International Journal of Engineering Research in Africa Vol. 47

Abstract: Utilization of secondary aluminium dross (SAD) as a constituent material in production of concrete is one of the recycling and value-added alternatives of reusing the waste due to the environmental friendliness, economy and improved performances associated with the material. This present study investigates the feasibility of incorporating SAD as a replacement binder in normal strength concrete (NSC). X-ray fluorescence (XRF) analysis revealed that the investigated SAD is rich in alumina content while exhibiting expansive property when tested via Le Chatelier apparatus. The studied fresh concrete samples blended with SAD recorded low workability and densities as the replacement levels increase. Compressive, split tensile and flexural strength tests conducted on the hardened concrete indicated a reduce strength as the percentage contents of the SAD increases when compared with the reference mixture. Moreover, the water absorption results also revealed higher water absorption capacity of the hardened concrete samples with increasing percentage contents of the SAD in the concrete samples. It is, therefore, suggested that blend of Portland cement (PC) with SAD content within 10% will be beneficial in the production of normal strength concrete for the structural purpose by the construction industry, while also limiting the impact of the aluminium waste on the environment.

Abstract: The behavior of unbounded post tension and reinforced concrete beams under elevated temperature was presented. The experimental work was consisted of two major phases. In the first phase, the objective was studying the mechanical performance of prestressed beam, prestressed beam with steel addition and reinforced concrete beams respectively were studied. In the second phase, the residual mechanical performance of prestressed beam, prestressed beam with steel addition and reinforced concrete beams under elevated 400oC, for 120 minutes durations. The failure mechanisms, ultimate load capacity, and deflection at critical sections were monitored. The numerical prediction of the flexural behavior of the tested specimens is presented in this paper. This includes a comparison between the numerical and experimental test results according to ANSYS models. The results indicate that the prestressed beam with steel addition and reinforced concrete beams had higher resistance to beams under elevated 400oC than that of prestressed concrete beam in terms of ultimate capacity. It is also shown that the reinforced concrete beams have higher resistance to beams under elevated temperature than that of prestressed beam, prestressed beam with steel addition.

Abstract: The present investigation was conducted to evaluate the influence of recycled aggregates on structural behaviour of reinforced concrete (RC) slabs. Concrete mixtures of 0.6 and 0.4 water/cement ratios were used to produce normal strength concretes and high strength concretes, respectively. Various concrete mixtures were prepared by replacing 19 mm natural coarse aggregates with 0, 25, 50, 100% recycled coarse aggregate (RCA) then used to cast RC slabs of size 500 x 300 x 100 mm thick, and 100 mm cubes. The two-way concrete slabs were reinforced orthotropically with Y12 steel bars. Workability, compressive strength, and split tensile strength properties of concrete were measured, while the RC slabs were subjected to monotonic loading until failure. The experimental results obtained were compared with theoretical failure loads predicted using the yield line theory. It was found that the use of RCA in concrete generally leads to reduction of workability and concrete strength in proportion with the RCA content incorporated into the mixture. The yield line method gave a conservative and accurate theoretical prediction of the actual ultimate loads for control concretes, predicting 10% lower values, but it exhibited loss of prediction accuracy for RCA concretes of normal strengths basically overestimating their failure loads. Accordingly, it would be unsafe to employ the yield line method for design of RCA concrete slabs of normal strengths. Generally, the adverse effects of RCA on concrete properties and structural behaviour can be mitigated significantly by adjusting mixture designs to higher strengths or by employing high strength concretes

Abstract: The occurrence of radionuclides in the raw materials from which the building materials are made is a potential radiation risk in buildings constructed from these materials. In this study, four historical buildings were investigated regarding the natural radioactivity of the used bricks. The gamma radiation was evaluated using the measured mass activities of the most important radionuclides and expressed by the gamma indexes (Iγ) and dose rates. The results proved that the activity concentrations of ²³²Th and ⁴⁰K radioisotopes in bricks are higher than worldwide values. Even though Iγ do not exceed the recommended value (Iγ ˂ 1), the absorbed dose rate for the structures in indoor air was calculated in the range 115.94-161.44 nGy/h which is twice the global average for this parameter.

