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This paper aims to investigate the use of calcined mussel shell (CMS) ash–cement mix in concrete that is found to increase the concrete resistance against carbonation.

The deposited ash from the calcination of the mussel shells at 1000°C was used to replace the ordinary Portland cement at 5 and 7 per cent of the cement weight. The test results from the control concrete specimens were compared to the test results from the experimental concrete specimens to analyse the effects due to the said replacements. Carbonation was carried out naturally in the environment where the concentration of the carbon dioxide gas was at 0.03 per cent, the relative humidity of 65 per cent and the temperature of 27°C for a maximum period of 120 days. Measurement of carbonation depth was taken in accordance to the BS EN 13295: 2004. The carbonation resistance of the concrete was assessed based on the degree of compliance with the common design life requirement of 50 years. The filler effect from the CMS was verified using the capillary absorption test (ASTM C1585: 2013) and the electron microscope.

Experimental concrete specimens containing 5 and 7 per cent of the CMS ash demonstrated better carbonation resistance compared to the control concrete specimens with a minimum attainable design life of 56 years which can reach a maximum of 62 years. Capillary absorption test results indicated that the concrete pores have been effected by the said filler effect and visual observation from the electron microscope confirmed, solidifying the statement.

The CMS ash is proven to contribute to the concrete’s resistance against carbonation. Also, the CMS ash is synthesized from waste materials which have contributed to the application of the green material in the concrete technology.