A Study of Seepage through Oba Dam Using Finite Element Method

Dams are constructed to impound water for flood control, water supply, irrigation, energy generation, recreation as well as pollution control. Yet destructive effects of water on them are enormous. Seepage has been implicated as a major cause of dam failure due to its potential to cause internal eruption of soil. Different methods have been identified to study the extent of seepage in earth dams.  Of the methods, flow net is commonly used due to its relative simplicity. However, it becomes more complex with zoned earthfill dams.  In this paper, Finite Element Method (FEM) is employed to study seepage behaviour in Oba dam. Though the method was developed for the analysis of aircraft structural problems, due to its versatility, it is found as tool to solve variety of other practical problems. Finite Element formulation of the governing equation was established and computer programme was written to solve it. The bottom of the dam was meshed using rectangular element mesh while the piezometric heads at nodal points were determined. Also, determine was the coordinates that define the phreatic surface of the seepage. The results obtained were compared with those obtained from flow net approach which served as control using t-Test technique. It was observed that there was no significant difference (p > 0.0005) between the results. Thus, the method is appropriate for the study. The added advantage of the FEM is that simulation of the seepage problem of the dam becomes easy. Keywords: Finite Element, seepage, Oba dam, piezometric head, phreatic surface

Appraising capacity building among engineering students in selected universities in Southwestern Nigeria

A journal article on capacity building in Nigerian universities for Engineering students.This paper examined capacity building among engineering students in selected universities in south-western Nigeria. One hundred and fifty-one final year engineering students took part in the survey. A structured questionnaire were administered to the respondents as a tool for data collection. The data collected were subjected to descriptive and inferential statistical analysis using SPSS. The results showed that 66.9% of the respondents had passion for their choice of engineering courses. Out of 110 students that had access to computer system, about 87.4% had related engineering application software on their personal computer while only 76.2% could use them proficiently. Based on the students' responses, 93% of them expressed that their departments lacked adequate and state-of-the art equipment for practicals, 54% stated that practicals were carried out occasionally, while 95.6% indicated that Students Industrial Work Experience Scheme (S1WES) was very relevant to their study of engineering. The ANOVA conducted on the data showed that SIWES had significant effect on the understanding of their core courses (p<0.005). Also, the core values of the universities were significant to capacity building. The paper concluded that Nigerian universities had potentials to develop the needed human capacity in engineering but they can do better through provision of adequate equipment, strengthening the SIWES programme and laying more emphasis on vocational as well as entrepreneurial skills

Strength development and crack pattern of coconut fibre reinforced concrete (CFRC)

Concrete fails suddenly under tension and cracks excessively when unreinforced. Steel rebar is conventionally used to reinforce concrete. However, it is expensive to many people in most developing countries. In tropical regions, natural fibres are abundantly available which when utilized will reduce cost of construction and improve performance.This paper focuses on the use of coconut fibres as reinforcement in concrete. Coconut fibres were extracted from coconut seeds and chopped into 40 mm in length. Concrete of mix ratio 1:2:4 was produced which contains coconut fibre of 1, 2, 3 and 4% by weight of cement.  Compressive strength and modulus of rupture of CFRC specimens were determined following standard procedures at curing ages of 7, 21, 28 and 56 days. Also, crack pattern was monitored. The results showed that the water-cement ratio increased from 0.62 to 0.70 as coconut fibres (CF) increased from 0 to 4%, while the compressive strength only increased up to 2% CF but dropped afterwards when compared with normal concrete (NC). At 28-day, flexural strength of CFRC were 2.73, 2.79, 2.88 and 3.01  at 1, 2, 3, and 4% CF content representing 107.5, 109.8, 113.4 and 118.5% of NC. There was gradual tensile failure in CFRC with minor to hair-like crack as compared to sudden failure with wide crack from tension zone to compression zone in NC. The study concluded that up to 2% content of CF is recommended for concrete reinforcement.   

