Evaluation of Different Surface Treatment Techniques Used to Improve Bond Strength between Old and New Concrete

Abstract

Nowadays, application of adding a fresh concrete layer (Overlay) to a hardened one (Substrate) has been used widely as a main in mass concrete, concrete replacement, and concrete jacketing. Deterioration of concrete structures usually begins at the surface of structural members, and progresses into the structure. The most common strengthening technique is adding a new concrete layer to increase the member effective size. To guarantee monolithic behavior, the bond strength between old and new concrete should resists the resulting stresses. Many researchers indicate that a proportion of the bond strength can be achieved depending on roughness of the old concrete surface. The main objective of the experimental program is to evaluate the different surface treatment techniques used to improve the bond strength between old and new concrete. The experimental work was designed to apply different bonding agents, moisture condition, overlay timing, and roughness technique. The bonding coats used differs in chemical base, setting time, and viscosity. Researchers deals with the surface preparation as the most important factor affecting the bonding strength enhancement. Two different surface roughness techniques were used to prepare the interface. Sixteen test slabs were fully roughened by hammering with at differentoverlay timing to be investigated in the epoxy adhesives between 0.0 to 8.0 hours. Ten test slabs were partially roughenedby chipping as a surface preparation technique of interface. In both surface roughness techniques, the moisture conditions were raised in normal set epoxy and latex between dry and saturated surface dry (SSD) moisture conditions.