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The study herein presented was conducted with the aim of developing a new lightweight aggregates concrete (LWAC) and a new ultra-high durability concrete (UHDC), both with low cement content. These were specifically designed to meet the requirements of an innovative two-layers composite precast concrete structural wall (high flowability, reduced density and minimum compressive strength of 45 MPa), composed of an outer layer in UHDC and an inner layer in LWAC. These mixtures were optimized with the goal of reducing the cement content, adopting a partial replacement by binary pozzolanic and limestone filler additions, this way improving the mechanical performance, the durability and the sustainability. All mixtures were characterized in both fresh and hardened states, addressing: consistency, main mechanical properties, and durability. The use of silica fume allows a reduction of circa 20–25% of cement to obtain similar strength performance. In addition, tensile and compressive strengths exhibited increases of circa 30% and 40%, respectively using silica fume, instead of fly ash. Regarding durability, the outer UHDC evidences no carbonation and high resistance to chloride diffusion. It was conclusive that to predict the service life for this solution, the chloride diffusion coefficient, D0, should be considered at 56 days age, due to the prolonged pozzolanic effect over time on resistance to chloride. It was proven that this new composite structural wall increases the service life in 30%, considering the minimum recommended covers by codes, or lower covers (circa 50%) can be used if the service life is set to 50 years.
Martins et al. (2024) studied this question.