Albert Adjaottor - Academia.edu (original) (raw)

Papers by Albert Adjaottor

KSCE Journal of Civil Engineering, 2011

The paper presents the experimental investigation conducted on Rice Husk Ash (RHA) concrete to ev... more The paper presents the experimental investigation conducted on Rice Husk Ash (RHA) concrete to evaluate the compressive strength and to study its durability properties. In the preparation of rice husk concrete, cement was replaced at various percentage levels such as 5%, 10%, 15% and 20%. Besides control concrete was also prepared for comparison purpose. Two grades of concrete, namely M30 and M60, were prepared. The strength of the concrete increased with the levels of percentage of replacement of 10% at which the increase in strength was 7.07% at 90 days compared to normal concrete. In the case of M60 grade concrete the compressive strength increases with the addition of super plasticizer. In general, Saturated Water Absorption (SWA) increased in the case of RHA Concrete up to 10% replacement level, but the same diminished with addition of super plasticizer. The porosity of RHA Concrete decreased from 4.70% to 3.45% when the replacement level increased from 5% to 20%. There is a further decrease with the addition of super plasticizer. The chloride ion permeability value of RHA Concrete was very low between 100-1000 coulomles, as compared to normal concrete. It was observed from tests that RHA concrete was more resistant to HCl solution than that of control concrete. The percentage of resistance against alkaline attack of M30 grade RHA concrete varied from 25 to 67 and the corresponding value for M60 grade was from 35 to 70 for replacement levels varying from 5% to 20%. Addition of 20% RHA showed higher resistance against sulphate attack for both continuous soaking and cyclic conditions. On the whole addition of RHA as CRM improves the strength and durability properties of concrete to considerable extent.

th day of germination with an estimated activity of 19.436 U/ml. The results also suggested that ... more th day of germination with an estimated activity of 19.436 U/ml. The results also suggested that the Wita 7 rice variety can be accredited for having good germination energy since nearly 100% of the rice seeds sprouted on the 4 th day of germination under the prevailing conditions. The malt yield was 57.14% with a corresponding malt loss of 42.86% on the 8 th day of germination.

Journal of Chemistry

The release of harmful particles from industries is one of the important sources of environmental... more The release of harmful particles from industries is one of the important sources of environmental pollution worldwide. The goal of this study was to determine the amounts of dust deposition and heavy metal pollution in the soils surrounding a cement mill in Konongo, Ghana. Topsoils (0-10 cm) were sampled at the four geographical axes of the factory within a radius of 400 m, while at the same time, about 500 g of cement was sampled with a hand trowel. A Frisbee dust sampler was used to examine the levels of dust depositions at the various geographical axes of the factory. The heavy metals such as cadmium (Cd), chromium (Cr), copper (Cu), zinc (Zn), and lead (Pb) were measured in a total of 20 soil samples using atomic absorption spectroscopy (AAS). The results obtained for climatic elements such as wind speed and direction, temperature, and relative humidity were 2.25, 25.7, and 49.5 m3/s, respectively. The average deposition of dust within the study period using the geographical axi...

Calcined clay pozzolan, the major mineral admixture used in Ghana to partially substitute ordinar... more Calcined clay pozzolan, the major mineral admixture used in Ghana to partially substitute ordinary Portland cement has gained massive recognition in the local construction industry because of its technical advantages and affordability. The most prominent undesirable property associated with the use of calcined clay pozzolans is slow setting and strength development, especially at early ages. This paper presents a study of the effect of Na2SO4 on the mechanical properties of high volume pozzolan cements. The cements containing 30 wt. %, 40 wt. %, 50 wt. % and 60 wt. % calcined clay pozzolan was activated with 1%, 2%, 3% and 4% Na2SO4. Some physical properties such as Blaine index, specific gravity, water demand and setting times were determined. The chemical compositions of the blended cements were also analyzed. The effect of Na2SO4 on compressive strength of blended cements was determined after 2, 7, 28 and 180 days. Durability studies on activated blended cements in aggressive med...

