Feasibility of Oyster Shell as Cement Material

Topics: Concrete, Compressive strength, Materials science Pages: 19 (4161 words) Published: June 21, 2013
Hindawi Publishing Corporation Advances in Materials Science and Engineering Volume 2013, Article ID 809247, 7 pages http://dx.doi.org/10.1155/2013/809247

Research Article Feasibility of Pulverized Oyster Shell as a Cementing Material Chou-Fu Liang and Hung-Yu Wang
Department of Civil Engineering, National Pingtung University of Science and Technology, 1 Hsuefu Road, Neipu, Pingtung 91201, Taiwan Correspondence should be addressed to Hung-Yu Wang; hywang@mail.npust.edu.tw Received 9 November 2012; Revised 27 February 2013; Accepted 4 March 2013 Academic Editor: Alex Li Copyright © 2013 C.-F. Liang and H.-Y. Wang. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This research intends to study the cementing potential of pulverized oyster shell, rich in calcium, when mixed with fly ash and soil. Cylindrical compacted soil and cubic lime specimens with different proportions of the shells and fly ash are made to study the strength variance. Soil, which is classified as CL in the USCS system, commercialized pulverized oyster shell, F-type fly ash, and lime are mixed in different weight percentages. Five sample groups are made to study the compressive strength of soil and lime specimens, respectively. The lime cubes are made with 0.45 W/B ratio and the cylindrical soils are compacted under the standard Procter compaction process with 20% moisture content. The results show that increment of shell quantity result to lower strength on both the soil and lime specimens. In a 56-day curing, the compressive strength of the lime cubes containing fly ash increases evidently while those carrying the shell get little progress in strength. The soil specimens containing fly ash gradually gain strength as curing proceeds. It suggests that mixtures of the shell and fly ash do not process any Pozzolanic reaction nor help to raise the unconfined strength of the compacted soil through the curing.

1. Introduction
Being an island, Taiwan is very rich in marine resources. Along the west coast of Taiwan, oyster farming is one of the most important production activities for the country’s economy. In general, most of the oyster shells are discarded with no further use once the flesh is stripped off; except that a small amount is used for art creation [1, 2]. As a result, oyster shell piles are common in areas of oyster production with no further utilization. Chemical and microstructure analyses reveal that oyster shells are predominantly composed of CaO [3, 4], similar to that of lime, which has been used for soil stabilization [5]. In addition, oyster shells can be utilized for producing medium- and high-quality cement [6]. The expandable nature of clay is reduced by the ion exchange from the interaction between calcium ions and clay. Quicklime creates coagulation if added with water. Thus, calcium ions are used generally as the primary component in the clay stabilization. There is no known chemical reaction between soil and lime except the ion exchange. In other studies for potential use, the shells are mostly used as additive or replacement of part of the cement in concrete.

For example, construction material mixed with crushed oyster shell and sand was used for sand compaction piles to improve soft soils underneath a breakwater port in Japan [7]. However, the lime contained in the shells does not provide improvement of concrete strength as the Pozzolanic products of concrete already contain lime, and therefore no positive effect is detected for concrete strength. According to [8], a pozzolan is defined as a siliceous and aluminous material, which in itself possesses little or no cementitious value but will, in finely divided form in the presence of moisture, chemically react with calcium hydroxide to form compounds possessing cementitious properties (Pozzolanic activity). No...
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