Mechanical and Environmental Performance of Concrete with Partial Replacement of Cement by Silica Fume and Scallop Shell Powder in Coastal Areas

CO2 emissions from cement production have significantly increased, leading to the search for alternative materials that optimize the process and reduce environmental impact. In this context, the present study investigates the use of microsilica (MS) and fan shell powder (PCA) as cement replacements. Material characterization tests were conducted, and six mix designs were made, including 5% PCA and 10% MS replacements individually, as well as combinations of 10% MS with 5%, 7.5%, and 10% PCA. Additionally, compression strength properties were analyzed at 3, 7, and 28 days, and flexural strength at 7 and 28 days. The findings regarding mechanical strength were favorable, except for the mix with 10% MS and 10% PCA, which indicates the maximum substitution percentage. Furthermore, a CO2 emission analysis was conducted according to the Greenhouse Gas Protocol, achieving a reduction of up to 11.16% compared to the control concrete. In conclusion, the study demonstrates that the combination of 10% MS and 5% PCA is the optimal replacement, improving compressive strength by 6.99% and flexural strength by 1.33%, while reducing CO2 emissions by 10.44%.