Cement production has a lot of adverse effects on the environment and the globe at large. With all these negativities, it becomes imperative to find alternative materials that are sustainable and environmentally friendly to reduce some of these adverse effects. Seashells are one of the numerous wastes that are quickly accumulating onshore coasts. Using seashells in cement aids in ridding seashells from seashores and landfills, and transforming these wastes to viable cementitious materials. This review paper summarizes past studies on using seashell ash powder as a partial replacement for cement in several proportions. The workability of concrete reduces with the addition of seashell ash. It also indicates a reduction in compressive strength of concrete whose cement content is partially replaced with seashells as compared to those of ordinary Portland cement (OPC). Also, at low percentages of 5%-15% ranges, the concrete absorption and porosity are less compared to standard. Though, with greater replacement levels of up to 25%-50%, these values are enhanced. The workability of concrete is reduced with the addition of higher percentage of seashell ash. After long curing periods, concrete permeability is also reduced, and the mechanical performance is enhanced.

The rate at which the construction industry explores and consumes non-renewable natural aggregates and other industrial products such as bitumen, lime, and cement during construction and rehabilitation of road pavements has over time proven to be environmentally degrading and non-sustainable. This, alongside the issues of high solid waste generation and inadequate disposal, has led to series of studies by various researchers to find methods to integrate these solid wastes as alternative materials in road construction and maintenance. This paper provides a simple yet detailed review of recent relevant studies conducted to understand the alarming rate of generation and the effects of reusing these waste materials in both flexible and rigid pavements. The review further outlines the advantages and disadvantages of the selected waste materials and compare the results with that of conventional materials in accordance with relevant standards while highlighting the performance, and life cycle environmental and economic sustainability implications. The study shows that the adoption of these materials offers efficiency in waste disposal while reducing the demand for natural aggregates and consequently, significantly reducing life cycle impacts and costs. The challenges limiting the effective practical implementation of these waste recycling techniques in the construction industry were discussed and possible solutions were suggested to encourage and ensure its utilization in road construction.

This study reviews recent literature on the mechanical and durability properties of concrete incorporating seashells as partial or full substitutes for conventional materials. The study summarizes various contributions elucidating the various waste seashells utilized, the growing worldwide aquaculture production, seashell material preparation and treatment, chemical composition, physical properties, and different mechanical and durability test methods adopted by previous studies such as compressive strength, split tensile strength, flexural strength, modulus of elasticity, freeze-thaw resistance, water permeability, air content, chemical attack, carbonation, and weight loss. The study showed that mechanical properties indicate reductions of different percentages with increases in substitution ratio at 5% to 75%, compared to control mixes. However, relative increases in mechanical strength were recorded with the increase in curing age up to 90 days. Influence of seashells on durability properties varied across various durability tests at different seashell percentages. In a nutshell, the use of seashells in concrete

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