Journal of Environment and Earth Science www.iiste.org ISSN 2224-3216 (Paper) ISSN 2225-0948 (Online) Vol.5, No.4, 2015 53 Hydraulic Conductivity of Compacted Lateritic Soil Partially Replaced with Metakaolin S. Y. Umar 1 * A. U. Elinwa 1 D. S. Matawal 2 1. Department of Civil Engineering, Abubakar Tafawa Balewa University, P. M. B. 0248, Bauchi, Nigeria 2. Nigerian Building and Road Research Institute, Abuja, Nigeria * E-mail of the corresponding author: umarsyusuf@yahoo.com Abstract The study investigates the potentials of using metakaolin (MK) to improve the properties of compacted lateritic soil for hydraulic barrier system for containment of municipal solid waste (MSW). Oxide compositions determined by the X-ray fluorescence (XRF) show that MK contains Silicon oxide, SiO 2 (53.4 %), Aluminium oxide Al 2 O 3 (34.2 %), Titanium oxide, TiO 2 (5.97 %) and Iron oxide, Fe 2 O 3 (3.84 %) in high proportion. The soil was replaced with 0 %, 5 %, 10 %, 15 % and 20 % MK and compacted using four compaction energy levels namely: the Reduced British Standard Light (RBSL), British Standard Light (BSL), West African Standard (WAS) or “Intermediate” and British Standard Heavy (BSH) over a range of molding water contents (10 - 25 %). Unconfined compressive strength (UCS) and hydraulic conductivity tests were conducted and the results obtained were used to evaluate whether the lateritic soil partially replaced with MK conforms with the specifications for barrier systems for MSW containment. The results of this study show a general improvement in UCS of the soil specimens with increase in the percentage replacement of MK. Results of the study also show that hydraulic conductivity values of the specimens permeated with leachate are better than the results of hydraulic conductivities obtained when de-ionized water (DIW) was used as the permeant fluid. The specimens replaced with 5-20 % MK and compacted using the BSH compaction energy yielded hydraulic conductivities on the orders of 6.3 x 10 -10 m/s to 2.2 x 10 -10 m/s when DIW was used as the permeant fluid. On the other hand, the specimens compacted using the WAS and BSH compaction energies and permeated with leachate yielded hydraulic conductivity values in ranging from 6.8 x 10 -10 m/s to 3.6 x 10 -11 m/s. These hydraulic conductivity values met the regulatory maximum hydraulic conductivity (i.e. ˂ 1 x 10 -9 m/s) for construction of liner and cover systems for MSW containment. Keywords: Compaction energy, Metakaolin, Hydraulic conductivity, Unconfined compressive strength, Municipal solid waste leachate, De-ionized water 1. Introduction In Nigeria, solid waste management is characterized by insufficient collection methods, insufficient coverage of collection systems and improper disposal (Ogwueleka 2009). Waste management has been one of the greatest challenges facing the Federal, State and Local governments in Nigeria. Municipal solid waste (MSW) containment is one of the most troublesome and most urgent problems facing the industrial community. According to (EPA 1988) contamination of groundwater by MSW leachate renders the groundwater and the area of contamination of aquifer unusable to domestic purposes. Hydraulic conductivity tests are often conducted on the soil barrier material intended for containment of MSW using the actual liquid to be contained or a liquid with representative properties (Lee et al. 2005). The hydraulic conductivity determines the ability of MSW leachate to flow through compacted soil matrix system under hydraulic gradient. Borgadi et al. (1993) stated that hydraulic conductivity is considered as the basic parameter of the design of hydraulic barrier systems and for characterizing liner performance and reliability. Results of laboratory hydraulic conductivity tests on compacted specimens are often used to determine compaction criterion for each soil. Such a compaction criterion can, in turn, be used as a guide for suitable construction of soil liners and covers in the field (Nwaiwu et al. 2005). The primary function of a clay liner is to prevent the release of contaminants from the landfill into underlying aquifer, hence the hydraulic conductivity of clay liner should be low to prevent advective transport (Cho et al. 2002). The engineering specifications for a compacted clay liner usually consist of a hydraulic conductivity of ˂ 1 x10 -9 m/s (Daniel 1990; Benson et al. 1994a; Mollins et al. 1996; Umar et al. 2015). According to Benson and Trast (1995), most regulatory agencies in the United States require that the hydraulic conductivity of clay liners be ≤ 1 x 10 -9 m/s. Compacted soil liners are frequently used in conjunction with geomembranes to form a composite liner, which usually consists of a geomembrane placed directly on the surface of a compacted soil liner. Shackelford et al. (2000) evaluated the hydraulic conductivity of geosynthetic clay liners (GCLs) permeated with non-standard liquids. They found that the hydraulic performance of GCLs that do not contain geomembrane depends on the hydraulic conductivity of the bentonite. Daniel (1993) showed that bentonite clay materials are the preferred hydraulic barriers because of their low hydraulic conductivity and good adsorption or retention capacity. Shackelford et al. (2000) indicate that the characteristically low hydraulic conductivities of (˂ 10 -8 cm/s) often reported for bentonites are primarily due to restriction of the pore spaces