The effect of South African quaternary supplementary cementitious blends on corrosion behaviour of concrete reinforcement in chloride and Sulphate media

The aim of this study was to assess the strength, durability properties and corrosion resistance of concrete samples using supplementary cementitious blended materials. In this investigation, three supplementary concrete materials (SCMs) were used together with ordinary Portland Cement (OPC) to form cementitious blends at different proportions. The supplementary materials are silica fume (SF), ground granulated blast furnace slag (GGBS) and fly ash (FA). Sixteen (16) different proportions of the cementitious blends were produced. Tests carried out on concrete samples include slump test, compressive strength, oxygen permeability, sorptivity, porosity, chloride conductivity test, resistance to chloride and sulphate attack. The electrode potentials of tested samples were also observed using electrochemical measurements. Concrete specimens prepared with 10%, 20%, 30%, 40%, up to 60% of blended cements replacement levels were evaluated for their compressive strength at, 7, 14, 28, 90 and 120 days while the specimens were evaluated for durability tests at 28, and 90 days respectively. The results were compared with ordinary Portland cement concrete without blended cement. Voltage, and temperature measurements were also carried out to understand the quality of concrete. The corrosion performance of steel in reinforced concrete was studied and evaluated by electrochemical half-cell potential technique in both sodium chloride, and magnesium sulphate solutions respectively. The reinforced concrete specimens with centrally embedded 12mm steel bar were exposed to chloride and sulphate solutions with the 0.5 M NaCl and MgSO4 concentrations respectively. An impressed voltage technique was carried out to evaluate the corrosion resistance of the combination of quaternary cementitious blended cement, so as to get the combination with optimum performance. Improvement of strength, durability, and corrosion resistance properties of blended concrete samples are observed at different optimum percentages for binary, ternary and quaternary samples. The effect of cementitious blends is recognized in limiting the corrosion potential of the tested SCM concrete samples. Generally, the cementitious blends with limited quantity of SF to 10% have the potential to produce satisfactory concrete. These should however be used for low cost construction, where high quality concrete is not required.Civil and Chemical EngineeringM. Tech. (Chemical Engineering

A Prey-Predator Defence Mechanism For Ad Hoc On-Demand Distance Vector Routing Protocol

This study proposes a nature-based system survivability model. The model was simulated, and its performance was evaluated for the mobile ad hoc wireless networks. The survivability model was used to enable mobile wireless distributed systems to keep on delivering packets during their stated missions in a timely manner in the presence of attacks. A prey-predator communal defence algorithm was developed and fused with the Ad hoc On-demand Distance Vector (AODV) protocol. The mathematical equations for the proposed model were formulated using the Lotka-Volterra theory of ecology. The model deployed a security mechanism for intrusion detection in three vulnerable sections of the AODV protocol. The model simulation was performed using MATLAB for the mathematical model evaluation and using OMNET++ for protocol performance testing. The MATLAB simulation results, which used empirical and field data, have established that the adapted Lotka-Volterra-based equations adequately represent network defense using the communal algorithm. Using the number of active nodes as a measure of throughput after attack (with a maximum throughput of 250 units), the proposed model had a throughput of 230 units while under attack and the intrusion was nullified within 2 seconds. The OMNET++ results for protocol simulation that use throughput, delivery ratio, network delay, and load as performance metrics with the OMNET++ embedded datasets showed good performance of the model, which was better than the existing conventional survivability systems. The comparison of the proposed model with the existing model is also presented. The study concludes that the proposed communal defence model was effective in protecting the entire routing layer (layer 2) of the AODV protocol when exposed to diverse forms of intrusion attacks

Lack of Maintenance Culture in Nigeria: The Bane of National Development

Lackadaisical attitude of Nigerians on maintenance culture has negatively affected infrastructural development which is critical and essential to a Nation’s development. Achieving vision 2020 goals would be attainable if existing structures and facilities are constantly maintained. Poor maintenance culture has drawn the nation a thousand steps backward and one of the stride actions that could salvage the country from the total mess of infrastructural decay is maintenance. This paper aimed at examining lack of maintenance culture through review of archival materials and participative observations. Poor leadership, corruption, attitudinal problem and lack of maintenance policy were identified as major causes of the menace. In conclusion, the paper recommends the inclusion of maintenance culture in national educational curriculum, maintenance policy formulation and appointment of facility managers among others as necessary steps towards making the country among the comity of developed nations. Keywords: Culture, Infrastructure, Maintenance, Maintenance Policy and National Developmen

