Browsing by Author "Jemal, Kedir"

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    Experimental Investigation on Interface Shear and Tensile Strength Between Old and New Concrete at Different Moisture Condition
    (Addis Ababa University, 2020-10) Jemal, Kedir; Esayas, Gebreyouhannes (PhD)
    This research work is dedicated to experimental investigation on interface shear and tensile strength between old and new concrete. Twenty Push-off specimens were cast on the experimental program of the shear test. Nine specimens were monolithically cast and eleven specimens were cast with an interface. The surface of the substrate concrete was left as cast. The shear specimen was tested by varying confinements i.e. without confinement bar, with 100 and 125 initial confining strains. In addition to the above parameters, environmental conditions i.e. dry and wet conditions were also considered in this research. It was observed from this experimental program that the presence of an interface between old and new concrete causes a reduction of shear and tensile strength. For shear specimens, a reduction in shear strength of 77.39 %, 54.07 % and 38.92% for without confinement, 100 initial confinement strain, and 125 initial confinements respectively were obtained. The presence of water also has an adverse effect on the shear strength of concrete a reduction of up to 10% was observed. Nine specimens were cast on the experimental program for the tensile test. Three specimens with interface and dog bone shaped mold were cast and tested using direct tensile test six cylindrical specimens were cast monolithically. This experimental program also indicated the presence of an interface between old and new concrete reduces tensile strength by 50%-70%. The roughness of the shear specimen was measured. For monolithically cast surface arithmetic mean deviation of the profile, Ra coefficient, was higher and for cast with interface sample, Ra was smaller. The roughness was measured for five specimens. Evidently, as mean roughness increases shear bond strength also increase. A model of the specimen for both shear and tension without an interface was simulated on a nonlinear finite element analysis program DuCOM-COM3 for monotonic loading. The ultimate load was captured in fair proximity with the model.