The long-term field study, which examined dry-mixed concrete blocks containing recycled glass as a partial aggregate replacement, found no signs of ASR-related internal cracking. The research indicated that the reaction products formed on the glass particle surfaces, preventing harmful expansion within the blocks.

This finding is crucial for cities facing landfill saturation and high demand for construction resources. By utilizing waste glass, Hong Kong's initiative tackles both waste reduction and the sustainable sourcing of building materials. Laboratory tests also supported field observations, reinforcing the efficacy of this method.

The study suggests that finely ground waste glass powder may offer further advantages in mitigating ASR effects. While specific outcomes can vary with glass types and production methods, this 15-year case study provides valuable real-world evidence for adopting recycled glass in future construction materials.