Eco-friendly stabilization of highway lateritic soil with cow bone powder admixed lime and plastic granules reinforcement

Modernization, industrialization and rapid changes in the modern lifestyle have resulted in massive waste materials in the environment. Scientists are continuously evolving innovative ways for efficient reuse/recycling and the safe disposal of waste materials. This study explores potential waste materials reuse in additive stabilization of a fair to poor highway lateritic soil (clay with low plasticity/silty clay) as a sub-base material and the impact of such additives in reducing the lime content during soil stabilization treatment. Soil samples obtained from road construction burrow pit in Ado-Ekiti, south-west, Nigeria were classified as CL group (clay with low plasticity), according to the Unified Soil Classification System (USCS) and A-6 material (silty clay) which is fairly poor highway material. Hydrated lime, Cow bone and plastic wastes were also locally sourced. Geotechnical tests (Compaction, Unconfined Compressive Strength test, direct shear and consolidation test) were carried out on the control and stabilized samples according to BS 1990. The results of the Unconfined Compressive Strength tests revealed that the 90 % lateritic soil +10 % lime and a combination of 6 % lime +7 % cow bone powder +1 % plastic waste (6 % L +7 % CBP + 1.0 %PP) mixes produced the best result for the lime stabilized and waste-lime stabilized soil samples, respectively. The direct shear tests, indicated a reduction in the soil’s cohesion (c) from 38 kN/m2 to 28 kN/m2 and an improvement in the angle of internal friction () from 29º to 45º for the optimum waste-lime mix. 10 % lime (L10) sample recorded comparatively lower c and values of 33 kN/m2 and 41º, respectively. The mix (6 % L +7 % CBP + 1.0 % PP) had improved the unsoaked and soaked CBR of 61.7 % and 37.6 %, respectively compared to the lime stabilized soil which recorded lower values of 57.8 % and 31.3 %, respectively. The permeability of the soil was reduced from 3.22e-03 cm/s to 9.12e-04 cm/s on the application of 10 % lime however the waste-lime optimal mix produced a lower value of 5.26e-04 cm/s. The results of the consolidation tests also revealed that the 6 % L +7 % CBP +1.0 % PP sample had a lower coefficient of volume compressibility (Mv) of 1.065e-04 m2/kN than the untreated samples which is 1.365e-04 m2/kN implying the stabilized mix is less susceptible to compressibility than the untreated samples. The durability results revealed that the sample recorded a strength of 201.7 kPa after being subjected to 3 wet-dry (w-d) cycles for 6 % L +7 % CBP +1.0 % PP sample, while the 10 % lime stabilized soil was found to have a strength of 148.5 kPa strength. Based on the findings, it can be concluded that the 6 % L +7 % CBP +1.0 % PP mix performed better than the 10 % lime stabilized mix with the waste materials substituting for 4 % of the lime and producing better results in terms of suitability as a highway sub-base material