Effect of oyster shell as an aggregate replacement on the characteristics of concrete

The aim of this study is to provide basic experimental data to help prevent environmental pollution and to pursue resource recycling by examining the use of waste oyster shells (OS) as concrete aggregate. The possibilities of manufacturing the waste into lightweight concrete and hollow concrete blocks are also examined. The physicochemical characteristics of OS are analysed and the materials and mechanical characteristics according to age are evaluated for fresh and hardened concretes. New chemical reactions and abnormal substances from the mixing of OS are found to be absent. Although problems in strength and workability with increased OS replacement rate of natural aggregates are generated, these can be resolved by using admixtures and stone powder. With respect to strength and workability, 10-13 mm is found be the optimum particle size range of OS as coarse aggregate. In addition, when the replacement rate of the coarse aggregate is 50%, the unit volume weight stands at 1993 kg/m(3), which represents roughly 10% lightening. Results from assessing the quality of the hollow concrete produced indicate that, even if 50% of the fine aggregate is substituted with OS, the absorption rate almost satisfies the standards. Utilisation of OS is therefore expected to be adequate.