Aims: This study examines the possibility of using seawater as an alternative to freshwater in concrete mixing and curing in areas prone to saltwater. The study was as a result of shortage and scarcity of Freshwater in some parts of the world; mostly in the coastal areas, where seawater is the only source of water. Place and Duration of Study: Seawater was obtained from Port Harcourt Tourist beach, River State, Nigeria was used to mix and cure a set of concrete cubes (CSW). And freshwater obtained from our Civil Engineering laboratory was used to mix and cure another set of concrete cubes (CFW) that serves as a control. The maximum days of curing were 28days. Methodology: Concrete cubes of 150x150x150mm3 were produced and cured with sea and freshwater respectively. The compressive strength of those cubes were determined using Compression Testing Machine. The studied variable was only water used for mixing and curing of the concrete cubes. Other constituents of the concrete: cement, fine aggregate, and coarse aggregate were kept constant. Results: It was found that the compressive strengths of concrete cubes mixed and cured with seawater at 7, 14, 21 and 28days were within the acceptable limits and a bit higher than those of cubes mixed and cured with fresh water. The variation in compressive strength of CSW and CFW at the 28th day of curing was just 1.45%. Hence, the seawater didn’t affect the compressive strength. Conclusion: With the little variation in compressive strength between the CSW and CFW at the 28th day of curing; it is recommended that seawater can possibly be used for concrete mixing and curing in areas where freshwater is not available; provided that the concrete is kept inherently dry to prevent corrosion. In addition, higher concrete covers can be provided when designing the concrete structures. Meanwhile, careful and adequate design, well-supervised construction, and curing should be ensured to improve the ingress resistance of the concrete structures. However, the long-term effect of the seawater on the properties of concrete and reinforcements were not investigated.
The study explores the assessment of mechanical properties of steel fiber reinforcement in concrete production. Aimed at replacing the high cost conventional reinforcement in building constructions. The identical steel fibers are utilized at varied volume fractions of 0%, 1%, 2%, 3%, 4%, and 5% by the weight of cement. Compressive strength, flexural strength, and split tensile strength are among the strengths taken into account in this investigation. Eight beams and four cylindrical samples were prepared for the tests. Results obtained indicated that adding steel fiber to concrete with different volume fractions and the same aspect ratio significantly improved the results for compressive strength and flexure strength. The experimental results showed that the fibers alter the failure character from splitting of the concrete by significantly increasing the cracking resistance, and thereby noticeably increase the load bearing capacity of the elements. Therefore, fiber reinforcement can be used in place of high yield reinforcements in a low cost structures.
Small-scale construction companies are predominant in developing countries and it is the most hazardous places in construction sites. Accidents mostly occur on construction sites due to a high level of safety ignorance and the nonchalant attitude of workers and management. The research aimed to investigate the actual behavior of workers at the selected sites regarding safety compliance, nutrition, alcohol use and smoking. This is highly necessary due to the high level of reported accidents and fatalities of the workers. And also recommend measures for improving how safety practices are implemented at a construction site. The interview and questionnaire approach was adopted to study the 150 participants. The data were analysed through SPSS. Research shows that 85% of construction workers are non-compliant with safety regulations because of their ignorance, poor safety training and lack of inspectors It was discovered that the majority of the small-scale contractors had no written health and safety policy within their companies and that made the level of understanding of the workers on safety and health policies very low. This has made the workers not care about wearing safety devices. The study was also extended to include behaviors related to food, alcohol and smoking. It was discovered that most of the workers don’t observe simple hygiene and eat junk meals at the site. They smoke and share cigarettes on the site, not knowing that it was a means of sharing communicable diseases.
This research investigated the optimization of locally sourced aggregate, mixed with variable cement ratios to determine its optimum compressive strength. Samples of standard sizes of local fine and coarse aggregate were obtained at the popular excavation sites. The concrete materials were weighed, batched, mixed, cast and cured using four different mix proportions of 1:2:4, 1.2:2:4, 1.4:2:4 and 1.6:2:4 of cement, fine and coarse aggregate at constant water/cement ratio of 0.5. A total of 48 concrete cubes of 150mmx150mmx150mm were produced, cured for 7, 14, 21 and 28 days and tested. Mathematical model equation relating the compressive strength of the local stone with variability of cement was developed using Response Surface Methodology (RSM). The significance and suitability of the equation was confirmed using the analysis of variance (ANOVA). The ANOVA for the quadratic and Surface Cubic model shows that the adjusted R2 of 0.9808 and F-value of 227.76 in compressive strength of the concrete is confidently accounted for by the independent variable. This demonstrates that the equation's predictions of compressive strength for various concrete structures are accurate. Therefore, utilization of local aggregate is advised for the construction of most of the dominant low-rise residential buildings in Anambra and other neighbouring States.
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