Papers by Keyword: Ultra High Toughness

Abstract: Good combination of high strength and high toughness has been considered as a critical factor of ultra-high strength steel plates. In this paper, a novel high strength steel plate of HSLA type containing Cu with 910MPa yield strength and 1163MPa tensile strength has been developed using an advanced TMCP (thermo-mechanical control processing) technology. The steel plates provide excellent combination of high strength, toughness and deformability. Microstructural evolution and mechanical properties of this steel during hot-working have been investigated. It is demonstrated that, at the relatively higher finish rolling temperature and cooling rate, the microstructure consists of acicular and granular bainite structures and a small amount of low bainite /martensite whose lath width is approximately 200~300nm. For the as-rolled conditions, despite the high strength and so low yield ratio, impact energy about 154J and fully ductility fracture at -90°C can still be obtained as documented for as-hot rolled plates.

Abstract: Ultra high toughness cementitious composite (UHTCC) shows a unique characteristic of limit the crack width with multiple fine cracks whether it is subjected to tensile load or bending load. The failure pattern of UHTCC exhibits saturated multiple fine cracks, so the durability of structures will be improved markedly by utilizing UHTCC partly or entirely instead of concrete. In this study, considering the tensile strain capacity of UHTCC, a formula for calculating the critical rebar corrosion ratio when the UHTCC cover cracking due to rebar corrosion through the theory of plasticity and cylindrical cavity expansion theory. The effectiveness of UHTCC for restraining the cover cracking due to rebar corrosion has been proved by a calculated example. The influences on critical rebar corrosion when the UHTCC cover cracking due to rebar corrosion have been analyzed. The analytical results showed that UHTCC could effectively retard the cover expansive cracking due to corrosion of reinforcing bars, and prolong the service life of concrete structures subjected to the environment being at risk of corrosion.

Abstract: Ultra high toughness cementitious composite (UHTCC) is a newly developed, high performance, fiber-reinforced cementitious composite with substantial benefit in both high ductility and improved durability due to its tight crack width. The failure pattern of UHTCC exhibits saturated multiple fine cracks, so the durability of structures will be improved markedly by utilizing UHTCC partly or entirely instead of concrete. In this study, a total of 20 beams, including reinforced concrete beams that the cover zone was replaced by UHTCC (the thickness is 15mm, not containing reinforcement, and 50mm, containing reinforcement, respectively), reinforced concrete beams and reinforced UHTCC beams, had been manufactured. A power supply was used to accelerate the corrosion process of reinforcing bars, inducing different degrees of corrosion (the corrosion ratio was 1%, 2%, 4% and 5%) into reinforcing bars. The time of the cracks occurred and the crack width were recorded and the beams having different corrosion ratios of reinforcing bars were then tested under four-point bending for their load-deflection relations. The results showed that UHTCC could restrict the corrosion expansive crack of cover effectively, convert the crack pattern, and delay the appearance of first corrosion expansive crack, thereby to raise the service life of reinforcement concrete structures or components. Meanwhile, the bending test of beams after accelerated corrosion showed that the beams with a cover replaced by 50mm UHTCC and reinforced UHTCC having smaller amount of strength reduction and a reasonable ductile failure after corrosion. The experimental results showed that UHTCC could effectively delay the cover expansive cracking due to corrosion of reinforcing bars retain the ductile properties of reinforced concrete beams after reinforcing bar corroded.