In a significant stride towards sustainable road construction, researchers have found that incorporating glass waste into cement-bound granular mixtures (CBGM) could enhance both performance and environmental benefits. The study, led by Justyna Stępień from the Department of Transportation Engineering at the Kielce University of Technology in Poland, explores how varying the content of glass cullet (GC) affects the mechanical and compaction properties of CBGM used in road base and subbase layers.
The research, published in the journal *Applied Sciences* (translated from Polish as “Applied Sciences”), addresses the pressing challenges of glass waste accumulation and the scarcity of natural aggregates. By examining GC contents ranging from 0% to 30%, Stępień and her team discovered that increasing the glass content systematically reduced the optimum moisture content (OMC) and maximum dry density (ρd,max). For instance, a mixture with 30% glass exhibited an 18% decrease in OMC and a 2.8% reduction in ρd,max.
One of the most compelling findings was the enhancement in compressive strength. “The highest value of R28, which is the compressive strength after 28 days, was obtained for the mixture containing 20% GC, reaching 9.4 MPa,” Stępień explained. This represents a 24% increase compared to the reference mix without glass. The relationship between GC content and compressive strength was best described by a second-degree polynomial function, indicating an optimum within the 10–20% range.
The strength enhancement was attributed to a combination of physical mechanisms, such as the filler effect and improved particle packing, as well as the chemical activity of fine glass fractions, which exhibit pozzolanic reactivity. “This synergistic effect is crucial for achieving both mechanical performance and sustainable use of secondary materials,” Stępień noted.
The study also highlighted that the 30% GC mixture met the minimum required strength while achieving the highest level of waste utilization and environmental benefit. This balance between mechanical performance and sustainability is particularly relevant for the energy sector, where the demand for durable and eco-friendly construction materials is growing.
The implications of this research are far-reaching. As the construction industry increasingly seeks to reduce its environmental footprint, the integration of glass waste into CBGM offers a promising solution. “This study provides a roadmap for optimizing the use of glass cullet in road construction, balancing performance and sustainability,” Stępień concluded.
The findings could shape future developments in the field, encouraging the adoption of recycled materials in road construction projects. By leveraging the benefits of glass cullet, the industry can move towards more sustainable practices, reducing waste and conserving natural resources. This research not only advances our understanding of material science but also paves the way for innovative, eco-friendly construction solutions.