Member Size and Coarse Aggregate Size Effect on Bond Strength of a Reinforced Concrete Member

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Addis Ababa University


The utilization of reinforced concrete as a structural material is derived from the combination of concrete that is strong and relatively durable in compression with reinforcing steel that is strong and ductile in tension. Maintaining composite action requires transfer of load between the concrete and steel. This load transfer is referred to as bond and is idealized as a continuous stress field that develops in the vicinity of the steel-concrete interface. The effectiveness of this bond strength between concrete and reinforcing steel is the most important and influenced by a wide range of parameters. From such parameters this study focuses on the effect of coarse aggregate and specimen size. The aggregate and specimen size effect on bond strength of concrete and deformed bar is investigated using tensile test method. The parameter includes; concrete of compressive strength of 25MPa with varying maximum aggregate sizes of 9.5mm, 25mm, and 37.5mm, reinforced concrete member sizes of 10cm*10cm*30cm, 12cm*12cm*40cm, 14cm*14cm*50cm with centrally embedded bars of diameters of 10mm,12mm and 14mm respectively are considered. By varying the aggregate size for each specimen the tensile test experiment was done by using Universal Testing Machine (UTM). From the experiment result increasing of specimen size decreases the average bond strength, this shows that by controlling of all other variables and only increasing of specimen size decreases bond strength of the member due to its brittleness behavior. In the study by increasing of aggregate size the bond strength for a given elongation is constant but the maximum bond strength and elongation decreases as the aggregate size increases, this is due to decreasing of number of aggregate and volume of paste in a given section.



average bond, development length, brittleness, reinforced concrete member, elongation, specimen size, aggregate size