Best Practices for Preparing Concrete Surfaces Prior to Repairs and Overlays

Full Description

One of the biggest problems impacting the long-term performance of concrete
repairs and bonded overlays is cracking of the repair material and repair material
debonding from the concrete substrate. There are many purposes for concrete
repair, including prolonging the useful service life of a deteriorated or distressed
structure or element, restoring the load carrying capacity and the stiffness, and
strengthening the structure. In most cases, for the repair to be successful,
monolithic action (acting as one unit) between the repair material and the
substrate concrete (the composite repair system) is needed. A prerequisite for
monolithic action is long lasting bond between the existing concrete substrate and
the repair material.
The mechanisms and characteristics of bond between existing concrete and repair
materials have been researched in the past. It is a very broad and generic
engineering task. Thus, the scope of existing guidance and specifications on
methods to ensure obtaining long-term bond is limited. This is mainly due to the
lack of understanding of some of the factors that affect bond strength and
durability of in situ repairs. Despite the relatively large pool of theoretical
knowledge, the practical issues related to surface preparation of existing concrete
to achieve long lasting bond are still inadequately addressed. This is
demonstrated by the small number of ongoing research projects in the field, the
current state of limited knowledge, the codes of practices, and in some cases the
continued poor performance of repairs and overlays.