Utilization of Oyster shell waste as a Fine Aggregate Substitute in mortar and its effect on workability and strength

Samuel Wilberforce Offei; Oyindamola Ayomide Okesanjo; Obalolorun Oluwatobi Ahemokhai; Ama Annorwah Ankamah

doi:10.36948/ijfmr.2026.v08i05.88310

Utilization of Oyster shell waste as a Fine Aggregate Substitute in mortar and its effect on workability and strength

Author(s)	Mr. Samuel Wilberforce Offei, Oyindamola Ayomide Okesanjo, Obalolorun Oluwatobi Ahemokhai, Ama Annorwah Ankamah
Country	Ghana
Abstract	The increasing generation of oyster shell waste and the continued demand for natural fine aggregates have created a need for sustainable approaches to waste utilization in construction materials. This study investigated the use of oyster shell waste as a partial substitute for natural fine aggregate in mortar and evaluated its effects on workability and compressive-strength development. Oyster shells sourced from fishing communities in Old Bortianor, Accra, Ghana, were washed, sun-dried, crushed and sieved for use as fine aggregate. Mortar mixtures were prepared with oyster shell replacement levels of 0%, 10%, 20%, 30% and 40% by mass, using a constant cement-to-fine-aggregate ratio of 1:3 and a water-to-cement ratio of 0.45. Workability was assessed using the slump test, while compressive strength was determined at 7, 14, 21 and 28 days using 50 mm cube specimens. The slump increased from 45 mm for the control to 50 mm at 10% replacement, after which it decreased to 42.5, 37.5 and 35 mm at 20%, 30% and 40%, respectively. Compressive strength increased with curing age for all mixtures. At 28 days, the control achieved 20.16 MPa, while the 10%, 20% and 30% replacement mixtures achieved 20.51, 20.34 and 20.13 MPa, respectively; the 40% mixture recorded 19.22 MPa. The findings demonstrate that oyster shell waste can be incorporated as a partial fine aggregate substitute while maintaining compressive strength close to the control at replacement levels up to 30% under the investigated conditions. The study provides locally derived evidence supporting oyster shell waste valorization as a potential resource for more sustainable mortar production.
Keywords	Oyster shell waste; fine aggregate replacement; mortar; workability; slump; compressive strength; sustainable construction; waste valorization
Field	Physics > Civil Engineering
Published In	Volume 8, Issue 5, September-October 2026
Published On	2026-10-05
DOI	https://doi.org/10.36948/ijfmr.2026.v08i05.88310

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Utilization of Oyster shell waste as a Fine Aggregate Substitute in mortar and its effect on workability and strength

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