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Clay soil obtained from the Gwagwalada area of Abuja in the Northern part of Nigeria was obtained and used for this study to determine the suitability of water pH on soil strength for waste containment facilities such as landfills and surface impoundments. Water pH influences the strength and durability of soils employed in these facilities and the potential for chemical reactions that can damage containment barriers. An unconfined compressive strength test was conducted using British Standard Light (BSL) and British Standard Heavy (BSH) compaction at varying water pH (i.e., Acidic, Neutral, and Alkaline water) to see the effect it can have on the life span of the clay as a liner material. High-quality liner materials must meet the minimum unconfined compressive strength requirement of 200 kN/m². According to the test outcomes, when the amount of lime in the soil increased, especially at 4% content, the maximum dry density (MDD) increased to 1.81, 1.78, and 1.71 Mg/m³, and the optimum moisture content (OMC) decreased to 15.0,14.0, 16.0% for BSL compaction similar trend to BSH. The MDD is 1.93,1.83, 1.90 Mg/m³, and OMC is 13.2, 14.0, and 12.4% for BSH compaction for acidic, alkaline, and neutral water, respectively. The unconfined compressive strength (UCS) decreases as moulding water increases. The UCS values meet the 200 kN/m² minimum requirement for soils compacted with acidic and neutral pH water for all compaction efforts. When treated with neutral water, the recommendation of 4% lime addition compacted at BSH for liner material construction at -2%, 0, +2% OMC. It is also recommended that alkaline water is unsuitable for constructing liners because it reduces the strength of treated soil. [ABSTRACT FROM AUTHOR]

Lateritic soil collected at Shika Zaria was stabilized with Cement (C) and sisal fibre (SF) to determine its effect on the unconfined compressive strength. The preliminary investigation conducted shows that it falls under A-7-6 (10) classification and CL. The soil was treated with cement-sisal fibre in concentrations of 0%, 2%, 4%, 6%, and 8% and 0%, 0.25%, 0.5%, 0.75% and 1% by dry weight of soil. The Sisal Fibre was treated with Sodium Borohydride (NaBH4) (1% wt/vol) for 60 minutes at room temperature to remove the cellulose content present in the Fibre. Compaction was carried out using Standard Proctor energy and the Maximum Dry Density (MDD) decreases from 1.85Mg/m³ for the natural soil to 1.6Mg/m³ at 4% cement/0.25% sisal fibre treatment. The Optimum Moisture Content (OMC) increases from 18% to 24.5% at 6% cement of 0.5% sisal fibre content. The Unconfined Compressive Strength (UCS) value increased from 186kN/m² for the natural lateritic soil to a peak value of 1942kN/m² at 4% cement /0.5% sisal fibre. This peak value is higher than the 1720kN/m² criterion for adequate cement stabilization of base courses. Analysis of variance was carried out using Microsoft Excel Analysis Tool Pak Software Package. Mini-tab R15 Software was used for regression analysis. Laboratory results were used to generate reliability indices using a FORTRAN based first order reliability program. The reliability analysis carried out indicates that the reliability indices were more pronounced for MDD and OMC which are also related to the UCS of the soil evaluated. Model 1 produced successful result in coefficient of variation (COV) range 1 - 50 % that can be used to predict field UCS of lateritic soil stabilized with Cement and sisal fibre for base and sub-base materials for pavement structures. [ABSTRACT FROM AUTHOR]

