Design of Fly Ash-Based Alkali-Activated Mortars, Containing Waste Glass and Recycled CDW Aggregates, for Compressive...

Traditional cement-based materials contribute significantly to global CO₂ emissions. Prior research has shown that alkali-activated systems offer a lower-carbon alternative. However, incorporating high volumes of recycled materials into these systems remains a challenge. It was already known that fly ash can serve as a precursor in alkali activation. The uncertainty around the role of secondary precursors and recycled aggregates in these systems drove this study. No prior work had resolved how these components interact under different curing conditions. This gap motivated an investigation into the effects of fine glass waste and recycled aggregates on compressive strength. The study aimed to address the limitations of current alkali-activated mortars. The goal was to improve both performance and sustainability.

This study aimed to optimize the compressive strength and environmental performance of alkali-activated mortars. The specific problem was the limited use of secondary precursors and recycled aggregates in these systems. The motivation stemmed from the need to reduce cement consumption and increase waste utilization. The authors sought to evaluate the role of fine glass waste and calcium-rich additives in these mortars. They also wanted to assess the impact of construction and demolition waste (CDW) aggregates on strength. The study focused on two stages of optimization: ambient and heat curing. Each stage examined the effects of material composition on mechanical properties. The ultimate goal was to develop a sustainable and high-performance mortar formulation.

The study used a hybrid alkali-activation model combining class F fly ash with calcium-rich precursors. The materials included ordinary Portland cement, calcium hydroxide, and fine milled glass waste. The researchers also tested limestone powder as a filler. Two optimization stages were conducted: one with ambient-cured samples and another with heat-cured samples. In the first stage, short-term compressive strength was measured. The second stage focused on 24-hour heat curing followed by 28-day testing. The effects of glass waste content and CDW aggregate replacement were analyzed. The compressive strength was evaluated using standard testing procedures. The study combined experimental design with material characterization techniques.

The highest compressive strength was achieved in heat-cured mortars containing 1% glass powder and 10% CDW aggregate replacement. These samples reached 31.4 MPa at 28 days. The inclusion of fine glass waste improved the mechanical performance of the mortars. The calcium-rich precursors played a key role in the activation process. Ambient-cured samples showed lower strength compared to heat-cured ones. The addition of limestone powder acted as an effective filler. The study found that CDW aggregates could partially replace natural aggregates without compromising strength. The results suggest that secondary precursors and recycled materials can coexist in alkali-activated systems.

The authors propose that hybrid alkali-activated mortars can achieve high compressive strength while incorporating recycled materials. The study suggests that fine glass waste and CDW aggregates can be used effectively in these systems. The findings indicate that heat curing enhances the mechanical performance of the mortars. The researchers propose that calcium-rich precursors are essential for activation. The study supports the use of secondary precursors in alkali-activated systems. The authors suggest that these mortars offer a sustainable alternative to traditional cement mixtures. The results highlight the potential for reducing cement consumption through material substitution. The authors conclude that further work is needed to scale up the application of these optimized mixtures.