Several stress-strain models were used to predict the strengths of steel fiber reinforced concrete, which are distinctive of the material. However, insufficient research has been done on the influence of hybrid fiber combinations (comprising two or more distinct fibers) on the characteristics of concrete. For this reason, the researchers conducted an experimental program to determine the stress-strain relationship of 30 concrete samples reinforced with two distinct fibers (a hybrid of polyvinyl alcohol and steel fibers), with compressive strengths ranging from 40 to 120 MPa. A total of 80 % of the experimental results were used to develop a new empirical stress-strain model, which was accomplished through the application of the particle swarm optimization (PSO) tech-nique. It was discovered in this investigation that the new stress-strain model predictions are consistent with the remaining 20% of the experimental stress-strain curves obtained. Case studies of hybrid–fiber–reinforced concrete constructions were investigated in order to better understand the behavior of such elements. The data revealed that the proposed model has the highest absolute relative error (ARE) frequencies (ARE10 % and the lowest absolute relative error (ARE > 15 %) frequencies (ARE > 15 %).
The most used material in the world after water is concrete, which depends mainly on its manufacture of cement leading to the emission of carbon dioxide (CO2), flying dust, and other greenhouse gasses (GHGs) resulting in pollution of the atmosphere. The emission of CO2 from cement production is approximately 5% of the global anthropogenic CO2. This research focuses on investigating the amount of CO2 emission from the Iraqi General Cement Company plants includes the cement factories of Kirkuk, Al-Qa’em, Fallujah, and Kubaisa, using the GHGs Protocol Measures Program (specifically cement based-method). The data required for cement production was provided by the Iraqi Ministry of Industry and Minerals throughout 25 years. The results showed that the largest amount of CO2 emissions cumulatively over 25 years was from the Kubaisa plant with an average emission amount of approximately 7,613,605 tons/25 years. While the lowest cumulative amount of emission was by Fallujah cement plant represented by about 868,341 tons/25 years. On the other hand, the highest and lowest production amount was from Kubaisa and Fallujah plants at 105% and 0.6% in 1989 and 2008 respectively relative to the design capacity. Shifting to renewable and clean energies that limit the amount of CO2 emitted to the atmosphere is highly recommended, although this requires facing problematic challenges.
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