This research attempts to empirically investigate the behavior of Raffia Palm Ash (RPA) concrete under elevated temperature of different percentages of RPA inclusion in the concrete. Raffia palm ash was obtained after the calcination of the raffia palm for 3 hours at 5500C. X-ray Florescence (XRF) analysis performed revealed that the sample of Raffia Palm Ash (RPA) is a Class C pozzolana, which contains 51.8% of (SiO2 + Al2O3 + Fe2O3) and has a specific gravity of 2.8. The compressive strengths were determined at 0 0C, 718 0C and 821 0C at 0 minutes, 15 minutes and 30 minutes respectively. The result revealed that workability of the concrete declined with the increment in the percentage of raffia palm ash in the concrete. The compressive strength of the concrete cubes as well decreased with the rise in temperature for the entire samples tested. The average loss in strength of the control (0% RPA) is about 15.3% at 7180C and 25.3% at 8120C while for Raffia palm ash concrete with 5% (optimum replacement) gives a minimum loss in strength of about 21.3% at 7180C and 28.5% at 8120C, which is about 6% at 7180C and 13.2% at 8120C, more than the control. The Scanning Electronic Microscopy (SEM) imaging indicates that the concrete subjected to temperature of about 821oC produces fewer flakes when compared to the concrete subjected to temperature of about 7180C. [ABSTRACT FROM AUTHOR]

The Nigerian-grown African birch timber was used to assemble I- section specimens which were tested in the laboratory for their compressive strengths. Solid square sections of the same specie were similarly tested for an apt comparison of results. A structural reliability analysis was carried out for these two sections to ascertain their performance as structural timber columns using statistical parameters that were determined for the deterministic design of the timber column. A FORTRAN-based program was also developed and used for the reliability analysis of the Nigerian-grown African birch columns designed to ascertain their level of safety using First-Order Reliability Method (FORM). The 'I'- section was found unsafe to bear the design load unlike its corresponding solid section. An identified I- section of (100 x 400mm) was found adequate (with Pf =1.22 x 10-02) whose compressive resistance corresponds to (200 x 100mm) of the solid section (with Pf =7.76 x 10-02) which is practically half the dimension of the I-section. This shows that the solid section has a capacity twice that of the 'I'- section of equal dimensions. However, considering the minimum dimension of the of the two sections capable of supporting the design load, the 'I'- section is more economical than the solid section since it offers a less effective area of 11,200mm2 compared to the solid section with an effective area of 20,000mm2. The 'I'-section also showed a higher capacity to bear the Euler load with greater lengths than the solid section because of its greater radius of gyration and rigidity value and would be rather preferable for long columns than the solid section. Considering the limited availability of larger dimensions of solid sections, the built-up I- section would be more relevant where large sized sections are required. [ABSTRACT FROM AUTHOR]

This research examines the shear strength of Sisal Fibre Reinforced Concrete (SSFRC). Sisal Fibre (SSF) addition was at 1% by weight of dry constituents, this is considered the upper limit for workable mixes in the absence of water reducing agents. Beams of various grades of concrete (20N/mm² to 40N/mm²) were tested and they all failed in shear. Experimental results of beams were compared with modified versions of the BS 8110 formula for shear strength in concrete, to determine the best fit. The inclusion of SSF at 1% addition increased the compressive strength of the concrete mix by an average of 16.9% and the shear strength by 16%. However, the shear strengths of the SFRC are only greater than those of normal concrete of corresponding compressive strengths by 9.5%. The equation proposed may be used to estimate the shear strength of SSF reinforced concrete at this level of fibre addition. [ABSTRACT FROM AUTHOR]

Lateritic stones abound in the tropical and semi tropical areas of the world more than the igneous and other standard rocks that are used as concrete aggregates and road chippings. The increasing utilization of natural aggregate for concrete production have created negative impact on the environment. Therefore searching for alternative material which has potential to replace the use of coarse aggregate from normalrocks in concrete mix either wholly or partially is very much in need. This research presents the engineering properties of concrete containing lateritic aggregate as partial coarse aggregate replacement. The coarse aggregate was replaced by 10, 20, 30, 40 and 50% with lateritic aggregate. All the specimens were cured and compressive strength test were carried out at the age of 7, 14, 21 and 28 days respectively. The result revealed that replacement of lateritic aggregate up to 30% was able to produce lateritic concrete exhibiting the target strength which is 30 N/mm². However, the slump decreases as the percentage of lateritic aggregate in the mix increases, this may be due to the porosity of the lateritic aggregate due to absorption of the water in the mix. The result of the two way analysis of variance shows that both lateritic aggregate and curing age (days) has significant effects of the compressive strength of concrete. [ABSTRACT FROM AUTHOR]