Effects of sulphuric acid on the compressive strength of blended cement-cassava peel ash concrete

Influence of sulphuric acid on compressive strength of concrete made with blended cement-cassava peel ash was investigated in this study. This is with a view to determining the level of resistance of such concrete to acidic exposure. Cassava peel ash (CPA) prepared from uncontrolled burning was used to substitute cement at 5, 10, 15 and 20% by weight of cement as binder. Concrete mix proportions of 1:2:4 (batching by weight) were prepared with the slump value within 6010 mm while water-binder ratios (w/b) were being noted. A total of 90 cubes of the concrete mixture of sizes 150 mm were cast and cured in fresh water (as control), 0.5, 1.0 and 1.5 M concentrations of sulphuric acid solution (H2SO4) for 7, 28, 56 and 90 days. The compressive strength was determined at the expiration of each curing age. The results showed that the w/b increased with increase in the quantity of CPA in the mixture. Compressive strength of concrete made with cement-CPA as binder and cured in fresh water was comparable to that of normal concrete when up to 15% CPA was used, but relatively low strength was obtained when cured in H2SO4 solutions, depending on the quantity of CPA. Leaching of Porlandite in the concrete cubes was observed with worse condition in the case of concrete containing 20% CPA in sulphuric acid solution of 1.5 M. The compressive strength reduced with increase in concentrations of the acid as well as with increase in the content of the CPA. It is concluded that CPA did not mitigate the adverse effects of sulphuric acid on the compressive strength of blended cement-CPA concrete

Performance evaluation of treated coconut fibre in cementitious system

Abstract In this study, concentrated cement pore solution (CPS) was prepared and coconut fibre was soaked in it, to mimic worst condition of cementitious medium. Four coconut fibre samples were studied; the first was untreated fibre (NT), the second sample was NaOH treated fibre, while the third and fourth samples were NT and NaOH fibres soaked in CPS for 28 days, respectively. Each fibre was characterized by determining their physical and mechanical properties. Hydrophilic/hydrophobic characters were determined by measuring contact angles in water, while surface morphology of the fibre samples were studied with the aid of scanning electron microscopy. EDS was used to determine the elemental composition of the fibres, while Thermogravimetric analysis was performed to assess thermal stability of the fibre samples. Crystallinity of the fibres as well as the functional group composition present in each fibre samples, was determined using XRD and FTIR respectively. The results showed that fibres treated with NaOH and those exposed to CPS had higher densities (1.94 g/cm3) than untreated fibre (1.64 g/cm3), while the tensile strength was greatly increased by about 120%. SEM images of the fibres indicated that NaOH and CPS caused removal of lignin and hemicellulose, making the lumens to be smaller compared to untreated fibre. Similarly, crystallinity of the fibre was increased due to NaOH and CPS treatment, compared to the untreated fibres. CPS was found to improve thermal stability of the fibres. It was concluded that CPS did not pose any threat to performance of fibre

Regression models for compressive strength of concrete under different curing conditions

Effect of different curing methods on the compressive strength of concrete was investigated. A total of 69 concrete cubes of size 150 mm was cast and cured under five different conditions (immersion in water, sprinkling with water, moist sand covering, polythene covering and air curing) for 3, 7, 14 and 28 days. At the expiration of curing ages, compressive strength was determined and regression analysis was conducted. The concrete cured with these techniques was equally subjected to water penetration test. The results showed that Polythene covering method produced concrete specimen with the highest compressive strength of 23.41 Nmm−2 followed by Immersion in water (22.86 Nmm−2). Regression models formulated for each condition indicated that the strength development was dependent on methods of curing. From the results, it was concluded that the compressive strength of concrete depends on the medium in which they were cured and there exist a positive correlation between the compressive strength of concrete and curing age

Regression models for compressive strength of concrete under different curing conditions

Effect of different curing methods on the compressive strength of concrete was investigated. A total of 69 concrete cubes of size 150 mm was cast and cured under five different conditions (immersion in water, sprinkling with water, moist sand covering, polythene covering and air curing) for 3, 7, 14 and 28 days. At the expiration of curing ages, compressive strength was determined and regression analysis was conducted. The concrete cured with these techniques was equally subjected to water penetration test. The results showed that Polythene covering method produced concrete specimen with the highest compressive strength of 23.41 Nmm−2 followed by Immersion in water (22.86 Nmm−2). Regression models formulated for each condition indicated that the strength development was dependent on methods of curing. From the results, it was concluded that the compressive strength of concrete depends on the medium in which they were cured and there exist a positive correlation between the compressive strength of concrete and curing age

