Title: Effect of Elevated Temperature on Mechanical Properties and Microstructure of Silica Flour Concrete

Abstract: An experimental investigation was conducted to evaluate the influence of elevated temperatures on the mechanical properties, phase composition and microstructure of silica flour concrete. The blended cement used in this investigation consists of ordinary Portland cement (OPC) and silica flour. The OPC were partially replaced by 0, 5, 10, 15 and 20% of silica flour. The blended concrete paste was prepared using the water-binder ratio of 0.5 wt% of blended cement. The fresh concrete pastes were first cured at 100% relative humidity for 24 hours and then cured in water for 28 days. The hardened concrete was thermally treated at 100, 200, 400, 600 and 800 oC for 2 hours. The compressive strength, indirect tensile strength, phase composition and microstructure of silica flour concrete were compared with those of the pure ordinary Portland concrete. The results showed that the addition of silica flour to OPC improves the performance of the produced blended concrete when exposed to elevated temperatures up to 400oC.

Title: Application of Biosurfactant Produced by Azotobacter Vinelandii AV01 for Enhanced Oil Recovery and Biodegradation of Oil Sludge

Abstract: The problem of petroleum waste management is giving a due consideration of the national level. Large quantity of dehydrated oil sludge, generated in the disposal process of oil-containing sewage in Indonesia that needs to be rendered harmless to human and to the environment. Microbial degradation has been accepted as an important method for the treatment of oil sludge by employing indigenous or extraneous microbial flora. The purpose of this study was to investigate the performance of biosurfactant in its attempt to recover oil from oil sludge and in enhanced biodegradation of oil sludge process. Measurement of biosurfactant production indicated that the maximum production occurred at the end of exponential growth phase (48h). The emulsification capacity of the biosurfactant also stables under thermal and ionic strength treatment that meet any requirement for application in the oil recovery and degradation. In the oil recovery preliminary test, biosurfactant have the capability to recover oil up to 15% from oil sludge. For oil sludge biodegradation assay, it was found that addition of petrofilic consortia increased the removal efficiency up to 55%, while addition of biosurfactant in this reactor increased the total efficiency of 70% after 70 days of incubation. These results suggest that both petrofilic consortia and biosurfactant addition stimulate the biodegradation and overcome the limitation of petroleum hydrocarbon degradation process.

Title: Correlating Tests of Progressively Damaged Concrete with NLU and AE Techniques

Abstract:This experimental program focuses on the application of non-linear ultrasonic (NLU) and acoustic emission (AE) techniques to evaluating concrete with compression induced distributed damages. Cubic specimens, 150 x 150 x 150 mm, were cast with w/c of 40%, 50%, and 60%. The nonlinear ultrasonic evaluation was based upon measuring the change in fundamental amplitude with increasing damage and output power level. The test results obtained were analyzed and the suitability of using nonlinear ultrasonic amplitude attenuation as a useful measure of damage growth in concrete was examined. In acoustic emission testing technique 4 sensors were used to listen to the wide range of events under various loading and unloading cycles. The data obtained was carefully examined for Kaiser effect and Felicity ratio was appropriately measured at different loading stages in order to assess the concrete deterioration. Normalized values of Felicity Ratio were plotted and compared with the nonlinear ultrasonic test data. A correlation between acoustic emission and nonlinear ultrasonic techniques in assessing damage growth in concrete was investigated.

Title: Effect of Nano-clay on Mechanical Properties and Microstructure of Ordinary Portland Cement Mortar

Abstract:The effect of nano-clay on the mechanical properties and microstructure of Portland cement mortar was investigated. The main objective of this research is to constitute a blended cement mortar with high mechanical properties. The nano-clay used in this investigation was nano-kaolin. The nano-metakaolin (NMK) was prepared by thermal activation of kaolin clay for 2 hours at 750 oC. The blended cement used in this investigation consists of ordinary Portland cement (OPC) and nano-metakaolin. The OPC was partially substituted by NMK of 0, 2, 4, 6 and 8% by weight of cement. The blended cement mortar was prepared using cement-sand ratio of 1:2 by weight with water-binder ratio (w/b ratio) as 0.5. The fresh mortar pastes were first cured at 100% relative humidity for 24 hours and then cured in water for 28 days. The compressive strength, tensile strength, phase composition and microstructure of mortar were investigated. The results showed that the compressive strength and the tensile strength of the cement mortars with NMK were higher than plain cement mortar with the same w/b ratio. The enhancement in tensile strength was 49%, whereas the enhancement in compressive was 7% at 8% NMK

Title: Application of Ultrasonic Testing Technique to Evaluation of Strength Development in Early Age Mortars

Abstract:This research consists of the usage of ultrasonic through transmission and wave reflection methods in evaluating the hydration reaction process of early age mortars with three different w/c. The acoustic wave characteristics were continuously monitored and compared with the strength development provided by the standard penetration resistance test. The experimental results reveal that the ultrasonic wave velocity and reflection coefficient have a strong linear relationship with the strength development in a log-log coordinate. Additionally, an abrupt increase in the wave velocity and frequency amplitude may be utilized as a tool to indicate an onset of the strength in the fresh mortars.

Title: Framework for Evaluating Quality Performance of Contractors in Nigeria

Abstract:The Nigerian construction industry produces nearly 70% of the nation’s fixed capital formation yet its performance within the economy has been, and continues to be, very poor. For example, the Nigerian construction industry’s contribution to employment has remained consistently at 1.0% over the last decade against the World Bank’s average observation of about 3.2% in developing countries. The last decade however exposed the declining level of clients’ satisfaction from the built facilities as a result of poor quality performance in addition to the perennial problems of time and cost overruns in the Nigerian construction industry. This has necessitated a radical change in industry practice in order to improve the quality of construction processes and the level of clients’ satisfaction arising there from by devising methodology for evaluating the quality performance of the contractors in order to assist construction clients in selecting quality-oriented organizations that will provide higher quality services and products within budget and on schedule. Therefore, the principal aim of this paper is to provide a methodology that will improve the quality of the design and construction processes and the level of customer satisfaction derived there from. This paper identified quality attributes relevant to the construction process and proposed a quality performance evaluation model that covers both the corporate and operational levels of a construction project. The paper also implemented the framework in the form of an investigative survey into the quality performance of building contractors in Nigeria as perceived by client organizations. The assessment was based on clients’ perception of the contractor quality practices based on the identified quality attributes.

Title: Formation Of Hydraulic Jumps On Corrugated Beds

Abstract:A study of the effect of different shapes of corrugated beds on the characteristics of hydraulic jumps was conducted. Experiments were performed for a range of the Froude number from 3 to 7.5. Five shapes of corrugations (sinusoidal, triangular, trapezoidal with two side slopes and rectangular) of the same amplitude and wavelength were tested. Two values of relative roughness t/y1 of 0.36 and 0.72 were studied. It was found that, for all shapes of corrugated beds, the tailwater depth required to form a jump was appreciably smaller than that for the corresponding jumps on smooth beds. Further, the length of the jump on the different corrugated beds was less than half of that on smooth beds. The integrated bed shear stress on the corrugated beds was more than 15 times that on smooth beds. For the same amplitude and wavelength, it was found that the effect of the shape of corrugations is relatively small. The results of this study confirm the effectiveness of corrugated beds for energy dissipation below hydraulic structures.