Abstract
Deterioration of concrete’s integrity under elevated temperature requires an alteration in its composition to have better thermal stability. Fibre-reinforced concrete has shown significant improvements in concrete strength and this paper aimed to investigate the influence of steel (ST) and polypropylene (PP) fibres on the behaviour of high-performance concrete (HPC) exposed to elevated temperatures. Six mixtures were prepared and cast by adding one or two types of polypropylene fibre (54 and 9 mm) at 0.25 or 0.5% and either singly or in a hybrid combination, along with a fixed volumetric content at 1% of five-dimensional hooked steel (5DH) fibres. At the age of 28 days, samples were heated to the targeted temperature of 800 °C and cooled down naturally to the laboratory temperature. Visual inspection, flexural, split tensile and compressive strengths were examined before and after the exposure to elevated temperatures. Results exhibited that the hybridization of long and short PP fibres, along with the ST fibres, has notably improved all residual mechanical properties of HPC and kept the integrity of concrete after exposure to elevated temperatures. In addition, PP fibres can significantly prevent spalling, but ST fibres were ineffective in mitigating explosive spalling in beams specimens.
Highlights
The production improvement on the mechanical properties of high-performance concrete (HPC) is recently acknowledged as a remarkable research advancement compared to normal concrete, which enables a variety of structures, that require high mechanical strength, durability, flowability, ductility and the ease of casting the concrete to be constructed [1]
The loss in mass will influence the mechanical properties of concrete [61,62,63], especially the tensile strength because it is more sensitive to the voids
This paper aimed to investigate the influence of steel and propylene fibres mixture on HPC behaviour after exposure to elevated temperatures
Summary
The production improvement on the mechanical properties of high-performance concrete (HPC) is recently acknowledged as a remarkable research advancement compared to normal concrete, which enables a variety of structures, that require high mechanical strength, durability, flowability, ductility and the ease of casting the concrete to be constructed [1]. The addition of polypropylene fibres in concrete has shown an improvement in the splitting tensile and flexural strength, but not in terms of compressive strength [8,9]. Another common fibre used in research is steel fibres which leads to an increase in concrete’s overall mechanical properties such as impact resistance [10,11], ductility [12,13], tensile [2,14] and flexural [15]. The mix design of HPC requires using superplasticizer, the lowest possible water to binder ratio, and may contain mineral admixtures such as silica fume, Metakaolin and fly ash which densifies its microstructure [23,24,25]
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