Bunyamin Bunyamin, Taufiq Saidi, Sugiarto Sugiarto, Muttaqin Hasan
Aceh in Indonesia is rich in marine resources and abundant fishery products such as oyster. Traditionally, fishermen only harvest oysters and discard the shells, which can cause pollution and environmental contamination. Waste Oyster Shells (WOS) contain a high percentage of calcium carbonate (CaCO3) that experiences thermal decomposition at high temperature, following the reaction CaCO3 → CaO + CO2 (ΔT = 825°C). At temperature > 900°C, dead-burned lime is formed, which severely influences CaO reactivity. However, the optimum temperature for producing high CaO content is still uncertain. Therefore, this study aimed to determine the optimum calcination temperature to produce high CaO content, assess initial setting time of WOS paste, and identify the best compressive strength of paste. For the experiment, WOS was used as a partial cement replacement (with a size of 0.075 mm) in paste at a proportion of 5% and calcined at temperature of 700°C, 800°C, 900°C, and 1000°C. The specimens used were an ebonite ring (dimensions: 70 mm bottom diameter, 60 mm top diameter, and 40 mm height) and a cube (dimensions: 5 cm × 5 cm × 5 cm). The experiment was conducted following the ASTM (American Society for Testing and Materials) standards and optimum compressive strength values were analyzed using ANOVA (Analysis of Variance) and Response Surface Methodology (RSM) through the Design Expert software. The results showed that WOS calcined at 1000°C increased CaO content by approximately 57.40%. Furthermore, the initial setting time test of 5% WOS paste at 1000°C showed a more uniform binding performance compared to conventional cement paste, with an initial setting time of 75 min and a penetration depth of 15 mm. In line with the analysis, optimum compressive strength of 71.028 MPa with a desirability value of 0.986 was achieved at 5% cement replacement and calcination temperature of 786.44°C. Copyright © 2025 The Authors. Published by Tech Science Press.
Doctoral Program, School of Engineering, Post Graduate Program, Universitas Syiah Kuala, Banda Aceh, 23111, Indonesia; Department of Civil Engineering, Faculty of Engineering, Universitas Iskandar Muda, Banda Aceh, 23234, Indonesia; Department of Civil Engineering, Universitas Syiah Kuala, Banda Aceh, 23111, Indonesia; Center for Environmental and Natural Resources Research, Universitas Syiah Kuala, Banda Aceh, 23111, Indonesia
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