Thin Solid Films, 1999

The room temperature oxidation process of thin TiN x ®lms, grown by DC reactive magnetron sputter... more The room temperature oxidation process of thin TiN x ®lms, grown by DC reactive magnetron sputtering, was studied by in-situ and real time spectroscopic ellipsometry, X-ray re¯ectivity, Auger electron spectroscopy, X-ray photoelectron spectroscopy and stress measurements. The ®lms were deposited at various negative bias voltages (V b) in order to vary the TiN x stoichiometry and then exposed to several gases and to air at room temperature. The oxidation rate was found to depend strongly on V b and thus on ®lm stoichiometry. Fast oxidation was observed in ®lms deposited at low uV b u, that contain nitrogen which is weakly bonded to Ti and can be easily replaced by oxygen. At high uV b u values (above 2 80 V) stoichiometric TiN ®lms were developed, that were stable and not prone to oxidation. The results showed that oxidation takes place in the bulk of the ®lm and can proceed up to about 10% transformation of titanium nitride into titanium oxide. The fastest step in the ®lm oxidation mechanism is diffusion of oxygen along the columnar grain boundary structure, followed by the reaction of oxygen with the weakly bonded TiN. The results suggest that the oxidation process proceeds with different stages involving formation of TiON, followed by a slow stage of TiO 2 formation. These microstructural changes are consistent with the evolution of compressive stresses in the ®lms and the increase in ®lm density and thickness and the decrease in surface roughness as determined by X-ray re¯ectivity.

Journal of Cleaner Production

Journal of Civil Engineering and Architecture, Mar 28, 2011

The Egyptian Journal of Remote Sensing and Space Science, 2021

Abstract Estimation and mapping of surface water quality are vital for the planning and sustainab... more Abstract Estimation and mapping of surface water quality are vital for the planning and sustainable management of inland reservoirs. The study aimed at retrieving and mapping water quality parameters (WQPs) of Owabi Dam reservoir from Sentinel-2 (S2) and Landsat 8 (L8) satellite data, using random forests (RF), support vector machines (SVM) and multiple linear regression (MLR) models. Water samples from 45 systematic plots were analysed for pH, turbidity, alkalinity, total dissolved solids and dissolved oxygen. The performances of all three models were compared in terms of adjusted coefficient of determination (R2.adj), and the root mean square error (RMSE) using repeated k-fold cross-validation procedure. To determine the status of water quality, pixel-level predictions were used to compute model-assisted estimates of WQPs and compared with reference values from the World Health Organization. Generally, all three models produced more accurate results for S2 compared to L8. On average, the inter-sensor relative efficiency showed that S2 outperformed L8 by 67% in retrieving WQPs of the Owabi Dam reservoir. S2 gave the highest accuracy for RF (R2.adj = 95–99%, RMSE = 0.02–3.03) and least for MLR (R2.adj = 55–91%, RMSE = 0.03–3.14). Compared to RF, SVM showed similar results for S2 but with slightly higher RMSEs (0.03–3.99). The estimated pH (7.06), total dissolved solids (39.19 mg/L) and alkalinity (179.60 mg/L) were within acceptable limits, except for turbidity (33.49 mg/L) which exceeded the reference thresholds. The S2 and RF models are recommended for the monitoring of surface water quality of the Owabi Dam reservoir.

An article published by International Journal of Waste Management and Technology;Vol. 2, No. 1, J... more An article published by International Journal of Waste Management and Technology;Vol. 2, No. 1, January 2014,

An investigation of the plasma nitriding mechanism under intensified conditions (average particle... more An investigation of the plasma nitriding mechanism under intensified conditions (average particle energy up to 1200 eV) was carried out using a triode configuration. The significance of the different physical processes taking place during intensified plasma nitriding, such as sputtering, implantation, defect generation, redeposition and diffusion were investigated experimentally, while theoretical predictions were obtained by using the TRIM (transport of ions in matter) code. A titanium-base alloy was selected as the substrate material. Sputtering yield in an inert atmosphere was found to exhibit three regimes as a function of incoming particle energy. The low energy and high energy regimes were found to be in agreement with the theoretical predictions while the intermediate regime showed a reduced level of sputtering yield independent of energy. This was the first time that such reduced sputtering yield was observed and was attributed to the onset of other physical processes such a...

