70 research outputs found
Comparative Analysis of Curing Methods: Natural and Activated Lateritic Concrete
This work was on non-activated and activated lateritic soil used in proportions of 0 % to 30 %, to replace fine sand by wt. %, in the production of lateritic concrete. A mix of 1: 2: 4 was used, and the cube samples were cured in four (4) curing media of water, sand, polythene, and sawdust. The aim was to evaluate the effects of these curing methods on the mechanical strengths, and other properties of lateritic concrete. The sensitivity of the generated data was characterized statistically and developing linear regression models for predictions. For the Non-Activated Laterite soil (NALS, control mix (0 %)), the design strength of 20 MPa was achieved by all the curing methods (standard and non-standard). However, for other replacement levels, water curing was adequate for 10 % and 30 %, sand at 10 %, and sawdust for 20 % and 30 %, respectively. On the other hand, for the Activated Laterite soil (ALS), the 20 MPa design strength was met only at 0 % replacement for all curing methods. Sawdust medium at 10 % also satisfied the 20 MPa strength
Effect of Salt Water in the Production of Concrete
In this research work, the effect of salt water in the production of concrete was investigated. A total of ninety (90) concrete cubes were cast for compression strength test i.e. forty five cubes were cast using fresh water and the other forty five cubes were also cast using salt water. Similarly, a total of ninety (90) concrete beams were cast for flexural strength test i.e. forty five beams were cast using fresh water and the other forty five beams were also cast using salt water. The concrete cubes and the beams were cured at 7,21,28,60 and 90 days respectively. The result of the average compressive strength of concrete obtained using fresh water of mix ratio (1:1.51:4.01), water cement ratio (0.47) ranges from 27.35-42.34N/mm2 while that of salt water ranges from 25.24-38.81N/mm2 for the hydration period of 7,21,28,60 and 90 days. The flexural strength of concrete obtained using fresh water of the same mix ratio and water cement ratio ranges from 6.60 – 11.20N/mm2 for 7,21,28,60 and 90 days hydration period while that of salt water ranges from 5.98-11.04N/mm2 for the same hydration period. For the mix ratio (1:1.61:4.03) and water cement ratio (0.55), the average compressive strength of concrete obtained using fresh and salt water ranges from 27.26-40.80N/mm2 and 24.68 – 39.13N/mm2 respectively while the flexural strength ranges from 6.55-11.13N/mm2 and 6.26-10.76N/mm2 for fresh and salt water respectively. For the mix ratio (1:1.66:4.24) and water cement ratio (0.50), the average compressive strength of concrete obtained using fresh and salt water ranges from 25.05 -38.13N/mm2 and 23.58-36.03N/mm2 respectively while the flexural strength ranges from 6.18-9.88N/mm2 and 6.15 – 10.39N/mm2 for fresh and salt water respectively. The initial and final setting time of cement using fresh water is 50mins and 587mins while that of salt water is 55mins and 605mins respectively
Evaluation of the Hydraulic Conductivity of Compacted Laterite-Metakaolin Mixtures for Solid Waste Leachate Containment
This paper presents the results of a study conducted to investigate the benefits of using metakaolin (MK) with laterite as liner material for containment of municipal solid waste (MSW). Laboratory tests were conducted on laterite specimens treated with MK at concentrations of 0 - 20 % by weight of the soil and compacted using four types of compaction energies. Hydraulic conductivity was determined based on permeation of the compacted laterite - MK mixtures with deionized water (DW) and municipal solid waste leachate (MSWL), respectively. Deionized water was the reference permeant fluid. The results showed that hydraulic conductivity generally decreased with increase in the percentage addition of MK to the soil. From an economic and sustainability point of view, it has been found from the results that 5 % MK can be added to soil and compacted at moulding water content of 14.1 % using the West African Standard (WAS) compaction energy to achieve the regulatory hydraulic conductivity of less than or equal to 1 x 10-9 m/s for compacted soil liner. The natural logarithm of the hydraulic conductivity experimental results were computed and used to develop regression equations for estimating hydraulic conductivity given MK contents and compaction energies. The results of the two-way analysis of variance (ANOVA) test carried out at 5 % level of significance showed that calculated F-statistics are statistically significant and the measured values of hydraulic conductivity compare well with the predicted values. The developed models can therefore be used to give good estimates of hydraulic conductivity of soils having similar properties with the laterite investigated in this study. Therefore, the developed models can be used to give good estimates of hydraulic conductivity of soils having similar properties with the laterite investigated in this study. Keywords _ Deionized water, Hydraulic conductivity, Leachate, Metakaolin, Municipal solid waste
