154 / 2022-04-29 18:13:15

Performance evaluation of recycled aggregate concrete incorporating limestone calcined clay cement (LC3)

Recycled aggregate concrete; limestone calcined clay cement; strength; chloride resistance; electrical resistivity; pore structure

Recycled aggregate concrete (RAC) incorporating limestone calcined clay cement (LC³) holds promise as a solution to the depletion of natural resources for construction materials and is a way to mitigate the environmental impacts of energy-intensive cement production. The ternary binder system demonstrates an overwhelming influence on the phase assemblage of RAC matrix (Fig. 1), and the kinetics of hydration reaction are altered from the early formation stage. The pore structure is significantly refined, and the porosity is reduced (Fig. 2). The ameliorated microstructure contributes to the significant improvement of the chloride penetration resistance of RAC without noticeably compromising its mechanical strength (Fig. 3 and Fig. 4). For RAC incorporating 50% LC³, the reduction ratio of the chloride rapid migration coefficient could reach 94% while the strength loss ratio is only 12% at 300 days compared to the reference group. The electrical resistance of RAC using LC³ is also remarkably improved because of the formation of a denser matrix as well as the reduction of available OH⁻ in the pore solution of LC³ blends. According to a life cycle assessment analysis, the environmental impact of RAC is significantly reduced with the maximum reduction ratio being 42% due to the incorporation of LC³ because cement is the largest contributor to both carbon emissions and energy consumption. The combination of recycled aggregate and LC³ is a promising approach to improving the overall performance of RAC and mitigating the environmental impacts for concrete production.