Study of Mechanical Properties of Structural Lightweight Concrete Reinforced with Hybrid Fibers

In this research the mechanical properties of structural lightweight concrete including compressive, tensile and flexural strengths and energy absorption using five types of fibres (industrial and scrap steel, glass, polypropylene and straw) in the form of single type of fibre or combination of two or three types of fibres have been studied. At the first stage, two reference samples of lightweight concrete and normal concrete without fibres are produced. At the second stage, samples of lightweight concrete with single type of fibres of volume percentages of 0.1, 0.25, 0.4, and 0.5 are made. At the third stage, samples of lightweight concrete containing twin combined forms of fibers with volume percentages of (0.1, 0.4), (0.4, 0.1) and (0.25, 0.25) are produced. At last stage, samples of lightweight concrete with triad combination forms of fibres with volume percentages of (0.1,0.1,0.3), (0.1,0.3,0.1) and (0.3,0.1,0.1) are produced. Obtained results indicate that samples with combination of two types of fibres have had the best behaviour compared to other samples. The highest compressive strength have been resulted from the combination of industrial steel and polypropylene fibres and the highest tensile and flexural strengths have been obtained from the combination of glass and polypropylene fibres. The highest energy absorption is related to the combination of industrial steel and glass fibres.