Hindawi Publishing Corporation he Scientiic World Journal Volume 2013, Article ID 547615, 10 pages http://dx.doi.org/10.1155/2013/547615 Research Article Effects of Using Pozzolan and Portland Cement in the Treatment of Dispersive Clay A. H. Vakili, 1 M. R. Selamat, 1 and H. Moayedi 2 1 School of Civil Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia 2 Department of Geotechnics and Transportation, Faculty of Civil Engineering, Universiti Teknologi Malaysia, 81300 Johor, Malaysia Correspondence should be addressed to M. R. Selamat; cemrs@eng.usm.my Received 30 April 2013; Accepted 4 June 2013 Academic Editors: C. M. Petrone and G. Ventura Copyright © 2013 A. H. Vakili et al. his 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. Use of dispersive clay as construction material requires treatment such as by chemical addition. Treatments to dispersive clay using pozzolan and Portland cement, singly and simultaneously, were carried out in this study. When used alone, the optimum amount of pozzolan required to treat a fully dispersive clay sample was 5%, but the curing time to reduce dispersion potential, from 100% to 30% or less, was 3 month long. On the other hand, also when used alone, a 3% cement content was capable of reducing dispersion potential to almost zero percent in only 7 days; and a 2% cement content was capable of achieving similar result in 14 days. However, treatment by cement alone is costly and could jeopardize the long term performance. hus, a combined 5% pozzolan and 1.5% cement content was found capable of reducing dispersion potential from 100% to zero percent in 14 days. he results indicate that although simultaneous treatment with pozzolan and cement would extend the required curing time in comparison to treatment by cement alone of a higher content, the task could still be carried out in a reasonable period of curing time while avoiding the drawbacks of using either pozzolan or cement alone. 1. Introduction Dispersive clays have been found in various types of climates and in various locations in Australia, Brazil, Iran, New Zealand, he United States, hailand, Mexico, Vietnam, South Africa, and many other countries [1–3]. Dispersion potential, measured in terms of percent dispersion, is a physicochemical phenomenon that is mostly inluenced by minerals in the clays and chemical contents of pore water [4– 6]. Whenever dispersive clay is exposed to water, especially with low salt concentration, the particles separate from each other, become dispersed, and get washed away such as in the progressive erosion phenomenon known as piping [7–12]. he origins of piping which could be cracks due to shrinkage, unequal settlement, or structural fractures need to be avoided at an early stage and the construction materials for earth dams, embankments, and foundations need to be erosion resistant [7]. Dispersive clays usually have high percentages of exchangeable sodium ion—Na + —which is susceptible to replacement by calcium and aluminum ions—Ca 2+ and Al 3+ [2, 9]. Changes in soil characteristics during chemical treatment are likely due to the cation exchange Na + with Ca 2+ and Al 3+ , reduction in the thickness of difused double layer, and the subsequent reduction in the repulsive forces of the clay particles [3]. In order to recognize a dispersive clay or to measure dispersion potential, researchers have recommended physical and chemical tests such as double hydrometer test in deter- mining percent dispersion (ASTM D 4221-99, 2000) [13], pinhole test in determining inal low rate through sample (ASTM D 4647-93, 2000) [14], and chemical tests in deter- mining related indexes namely electrical conductivity (EC), sodium absorption ratio (SAR), and percent sodium (PS) (ASTM D 4542-95, 2000) [15]. Dispersion potential lessens with rising EC, while EC rises with increasing electrolyte or cation concentration in clay. Dispersion potential rises with increasing PS in clay [16–19]. he criteria for evaluating dispersion potential of a clay sample using results from the double hydrometer test have been presented by Sherard and Decker (1977) [20]. Clay with