Bond Behaviour for Normal and High Strength Concrete

Abstract

his study includes a series of pullout tests which contain fifty four specimens with short bonded length (5db) to study the effect of many variables on bond strength for normal and high strength concrete. The variables are: (bar diameter, concrete compressive strength and cover). The study also studies the effect of each variable on bond strength, and suggests two equations to link bond strength with the variables mentioned above. The test results show that, the bond strength increases with the increase of compressive strength and/or cover and decreases with the increase of bar diameter and vice versa. Also, the test results obviously show that, increasing compressive strength reduces the need for cover, where with the increase of the compressive strength from 20 MPa to 75 MPa, the need for cover reduces by34% for the same bar diameter depending on nonlinear regression analysis for the resultant of experimental work, two equations are suggested in this study, the first links the variables (bar diameter, concrete compressive strength and cover) with bond strength where the value of (R) is 0.923. While the second equation links the ultimate bond strength with the variables mentioned above where the value of (R) is 0.927.