Experimental Investigation on Bond Strength Behavior of Reinforced Concrete Members Using Waste Marble as Coarse Aggregate
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Date
2023-12
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Addis Ababa University
Abstract
The expansion of the construction industry increased the demand for concrete. This results in the depletion of natural resources due to continuous quarrying. In another way, the waste generated from the marble industry will affect the environment. The use of waste in construction saves natural aggregate, energy and preserves the environment. Previous studies focused on the strength and durability properties of marble aggregate concrete and there is no sufficient literature that investigates the bond strength behavior marble aggregate concrete as it enables the use of marble aggregate in structural members.
Therefore, in this research the bond strength behavior of reinforced concrete using waste marble as coarse aggregate was investigated via Pull-out test. Deformed bars of diameters 12 mm, 14 mm, and 16 mm and length 1000mm were centrally placed in the cylindrical molds of dimensions 150 mm ×300 mm with an embedment length of five times the diameter of the bar. The bars were embedded in five different concrete mixes varying the quantity of marble replacing coarse aggregate at a ratio of 25% in C-30 concrete mixed using constant water-cement ratio. At the test date, each specimen was initially setup carefully and then an axial load was imposed on the bar at the loaded end and the slip was measured at free end. In this way pull-out test was conducted on a total of 45 specimens at the age of 28 days.
Test result indicates that compressive and splitting tensile strength of the concrete increases as the quantity of marble replacing natural coarse aggregate increases up to 50% and then decreases. Bond strength is consistent with the result of compressive and tensile strength of the concrete. For all diameter 12mm,14mm and 16mm bars the average bond strength of marble aggregate concrete is comparable with the control concrete as the percentage of marble in the mix increases up to 75%. However, the average ultimate bond strength significantly decreased in 100% marble coarse aggregate concrete because of low tensile strength of marble compared to natural aggregates. Furthermore, bond strength decreases as the diameter size of the bar increased due to nonlinear stress distribution along the embedment length of larger diameter size bars. The experimental result exceeds the bond strength calculated using equations proposed by nine different researchers. Both ES EN 1992-1-1:2015 and ACI 318-08 codes underestimated the average bond strength values of all steel bars embedded in all concrete mixes.
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Keywords
Waste Marble, Coarse Aggregate, Concrete, Bond Strength, Pull-out test, Slip