Abstract: Bridge Scour is the localized loss of the geomaterials around the foundation of a bridge as a result of the movement of water around it. Scour is a great risk to the stability of a bridge’s foundation, thus leading to collapse, loss of lives and setback in a nation’s socio-economic life. Artificial Neural Networks (ANN) are collections of simple, highly connected processing elements that learn according to sets of input parameters and use that to simulate the networks of nerve cells of humans or animal central nervous system. The Asa Dam Bridge, one of the longest bridges in Ilorin, Kwara State, Nigeria, has five (5) spans of 20m each. The bridge connects Ilorin to the Ogbomosho Express way (leading to the western part of the country) and the Eyenkorin-Jebba road (leading to the north). Thus, the bridge has a high economic value. In this research, factors such as flow depth, average flow velocity of the river and median sediment size were investigated to show how they affect the depth of scour around the bridge pile foundation. Data were taken for a period of 48 weeks and ANN was applied to predict and generate a model that shows how these factors relate to the scour depth of the riverbed. The model revealed that the hydraulic parameters and soil grading around the pile cap of Asa River Bridge bears significant influence on the scour depth of its foundation. The model was compared with five (5) other established scour equations.

Abstract: The lowest purchase price is the easiest criterion in tendering for civil engineering. However, in view of the longevity of these buildings and their social significance, this criterion is insufficient. Renovation and maintenance costs play an important role in the construction life cycle and need to be taken into consideration, too. The structural design clearly influences the operating costs of the building, which can be predicted. The paper presents an example of how to approach this issue. The methodology is focused on bridge structures. The paper presents a software application for the calculation of renovation and maintenance costs which are generated from the following structural elements: abutments, pillars, deck (bearing structure), bearings, bridge deck insulation, drainage, roadway, cornice, railing, crash barriers, expansion joints and noise barriers. The structural elements can be specified in the application in predefined type / material variants. If the user uses material that is not included in the database, this situation is solved by adding the appropriate element to the database. If a combination of materials is used for one component, these materials are defined as separate structural elements. Bridge structures are evaluated over a lifetime of 100 years.

Abstract: Building materials and constructions pose a serious impact on the environment. Applying assessment tools such as life cycle assessment (LCA), it is possible to determine the environmental characteristics of materials, specific constructions or whole buildings. Today, however, there is a large amount of software that is freely available or bound by a license agreement. This paper is aimed at on comparison of the two different LCA software to evaluate the impacts of the selected construction: freely available software and software fixed by a license agreement. The comparison within the mandatory boundaries from cradle-to–gate includes the main environmental impacts such as climate changes, acidification, and embodied energy. The findings revealed that the results for the environmental parameters of constructions differ significantly regarding some structures, even though the input database was the same.

Abstract: Increasing concerns about negative environmental impacts of building structures call for higher demands on the design of environmental friendly buildings. This article is aimed at assessing the overall environmental impact of buildings throughout its life cycle as well as on environmental impact of all building materials and building services for single-family homes. This analysis examines the role of utilized green environmental technologies for the following selected impact categories: GWP - global warming potential, EP - eutrophication potential, AP - acidification potential POCP and photochemical ozone formation potential expressed in kg CO_2eq, PO₄^3-_eq, SO_2eq and ethylene within the “Cradle to gate with options” boundary. The LCA assessment methodology and eToolLCD software have been used to model the effects of houses’ life cycle.

Abstract: This paper reviews local and bio-sourced materials for construction through their thermomechanical characteristics, but with an emphasis on their thermal conductivity that allows us to assess the thermal performance (insulation) of these materials. Then, we discuss the energy problems in Mauritania, while highlighting the local and bio-sourced materials existing in this country. These materials could be an alternative to solve these energy problems. Finally, we focus on the thermal performance of Typha Australis, a plant that grows abundantly in fresh water mainly in Senegal and Mauritania, which would have good advantages over the thermal performance of the building.

Abstract: This article wants to introduce modular green roof systems and their usage in the world as well as in the Czech Republic, because green roofs are now used more than they have been constructed in any era in the history. Their construction is almost same as it was in previous centuries, so the obvious solution for their improvement is in the construction of themselves. Especially in the improvement of their construction time which should be lower with usage of modular system than at classical layer system of the green roofs. This research also wants to speak about construction system for individual types of green roof. Where the purpose of this article is to set optimal solution for modular green roof panel which will be economical and environmentally friendly.