Effect of Coarse Aggregate Sizes and Replacement Levels on the Strength of Palm Kernel Shell (PKS) Concrete

The maximum coarse aggregate size used in concrete can impact on its strength. An investigation of the effect of coarse aggregate size and replacement level of granite with palm kernel shell (PKS) on the compressive and tensile strengths of PKS concrete were investigated. Mix proportion by weight of 1:1½:2 with w/c of 0.50 were used. All samples were tested at 7 and up to 90 days. Results showed that both compressive and splitting tensile strengths increased with increase in aggregate sizes. Both strengths however decreased with increase in replacement levels of granite with PKS. Optimum replacement level of granite with PKS was 25% with compressive and tensile strengths of 22.97 N/mm2 and 1.89 N/mm2 respectively at maximum coarse aggregate size of 20 mm. However, at 50% PKS content, which results in lightweight concrete, compressive strength was 18.13 N/mm2 which is above the minimum value of 17 MPa for lightweight concrete

Influence of Curing Age and Mix Composition on Compressive Strength of Volcanic Ash Blended Cement Laterized Concrete

This study investigates the influence of curing age and mix proportions on the compressive strength of volcanic ash (VA) blended cement laterized concrete. A total of 288 cubes of 100mm dimensions were cast and cured in water for 3, 7, 28, 56, 90 and 120 days of hydration with cement replacement by VA and sand replacement by laterite both ranging from 0 to 30% respectively while a control mix of 28-day target strength of 25N/mm2 (using British Method) was adopted. The results show that the compressive strength of the VA-blended cement laterized concrete increased with the increase in curing age but decreased as the VA and laterite (LAT) contents increased. The optimum replacement level was 20%LAT/20%VA. At this level the compressive strength increased with curing age at a decreasing rate beyond 28 days. The target compressive strength of 25N/mm2 was achieved for this mixture at 90 days of curing. VA content and curing age was noted to have significant effect (α 0.5) on the compressive strength of the VA-blended cement laterized concrete

Exchange Rate Volatility and Sectoral Export of Nigeria: Case of Oil and Non-Oil Sectors

The study explored the effects of exchange rate volatility on the exports performance of both oil and non-oil sectors. The paper employed the econometrics method of GARCH in measuring volatility of exchange rate and seemingly unrelated regression method (SUR) in estimating the coefficient of the two system equation. ARCH and GARCH results suggested that the exchange rate is volatile , while SUR model shows that exchange rate has negative effect on the two sectors , though statistically not significant. Therefore, for the country export to improve, the country should adopt inward looking policy in order to enhance her capability to export and reduce the vulnerability of the country to the external shocks. This research will go a long way in addressing the behavior of Nigeria export in a correlated innovation and shocks system that goes along with international trade flow

Integrating Resistivity Techniques for Optimum Groundwater Exploration and Development within a Hotel Facility in Osogbo, Southwestern Nigeria

This work is an attempt to combine dipole-dipole profiling and vertical electrical sounding techniques of electrical resistivity methods to investigate the groundwater potential within the premises of a 3-star hotel facility in Osogbo, Nigeria by delineating the geoelectric layers, delineating the low resistivity layers, determining the lithologies and hence, delineating the groundwater bearing zones. The five vertical electrical sounding data were collected along two pre-surveyed dipole-dipole traverses at right angle to each other beside the fences of the premises using the ABEM SAS 300c terrameter. The observed data were interpreted quantitatively using curve matching and computer-assisted iteration method using the WinResist and Dipro software. The results of the inversion show that the lithology comprises of the top soil and an intermittent sequence of sand and lateritic clay having varying resistivity and thickness. The aquiferous layer was observed to be located at a depth of 23 m to 25 m due to the low resistivity and high thickness of the aquiferous layer. The result of the 2-D imaging closely correlates with the result of the vertical electrical sounding. Thus, combining these techniques in groundwater investigation has achieved similar result as the Werner technique and has reduced ambiguity and error in positioning for drilling. Keywords: Resistivity, Groundwater Exploration, Dipole-Dipol

Assessing the Mechanical Performance of Ternary Blended Cement Concrete Incorporating Periwinkle Shell and Bamboo Leaf Ashes

The study investigates the mechanical properties of concrete incorporating Periwinkle Shell Ash (PSA) and Bamboo Leaf Ash (BLA) as cementitious binders. Concrete cube (100mm) prepared from a standardized prescribed mix of 1:2:4, batch by volume was taken as the reference mix. The cement component in the reference mix was replaced with combined % weight of periwinkle shell ash (10-30%) and bamboo leaf ash (10% fixed) given five blended mixes. Water-cement ratio of 0.60 was adopted for the reference and blended mixes. A total of 144 cube specimens were evaluated for compressive and tensile splitting strength at four curing ages up to 56 days. The results indicated that the compressive strength generally increases with curing age, and that the mix containing 80% cement-10%PSA-10%BLA, outperformed that of the reference mix at 28 and 56 days. The tensile splitting strength increase with curing age and decreases as the % weight of PSA increases from 15% to 30%. A higher tensile splitting strength value was attained with mix 2 than the reference mix at 14, 28 and 56 days.  The regression equation for the strengths relationship was obtained as FSP = 0.141 (Fcu) 0.873. The study concluded that mix 2 proportion is adequate for the production of ordinary structural mix concrete. Keywords: periwinkle shell ash, bamboo leaf ash, blended cement concrete, compressive strength, tensile Splitting strengt