The Influence of Fly Ash on the Mechanical Performance of Cementitious Materials Produced with Recycled Cement

[Abstract:] Concrete is the most widely used construction material in the world; as such, the best way to promote a more sustainable construction industry is to improve the environmental performance of this material. Since cement production is the main source of the high environmental impact of concrete, due to the high calcination temperature that clinker requires, replacing this binder with recycled cement would allow for the establishment of a new concrete design with a much lower ecological footprint. This research intends to analyse the mechanical performance of mortars with recycled cement and fly ash. Mixes with two replacement ratios of recycled cement (5% and 10%) were studied separately or in combination with fly ash (10% and 20%). An exhaustive experimental programme was designed to assess the variation in air content, density, compressive and flexural strengths, modulus of elasticity, and ultrasonic pulse velocity. The results suggest that the simultaneous use of recycled cement and fly ash improves the mechanical performance of mortars relative to those with recycled cement only or fly ash only.