Assessment of Lateritic Soil Stabilized using Metakaolin

Abstract

Laterite is the predominant type of soil encountered, in Nigeria during the foundation of any civil engineering construction. Since the foundation of all civil engineering structure rest on the soil, it is important to assess the geotechnical properties of the soil and their suitability for civil engineering construction process. This study, made an attempt to assess the geotechnical properties of lateritic soil treated with metakaolin and also determine the peak (optimum) quantity of metakaolin (MK) that could be used as road construction material as such reduce the high cost and emission of greenhouse gas during production of industrialized manufactured soil stabilizers such as cement, lime and bitumen. All test analysis carried out were conducted in compliance with the British standard. The engineering tests conducted on and stabilized soil samples include: Chemical composition on Metakaolin using XRF, Mineralogical composition on the natural soil using XRD, wet Sieve Analysis (hydrometer test), consistency Limit, moisture-density relationship Test, California Bearing Ratio test (CBR), Specific Gravity, Unconfined compressive Test (UCS) and Durability assessment test. Metakaolin (MK) obtained after calcination of kaolin in a furnace (muffler furnace) at a temperature of about 7500C was added in steeped concentrations of 2, 4, 6, 8 and 10%, by dry weight of soil for Atterberg limit test, compaction test, California bearing ratio test (CBR), Unconfined compressive strength test (UCS) and Durability assessment test. Compaction effort was achieved using British Standard Light (BSL) and British Standard Heavy (BSH). The chemical analysis test (oxide composition) provided on metakaolin shows the major oxide present in the it are silicon oxide, Aluminium oxide and iron oxide as such classified as a good pozzolanic material (class F). From the mineralogical analysis test (X-ray diffraction) the predominant mineral found in the soil are quartz and feldspar, making the soil to be a coarse grain material Result of wet sieve analysis (hydrometer test) and consistency limit test were used to classify the soil. The natural soil sample was classified as A-4(3) according to AASHTO soil classification system and (SM) in the unified soil classification system. The natural soil type is silty sand with Liquid Limit of 38.3% and Plastic Limit of 25.9% and Plasticity Index of 12.4%. From the compaction test conducted it was observe that upon addition of metakaolin content to the soil at different percentages, increases the maximum dry density (MDD) and decreases the optimum dry density (OMC) up to 6% metakaolin content. The result of UCS test revealed that specimen cured for 3, 7, 14 and 28 days shows a gain in strength from a natural soil value of 49, 400, 468 and 745kN/m2 to a peak value of 136, 951, 1155 and 1350kN/m2at 6% MK content and 61, 478, 551 and 871kN/m2 to a peak value of 174, 1350, 1588 and 1881kN/m2 at 6% MK content when compacted using BSL and BSH energy level respectively. The U-unsoaked CBR values increases from a natural soil values of 32% and 42% to a peak values of 68% and 76% at 6% metakaolin content, when compacted using BSL and BSH energies respectively. While the soaked CBR values also increases from a natural soil values of 11% and 15% tom a peak values of 32% and 40% at 6% metakaolin content, when compacted using BSL and BSH energies respectively. The durability assessment test result shows that the loss in strength values increases with increase in soaking period. Based on the strength test results obtained a peak (optimum) of 6% MK content could be used to achieved a desired sub-base material for light traffic roads.