A Study into the Use of Recycle Iron and Steel Slag as an Alternative Aggregate in Concrete Production

The study researches into the use of recycle iron and steel slag as an alternative aggregate to granite in concrete production. X-ray diffract meter (XRD) and scanning electron microscopic (SEM) were implored to assess the mineral composition and morphology of the aggregate; mechanical properties of the aggregates that were assessed includes sieve analysis, water absorption, bulk specific gravity and Los Angeles abrasion value. In this study the workability of fresh concrete was assessed using slump and compacting factor tests and the strength of the concrete was assessed using the uniaxial compressive strength test to establish the suitability of recycle iron and steel slag aggregate as alternative aggregate in concrete production. Concrete of M20 grade was considered for a water cement ratio of 0.60 using 1:2:4 mix ratio, slag aggregate replacements were observed from 0 to 100% at interval of 10%.  The results of experimental investigations carried out to evaluate the fresh and hardened concrete properties showed that the slump value at 100% granite was 17mm (true slump) while at 100% slag was 28mm (shear slump); while the compacting factor are 0.79 at 0% slag replacement and 0.87at100% slag replacement; which confirms that concrete casted with granite is more workable than concrete casted with slag aggregate. The compressive strength at 7,14, 21 and 28days for the control cubes of 0%, 50% and 100% slag content are; 23.11, 21.78, 24.44 and 27.79N/mm²;  13.78, 20.00, 20.67 and 29.89N/mm² ; and 19.56, 22.67, 24.00 and 23.33N/mm² respectively. The results showed that maximum strength is obtained at 50% slag replacement; though all the results met the requirement of 20N/mm² by standard BS 5328: part 1: 1997. The results of mineral composition and morphology showed that granite and slag aggregates contained (70.2, 11.56, 1.19, 1.12, 0.96, 0.75, 3.26, 3.41, 0.00, 0.08 and 0.05) % and (13.7, 1.68, 10.32, 24.08, 45.16, 7.31, 0.19, 0.04, 0.03, 0.81 and 5.89) % of minerals composition respectively. The water absorption, abrasion value and specific gravity of granite and slag aggregate are (0.12%, 20.0 and2.20) and (0.82%, 23.0, and3.54) respectively. The result showed that the slag aggregate is more porous and absorbed water than granite aggregate and great care must be taken when using slag aggregate in concrete production as reduced water-cement ratio as compared to granite aggregate is required for better performance ; adequate stalking is also required prior to usage.  Based on overall observations it could be recommended that slag could be utilized as coarse aggregate in concrete production either as partial or full replacement of granite aggregate. Keywords: granite, iron and steel slag, X-ray diffract meter (XRD), scanning electron microscopic (SEM), mineral composition and morphology

NOVEL AIRFOIL DESIGN FOR SMALL HORIZONTAL AXIS WIND TURBINE: A PRELIMINARY RESULT

Various research efforts have been directed towards the design and re-design of wind turbine systems. This is in order to have more efficient, better performing and cost effective turbine systems. Based on this, efforts have been focused on wind turbine rotor design with emphasis placed on its aerodynamics. This is because the important criterion of a wind turbine rotor is the airfoil. It is the element that produces the forces that makes the turbine rotate. This research builds on existing knowledge and aims to further deepen knowledge in the field of wind turbine rotor design. The study designed and analysed a new airfoil for use in a small horizontal axis wind turbine. It employed the flow stage airfoil behaviour together with analytical software tools that include XFLR5, AirfoilPrep_v2.02.01, WT_Perf, and MATLAB.. Three well known and tested airfoils were employed and the coordinates were interpolated to create a new, more efficient and better performing small wind turbine rotor airfoil. The outcome showed the new airfoil performs better with good glide ratio over longer angle range, chord distribution and blade twist among other things. The parameters of the new airfoil were such that 10.17%, 26.49%, 6.26% and 45.0% of the chord characterised the maximum thickness and its position, and the maximum camber and its position respectivel

