VOL. 11, NO. 11, JUNE 2016 ISSN 1819-6608 ARPN Journal of Engineering and Applied Sciences © 2006-2016 Asian Research Publishing Network (ARPN). All rights reserved. www.arpnjournals.com 7254 AN EXPERIMENTAL STUDY ON DUST SHELL AS AN ADMIXTURE IN SOFT SOIL STABILIZATION Mardiha Mokhtar, Nor Baizura Hamid, Siti Aimi Nadia Mohd Yusoff and Salina Sani Research Centre for Soft Soils (RECESS), University Tun Hussein Onn Malaysia, Johor, Malaysia E-Mail: Mardiha@uthm.edu.my ABSTRACT Soil stabilization with cement has been extensively used for the improvement of soft clay soils, in enhancing the shear strength and limiting the deformation behaviours. The alternative cheaper admixture agents are essential since high costs are involved in the manufacture of cement production. The possibility of admixing cement with waste products such as dust shell (DS) as admixture for stabilizing soft soils will be presented in this paper. This study was aimed at assessing the usefulness of cement-dust shell (DS) as an effective soil admixture for improving some properties of clay soils. The stabilized specimens were prepared with the kaolin admixed with 5 % cement and various quantities of dust shell. Observation are made for the change in the properties of soil such as Atterberg Limits, Maximum dry density (MDD), Optimum moisture content (OMC) and Unconfined compressive strength (UCS). Result shows that the addition of dust shell slightly increases the maximum dry density and reducing optimum moisture content. In addition, the unconfined compressive strength of 5% cement-treated with dust shell samples increases with an increase of the amount of dust shell. This study indicates that cement-dust shell has a potential as an alternative soft soil stabilizer in soft soil stabilization with highlight the economical and environmental friendly material utilize. Keywords: cement, dust shell, soft soil stabilization, maximum dry density (MDD), optimum moisture content (OMC), unconfined compressive strength (UCS). 1. INTRODUCTION Clay soils are normally associated with volumetric changes when subjected to changes in water content due to seasonal water fluctuations. Kaolinite clays are among the soils that are affected by these problems. The minerals are formed under tropical weathering conditions in areas where precipitation is relatively high, and where drainage is good, which enables leaching of cations and iron from acidic granitic rocks [1,4]. Kaolin deposits are considered to have poor engineering characteristics, exhibiting expansive properties, high plasticity, poor workability, and low shear strength. This may cause severe damage to civil engineering structures and facilities. Hence, these soils must be treated prior to construction operations, so that desired properties can be achieved. In such problematic clays, chemical stabilization techniques have proven to be effective [2].The chemical stabilization of clays using cement is a common method that can be used to improve properties of soil to provide a workable platform for construction projects [3]. Cement is often used as an additive to improve the strength and stiffness of soft clayey soils, as stated by many authors [4]. They indicate that mixing cement into the soil leads to formation of a new structure within the soil grain accumulation. Traditionally, Portland cement and hydrated lime are commonly used for the soil stabilization. However, industrial by-products, construction and demolition waste and other waste materials ordinarily considered as environmental problems, are gradually finding applications in soil stabilization. Periwinkle and oyster shells have been used in concrete and other areas of civil engineering; but no technical information on the assessment of the utilization of crushed waste periwinkle shells for geotechnical engineering applications [5]. In this paper, further discusses the development of engineering behavior of cement-dust shell- treated kaolin clay and to identify its potential in geotechnical engineering applications. This paper therefore describes the initial laboratory tests of a planned extensive testing programmed to assess the effectiveness of the dust shells as an alternative stabilizer. 2. MATERIALS AND METHODOLOGY In order to investigate the effect of dust shell on the physical and engineering properties, the treated and untreated kaolin were subjected to laboratory tests. These include Atterberg limits test, compaction test and unconfined compressive strength test (UCS). The soil tested in this study is kaolin clay. It was mixed with 5 and 10% of cement, 3, 5 and 10% of dust shell and the combination of 5% cement with 3, 5 and 10% of dust shell. Table-1 summarizes basic properties of untreated kaolin. There are two major chemical reactions which are induced by the addition of cement to clay and govern the soil cement stabilization process: the primary hydration reaction of the cement and water, and the secondary pozzolanic reactions between the limes released by the cement and the clay minerals [8]. The XRF analysis was conducted with the Bruker AXS machine running on the SPECTRA Plus analysis programme. The test was conducted to determine the chemical composition of the raw materials, i.e. cement and dust shell. Chemical compositions of the respective raw materials are given in Table 2. From the composition, it can be seen that Dust Shell contains high percentage of CaO (lime) up to 66.99, hence it shows that dust shell have a potential as an alternative to replace cement in pozzolanic reaction.