Advanced Materials Research Vols. 18-19

Abstract: Rock slope failure mechanisms were assessed in this study using KOPEC and RCC quarries as case studies in Oyo state. Discontinuities such as joints and bedding planes were obtained through face mapping and scanline survey of the excavated slopes of the quarries. Stereographic projections of the discontinuities were generated using ROCKPACK III and the stereonets analyzed in accordance with Markland’s plane failure analysis. The results of the analyses show that there are possibilities of plane failures in the south- east region of KOPEC quarry slope face and south –west region of RCC quarry slope face. It is therefore recommended that constant monitoring of the slope failure should be done and the slope angle should be less than 700 and 600 for KOPEC quarry and RCC quarry respectively.

Abstract: The paper focuses on the effect which varying the type of sand used in concrete will have on the compressive strength of concrete and seeks to determine the suitability of each sand for use in concrete works. The sand samples used include Okhoro, Ikpoba, Ovia and Okhuahiaerosion sands and Ikpoba, Ovia and Okhuahia river sands. Particle size distribution of the sands was first determined and the result was used to design grades 20, 25, and 30 concretes to Department of Environment (DOE) mix design method. Twelve cubes were cast from one particular sand sample and three cubes were tested at 7, 14 and 28 days for each grade of concrete respectively .The result revealed that the sand samples that are well graded gave the highest compressive strength; while the poorly graded sands gave lower strengths. Okhuahia river sand gave the strongest concrete followed by Ikpoba, and Ovia river sands, Okhuahia, Ikpoba, Ovia and Okhoro erosion sands. Particle size distribution within a sand zone probably did not affect strength but the impurity content did. However, the inter-zonal differences in particle sizes probably did affect strength. The result also showed that only the river sands and Okhuahia erosion sand are good for concrete making.

Abstract: This paper examines the production of calcite and calcite-cement stabilized laterite hollow blocks as low-cost masonry units. First, is the production of laterite hollow blocks solely stabilized with finely ground limestone or calcite followed by the production of laterite hollow blocks stabilized with calcite-cement composite. Laterite was sourced from three locations: Asoro, Evbuotubu and Ugbowo. Blocks were produced using a specially constructed machine with percentages of calcite and calcite-cement content varying from 4% to 16% respectively at compactive pressures of 10.32 and 13.75N/mm2. Equal amounts of calcite and cement are used in the composite. The blocks were then tested for 7, 14 and 28 days strengths after curing. The results show that laterite blocks stabilized with calcite alone do not satisfy the Nigerian Industrial Standards or British Standards for blocks but those stabilized with 8% calcite-cement content, i.e., 4% calcite with 4% cement do, at moulding pressure of 13.7 N/mm2. Based on the local cost data, the results also show that calcite-cement stabilized laterite hollow blocks are 17% cheaper than an equivalent cement-stabilized hollow block and 46% cheaper than the low quality sandcrete blocks sold in the market.

Abstract: The behaviour of the core of rockfill dam with slanting clay core was investigated with the Jebba main dam, Nigeria as a case study. The stress-deformation behavior of the dam was studied using the finite element mathematical modeling technique. The actual fill properties were utilized and two loading scenarios-no water and full reservoir operations-were investigated. At full reservoir, the actual seepage line, as recorded over the years was used. The linear total stress analysis using the finite element method of analysis was employed to analyze the dam section. Following the finite element mathematical modeling and computer simulations of the models, deformations and stresses distributions were determined. The results showed that the observed longitudinal cracks at the Jebba main dam crest are as a result of potential cracks in the dam core section. The cracks observed at the crest, from analysis, commenced from the dam’s core upstream face, downstream face and core crest. This may have resulted from probable hydraulic fracturing and tensile stresses developments in these regions. The results also showed likely loss of integrity of core due to cracks. However, total collapse may not be experienced but dam performance may be impaired and alarming visible cracks may not be ruled out over time.

Abstract: The purpose of this study was to determine the effect of particle size on the mechanical properties (Modulus of Elasticity, Modulus of Rupture, and Internal Bond) and physical properties (thickness swelling and water absorption) of rice husk particleboard. The particle sizes used were 1.0mm, 1.18mm, 2mm, 2.36mm and 2.80mm. Each was mixed with a constant resin (urea formaldehyde) concentration of 20% of oven dry weight of rice husk particles. The results showed that as the particle size increased, the particleboard’s mechanical and physical properties decreased. For example, the modulus of elasticity, modulus of rupture, internal bond, thickness swelling and water absorption for 1.0mm particle size particleboard were 1590N/mm2, 11.11N/mm2, 0.28N/mm2,10.90% and 38.53% respectively, while for 2.8mm particle size they were 1958N/mm2,14.2N/mm2, 0.44N/mm2, 11.51% and 47.21% respectively. Overall results showed that particleboard made from rice husk exceed the EN standard for modulus of elasticity, modulus of rupture, internal bond. However, thickness swelling values were poor. Hence, the smaller the particle size the better the properties of the particleboard.

Abstract: A material was made from cement/waste paper/sludge mixture and tests were carried out on it to ascertain its suitability as a ceiling board material. The tests included water absorption, drying shrinkage, flexural strength, thermal conductivity, and compressive strength. The results showed that the material possesses good properties as a ceiling board material.

Abstract: In this study, pulse velocities calculated from the time taken by pulses emitted by a transducer to traverse a known thickness of the concrete is utilized in building up a correlation between pulse velocity and strength of concrete cubes and between pulse velocity and age of concrete. Three different arrangements of transmitters and receivers were studied to cover the varieties of problems likely to be encountered on a site. These are direct transmission, semi-direct transmission and indirect transmission. For a particular mix proportion and aggregate size a calibration curve was obtained for in-situ testing of concrete. These curves can be used to determine the relative in-situ strength of similar members or structures.

Abstract: The ability to view constructions virtually before using the real resources to construct them has been of main interest in civil engineering over a long period of time. This has been achieved partially through virtual reality. Virtual Reality helps in visualizing the operations on computer generated jobsites and to study the available alternate plans. Even though the latest software in virtual reality helps us in designing and drawing the plans, the question of reality still arises. The plans that are done in computer sometimes do not match with the real practical applications. This shows that it is difficult to bring the experiences of practical world into the computer. In order to overcome the gap between the real and virtual environments, this paper highlights the use of Augmented Reality (AR) in all the areas of civil engineering instead of using Virtual Reality. This paper describes the developing augmented reality technology and its various application domains in civil engineering.