An Octopus-Inspired Intrusion Deterrence Model in Distributed Computing System

The study formulated and evaluated a model for effective management of maliciousnodes in mobile Ad-hoc network based on Ad-Hoc on- demand distancevector routing protocol. A collaborative injection model called CollaborativeInjection Deterrence Model (CIDM) was formulated using stochastic theory.The definition of the model was presented using graph theory. CIDM wassimulated using three different scenarios. The three scenarios were then comparedusing packets delivery ratio (PDR), routing load, throughput and delayas performance metrics. The simulation result showed that CIDM reduce considerablythe rate of packets dropped caused by malicious nodes in MANETnetwork. CIDM did not introduce additional load to the network and yet withproduce higher throughput. Lastly, the access delay with CIDM is minimalcompared with convectional OADV. The study developed a model to mete outa punitive measure to rogue nodes as a form of intrusion deterrence withoutdegrading the overall performance of the network. The well known CRAWDADdataset was used in the simulation

Experiments on Co-Digestion of Cow Dung and Water Hyacinth (EichhorniaCrassipes) for Biogas Yield

Water hyacinth (Eichhorniacrassipes) is one of the worl

Novel airfoil design for small horizontal axis wind turbine : A preliminary result

Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.Various research efforts have been directed towards the design and re-design of wind turbine systems. This is in order to have more efficient, better performing and cost effective turbine systems. Based on this, efforts have been focused on wind turbine rotor design with emphasis placed on its aerodynamics. This is because the important criterion of a wind turbine rotor is the airfoil. It is the element that produces the forces that makes the turbine rotate. This research builds on existing knowledge and aims to further deepen knowledge in the field of wind turbine rotor design. The study designed and analysed a new airfoil for use in a small horizontal axis wind turbine. It employed the flow stage airfoil behaviour together with analytical software tools that include XFLR5, AirfoilPrep_v2.02.01, WT_Perf, and MATLAB.. Three well known and tested airfoils were employed and the coordinates were interpolated to create a new, more efficient and better performing small wind turbine rotor airfoil. The outcome showed the new airfoil performs better with good glide ratio over longer angle range, chord distribution and blade twist among other things. The parameters of the new airfoil were such that 10.17%, 26.49%, 6.26% and 45.0% of the chord characterised the maximum thickness and its position, and the maximum camber and its position respectively.dc201

Novel airfoil design for small horizontal axis wind turbine : A preliminary result

Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.Various research efforts have been directed towards the design and re-design of wind turbine systems. This is in order to have more efficient, better performing and cost effective turbine systems. Based on this, efforts have been focused on wind turbine rotor design with emphasis placed on its aerodynamics. This is because the important criterion of a wind turbine rotor is the airfoil. It is the element that produces the forces that makes the turbine rotate. This research builds on existing knowledge and aims to further deepen knowledge in the field of wind turbine rotor design. The study designed and analysed a new airfoil for use in a small horizontal axis wind turbine. It employed the flow stage airfoil behaviour together with analytical software tools that include XFLR5, AirfoilPrep_v2.02.01, WT_Perf, and MATLAB.. Three well known and tested airfoils were employed and the coordinates were interpolated to create a new, more efficient and better performing small wind turbine rotor airfoil. The outcome showed the new airfoil performs better with good glide ratio over longer angle range, chord distribution and blade twist among other things. The parameters of the new airfoil were such that 10.17%, 26.49%, 6.26% and 45.0% of the chord characterised the maximum thickness and its position, and the maximum camber and its position respectively.dc201

Demographic Characteristics and the Attraction to Facilities in Shopping Malls: A Case of Ibadan, Nigeria

The paper aimed at determining the demographic features of customers in shopping mall that are prone to be attracted by facilities in the malls. The five shopping malls in Ibadan, Nigeria were studied. The research which is a cross-sectional survey adopted the intercept approach to customers resulting to the distribution of 143, 126, 127, 145 and 126 shoppers of the respective malls. A response rate of over 80% was attained and data collected was analysed using the weighted mean and confirmation test on the significance of result was achieved using the Chi-Square test of significance at 95% confidence level. Out of the four demographic features studied, it was discovered that only gender had significant result as females were more likely to be attracted to facilities provided in shopping malls than their male counterpart. The researchers hereby advocated gender sensitivity in erecting facilities in malls as that might enhance patronage