|
Ultra-high performance concrete (UHPC) is characterized by compressive strength above 120 MPa and high durability. It is a known fact that, the properties of concrete are improved with the addition of fibres. The steel fibre (SF) is generally used for most structural purposes. A lot of research revealed that the steel fibre in concrete could make effectively improve the interfacial transition zone between cement paste and aggregate, and constraint the occurrence and development of concrete crack. A main advantage of steel fibre reinforced concrete is high energy absorption capacity and high toughness. The steel fibres are able to bridge the cracks and transfer the stress across the cracks. The polypropylene fibres (PF) are used to improve mechanical and physical properties, especially splitting tensile strength, flexural strength and long-term concrete shrinkage. The influence of the fiber content and the curing period on the physical and mechanical properties of steel and polypropylene fiber reinforced UHPC were studied by some researchers. No investigation in the literature is currently available on the properties of UHPC with SF and PF after long-term curing. This study has investigated the effect of age on the mechanical properties of hooked-end steel and polypropylene fiber reinforced ultra-high performance concrete. Various physical properties are evaluated, i.e.: absorbability, density, open porosity, velocity of propagation of ultrasonic pulses through concrete. Compressive strength, splitting tensile strength, flexural tensile strength and modulus of elasticity were determined at 28, 56 and 730 days. Comparative strength development of fiber reinforced mixes at 0.5%, 1%, 1.5% and 2% by volume fractions in relation to the mix without fibers was observed. Good correlations between the compressive strength and the ultrasonic pulse velocity, and the compressive strength - tensile strengths are established. Steel and polypropylene fibers significantly increased the compressive strength, splitting tensile strength, flexural tensile strength and modulus of elasticity of UHPC after 2 years. It seems that steel fiber reinforced UHPC has better properties than the polypropylene fiber reinforced UHPC.
|
