In the refurbishment and coatings industry, engineers are often looking to guarantee the service ‘lifespan’ of a structure. What does this actually mean and what are the important factors to consider? Mark Lemon, Managing Director of CSC Services, discusses this in the short article below.
At a basic level, every structure has a service life, meaning the expected years it can be expected to perform its function. Factors such as carbonation, abrasion, atmospheric chlorides or exposure to harmful chemicals can however, affect this service life, especially in harsh environments such as wastewater treatment plants. Once corrosion takes hold, it often does so quickly and can take a structure out of service or lead to service failure.
By guaranteeing a structure for its service lifespan, engineers want to protect against chemical attacks, joint leaks, cracks and surface corrosion so that the service life is not interrupted. The required service life is therefore a key consideration in the specification of a protective coating.
On large scale infrastructure projects, designers and engineers may be looking for specialist mortars and coatings to protect such structures for one hundred year or over. For tanks and water related structures, guarantees are usually sought for between ten and twenty five years.
Whatever the guarantee requirement, there are important factors to consider:
There are many product manufacturers on the market, so do your research and make sure you’re specifying the best coatings.
Don’t be afraid to look for and ask for references. Flexcrete recently reported independent tests had confirmed their Cementitious Coating 851 provides an effective barrier to chlorides for at least 28 years. Websites should contain case studies of the products.
If you’re working with a specialist contractor such as CSC Services, they can help and support you with this. They work in partnership with many of the leading manufacturers and can offer up to date and impartial advice. Manufacturers such as Sika Liquid Plastics will guarantee work to protect against the failure of water tightness caused by incorrect design, defective materials or poor workmanship, through the issue of their Product/Extended Product Guarantee and Final Inspection Certificates. If audited and approved contractors are used, guarantees can provide coverage for 10, 15, 20 and 25 years depending on the specification. Clients are guaranteed quality, assurance and peace of mind by using QA Contractors as they have been fully audited and trained.
Quality workmanship is integral when it comes to the success of any coatings scheme of work. All too often, coatings will fail due to incorrect substrate surface preparation. Surfaces generally need to grit blasted or hydro blasted to form a mechanical key. Correct substrate surface preparation of concrete, for instance, involves correct application of pore fillers and fairing coats to address blow holes or honey combing in concrete surfaces. Fairing coats need to be applied correctly to leave the required surface profile.
CSC Services always recommends using a specialist contractor to advise on coatings for specific environments. Some products have high abrasion resistance, tensile strengths and high elongation properties. Using a high tensile strength coating with no elongation properties on a substrate where movement may occur will result in cracks and failure in the coating. A lack of specialist knowledge may result in incorrect mixing of products.
Using a specialist contractor will ensure the correct application method of a product at the correct application temperature. Various products require certain environmental conditions. Dew points, temperature, humidity and air flow need to be considered to avoid condensation, causing a failure in the curing process.
Curing time is also a key consideration. Coating products require a certain amount of time to chemically bond as specified in the technical data. Not leaving sufficient time may mean the product fails. After curing, the product should be fully cleaned and inspected for fails.
You should always ensure a contractor is fully trained in the application of materials you wish to specify.
It is however, important to remember, that the life expectancy of a guaranteed material will often be subject to the acceptance of an inspection regime, with localised repairs undertaken as required. For a cementitious coating, for example, this may be quite a simple process of cutting back to the sound substrate, cleaning the surrounding area and applying a top level of the specified coating to the affected area. The important part is regular inspection to identify potential problems before they take hold.