Since there is a very wide range of systems available, it is very important that the right one is chosen for the specific application in mind. Assuming that the correct choice is made, it is then very important that the correct procedures are used on site and in the case of pre-cast factory products.
Correct proportioning and thorough mixing of resin and activator or catalyst is required in order to achieve the correct curing rate and this must also be consistent throughout the product. Application should also be within the speci- fied temperature range and sufficient time allowed for the desired properties to be achieved. For example, incorrect mixing can result in some areas being hard whilst other parts remain soft or rubbery.
On-site use invariably requires a good bond to an existing concrete or steel substrate and this can only be achieved if the surfaces are clean and any loose material or corrosion products are removed. Good interfacial contact is required which can usually be achieved by the use of primers. In addition, whilst some systems are formulated for application to damp surfaces, the majority require that the surface moisture content be reduced to <5% during application and cure. Capillary movement of moisture from deeper within the substrate may occur later and lead to reduction of bond or blistering in the case of floorings and coatings. Little is known about the factors driving this process but they probably involve the pore size distribution of concrete, presence of interfacial soluble compounds and the source of moisture. Osmotic blistering may occur on steel and concrete substrates through water ingress as a result of salts on the steel surface (poor cleaning) or, in the case of concrete, the use of incorrect primers containing water-soluble compounds, (Dively, 1994; FeRFA, 1990). In addition to the above, long-term adhesion depends on factors such as level of applied stress, fatigue, exposure to moisture, and temperature fluctuations.
