Papers by Author: Adrian O. Eberemu

Abstract: Increase in the rate of generation of household waste (i.e Municipal Solid waste, MSW) in Nigeria necessitated the growing demand for a safe way to dispose MSW. When MSW comes in contact with water, it generates leachates, a poisonous fluid, that are harmful to humans. The use of landfill system for disposal of MSW has been a good approach for waste disposal. This study evaluated the effect of some hydraulic conductivity (H) parameters (i.e void ratio, degree of saturation and microbial suspension) and permeating fluids on the interaction of lateritic soil subjected to varying steps of treatments with Bacillus coagulans (B. coagulans) and subject to leachate environment for landfill application. Soil was mixed with 0 to 2.4 × 10⁹ cells/ml of B. coagulans. After mixing and compaction, Calcium solution was introduced by gravity on the compacted soil samples and were permeated to percolate to a point of partial saturation. After application of Calcium solution, compacted samples were saturated in water for 24 to 48 hours up until fully saturated, thereafter subjected to H test using water as well as leachate as permeating fluids for a period of 91 days. Results show that void ratio values varied in the ranges 0.550-0.471 and 0.481- 0.485 for specimens where water and leachate were used as permeation fluids. Degree of saturation varied meaningfully with permeation fluids. H values varied in the ranges 1.51 x 10^-9 -1.71 x 10^-9 m/s and 6.84 x 10^-10 - 8.27 x 10^-10 m/s for specimens where water and leachates were used as permeation fluids. Soil-leachate interaction study and micro structural investigations revealed that the modified soil is well-matched with leachate and met the regulatory H value of 1.0 × 10^-9 m/s for used in landfill applications.

Abstract: Lateritic soil treated with up to 20% glass cullet content was subjected to grain-size distribution, consistency tests, specific gravity tests, compaction using standard proctor, California Bearing Ratio (CBR), unconfined compression test, direct shear test and permeability tests. The study showed increase in grain sizes resulting in coarser soil, changes in moisture-density relationship, resulting in lower Optimum Moisture Content (OMC) and higher Maximum Dry Density (MDD), an increase in CBR, an increase in unconfined compressive strength (UCS); changes in cohesion-frictional angle relationship resulting in lower cohesion (c) and higher angle of internal friction (Φ) and an increase in co-efficient of permeability, k, with increased glass cullet treatment. These results show an improvement in geotechnical properties, making glass cullet-lateritic soil blend; a potentially good highway material and suggesting the suitability of the blend for embankments, structural and non-structural fill and retaining wall backfill.

Abstract: Large quantities of groundnut shell ash (GSA) are generated from the combustion of groundnut shell, disposed in large quantities on production sites while large volume of reclaimed asphalt pavements (RAP) aggregates are also generated during pavement rehabilitation and reconstruction and disposed along road alignments. This paper presents results of the laboratory evaluation of the effect of compactive efforts on the strength properties of GSA stabilized RAP with a view to determining its suitability as highway pavement material in pavement constructions. The RAP-GSA mixtures were subjected to Reduced British Standard light, RBSL (reduced Proctor); British Standard light, BSL (standard Proctor); West African Standard, WAS and British Standard heavy, BSH (modified Proctor) compactive efforts to determine the compaction characteristics, California bearing ratio (CBR), durability and water absorption characteristics. Test results show that the properties of RAP improved with GSA treatment. The particle grading improved from 99.13 % coarse aggregate and 0.87 % fines, with AASHTO classification of A-1-b for 100 % RAP, and 9.08 % coarse aggregate and 90.92 % fines, with AASHTO classification of A-4 for 100 % GSA to 15.6691.72 % coarse aggregate and 8.2884.32 % fines, with AASHTO classification in the range A-4 (silty soil) to A-1-a (granular materials), for the various RAP-GSA mixes. Maximum dry density (MDD) decreased while the optimum moisture content (OMC) increased with higher GSA content in the RAP + GSA mixes and with decreased compactive effort from BSH to RBSL. Optimum CBR values of 35.1% (unsoaked) and 44.1% (soaked) recorded for 90% RAP + 10% GSA mix achieved with BSH compactive effort, satisfied the durability requirements with insignificant expansion and water absorption and can be used as subbase material in flexible pavements construction. This research provides the results of evaluation of the effect of compactive efforts on the strength properties of GSA stabilized RAP as highway construction material, as it is based on CBR determination. Further work may be encouraged to assess resilient modulus of this material under cyclic load.

