Investigation of the Geotechnical Engineering Properties of Laterite as a Subgrade and Base Material for Road Constructions in Nigeria

This project is an in-depth investigation of the geotechnical engineering properties of subgrade and base soils used in the construction of Omolayo Road in Akobo Area of Lagelu local government, Oyo State, Nigeria. Subgrade samples were collected at chainages 0+000, 1+000, 2+000, 3+000 and 4+000 respectively at depths ranging 0.5m to 1.0m, while the base sample was collected from one of the heaps of laterite brought from the borrow-pit at Oluwo area along New Ife Express Road, Oyo State, Nigeria. The samples were subjected to the following laboratory tests; Particle (grain) size analysis, Atterberg limit test, Compaction test, California bearing ratio (CBR) test and Specific gravity test. The particle size analysis results showed that all samples, both subgrade and base were well graded since their Uniformity Coefficients were greater than 15. It further revealed that base sample were more plastic compared to subgrade samples since it has highest percentage of clay passing sieve no. 200 (75µm) i.e. 27.60%. This indicates that samples with high silt clay content are susceptible to volume changes when wet. The liquid limit and plastic index range from 24% to 48% and 2.7% to 25% respectively with base sample having the highest in both cases. This shows that base sample has high clay content and its load bearing capacity could be reduced when wet. The maximum dry densities ranged from 1.90mg/m3 to 2.19mg/m3 and Optimum moisture contents range from 5.4% to 14.2% respectively. The California bearing ratio is from 78% to 132% (unsoaked). The Specific gravity results ranged from 2.65 to 2.68. The samples were classified using AASHTO classification. The AASHTO system classified the subgrade samples as A-1-b and A-2-4 constituting 50% and 33.3% respectively, and base sample classified as A-2-7 constituting 16.6%. This shows the subgrade samples are excellent to good while base sample is fair to poor. Keywords: Laterite, subgrade, base, particle size analysis, atterberg limit, compaction test, California bearing ratio, Specific gravit

Investigation of the Properties of “Pure Water” Sachet Modified Bitumen

The increasing volume of traffic loads on our roads is currently a challenge on flexible pavement design and construction.  Factors such as durability, strength and economic needs have to be considered in the design and construction of road pavement.  Many researches have been conducted to explore supplementary material that can make a durable asphalt pavement. It is not unfamiliar that the modification of bitumen with the use of polymers enhances its performance characteristics but at the same time significantly alters its rheological properties. One of the environmental issues in most regions of Nigeria is the large number of polymeric wastes made from polyethylene water sachet (PWS) popularly called “Pure Water” Nylon deposited in domestic wastes and landfills. This study was conducted to investigate the effect of PWS on the properties of conventional bitumen and suitability of discarded PWS as bitumen modifier and to reduce the environmental effects of PWS disposal.  Bituminous blends containing PWS at various percentages 2.5%, 5%, 7.5%, 10%, 12.5% and 15% weight of conventional bitumen. Penetration, softening point and float tests were carried out on the samples to evaluate the penetration index, viscosity, stiffness modulus and the suitability of PWS as bitumen modifier. Sieve analysis and infrared spectroscopy of the shredded PWS sample were also carried out. Result obtained from tests was compared between control sample (0% PWS) and PWS modified samples. The test results show that PWSs influence more on the penetration of the modified sample with the increase in the viscosity of the bitumen as can be observed by the decrease in the value of penetration with the increase in concentration of PWS. The penetration index values of Samples 2.5% PWS and 7.5% PWS makes them to be classified as blown bitumen and the PI value of Sample 5% PWS makes it less susceptible to temperature changes and can be classified as oxidized bitumen. PWS is a cheap and readily available material in construction when used appropriately in bitumen and the recycling of PWS for asphalt base roads helps alleviate an environmental problem and saves energy. Keywords: Bitumen, pure water sachet (PWS), infrared spectroscopy analysis, penetration test, softening point, viscosity tes

Influence of Human Activities on the Water Quality of Ogun River in Nigeria

The quality of Ogun River in south-west, Nigeria was investigated by a field survey; covering the dry season and rainy season. Water samples were collected from seven sites (including an Abattoir, a market, residential community and a brewery); analysis of the physico-chemical parameters using standard methods and their environmental effects on the river were investigated. Generally, the value/degree of dissolved oxygen, phosphate, BOD, COD, pH, temperature, hardness from the sites during the rainy and dry seasons were compared with the World Health Organization (WHO) standards for domestic and commercial water. The traces of some hazardous physical and chemical impurities in the river were above the acceptable limits; and thereby pose a health risk to several rural communities who rely heavily on the river primarily as their source of domestic water. The study revealed a need for continuous pollution monitoring and management program of surface water in Nigeria. Keywords: surface water, water quality, water pollution, field survey, physico-chemical analysi

Evaluation of splitting tensile and compressive strength relationship of self-compacting concrete

Research findings have reported a behavioural relationship between the splitting tensile strength and compressive strength of concretes. This work studied both the experimental and analytical relationships that exist between splitting tensile strength and compressive strength of both vibrated concrete (VC) and self compacting concrete (SCC) of similar grades. Both concrete types were designed to achieve target compressive strength of 20 N/mm2, 30 N/mm2 and 40 N/mm2 at 28 days. The compressive and splitting tensile properties were measured on cylindrical concrete specimens of 150 mm diameter × 300 mm length at 28-days using a compression testing machine. The analytical work tested seven different reported models relating the two measured parameters for VC on SCC, while the Welch 2 sample t-test statistical technique was adopted to check the normality and equality of variance of the results. Experimental findings revealed that the ratio of the splitting tensile to compressive strengths for VC and SCC decreases with increasing compressive strength, and the analytical study revealed that similar analytical model could be adopted for both concrete types as there is no statistically detectable difference between their results. Keywords: Vibrated concrete, Self-compacting concrete, Compressive strength, Splitting tensile strengt