Influence of class F fly ash and curing temperature on strength development of fly ash-recycled concrete aggregate blends

The environmental footprint for Portland cement production contributes to significant carbon dioxide emissions, particularly in the civil engineering industry. Alternative low-carbon binders to Portland cement have been increasingly sought in recent years by road construction companies. Fly ash (FA) is the by-product of coal-fired electricity generation in many developed and developing countries, and is traditionally stockpiled as a waste material at power plants. Recycled Concrete Aggregates (RCA) generated from demolition industries, has in recent years gained acceptance as cement stabilized pavement material. In this research, FA was evaluated as an alternative low-carbon binder for the stabilization of RCA as a road construction material. The substantial reduction in environmental impact of replacing general Portland cement by alternative binders such as FA, along with economic advantages of utilization of FA in construction activities tackles the negative landfilling impacts and carbon footprint of stabilization activities at the same time. The strength characterization of RCA stabilized with various FA content was evaluated by undertaking Unconfined Compressive Strength (UCS) tests on samples cured at ambient room temperature and at 40 °C. The durability of the FA stabilized RCA under simulated traffic loadings was furthermore evaluated by performing repeated load triaxial tests to determine the resilient modulus (MR) of RCA samples when stabilized with FA. The micro-scale formation of bonds between the aggregates with different FA content and its effect on the strength of the stabilized RCA specimens was furthermore studied. RCA stabilized with 15% FA was found to be the optimum blend for road stabilization applications.