Abstract: Desiccation studies are an integral part of material selection for waste containment systems. Laboratory studies on compacted tropical clay (with illite as the dominant clay mineral sourced from an excavation site) treated with up to 16% rice husk ash (RHA); an agro-industrial waste to evaluate its desiccation induced shrinkage and hence its suitability as a cover material in waste containment systems were carried out. Soil-RHA mixtures were compacted using three compactive efforts at -2, 0, 2 and 4% of optimum moisture content (OMC). Compacted samples, extruded from the compaction mould were allowed to air dry in the laboratory for a 30 day period after which they were subjected to two cycles of wetting and drying. Results show that changes in mass and volumetric shrinkage strain (VSS) were large within the first five days of drying and were affected by the compactive effort. VSS increased with higher moulding water content, water content relative to optimum and RHA treatments. VSS were affected by the compactive effort. Acceptable compaction planes were obtained for up to 12% RHA treatment. After two cycles of wetting and drying, it was observed that the rate of capillary rise within the compacted soil increased with lower compactive effort and higher rice husk ash treatment. Lower amount of cracking was observed in soil specimen with higher rice husk ash treatment and higher cracking in soils with lower rice husk ash content. Increased compactive effort reduced the effect of swelling during wetting; showing the suitability of the material as a cover in municipal waste containment facility and beneficial reuse of this agro waste product.

Abstract: Laboratory study on compacted tropical clay treated with up to 16% rice husk ash (RHA), an agro-industrial waste; to evaluate its hydraulic properties and hence its suitability in waste containment systems was carried out. Soil-RHA mixtures were compacted using standard Proctor, West African Standard and modified Proctor efforts at-2, 0, 2 and 4% of optimum moisture content (OMC). Compacted samples were permeated and the hydraulic behaviour of the material was examined considering the effects of moulding water content, water content relative to optimum, dry density and RHA contents. Results showed decreasing hydraulic conductivity with increasing moulding water content and compactive efforts; it also varied greatly between the dry and wet side of optimum decreasing towards the wet side. Hydraulic conductivity generally decreased with increased dry density for all effort. Hydraulic conductivity increased with rice husk ash treatment at the OMC; but were within recommended values of 1 x 10^-7 cm/s for up to 8% rice husk ash treatment irrespective of the compactive effort used. This shows the suitability of the material as a hydraulic barrier in waste containment systems for up to 8% rice husk ash treatment and beneficial reuse of this agro-industrial waste product.

Abstract: Accidental or deliberate operational discharges of organic chemicals or wastes containing organic chemicals induce geochemical reactions with resultant adverse effects on basic geotechnical properties of the soil. To utilize soil materials from such sites for engineering construction or as foundation soil, stabilization must be carried out. In this study, cement kiln dust (CKD) was applied to lateritic soil contaminated with three different types of commonly occurring organic chemicals namely benzene, ethanol and kerosene to evaluate the restoration and improvements in the engineering properties. Contamination was simulated in the laboratory by adding known quantities (2.5, 5, 7.5 and 10%) of each of the chemicals separately to lateritic soil samples and allowed to air dry for 14 days before stabilizing with 10% CKD. Performance was evaluated on Atterberg limits, compaction characteristics, strength properties and hydraulic conductivity of the contaminated soil. Strength and hydraulic conductivity specimens were compacted with British Standard Light (BSL) compactive effort at predetermined optimum moisture content. Results showed that the simultaneous effects of the cementing and pozzolanic action of the CKD rejuvenated the geotechnical properties of the soil, in most cases comparable to the properties at the original pristine condition. Studies on durability and long term competent performance of the stabilized contaminated soil specimens is in progress.

Abstract: This paper presents the results of the laboratory evaluation of the characteristics of lateritic soil stabilized reclaimed asphalt pavements (RAP), using 0 – 2% cement, subjected to British Standard Light (BSL) compactive effort to determine their index, compaction and california bearing ratio (CBR) results. The result of the laboratory tests show that the properties of RAP improved when stabilized with lateritic soil, using up to 2% cement. The particle size distribution improved from poorly graded sandy GRAVELLY material for 100% lateritic soil and very sandy GRAVELLY material, to the gradation described as well graded very sandy GRAVELLY material for lateritic soil stabilized RAP, using up to 2% cement. The CBR results obtained from the study show that using the Nigerian General Specifications, 180% CBR value criterion, the maximum CBR of 55% (soaked) for the mix proportion; 40% Laterite + 58% RAP + 2% Cement for A-2-7(2) soil prescribed by the latter is not adequate for stabilization of base coarse. However, judging by the 24-hour strength gain from 17.9 (unsoaked) to 55% (soaked) CBR values, the material can be used as subgrade and subbase materials.