Olatokunbo M. Ofuyatan

ASSESSMENT OF DOSE INTAKE OF TOXIC ELEMENTS IN GROUNDWATER SAMPLES FROM ABUJA, NORTH CENTRAL NIGERIA

This study measured the concentrations of toxic carcinogenic and non-carcinogenic elements present nin groundwater using Inductively Coupled-Plasma Mass Spectrometry (ICP-MS). The concentration nvalues obtained were used to calculate the life average daily dose (LADD) exposure of the people nwhom rely on groundwater for consumption in Abuja, Nigeria. The highest LADD for the ncarcinogenic toxic element chromium (Cr) was 2.7 x 10-5 μg kg‒1 day‒1, whereas it was 3.3 x 10-4 μg nkg‒1 day‒1 for the non-carcinogenic toxic element lead (Pb), identified in water samples collected by nthe Water Board. These LADD magnitudes of 10-5 and 10-4 for both carcinogenic and noncarcinogenic ntoxic elements in groundwater are far below the International Reference Dose according nto the United States Environmental Protection Agency (USEPA) in 2008, which has a value of 10-1. nThe low magnitudes found in water samples may not pose significant health risks to the local npopulation. The relevant authorities should, therefore, continue to monitor the impact of human nactivities on metal pollution in this area and take effective measures to control contamination of the npublic water supply

LIFE AVERAGE DAILY DOSE OF RADIUM-226 ON SOME WATER SAMPLES COLLECTED AT GIRI AND KUJE AREA OF ABUJA, NORTH-CENTRAL NIGERIA

226Ra concentrations were studied to represent the radiological risk of groundwater of the Giri and Kuje nareas of Abuja, North-Central Nigeria. Two borehole water samples were collected from the Giri and nKuje areas of Abuja with a hand-dug well and Abuja Water Board as control. Inductively Coupled nPlasma Mass Spectrometry (ICP-MS) was used to measure the concentrations of radionuclide of 226Ra nexposed to the dwellers. The activity concentrations of 226R in groundwater supplies for drinking and ndomestic purposes ranges from 443

Engineering properties of concrete made from gravels obtained in Southwestern Nigeria

Abstract This study investigates the engineering properties of concrete produced from gravels and also verify the suitability of local gravel aggregates obtained from Southwestern Nigeria in place of crushed granite. Preliminary investigations were carried out in five selected states (Ogun, Oyo, Osun, Ondo and Ekiti) in Southwestern Nigeria to determine the registered gravel mining pits. Fifteen gravel mining pits based on age and scale of mining operations were selected for this study. Appropriate gravel constituents in concrete mix were determined using Gs factor. Concrete cubes 150 mm, 150 × 300 mm2 cylinder modes and 150 × 150 × 750 mm3 beams were cast with collected gravel. 1:2:4 mix ratio was employed. Sieves analysis, density, water absorption were carried out on aggregates, while compressive, flexural and split-tensile strengths of the concrete were determined for 28 days using ASTM and BS methods. High concrete strengths resulted from high FM, low AAV and average Gs of gravels. Gravel location with highest compressive, flexural and split-tensile strengths of concretes had 24.8, 3.5 and 2.8 N/mm2 satisfying the minimum requirement of BS 811:1997 while that with lowest strengths had 9.6, 2.2 and 1.7 N/mm2, respectively. Sources of gravel highly influence compressive, flexural and split-tensile strengths of the cubes and beams.

Strength and microstructure of eco-concrete produced using waste glass as partial and complete replacement for sand

Abstract The sustainable benefits of waste glass usage in concrete include the possibility of reducing solid waste and greenhouse gas emission and preservation of raw materials. This current study examines the effect of recycled waste glass as a partial and complete substitute for natural sand in producing eco-friendly concrete. The recycled waste glass was proportioned in levels of 25, 50, 75 and 100% by weight to substitute sand in the concrete using a mix ratio of 1:2:4 (cement:sand:gravel) at a W/C ratio of 0.5 targeting 20 MPa strength at 28 days. Tests, which include X-ray fluorescence (XRF), were conducted on the waste glass and cement materials; slump test was performed on the freshly prepare concrete at different percentage glass content. Compressive and tensile strength tests were performed on 60 specimens after 3, 7, 28 and 90 days of curing. The concrete microstructure was examined using the scanning electron microscope (SEM). Results showed that workability and the mechanical strength of the concrete produced decreased with increasing waste glass content. However, concrete containing 25% and 50% waste glass contents showed significant enhancement in strength, but it is recommended that the optimum glass content should be 25% for the production of sustainable eco-concrete.