A comprehensive experimental program was performed to recycle high contents of seashell waste as fine aggregate or cement substitution. This effort strongly contributes toward preserving natural resources and mitigating various toxic substances emitted into the atmosphere during cement manufacturing. The first part of this study was dedicated to study possibility of 100% fine aggregate substitution in mortars and concretes whose mechanical properties are comparable to those made by natural sand. Efficiency of this approach was demonstrated by representing several mortar/concrete compositions. In the second part, 10 types of blended cement, with binary composition of seashell powder (up to 30% by mass) and ordinary Portland cement (OPC), were prepared and their physical/chemical properties were studied in comparison with characteristics of OPC. Mortars made of these blended cements, were produced and their properties including water demand and compressive/flexural strength were characterised. All the blended cements presented 28-day compressive/flexural strength relatively close to that of OPC. Furthermore, incorporation of seashell powder resulted in extending setting times (advantageous for constructing in hot climate), and reducing water demand (beneficial for enhancing mechanical strength) of the mortars. The requirements specified by several standards were extensively used to ensure performance of the proposed sand and cements.

The environmental consequences of human activities, e.g., the depletion of non-renewable fuel resources, consumption of natural raw materials, and release of huge amounts of CO₂ into the atmosphere, resulted in new challenges in materials engineering. Based on these challenges, building materials must fulfil not only mechanical performance criteria, but also produce the least environmental impact accompanied by their production. In the present study, the possibility of employing scrap tire recycled steel fibres (RSF) as a substitution to industrial steel fibres (ISF) for developing more sustainable fibre-reinforced concretes was explored by adopting a life-cycle approach, integrated both environmental and mechanical properties. Four different fibre-reinforced self-compacting concretes–FRSCCs–were tailored by means of replacing the ISFs partially/totally (i.e., 0%, 50%, 67%, 100% by mass of) with the recycled ones. The effect of applying various dosages of RSFs on mechanical behavior of FRSCC–namely compressive, flexural, and splitting tensile responses–were evaluated experimentally. The environmental impacts associated with the production of each FRSCC were also assessed through life-cycle analysis. The potentiality of the RSFs to be used as concrete reinforcement with a comparable mechanical performance to that of ISF-reinforced concrete and lower environmental footprint was evaluated through a consolidated environmental and mechanical index (EM). In this study, using RSFs instead of industrial fibres for developing FRSCC has provided up to 37% higher EM index. The results confirmed the promising prospects for the application of RSFs in developing more eco-efficient and sustainable reinforced concrete.