In developing countries, one of the usual practices is the uncontrolled, open burning of corn stalk (CS) or its utilization as a fuel. It is known that the ash obtained under uncontrolled burning conditions constitutes blackish and unburnt carbon particles as well as whitish and grayish particles (representing crystallization of silica) due to over burning. However, controlling the burning process can improve the quality of ash produced to effectively use it in cement-based materials. Hence, this research was aimed at exploring the pozzolanic properties of corn stalk ash upon calcination and grinding, for it to be used in the manufacturing of sustainable cement-based materials. In order to obtain a suitable corn stalk ash (CSA), which can be used in cement/concrete, a research investigation consisted of two phases. In the first phase, calcination was carried out at 400°C, 500°C, 600°C, 700°C, and 800°C for 2 hours. The tests applied on the resulting ashes were weight loss, XRD, pozzolanic activity index (PAI), Chapelle, Fratini, and consistency. From XRD spectra, it was found that, at lower temperatures, silica remained amorphous, while it crystallized at higher temperature. Ash combusted at a temperature of 500°C possessed largest pozzolanic activity of 96.8%, had a Fratini CaO reduction of 93.2%, and Chapelle activity of 856.3 mg/g. Thus, 500°C was chosen as an optimum calcination temperature. In the second phase, the ash produced at 500°C was grinded for durations of 30, 60, 120, and 240 minutes to ascertain the optimum grinding times. Resulting ashes were examined for hydrometer analysis, Blaine fineness, Chapelle activity, and pozzolanic activity. Experiment outcomes revealed a direct relationship between values of Blaine fineness, surface area, Chapelle activity, PAI, and grinding duration. It was concluded that CSA can be used as a pozzolan, and thus, its utilization in cement/concrete would solve ash disposal problems and aid in production of eco-friendly cement/concrete.
Objective: To determine the calculating justification methods of fibre-reinforced spans and scientific evidence of the structural method of dispersed reinforced concrete constructions in drily-hot climate for high-speed mainline railroads, to reveal advantages connected with fibre application in the process of construction, to determine the ways of total costs reduction while providing qualitative reliability characteristics of spans under construction. Methods: Comparative analysis, mathematical modeling. Results: Calculating principles of fibre-reinforced elements of spans were specified. The study was aimed at application solving, with regard to climate in Uzbekistan, and determined the parameters of Lр = 66 m fibre-reinforced concrete span, specified by the objective of scientific study concerning the bridgework for high-speed mainline railroad. Practical importance: Methodological foundation for fibre-reinforced concrete spans calculation was developed.
Ground floor reinforced concrete columns are vulnerable to blast loading of close by distance (i.e. less than 3 1/3 m/kg ). In this work, a 25-story commercial building was designed in lowseismic and high-seismic regions respectively to find the typical column dimensions and reinforcements. A finite element model was developed to simulate above mentioned blast loading scenarios and to evaluate effectiveness of FRP retrofit. The model was found to be adequate in capturing the trends of deformation and damages as expected and effectiveness of FRP in providing additional confinement. The qualitative results thus obtained are presented.Structures Congress 2020 Downloaded from ascelibrary.org by 44.224.250.200 on 07/16/20.
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