Bond Performance of Locally Made UHPC with NSC at Elevated Temperatures

Abstract

Numerous techniques have been used for the rehabilitation of existing RC structures. Concrete or steel jacketing, fiber-reinforced polymer wrapping are commonly available techniques. To improve the response of bridge piers, fundamental approach employed in experimental investigations, is the confinement of concrete. Various techniques improve the strength and durability but few drawbacks, such as increase in weight of structures in concrete jacketing, fire resistance and debonding are a few drawbacks. Cementitious composites having compressive strength greater than 17 ksi, lie in the category of Ultra High-Performance Concrete. UHPC is a composite cementitious material with superior mechanical properties as compared to normal strength concrete. High packing density, low water cement ratio, high binder ratio, addition of high range water reducing admixtures and steel fibers results in increase in compressive strength by 3-5 times as that of ordinary Normal Strength Concrete. This study was carried out to investigate the response of Ultra High-Performance Concrete using Normal Strength Concrete as a substrate under varied loading conditions to simulate the actual forces on bridge piers, namely slant shear, bi surface shear and split tensile. Variation in substrate surface treatment (As cast, drill holes and grooves), inclusion of micro steel fibers and their effect on elevated temperatures was also studied. The experiments showed that the strength of bond decreases with the elevation in temperature. Drill hole technique exhibited the highest bond strength in bi surface shear. Whereas inclusion of steel fibers in UHPC resulted in increase in strength of bond due the bridging effect created between overlay and substrate.