064 RCI 0417

RCI April 2017

LRWA VIEWPOINT Why use one liquid system over another? the science explained… Terry Wain, technical secretary at the Liquid Roofing and Waterproofing Association (LRWA), explains the versatility of liquid waterproofing systems, and why he feels certain Liquid roofing and waterproofing systems offer a highly durable solution for both new build applications and the refurbishment of existing roof, balcony and walkways. Yet, what isn’t as widely published is that there isn’t one single liquid technology suitable for every project. Liquid systems are made up of different chemistries, meaning some are far better suited in certain applications than others. The LRWA, for example, consists of many manufacturer members, all offering excellent waterproofing solutions with varying chemistries. In this article, I will provide an overview of three of the lesser known liquid chemistries – polyurea technology, cold applied liquid bitumen and Thermoplastic Block Copolymers (SEBS) – and explain the qualities of each technology. Polyurea technology First developed 40 years ago, polyurea technology is now an advanced liquid coating system offering many advantages to the building owner and contractor. Polyurea’s main, major benefit is its quick curing qualities – ideal in applications whereby area access cannot be restricted for many hours. It is often tack-free within 10 to 60 seconds after application and can be trafficked within the hour, returning an area to service quicker than other coatings – an attractive quality in the UK’s unpredictable climate. Typical applications of polyurea includes roofing but it is also often specified for podium decks plus applications on balconies, bridge coatings, waste water treatment plants, landscape and water containment, aquarium linings, water parks, and play grounds. Polyurea systems provide excellent adhesion to substrates including concrete, cementitious screeds, metal, plywood, asphalt and bitumen sheets. Epoxy or polyurethane primers are normally used to seal the substrate and enhance the bond. Polyurea is a two-component system which during installation can require specialist mixings and application apparatus, such as plural component spraying equipment which should only be used by trained operatives. Suppliers of specialist equipment are more easily accessible 064 APRIL 2017 RCIMAG.COM chemistries are best suited for different applications today, but there are also hand-applied systems that don’t need specialist mixing equipment if operatives prefer. Polyurea technology can be used in any new build or refurbishment project as systems are often quick and easy to apply, durable and are UV stable. Polyurea is also solvent free and produces minimal odour – meaning it’s often a popular choice for projects on occupied or sensitive buildings such as schools or hospitals. Cold-Applied Bitumen Bitumen technology has been used as a waterproofing solution for centuries. First developed in the 1800s when natural bitumen was combined with jute or straw to provide a waterproofing solution, modern day technology has developed this technology to what is now one of the most popular construction materials. The coefficient of thermal expansion of bitumen is considerably greater than most popular construction materials such as concrete or steel, meaning once applied it is less likely to crack. Bitumen is versatile, easy to apply and maintain, durable and multi-functional and can be used in a reinforced membrane or adhesive. Although five-year guarantees of bitumen-applied roofs were the norm in the 1970s when it became extremely popular as a liquid waterproofing solution, there are examples of these systems that have remained in service, untouched, for more than 35 years. Now, rubber modified bitumen emulsions and solutions are being used commercially to provide cost effective, high performance waterproofing with a lifespan of 20 years or longer. Bitumen has experienced many developments over time – the introduction of highly insulated structures meant systems needed to cope with greater extremes of temperature – hotter summers and colder winters resulted in higher levels of thermal expansion and contraction – thus, the introduction of rubber-based polymers was developed into product formulations. The use of foam insulation in a warm roof construction also meant greater puncture resistance was also required, and this was achieved by replacing the original jute reinforcement with polyester and the use of high performance carrier membranes. Thermoplastic Block Copolymers (SEBS) This technology was first developed more than There isn't one single liquid technology suitable for every project as liquid systems are made up of different chemistries


RCI April 2017
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