Fibers have been considered an effective material that was used to improve the concrete's weak properties, namely its tensile strength, ductility, and crack resistance. Thus, the current study highlights two major objective, the former is the fibers shapes and types on the mechanical properties of the fresh and hardened concrete while the latter explores the impact of the fiber contents on the concrete mechanical properties developments. To achieve these targets six types of fibers (five of them made of steel and the last was polyolefin fibers) with various shapes are utilized. The tests were carried out to investigate the fibers shape and material contribution in the concrete mix properties improvement. The samples were subjected to destructive and non-destructive tests such as workability, compression, bending, and splitting. The non-destructive tests include ultrasonic pulse velocities and the Schmidt Hammer test. Three kinds of fibers (two of steel and one of polyolefin fiber) are used with variable content ratios of 0.5, 0.75, 1.0, and 1.5% to study the fiber content effect. Generally, the workability of fresh concrete has a reverse relationship with fiber presence and fiber content ratios. The compressive capacity, splitting and flexural strength has a direct proportion with fibers contents. The hooked steel fibers appeared the best results in terms of shape comparison. Doi: 10.28991/CEJ-2022-08-11-07 Full Text: PDF

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In this research, the structural behavior of reinforced concrete brackets cast with concrete containing different types of fibers was studied. Seven samples of reinforced concrete corbels were cast and tested. One specimen was cast without fiber as a reference, and the other samples were made with six different types of fibers at a constant volume fraction (1% of the total concrete volume). The fibers used in the research were made of two different materials: steel and polyolefin. One specimen was cast with polyolefin fiber, and in the five remaining samples, steel fiber was used. Straight, crimped, and three different dimensions of hooked fiber were used. The results showed that the corbels with straight and hooked end steel fiber (6, 5, and 3 cm length), crimped steel fiber sized 3 cm, straight steel fiber sized 12 mm, and straight polyolefin fiber sized 6 cm showed 69.2%, 57.7%, 38.5%, 61.5%, 92.3%, and 100% higher cracking loads than the control corbel made with normal concrete, respectively, as well as exhibiting (51.7%, 48.3%, 31.0%, 24.1%, 12.1%, and 3.4%) higher ultimate loads than the control corbel. From these results, it can be concluded that the shape of the steel fiber clearly affects the ultimate load. For the same length, and despite the lack of aspect ratio, steel fibers gave an increase in the maximum load of 46.6% when compared with polyolefin fibers. Doi: 10.28991/CEJ-2022-08-03-08 Full Text: PDF

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The construction industry has a multifaceted relationship with most sectors of the economy in all nations, as well as playing a vital role in social and economic development. One of the main factors that affect the development of the construction industry is labour productivity. The aim of this paper is to identify and rank the importance of the factors perceived in the literature to influence labour productivity in the Iraqi construction industry using Basra city as a case study. From the literature a total of 59 main factors were identified that may affect labour productivity on construction sites. These factors were classified into ten primary groups: (1) Managerial; (2) Environmental; (3) Manpower; (4) materials and equipment; (5) Schedule; (6) Safety; (7) Quality; (8) Motivation; (9) Technical; (10) External. The statistical analysis of these factors was prepared by using the Relative Importance Index (RII) and SPSS 23 programme. The grades obtained made it possible to assess the comparative importance of the factors as perceived by respondents.  The study provides comprehensive and explicit data for the construction contractors working in Iraq before providing the proposal for the bids taking in account the risks and the challenges mentioned in the study. Also it observed that the Iraqi government authority enforcement is essential to ensure that the construction labour productivity is fulfilled without losing in time and money. A structured questionnaire survey was sent to construction project managers, as a target group and the results showed in order to improve labour productivity in Basra city in particular and in Iraq in general. The results are show that the ten essential factors affect on construction labour productivity with different level of importance. In addition, all types of corruption must be considered to be serious problems affecting labour productivity.  Enforcement, conduct education and training for manpower by using new techniques are decreasing the difference between estimated and actual labour productivity.