Critical review on the application of artificial intelligence techniques in the production of geopolymer-concrete

Abstract The need to employ technology that replaces traditional engineering methods which generate gases that worsen our environment has emerged in an era of dwindling ecosystem owing to global warming has a negative influence on the earth system’s ozone layer. In this study, the exact method of using artificial intelligence (AI) approaches in sustainable structural materials optimization was investigated to ensure that concrete construction projects for buildings have no negative environmental effects. Since they are used in the forecasting/predicting of an agro-waste-based green geopolymer concrete system, the intelligent learning algorithms of Fuzzy Logic, ANFIS, ANN, GEP and other nature-inspired algorithms were reviewed. A systematic literature search was conducted to identify relevant studies published in various databases. The included studies were critically reviewed to analyze the types of AI techniques used, the research methodologies employed, and the main findings reported. To meticulously sort the crucial components of aluminosilicate precursors and alkaline activators blend and to optimize its engineering behavior, laboratory methods must be carried out through the mixture experiment design and raw materials selection. Such experimental activities often fall short of the standards set by civil engineering design guidelines for sustainable construction purposes. At some instances, specific shortcomings in the design of experiments or human error may degrade measurement correctness and cause unforeseen discharge of pollutants. Most errors in repetitive experimental tests have been eliminated by using adaptive AI learning techniques. Though, as an extensive guideline for upcoming investigators in this cutting-edge and developing field of AI, the pertinent smart intelligent modelling tools used at various times, under varying experimental testing methodologies, and leveraging different source materials were addressed in this study review. The findings of this review study demonstrate the benefits, challenges and growing interest in utilizing AI techniques for optimizing geopolymer-concrete production. The review identified a range of AI techniques, including machine learning algorithms, optimization models, and performance evaluation measures. These techniques were used to optimize various aspects of geopolymer-concrete production, such as mix design, curing conditions, and material selection

Performance evaluation of concrete made with sands from selected locations in Osun State, Nigeria

It is common practice among most local contractors in Nigeria to produce concrete with any available sand, disregarding its attendant effect on concrete performance. Sands obtained from popular quarries in Osun State, Nigeria were investigated to determine their suitability for concrete production. The sands were labelled A, B, C, D and E. Physical and chemical properties as well as grading characteristics of the sand samples were determined using standard procedures. Impurities in the sands were equally evaluated. Strength and water demand of the concrete produced from these sands were also examined. The results showed that all the sands contained high silica with traces of alumina in almost the same quantity except Sand E that had relatively low silica but higher alumina. Particle size distribution of the sands indicated that Sand A had more fine particles with fineness modulus of 1.95 while sand D was coarser (2.79) and other sands (B, C and E) were within the range of 2.7 and 2.6. The specific gravities of the sands fell in the range of 2.5–2.7 except Sand A, which was 2.2. The strength of the concrete made from each of the sands equally differed significantly, with Sand E having the highest strength (23.5 N/mm2). Water absorption results indicated that Sands A and C may pose durability challenges due to higher water absorption compared to other sands. The study concluded that the selected sands had influence on the performance of concrete and it was recommended that all except Sand A, could be used for specific construction application. Keywords: Compressive strength, Aggregates, Organic matter, Particle size distribution, Water deman

Plant based chemical admixtures – potentials and effects on the performance of cementitious materials

While today, engineers can choose from a wide range of rheology modifying admixtures, in some parts of the world, these are difficult to access, due to their complex processing. However, alternatives can be bio-based polymers such as polysaccharides from various sources. These are easily accessible all over the world, do not demand for complicated processing, and typically they are more sustainable than many established materials, which are crude oil-based. The paper presents the effects of acacia gum, cassava starch and the gum of triumfetta pendrata A. Rich on the rheological performance of cementitious systems. It is shown that acacia gum can be as efficient as polycarboxylate based superplasticisers, cassava starch can reduce the yield stress slightly with little effect on the plastic viscosity, and the gum of triumfetta pendrata A. Rich increases the thixotropy of cement pastes with plasticizing polymers significantly