load -slip relations of old and new concretes with different interface roughness.

What is it about?

it is about the bond stresses between old and new concrete using push-off test and three different interface cases. The results showed that the interface surfaces treated by epoxy exhibited the maximum average shear strength and the maximum average load compared with the smooth and sandblasted surfaces. The sandblasted interface surfaces resulted in a slightly lower average of failure slip than the epoxy interface. While the smooth interfaces show nonobvious load-slip relations, the epoxy treated surfaces revealed linear shapes and the sandblasted surfaces showed nonlinear shapes.

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Why is it important?

From the results gained throughout this experimental study of the interface between two concretes having different ages and different bond surfaces without using steel reinforcement, the following conclusions can be recorded: 1. The smooth interface group showed the lowest average shear strength and the lowest average load. 2. The interface surfaces treated by epoxy exhibited the maximum average shear strength and the maximum average load compared with the smooth and sandblasted surfaces. 3. The sandblasted interface surfaces resulted in a slightly lower average of failure slip than the epoxy interface. 4. While the smooth interfaces show nonobvious load-slip relations, the epoxy treated surfaces revealed linear shapes and the sandblasted surfaces showed nonlinear shapes. 5. All tests showed an oscillation in the shape of the load-slip relation as a result of particles rearrangement at the same slip. 6. Although the international codes presented so many relation formulae, this media needs more studies to reach the accurate load-slip relation. In this study, the most efficient type of concrete bonding was to use epoxy but more types of glues are needed to be studied more broadly

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