Abstract: Laboratory studies to investigate the effect of Bagasse Ash (BA) admixture on the engineering properties of lime treated black cotton soil was carried out. Black cotton soil is classified as A-7-6 or CH respectively. Bagasse ash is obtained from burning the fibrous residue from the extraction of sugar juice from sugarcane. The results obtained show that the moisture density relationship follows a trend of increasing optimum moisture content (OMC)/decreasing maximum dry density (MDD) at the Standard Proctor compaction energy. California bearing ratio (CBR) values obtained are lower than the 80% CBR criterion for untreated base course materials. The peak CBR value obtained was 31% at 8 %lime/ 4%BA. This value meets the recommended criteria for subgrade materials. The Unconfined compressive strength (UCS) at 7 days is lower than the 1034.25kN/m2 evaluation criterion for adequate lime stabilization. On the basis of the soaked CBR and durability values, it is recommended that black cotton soil can be stabilized for road construction using a 8 % lime/ 4 % BA blend of admixture at standard proctor compaction. However, due to the relative high cost of lime and large quantity that shall be required to achieve stabilization, further study and consideration should therefore be given to the use another additive such as cement to augment and lower the percentage of lime and thus the cost of stabilization.
Abstract: In this paper, sawdust concrete with nominal mixes 1:1:2, 1:1½:3, 1:2:4, 1:3:6 and 1:4:8 were subjected to durability test. The 28-day water absorption of the mixes are 5.69, 8.97, 8.29, 7.83 and 11.11%, 28-day linear shrinkages are 0.67, 0.50, 1.83, 1.83 and 1.95%, respectively. The 28-day thermal conductivities are 0.229, 0.232, 0.229, 0.223 and 0.176W/m.K., respectively. The 28-day compressive strengths of mixes 1:1:2 and 1:1½:3 are 18.33 and 8.78 N/mm2, respectively, while their 28-day flexural strengths are 1.71 and 1.33 N/mm2, respectively. These values indicated that they are good and durable concrete and can be used for construction of rigid pavement.
Abstract: The purpose of this study is to carry out tests on concrete made with a typical Benin City silty sand and determine the major concrete quality indicators such as pulse velocity, water/cement ratio and compressive strength in order to justify the continued utilization of such sands in concrete production in and around Benin City. To do this, concrete made with the selected sand were designed using DOE mix design method and test cubes were cast in three batches. Two cubes were cast for each of the sixteen consecutive tests carried out and averages taken for each design grade strength of 10,20,30,40 and 50N/mm2. Also, pulse velocity and rebound hammer tests were carried out on the cubes before testing the cubes destructively. The results show that concrete produced with the Benin City silty sands are of good quality in all respect but generally characterized by low 28th day – characteristic strength. The sands should therefore be used in construction provided that the mean strength aimed at during design is sufficiently higher than the characteristic strength by the strength margin (ks) from structural point of view to enable every part of the structure have adequate strength.
Abstract: The purpose of this study is to see if varying the vibration time and sand type during moulding of blocks would affect the strength of the blocks. To this end, seven types of sands: Okhuahie and Ovia river sands; Okhuahie, Ovia, Ikpoba flood and Okhoro erosion sands were collected for the study. A total of 315 blocks each in 150mm and 225mm sizes with cement to sand ratios of 1:6 were made using the seven brands of sand. The blocks were vibrated for 10, 15, 20, 25, and 30 seconds and tested for compressive strength at 7 days, 14 days and 28 days respectively. The result showed that the relationship between compressive strength of the blocks and the vibration time for various sand types was linear up to vibration time of 30 secs. The sand type also influenced the strength of the blocks as Okhuahie river sand gave the highest compressive strength followed by Ovia river sand and the least was Okhoro erosion sand. At least 52% increase in compressive strength of 150mm and 225mm sandcrete blocks were achieved by raising the vibration time from 15 seconds to 25 seconds in the seven types of sand and 100% increase was achieved by raising the vibration time from 15 to 30 seconds.
