Adhesive failure is the inability of an adhesive to stick to a surface. During this type of failure, the adhesive fails to hold together two surfaces and as a result, separates from the substrate [a]. There are several types of adhesives which include mortar, cement, epoxy, methacrylate, etc. Epoxy and methacrylate are considered structural adhesives. In this case, structural adhesives are synthetic adhesives with strong load-bearing capabilities.
These types of adhesive failures can be caused by shear or tension forces. However, in most cases, these types of failures occur due to incorrect processes used for initial production. Adhesive production organizations sometimes fail to differentiate between bond strength and durability [b]. When standard tests are performed, it may be evident that the bond strength is adequate, however, these tests fail to verify that the adhesive will be durable throughout its services. As a result, structures are left vulnerable to adhesive failure.
In order to attempt to prevent these types of failures, steel substrates are cleaned thoroughly and then covered in a protective coating. In terms of concrete surfaces, excess moisture vapor in or below the concrete slab is usually the cause for adhesive failures. To prevent this, the concrete mix should use low water to cement ratios, apply a vapor barrier, and adequately cure the concrete slab so that maximum strength and low permeability can be reached. [c]
Failure Mechanisms 