This research describes the work undertaken to enhance the geotechnical and physicochemical properties of cement-lime-treated lateritic soils using Metakaolin (MK), within the context of both soil mechanics and earthen construction materials, and with specific reference to stabilized earthen unfired construction, i.e.laterised mortar and pastes.It sets out by critically reviewing and discussing each of the key types of stabilizers applied herein viz. Cement, lime and metakaolin (MK). While exploring the pros and cons associated with the application of these binders and possible recommended remedies. Further, the justification for the inclusion of metakaolin is provided.
　　Lime treated lateritic soils are among the commonly applied construction materials in tropical and subtropical regions where they are widely distributed, due to the humid climate. However, the long-term performance of this material has been greatly influenced by the changes in the geo-environment, for instance, under the action of contaminants lime-treated laterite may not perform as well as it would have in their absence. To characterize the behavior and response of these materials in changing environments, determining the degree of acidity or alkalinity i.e. pH has been adopted by most scholars, and it has been shown that pH has a profound effect on the solubility of soil mineral constituents and strength.To investigate these issues experimental setups were established to monitor the effect of aggregate size,the addition of Meta-Kaolin (MK) and exposure to sulphuric acid on pH, Electrical conductivity (EC) and cations depletion of lime treated laterite.The results show that MK lowers the pH slightly in the short term and tends to maintain a very narrow range in the long term. Moreover, this property significantly influences the erosional and permeability properties. It was also observed that for the same percentage of lime a sample with 5mm maximum aggregate had a pH slightly higher than the one with 0.5mm maximum aggregate size sample. Further, a decrease in the amount of Ca2+concentrationinevitably translates into a decrease in pH values and EC for a lime-laterite mixture.
　　Further, this work also aimed at assessing the durability of lateritic mortars through treatment with pozzolans such as Meta-Kaolin(MK), lime, and cement, which exhibit good strength and resistance properties, partially or collectively. Moreover, Lime-Metakaolin admixtures have been applied in the past as mortars, plasters, and sealers and studies indicate that they exhibit good strength and resistance properties. Laterised mortars and pastes like most earthen materials are held as economical options for low-cost housing and historical architecture. However, the durability of lateritic mortars and pastes has been of great concern to the scholars, besides, there is a need to exploit the full potential of laterite as a low-cost building material in earthen structures. To this end, experimental setups were established which involved investigating the effect of Meta-kaolin, cement,and sand on Lime-treated Laterite, the unconfined compressive strength (UCS), the effect of drying and wetting cycles, the influence of water content and frost resistance, the water adsorption capacity. The results show that the amount of water present in a mortar significantly affects the strength and consequently the long-term water retention behavior, in addition, lateritic mortars showed excellent sorptivity. Moreover, the mortar exhibited good resistance to drying and wetting cycles, especially when sand was added to the mortar. Further, the mortar showed reasonable frost resistance under repeated freeze and thaw cycles, especially for an earthen mortar.