Abstract: In recent years, the need to monitor for Deformation in Engineering Structures such as Dams, Bridges and Tall buildings have become more necessary as a result of reported failures of many of these structures with catastrophic consequences globally. Global Positioning System (GPS) is highly automated and less labour intensive than other conventional techniques used in structural deformation monitoring. For most applications, such as National Geodetic Control Network, Urban Control Network and other Engineering Control Network, an accuracy in the cm level for most GPS work is quite adequate. For Structural deformation monitoring however, the required accuracy is in millimeters. In this paper, the use of Static Differential GPS method with multiple receivers for high precision measurement was investigated using the monitoring Stations at Ikpoba Dam as case study Scenerio. Four units of LEICA 300 Dual Frequency GPS receivers were deployed for code and carrier phase measurements with observation session of 1hr at a sampling rate of 15 sec. Baseline Processing and Least Squares Adjustment of observation was carried out in WGS 84 and NTM reference frames using the LEICA SKI-PRO Processing software and Move. Analysis of the results revealed that the number of outliers in the observation were <5% and the accuracy of horizontal and vertical coordinates were 4mm maximum for horizontal and 2mm maximum for vertical. The study revealed that in areas with favourable satellite constellation and appropriate reduction or elimination of multipath and other noise like errors, Static Differential GPS techniques with a combination of code and carrier phase measurement gives good results for structural deformation monitoring.
Abstract: The potential of periwinkle shell as coarse aggregate for concrete was studied in this paper. The properties of concrete made with periwinkle shell as coarse aggregate were examined. Test conducted on the concrete was compressive strength test. Prescribed mix designs of 1:1:2, 1:2:3, 1:4:6, 1:2:4 and 1:3:5 were used to produce concrete cubes used for testing. The different constituents that make up the periwinkle concrete are presented in ratio form as cement: sharp Sand: Periwinkle shell. Batching was done by volume and the corresponding weight recorded. The cubes were made and tested at hydration periods of 7, 14, 21 and 28 days to determine the compressive strength of the periwinkle shell concrete. The results show that periwinkle shell has a bulk density of 517kg/m3 and specific gravity of 2.05. The results also shows that design mix of 1:1:2, 1:2:3 and 1:2:4 with compressive strength of 25.67 N/mm2, 19.50N/mm2 and 19.83N/mm2 at 28 days hydration period respectively met the ASTM-77 recommended minimum strength of 17N/mm2 for structural light weight concrete while mix design of 1:4:6, and 1:3:5 with compressive strength of 14.00N/mm2 and 16.50N/mm2 respectively did not met the standard.
Abstract: This paper determined the torsional strength of steel reinforcements used in the construction industry in Nigeria and compares their Modulus of Rigidity with available standards. Fifteen test specimens were examined from the reinforcing steel of various sizes ranging from 8mm to 20mm diameter which were sourced randomly. The samples were tested with the Torsion Testing Machine until failure. The initial parameters such as gauge length and diameter were considered before the application of torque. The failure torque for the 8mm, 10mm, 12mm, 16mm and 20mm steel reinforcements obtained from the test are 15Nm, 28.81Nm, 77.09Nm, 191.89Nm and 368.99Nm respectively. The result showed that the torsional strength of reinforcement available in the construction industry is below the standard modulus of rigidity of 21000N/mm2 by about 15%.
Abstract: The paper explores power quality disturbances on a specified section of the distribution network of a Textile Industry in Kaduna State of Nigeria. The 33kV PHCN incoming to the industry is stepped down to 11kV by a 7.5MVA, 33/11kV three-phase transformer. This transformer supplies various 11/.415kV transformers present in the distribution network. Another 11kV PHCN incoming is used in event of any failure from the 33/11kV transformer. The paper focuses on Transformer No. 1, a 150kVA, 11/.415kV three-phase transformer operating at 0.9 power factor, located at printing and dying (P/D) building 1. Majority of the loads on it are inductive. Measurements were taken at the secondary terminal of this transformer by the use of the Harmonitor 3000 power analyzer, which generates the voltage and current waveforms, power factor, voltage and current total harmonic distortion and the apparent power of the red, yellow and blue phases of the transformer. Analyses of these data reveal the disturbances due to harmonics in the phases and neutral of the transformer. The effect of the harmonic current is seen as poor power factor of the transformer. Considering the observations and analyses of the power quality of the transformer 1 (P/D), the paper proposes some recommendations for improving the power quality of the distribution network under study.