Limit of durability of bond strength of concrete overlay : examples exposed to marine environments

Abstract

The use of concrete topping, also referred to as overlay, is an increasingly studied topic, whereby bonding can be achieved not only by means of an adhesive but also by varying the surface treatment at the interface. Such surface variations can be achieved by smoothening, roughening, introducing shear stirrups or else with the introduction of reinforcement. Some studies have also adopted a combination of the different options available. Special care is needed to ensure that the entire surface area is acceptable to bonding and there is no sign of delamination. When exposed to the marine environment, an important factor is salt. Salt plays an important role in terms of corrosion, as salt particles penetrate via the concrete pores. Concrete is affected in different ways by different salt compounds. This study identifies the effect of salt particles spread along the interface; and added to the overlay mix. Keeping a constant curing age of 56 days, the study will determine variations in aggregate, concrete grade, surface treatment preparations (smooth and rough), additive and salt for 36 beams and 60 standard concrete blocks; and will test each mix for compressive strength. The rate of roughness seemed to increase the horizontal resistance probably because of the depth of indentations that were marked on some of the concrete surfaces. Furthermore, the salt particles increased the compressive strength, and decreased both the tensile and horizontal shear strength.