EVALUATION OF STRENGTH PROPERTIES OF NON-LATERITIC SOILS ENHANCED WITH ACTIVATED METAKAOLIN FOR ROAD CONSTRUCTION

Non-lateritic soils (NLS) are not normally suitable for use as road construction materials due to difficulties that arise during construction. As such, treatment serves as a solution for improving the adverse effects. This study explores the potential of alkali-activated metakaolin (MK) for strength improvement of NLS intended for use as road construction materials. Based on design of experiment using design expert 13 software, the soil is treated to evaluate the effectiveness of varying blends of 5, 17.5 & 30 % of MK to dry weight of soil and 1, 5.5 & 10 molar concentrations of NaOH and compacted using three compactive effort; British standard light, West African standard and British standard heavy. Unconfined compressive strength (UCS) and California bearing ratio (CBR) tests were conducted. Scanning electron microscopy (SEM) analyses were also performed on the best blends. Results show that some activated MK/NLS blends met the 1500-3000 kN/m 2 7 days UCS criterion stipulated by the Nigerian General Specification (NGS) 2013 for road base. Similarly, all the activated MK/NLS blends suffice for use as sub-base in road construction having met the 750-1500 kN/m 2 7 days UCS requirement. A strength of 30 or 80 % soaked CBR is recommended by NGS 2013 for sub-base or base course, in this regard, all blends met the minimum strength criteria of either sub-base or base course material. SEM results showed an enhanced aggregation and modification in the fabric orientation of the soil particles which is believed to produce a higher strength soil structure as evident from the UCS & CBR tests results.