Concrete is used and applied in various ways in the building sector. It is the most common and adaptable material used in many different types of residential and commercial construction works worldwide. This is because of its inherent properties, durability, and increased strength with aging, high reflectivity, and ability to stand against natural disasters. Cement, water, and aggregates are the primary ingredients used in concrete making (Raheem et al. 2021). Sadly, the primary components utilized in the manufacture of conventional concrete are harmful to the environment. The cement industry is faced with the challenge of the reduction of CO2 emissions and also the need to meet high global demands. The manufacturing of ordinary Portland cement makes use of large amounts of energy and releases a high percentage of CO2 into the atmosphere. About 4.1 billion tonnes of cement were estimated to have been produced globally in the year 2022, and each ton of cement produced releases 0.6 t CO2 of each ton produced which largely contributes to the issue of global warming (Garside, 2023; Soomro et al. 2023). In a bid to achieve net zero emissions by the year 2050, measures are put in place to reach the desired goal by utilizing several supplementary cementitious materials to partially or fully replace cement in concrete production.
Supplementary cementitious materials (SCMs) include materials that add to the properties of cement-based materials hydraulically or by pozzolanic action. The supplementary cementitious materials can consist of the following materials; palm kernel ash, rice husk and seashell ash, ground blast furnace slag, and silica fume, (Eziefula et al. 2018, 2020). The use of these SCMs brings about cost reduction, improvement in the technical features of the concrete, and more especially in the lessening of pollution and management of waste. Seashells have always been processed into the ash and used as supplementary cementitious materials for they are largely abundant. The quantity of seashells deposited as waste is so much, because the focus has been on the harvesting of the snail meat without due consideration to the disposed shells. It has been reported that about eight million tonnes of waste seashells (shrimps, crabs, lobster shells), also more than ten million tonnes of waste mollusk seashells are produced every year worldwide (Topić et al. 2023). Periwinkle is a seafood and belongs to the gastropod mollusks. They are widely available in the rivers and coasts in Nigeria, and when eaten, their shells which are majorly composed of CaCO3 (up to 96%) are discarded as waste (Luhar et al. 2019). The shells are frequently disposed away in large quantities in open spaces and landfills, which causes serious pollution problems. In a bid to convert the discarded periwinkle shell waste into a useful resource, researchers have been working on its use, particularly in concrete production. The periwinkle shells/ash has been studied to envisage its potential usage in concrete production as a partial replacement for fine aggregates, coarse aggregates, and cement. Bamigboye et al. (2016) employed periwinkle shell as a fractional substitute for both fine and coarse aggregates, reporting that up to 30 wt% of the periwinkle shell for the fine aggregate as well as the coarse aggregates will result in compressive strengths of up to 20 N/mm2. They reported that as the periwinkle shells increased from 1-100%, resulted to decrease in slump values, and that up to 6.8% was saved in cost when 30 weight percent periwinkle shells were utilized in concrete making. In the investigation carried out by Afolayan et al. (2019) on the replacement of cement partially with periwinkle shell ash, their results showed an increase in compressive strength for 5 wt% periwinkle shell ash and 40 mm sisal length, after which the compressive strength decreased on the sisal fibre-reinforced concrete. The authors agreed that as the days of curing increased to the maximal period of 28 days, the optimal compressive strengths were obtained for the tested samples as the curing days were varied. Compressive strength up to 28.8 N/mm2 was achieved with the combination of sisal fiber and the periwinkle shell ash. Umoh and Ujene (2015) studied the effect of sodium nitrate on the compressive and tensile splitting strengths of cement concrete blended with periwinkle shell ash. The authors resolved that the addition of 2% NaNO3 and 30 wt% periwinkle shell ash resulted in optimal compressive and tensile splitting strengths of the produced concrete.
Sand mining for construction has become a quiet environmental challenge all over the world that goes on unmonitored by the government. It has been reported that over 50 billion tonnes of sand is mined yearly worldwide, and the excavation has caused much havoc on the supply of food and water, the lives of aquatic animals, and the entire human well-being (Luhar et al. 2019; Sennott 2023). To produce eco-friendly and sustainable concrete, the waste materials that cause environmental pollution have the possibility of being used as partial substitutes for sand in concrete production and also reduce sand excavation issues. Some of these waste materials include; sea shells, agricultural wastes, fly ash, quarry dust, waste plastics, steel slag, sawdust, and rice husk ash amongst others (Meko and Ighalo 2021). Quarry dust is released as a result of crushing operations, and they pose serious pollution to water, land and air. In a bid to put them to good use, they are utilized in replacing fine aggregates in concrete production. Scholars have reported enhancement in the mechanical properties of concrete that replaced fine aggregates with quarry dust (Febin et al. 2019; Oorkalan et al. 2020; Ponnada et al. 2020).
The production of concrete can be made more environmentally friendly by utilizing multiple waste materials, while also reducing costs. Most studies have shown that combining two or more waste materials as aggregates in producing sustainable concrete for buildings can enhance certain properties under investigation. Martínez-García et al. (2024) studied the limit of replacing mussel shell aggregates in mortars. They reported that using 25% of mussel shells as replacements for conventional aggregates would yield coating mortars that can fulfill the standard requirements for various applications. They also highlighted the replacement with mussel shells will bring about a great reduction in environmental pollution. Ogundipe et al. (2021) investigated the strength characteristics of lightweight concrete made by partially replacing granite with palm kernel shells and periwinkle shells. The authors established that the combination of the shells resulted to a light weight concrete, and to obtain concrete that is relatively light and would carry reasonable amounts of load, 5 wt% periwinkle shell and 5 wt% palm kernel ash should be utilized. There is no known literature on the combination quarry dust and periwinkle shell ash waste materials as individual constituent replacements in the same sustainable concrete. There is also need to add to the existing knowledge and create enough data on the usage of these discarded/waste materials for making of concrete because of how important concrete structures are to humans; and the increasing population growth that places so much demand on their diverse applications. Thus, study aims to examine the usage of quarry dust (QD) and periwinkle shell ash (PSA) as partial or full replacements for fine aggregate and cement respectively.