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Volume 11 (4); 25 July, 2021
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Research Paper
Performance of Fly Ash as Replacement for Non-Renewable Constituent in Asphaltic Concrete for Road Development
Chukwuka E, Olugbenga O, Olufikayo A and Isiaka OO.
J. Civil Eng. Urban., 11(4): 25-33, 2021; pii:S225204302100004-11
DOI: https://dx.doi.org/10.54203/jceu.2021.4
Abstract
The non-renewable constituent used in asphalt concrete consumed large amount of materials resulting an increase in the price of asphalt mixture and consequently the cost of road development. On the other hand, huge industrial waste being generated daily from human activities causes environmental degradations. Thus, the study evaluates the performance of fly ash (FA) in asphalt concrete development targeted for road application. The aggregate, bitumen, and fly ash were characterized before being used. The stone dust in asphalt mixture was replaced with FA in predetermined proportions of 2, 4, 6, and 8% to produce a cylindrical specimen of asphalt mixture concrete. Marshal stability test, flow test, X-ray diffraction (XRD), X-ray Fluorescence (XRF) and Scanning Electron Microscope (SEM) was conducted on the composite samples. From the results, stability values of 7.39, 7.70, 7.90 and 8.22 KN was obtained at 2, 4, 6 and 8% replacements, respectively. Hence, the optimum value of 8.22 KN obtained from 8% partial replacement with FA is adequate for heavy traffic while other partial replacement from 2- 6% with stability within the range of 7.39-7.90 KN is suitable for medium traffic in accordance with the criteria for the marshal mix design method provided by Asphalt institute (1997). Corresponding values of 3.7, 3.5, 3.3 and 3.0 mm was obtained for the flow. The flow, air void, void in mineral aggregates and void filled with bitumen results all satisfied Nigeria general specification for road and bridges (1997). Therefore, fly ash can be used as partial replacement in asphaltic concrete to enhance the performance of the mix with a reduced cost for pavement construction.
Keywords: Asphalt Concrete, Fly Ash, Road, Stability, Transportation
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Research Paper
Comparison of Generalized Extreme Value, Log Normal and Weibull Distributions for Assessment of Low-Flow
Vivekanandan N.
J. Civil Eng. Urban., 11(4): 34-41, 2021; pii:S225204302100005-11
DOI: https://dx.doi.org/10.54203/jceu.2021.5
Abstract
Assessment of low-flow is an important aspect for water quality management, reservoir storage design, determining minimum release policy and safe surface water withdrawals. For which, the annual minimum d-day average flow is generally adopted procedure for characterizing the low-flow in a stream, which can be obtained by averaging the flow using moving average method for ‘d’ consecutive days viz., 7-, 10-, 14- and 30- days. This paper presents a study on comparison of three probability distributions such as Generalized Extreme Value, 2-parameter Log Normal (LN2) and Weibull adopted in estimation of low-flow for river Cauvery at Kollegal gauging site. The parameters are determined by three methods viz., method of moments, maximum likelihood method and L-Moments (LMO), and are used for estimation of low-flow. The adequacy of fitting probability distributions adopted in low-flow frequency analysis is evaluated by quantitative assessment through Goodness-of-Fit (viz., Chi-Square and Kolmogorov-Smirnov) and diagnostic (viz., correlation coefficient and root mean squared error) tests, and qualitative assessment using the fitted curves of the estimated low-flow. The results of quantitative and qualitative assessments indicate that LN2 (LMO) is better suited amongst three distributions adopted in estimation of 7-, 10-, 14- and 30- day low-flows for river Cauvery at Kollegal site.
Keywords: Chi-Square, Correlation Coefficient, Low-flow, Generalized Extreme Value, Kolmogorov-Smirnov, L-Moments, Log Normal, Root Mean Squared Error, Weibull
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