Abstract
The present study prepared calcined oyster shell powder having chemical composition and crystal structure of calcium oxide and lime, respectively, and investigated the fresh and hardened properties of cement mortar incorporating calcined oyster shell powder as an additive. The test results indicated that the hydration of calcined oyster shell powder promoted the additional formation of Ca(OH)2 at the initial reaction stage, thereby increasing the heat of hydration. In particular, the volumetric increase of calcined oyster shell powder during hydration compensated the autogenous shrinkage of mortar at early ages, ultimately leading to a clear difference in the shrinkage values at final readings. However, an excessive incorporation of calcined oyster shell powder affected the rate of C–S–H formation in the acceleratory period of hydration, resulting in a decrease in the compressive strength development. Meanwhile, the degree of flow loss was inconsequential and rapid flow loss was not observed in the specimens with calcined oyster shell powder. Therefore, considering the fresh and hardened properties of cement mortar, the incorporation of calcined oyster shell powder of approximately 3% by weight of cement is recommended to enhance the properties of cement mortar in terms of compressive strength and autogenous shrinkage.
Highlights
There has been consistent effort to recycle wastes including industrial by-products in order to accomplish a sustainable society through resources recycling
The heat evolution of specimen incorporating calcined oyster shell powder of 12% slightly increased as hydration proceeded, though incorporation of calcined oyster shell powder to cement did not significantly affect the cumulative heat evolution
The autogenous shrinkage value of the specimen incorporating calcined oyster shell powder of 6% was similar to that of control specimen, calcined oyster shell powder addition shellgenerally powder reduced of 6% was similar to that of control specimen, calcined oyster shell powder addition the autogenous shrinkage of cement mortar
Summary
There has been consistent effort to recycle wastes including industrial by-products in order to accomplish a sustainable society through resources recycling. In South Korea and other countries, disposal of the oyster shell requires transportation to a designated area since oyster shell is classified as an industrial waste by the waste control act [1]. Belated treatment of oyster shell waste results in various environmental concerns such as shortage of disposal area, significant disposal cost, odor, disfigurement, and rainwater-induced coastal pollution [1,4]. Against these backdrops, appropriate recycling of oyster shell waste is necessary to provide efficient and ecofriendly means of treating these wastes
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