Study On Bond Stress-slip Behavior Of Hybrid Fiber-reinforced Recycled Aggregate Concrete

The waste concrete produced by the demolition of existing buildings cause a lot of construction waste storage,disposal and landfill problems.The waste concrete used as a substitute for the original aggregate of concrete,eliminates the problem of landfill and the exhaustion of aggregate resources having remarkable economic,social and environmental benefits.The investigations on mechanical properties of recycled aggregate concrete have been carried out worldwide.However,at present recycled aggregate concrete is being used for low-level applications like subgrade and non-load bearing elements.To further promote the highgrade application of recycled aggregate concrete,it is necessary to study various mechanical properties and structural performance.In this research study,composite fibers are added in concrete to control cracks,improve tensile strength,bond toughness,bond ductility,and improve the impact resistance and deformation characteristics of concrete.This research focuses on the study of the structural properties of recycled aggregate concrete,and studies the effect of the addition of mono and hybrid fibers on the bond stress-slip behavior of reinforced recycled aggregate concrete.Two different types of fibers were used in the experimental program: Crimped steel fiber and polypropylene fiber with different proportions in mono and hybrid form.In the study of bond stress slip properties,the embedded length of the beam specimen is 5 times the deformed steel bar diameter.Ten different proportions of concrete were prepared,and for every proportion one beam and four cylindrical specimens were cast.It was found by the study that the steel and polypropylene fibers increased the concrete compressive strength.The use of polypropylene fiber can resist initial cracks,shrinkage,and steel fiber can improve the strength performance.When the recycled aggregate is added to the concrete,the mechanical properties(i.e.bond strength)have lower values as compared to the natural aggregate concrete.The crimp steel and polypropylene fiber materials revealed a positive influence on the peak bond strength of recycled aggregate concrete.The bond stress-slip test results revealed that both types of fibers contribute to ameliorate the peak bond stress and also to improve the ascending branch of the bond stress versus slip curve in terms of stiffness.The results of bond stress slip behavior of the reinforced recycled aggregate concrete were compared.It was proved that adding the mono and hybrid fibers to the concrete significantly improves its performance,in terms of its peak bond stress slip behavior,bond toughness,bond stiffness and ductility of the recycled aggregate concrete.