Hirozo Mihashi

Corrosion durability of strain hardening fibre-reinforced cementitious composites

Abstract This paper presents some experimental results on the corrosion durability of cracked reinforced concrete beams made with plain mortar and strain hardening fibre-reinforced cementitious composites (SHFRCCs) containing polyethylene and steel-polyethylene hybrid fibres. All beams are subjected to cyclic wetting and drying using water containing 3% sodium chloride (NaCl). In addition, an external potential is also applied to the reinforcement to accelerate the corrosion. Corrosion of steel bars is monitored through a pair of sensors attached to the reinforcing bar in each beam. Test results show that beams containing SHFRCC material exhibited better corrosion protection than that of plain mortar beams. Among all specimens, beams containing hybrid steel-polyethylene fibre-reinforced SHFRCC exhibited the best corrosion protection.

Characteristics of secondary flexures in uniaxial tension test of concrete

In the uniaxial tension test of concrete, inevitably some secondary flexures occur. However the characteristics of the secondary flexures are not well understood among others because of the complexity of performing the uniaxial tension test without the flexures. In this paper the uniaxial tension test in which secondary flexures are minimized, by a specially developed device, are compared to the tests where secondary flexures are left to develop freely. Experimental results and theoretical calculations are shown for the influence of secondary flexures on load-deformation curves, tensile strength and strain energy of the specimen. Plural flexures which grow finally plural cracks were also analyzed concerning to an experimental result. It is concluded that secondary flexures should be minimized, because they produce considerable error to the load-deformation curve and tensile strength. Furthermore, secondary flexures should be controlled continuously during the test because the minimized state is an unstable equilibrium of strain energy in the specimen. And the flexures can only be minimized by using a notched specimen because plural flexures occur in an un-notched specimen.