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Author(s):
Seidu Tijani, Rotimi Juwon Abdulazeez.
Page No : 1-14
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Effect of Voltage variation on the Geotechnical Properties and Removal Efficiency of heavy metal contaminants from contaminated soil using Electrokinetic Remediation Technique
Abstract
A lot of research work has shown that despite the effectiveness of the electrokinetic remediation technology in decontaminating heavy metal contaminated soils, more work is still required to fully understand the role of voltage in the remediation process. There is need to establish the optimum voltage that would best remove heavy metals from such contaminated soil and its attendant effect on the geotechnical properties of the remediated soil. Effect of voltage variation on the removal efficiency of lead, copper and the geotechnical properties of remediated heavy metal contaminated soil using electrokinetic remediation technique was investigated in this research. The contaminated soil was remediated by applying direct current (DC) to the remediation setup at 0.5V/cm, 1.0V/cm, 1.5V/cm and 2.0V/cm. The concentration of the heavy metals after remediation were determined using the Oxford Instrument Analyzer to evaluate removal efficiency, geotechnical properties tests were also conducted on the soil specimens at each phase of remediation. The results showed that the lead removal efficiency was highest at 2.0V/cm (86%) with the shortest remediation time of 5days and lowest at 0.5V/cm (39%) at 9days. 52% of copper was removed at 2.0V/cm in 5days and 29% at 0.5V/cm after 9days of remediation. At 1.0V/cm, the lead and copper removal efficiency are 75% and 40% respectively. There was no significant change in the Specific Gravity of all the soil samples with the test results lying between 2.0 and 2.2. The soil is generally silty fine sand with not less than 40% passing the sieve no.200 (75micron). 45% passed through sieve 75micron for unremediated soil and slightly reduced to 40%, 40.4% and 40.2% for 30V, 45V and 60V respectively. The soil is non-plastic with the liquid limit of between 25.8% and 29.5% belonging to the A-4 group of soil. The maximum dry density improved across all the three compactive efforts, from 1.8390g/cm3 to 1.8480g/cm3 with WAS compactive effort and from 1.8000g/cm3 to 1.8320g/cm3 with BSL method with an average optimum moisture content of 10%. The CBR values increases with increase in voltage applied. The unsoaked CBR values averagely increased with 31%, 18% and 7% for BSH, WAS and BSL compactive efforts respectively. The durability index with resistances of 89% and 90% to loss in strength was recorded at 1.0V/cm and 1.5V/cm respectively, this, when compared to the resistance to loss in strength of 71% in unremediated soil has respectively 25.3% and 26.8% durability advantages. There was also a consistent increase in the UCS values, from 381kN/m2 to 474kN/m2 and from 351kN/m2 to 447kN/m2 when WAS and BSL methods of compaction were used. Generally, there was improvement in the geotechnical properties of the remediated soil. These improvements are maximum at 1.0V/cm and 1.5V/cm with little or no further improvement at 2.0V/cm. It is recommended that 1.0V and 1.5V are suitable for remediation purpose since it requires low energy consumption.
| 2 |
Author(s):
Muhammad Auwal Ibrahim, Shashivendra Dulawat, Esar Ahmad (Ph.D.), Ibrahim Abdullahi Ibrahim, Umar Shehu Ibrahim, Salihu Sarki Ubayi, Idris zakariyya Ishaq.
Page No : 15-25
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A Review on the Curing of Concrete using Different Methods.
Abstract
The hardened properties and durability of concrete are dependent on the moisture and temperature condition of the concrete during its hydration process. This review explores various methods of curing concrete focusing on their effectiveness in improving the performance and sustainability of concrete structures. Traditional method of curing such as ponding, sprinkling and the modern curing techniques such as curing compounds, self-curing agents and steam curing are compared. The advantages and disadvantages of these methods are highlighted and Water curing is found to be the most effective method of concrete curing, for it allows for the maintenance of adequate moisture and temperature, and it did not change the macro and microscopic structure of the concrete. . the research methodology are extensive literature, experimental studies and performance evaluations. The review aimed in providing a comprehensive understanding of the best curing practices for different project and working conditions.
| 3 |
Author(s):
Ibrahim A. O., Jimoh A. O., Olaniyi O. A., Abioye T., Oluwapelumi O. A..
Page No : 26-35
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Comparative Analysis of the Strength of Concretes Made from Different Aggregates.
Abstract
The paper aimed to explore the replacement of river sand in concrete with iron fillings and sawdust at various percentages (10%, 20%, and 30%). The study used a 1:2:4 mix design and a water-cement ratio of 0.5. Wooden square cubes of dimensions 100 x 100 x 100 mm were employed, resulting in 42 concrete cubes. . Tests were conducted to assess particle size distribution, specific gravity, bulk density, aggregate impact value, aggregate abrasion value, and compressive strength at 7th and 28th days of curing. Notably, after 7 days, compressive strength results showed that concrete with a 10% iron fillings replacement (18.5 N/mm²) had a higher average strength than concrete with 100% river sand (17.6 N/mm²). However, as the percentage of iron fillings increased to 20% (9.8 N/mm²) and 30% (7.1N/mm²), the compressive strength decreased. On the other hand, concrete with sawdust replacements at 10% (3.7 N/mm²), 20% (1.4 N/mm²), and 30% (0.5 N/mm²) exhibited significantly lower load-bearing capacity. These trends persisted at the 28th day, with the compressive strength decreasing with increasing percentages of iron fillings (10%: 20.3 N/mm², 20%: 11.2 N/mm², 30%: 11.6 N/mm²) and sawdust (10%: 3.4 N/mm², 20%: 2.3 N/mm², 30%: 1.4 N/mm²). The findings suggest that a low percentage of iron fillings can be used in combination with river sand to maintain load-bearing capacity, but sawdust or wood particles should be avoided as they adversely affect compressive strength. This research contributes valuable insights into the use of these materials in concrete mixtures.