Effects of the Addition of Sawdust Ash and Iron Ore Tailings on the Characteristics of Clay Soil
An evaluation of the effects of additives and firing temperatures on clay bricks characteristics was studied. The two (2) additives used were sawdust ash (SDA) and iron ore tailing wastes (IOTW), and the five (5) firing temperatures of 400o C to 1200o C at intervals of 200o C were applied. The fired bricks were tested for linear shrinkage, water absorption, density, and compressive strength. The results of the investigations showed that firing temperature improved the clay brick characteristics across all replacement levels. However, the SDA additions increased the linear shrinkage and the water absorption but decreased the density and compressive strength. On the other hand, the addition of IOTW to the clay-SDA mixture, reduced both the linear shrinkage and water absorption of the clay bricks, and increased the density and compressive strength. The statistical values and the regression models derived on the experimental data using Minitab 18 Software were significant
Hydraulic Conductivity of Compacted Lateritic Soil Partially Replaced with Metakaolin
The study investigates the potentials of using metakaolin (MK) to improve the properties of compacted lateritic soil for hydraulic barrier system for containment of municipal solid waste (MSW). Oxide compositions determined by the X-ray fluorescence (XRF) show that MK contains Silicon oxide, SiO2 (53.4 %), Aluminium oxide Al2O3 (34.2 %), Titanium oxide, TiO2 (5.97 %) and Iron oxide, Fe2O3 (3.84 %) in high proportion. The soil was replaced with 0 %, 5 %, 10 %, 15 % and 20 % MK and compacted using four compaction energy levels namely: the Reduced British Standard Light (RBSL), British Standard Light (BSL), West African Standard (WAS) or “Intermediate” and British Standard Heavy (BSH) over a range of molding water contents (10 - 25 %). Unconfined compressive strength (UCS) and hydraulic conductivity tests were conducted and the results obtained were used to evaluate whether the lateritic soil partially replaced with MK conforms with the specifications for barrier systems for MSW containment. The results of this study show a general improvement in UCS of the soil specimens with increase in the percentage replacement of MK. Results of the study also show that hydraulic conductivity values of the specimens permeated with leachate are better than the results of hydraulic conductivities obtained when de-ionized water (DIW) was used as the permeant fluid. The specimens replaced with 5-20 % MK and compacted using the BSH compaction energy yielded hydraulic conductivities on the orders of 6.3 x 10-10 m/s to 2.2 x 10-10 m/s when DIW was used as the permeant fluid. On the other hand, the specimens compacted using the WAS and BSH compaction energies and permeated with leachate yielded hydraulic conductivity values in ranging from 6.8 x 10-10 m/s to 3.6 x 10-11 m/s. These hydraulic conductivity values met the regulatory maximum hydraulic conductivity (i.e. ? 1 x 10-9 m/s) for construction of liner and cover systems for MSW containment. Keywords: Compaction energy, Metakaolin, Hydraulic conductivity, Unconfined compressive strength, Municipal solid waste leachate, De-ionized wate
A Lesson from Vernacular Architecture in Nigeria
Contemporary architecture has its roots from the vernacular. Every cultural group in the world has its own form of vernacular though the approach may vary from place to place and from people to people. Vernacular architecture has many values which are relevant to contemporary architecture today. This paper looks at vernacular architecture in Nigeria as practised by two ethnic groups who have varying climatic, religious and socio-cultural practices. The approaches to architecture by these two groups, i.e. the Hausas and Igbos, are looked at with the intention of finding positive values in the vernacular which can be applied to the contemporary. One of such values as seen in this paper is the harmony of traditional building materials with nature. Local building materials are able to meet housing needs without having a detrimental effect on the environment. More emphasis should therefore be given to local building materials in the building industry today. The paper concludes by stating that for contemporary architecture to adequately meet the needs of man today, vernacular values which apply to the cultural and climatic needs of such places should be selected and imbibed
Characteristics of Ordinary Portland Cement Paste Containing Rice Husk Ash and Conplast
An experimental investigation on rice husk ash (RHA) and Conplast SP 430 (CP-admixture) was carried out to evaluate their effects on the paste characteristics (soundness, consistency, initial and final setting times). The cement content used was 300g and the brand was ‘Ashaka’ Portland cement conforming to BS EN 12 1973. Various combinations of the mixtures OPC-RHA-CP-admixture were used to establish performance characteristics of the pastes. Statistical characteristics, and linear regression models (no-transformation, λ = 0.5, and Box-Cox transformation) were developed on the experimental data for decisions on their performances.