Journal of Environmental Protection, 2021

ACI Materials Journal, 2019

Volume 6A: Energy, 2014

Due to the ever-reducing conventional petroleum resources, considerable research on renewable ene... more Due to the ever-reducing conventional petroleum resources, considerable research on renewable energy sources such as biodiesel as a possible “greener” substitute fuel for internal combustion engines is needed. This study aims to compare the engine performance and emission results of various blends of pure diesel and a multi-feedstock (MFS) biodiesel when used in a naturally aspirated air-cooled, single-cylinder direct injection diesel engine. The engine was coupled to a dynamometer for torque measurement and output data transmitted to a PC for post-processing and displayed using customized programs in the computer. Engine combustion products — Nitrogen Oxide emissions (NOx), Hydrocarbons (HCs), Carbon monoxide (CO) and Carbon dioxide (CO2) — were measured and are presented alongside performance properties including brake-specific fuel consumption (BSFC), engine efficiency, torque and power. The experimental results show that, relative to diesel, biodiesel had approximately 3–24% dec...

MRS Proceedings, 1991

ABSTRACTWe describe a new laboratory-scale aerosol process for producing AIN powder. A two-stage ... more ABSTRACTWe describe a new laboratory-scale aerosol process for producing AIN powder. A two-stage reactor design is used. In the first stage, triethyl aluminum (TEA = AI(CC2H5 )3) and NH3 react to form an aerosol adduct in a laminar flow diffusive mixing zone. The aerosol then enters the furnace stage, where it is converted to AIN. We have examined the influence of the major operating variables (e.g., inlet TEA concentration, reactor residence time, and furnace temperature) on the particle size and distribution, yield, and efficiency. For example, increasing the TEA concentration from 0.12 to 1.30 µmol/cm3 causes an increase in the mean particle diameter (from 0.07 to 0.13 Pim), a slight increase in polydispersity (from 0.31 to 0.43), and a decrease in yield efficiency (from 90% to 73%). In contrast, decreasing the reactor residence time (by increasing the flow rate) has little effect on mean particle diameter, but causes a significant increase in yield efficiency (approaching 100%)....

Journal of Materials Science and Chemical Engineering, 2014

Calcined clay pozzolan has been used to replace varying portions of high alkali Portland limeston... more Calcined clay pozzolan has been used to replace varying portions of high alkali Portland limestone cement in order to study its effect on the alkali-silica reaction (ASR). Portland limestone cement used for the study had a total Na2Oeq of 4.32. Mortar-bar expansion decreased as pozzolan content in the cement increased. The highest expansion was recorded for reference bars with no pozzolan, reaching a maximum of 0.35% at 42 days whilst the expansion was reduced by between 42.5% and 107.8% at 14 days and between 9.4% and 16.4% at 84 days with increasing calcined clay pozzolan content. Mortar bars with 25% pozzolan were the least expansive recording expansion less than 0.1% at all test ages. X-ray diffractometry of the hydrated blended cement paste powders showed the formation of stable calcium silicates in increasing quantities whilst the presence of expansive alkali-silica gel, responsible for ASR expansion, decreased as pozzolan content increased. The study confirms that calcined clay pozzolan has an influence on ASR in mortar bars and causes a significant reduction in expansion at a replacement level of 25%.

Wiley Encyclopedia of Electrical and Electronics Engineering, 1999

Modern Methods and Advances in Structural Engineering and Construction(ISEC-6), 2011