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Increased productivity and improved working environment have had high priority in the development of concrete construction over the last decade. The major impact of the introduction of self-compacting concrete (SCC) is connected to the production process. The productivity is drastically improved through the elimination of vibration compaction and process reorganization. The working environment is significantly enhanced through avoidance of vibration induced damages, reduced noise and improved safety. Additionally, SCC technology has improved the performance in terms of hardened concrete properties like surface quality, strength and durability. The main objective of this research was to determine the optimum content of fibers (steel and polypropylene fibers) used in SCC. The effect of different fibers on the fresh and hardened properties was studied. An experimental investigation on the mechanical properties, including compressive strength, flexural strength and impact strength of fiber reinforced self-compacting concrete was performed. The results of the investigation showed that: the optimum dosage of steel and polypropylene fiber was 0.75% and 1.0% of the cement content, respectively. The impact performance was also improved due to the use of fibers. The control mix specimen failed suddenly in flexure and impact, the counterpart specimens contain fibers failed in a ductile manner, and failure was accompanied by several cracks.

Highlights• PEG 400 admixture was used in concrete mixes produced for hot weather conditions • Dry materials, mixing water and curing temperatures simulated hot weather • Properties of PEG samples were found to be superior to the control concrete • Results cannot to attributed only to prevention of pore water escape by PEG 400 • A proposal was made to explain the results based on information from the literature ABSTRACT Hot climates prevail in many regions of the globe. The average summer temperature of hot arid areas is in the range of 40-50°C with temperatures exceeding these values under direct solar radiation. Curing concrete in these regions may be challenging due to limited availability of suitable water for curing and/or rapid loss of curing water by evaporation. For many years self-curing admixtures were recommended as an alternative to water curing, however, limited studies have been conducted on their performance in hot weather conditions. In this investigation, the effects of a hot climate on the fresh and hardened properties of self-curing (SC) concrete and normal conventional concrete (NC) in hot weather were studied. A watersoluble polymer self-curing agent, polyethylene glycol (PEG 400), was added to the SC mixes. The testing parameters were concrete dry materials (25 or 50 O C) and/or mix water temperatures (5, 20 or 35 O C) at the time of mixing. NC samples were continuously water cured at 25 or 50 O C, whereas the SC ones were air cured at the same temperatures. The tested properties were workability, compressive strength, splitting tensile strength, and flexural strength. It was found that SC outperformed NC under varying conditions. The results could not be simply attributed to the retention of mix water by the self-curing admixture. A more comprehensive explanation for the observations is proposed.

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The main aim of this research is studying the effect of hot weather on the properties of self-compacting concrete and conventional concrete in both fresh and hardened state. Also, this research extends to improve the behavior of self-compacting concrete in hot weather. The main parameters were surrounding weather temperature (5°C, 20°C and 35°C), concrete materials temperatures’ (25°C, 50°C), curing temperatures (25°C and 50°C) and admixtures (using a retarder). Two stages were carried out to achieve the research aim. The behavior of self-compacting concrete compared to conventional concrete was evaluated in the first stage. Based on the first stage, attempts to enhance the concrete properties were evaluated in the second stage. Precautions on mixing and placing concrete in these climates are considered. Results are a drive in terms of; workability tests, compressive strength, splitting tensile strength, and flexural strength. Test results showed that self-compacting concrete behavior and strengths were better than conventional concrete. Slump test, J-ring and V-funnel test were used to evaluate the fresh properties of the self-compacting concrete. Drying shrinkage of self-compacting concrete in hot weather were also evaluated.

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