Physio-Chemical Characteristics and Acid-Sulphate Reactions of Moringa Oleifera Seed Powder Cement Paste and Concrete
The evaluation of the effect of using moringa oleifera seed powder (MOSP) to partially replace cement by wt. % has been carried out. A mix parameter of 1: 1.7: 2.5, with designed strength of 20 kN-m2 , and a cement content of 420 kg-m3 , water-cementitious ratio of 0.5, to produce concrete specimens to which percentages of MOSP by wt. % of cement were added and cured for 90 days. Basic characteristics of the MOSP material were determined (Consistency and Setting times), and the concrete parameters workability, density, water absorption and compressive strength were also determined. The analysis of the experimental data collected on MOSP and MOSP-concrete confirmed that MOSP is substantially silicate (Quartz and Cristobalite). These have greatly to a large extent imparted on the quality of MOSP-concrete produced good quality concrete. The optimum replacement was at 0.2 % wt. % of cement
A Lesson From Vernacular Architecture in Nigeria
Contemporary architecture has its roots from the vernacular. Every cultural group in the world has its own form of vernacular though the approach may vary from place to place and from people to people. Vernacular architecture has many values which are relevant to contemporary architecture today. This paper looks at vernacular architecture in Nigeria as practiced by two ethnic groups who have varying climatic, religious and socio-cultural practices. The approaches to architecture by these two groups, i.e. the Hausas and Igbos, are looked at with the intention of finding positive values in the vernacular which can be applied to the contemporary. One of such values as seen in this paper is the harmony of traditional building materials with nature. Local building materials are able to meet housing needs without having detrimental effect on the environment. More emphasis should therefore be given to local building materials in the building industry today. The paper concludes by stating that for contemporary architecture to adequately meet the needs of man today, vernacular values which apply to the cultural and climatic needs of such places should be selected and imbibed
A review of tertiary BIM education for advanced engineering communication with visualization
SPECT with Tc-99m-labeled agents is better able to detect viability after nitrate administration. Nitrates induce vasoclilation and may increase blood flow to severely hypoperfused but viable myocardium, thereby enhancing tracer delivery and improving the detection of viability. Quantitative data on the changes in blood flow are lacking in SPECT but can be provided by PET. The aim of the present study was to use PET to evaluate whether nitrate administration increases blood flow to chronically dysfunctional but viable myocardium. Methods: N-13-Ammonia PET was used to quantitatively assess blood flow, and F-18-FDG PET was used as the gold standard to detect viable myocardium. Twenty-five patients with chronic ischemic left ventricular dysfunction underwent N-13-ammonia PET at rest and after nitrate administration. Results: A significant increase in nitrate-enhanced blood flow was observed in viable segments (from 0.55 +/- 0.15 to 0.68 +/- 0.24 mL/min/g, P <0.05). No statistically significant change in blood flow was observed in nonviable segments (0.60 +/- 0.20 vs. 0.55 +/- 0.18 mL/min/g). A ratio of at least 1.1 for nitrate-enhanced flow to resting flow allowed optimal detection of viable myocardium, yielding a sensitivity of 82% with a specificity of 100%. Conclusion: N-13-Ammonia PET showed a significant increase in nitrate-enhanced blood flow in viable myocardium, whereas blood flow remained unchanged after nitrate administration in nonviable myocardium. Nitrate use during myocardial perfusion imaging will lead to improved assessment of myocardial viability
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