Waterproofing a concrete structure that sits only about 100m from the sea and 6 meters below sea level creates a challenge - a challenge that Waterproofing Systems Ltd was able to address with their Rawmat bentonite membrane system.
Bentonite is a natural clay formed from volcanic ash which can swell to form an impermeable mass, preventing the passage of liquid. Natural sodium bentonite clay will absorb water and expand up to 16 times its dry volume when in contact with water. When confined, e.g. between the ground and the floor slab, the tendency to swell generates substantial swell pressures, preventing the passage of water
When correctly installed, the Rawmat/Rawseal acts as an effective hydrostatic seal. An important factor affecting the amount of swell achieved, is the quality of water hydrating the bentonite. The significant advantage of the pre-hydrated system is that the initial hydration occurs under factory-controlled conditions.
Waterproofing Systems Ltd begins supplying the Rawmat pre-hydrated bentonite to the Britomart main tunnel.
Waterproofing Systems secures the Concourse Tunnel using Rawmat/Rawseal.
The existing roof was comprised of an asphalt sheet membrane, covered in a concrete screed and pavers. The roof area of 1080m2 required complete renovation. The pavers/screed was removed and substrate repairs were completed. A perforated base sheet was installed followed by the Glasflame 2mm/Polyflame 4mm torch-on system. A Sunguard UV coat was then applied. Eterno roof vents were also installed to allow moisture to escape for the concrete substrate.
The CPO roof has a 1.8 metre high parapet around the perimeter which had previously been waterproofed with an asphalt sheet. This old membrane was removed and the parapets were cleaned. Gripset 51 bitumenous rubber membrane was used as a primer, onto which the Gripset RD acrylic membrane was applied. Gripset RD is a flexible elastomeric liquid membrane designed to waterproof a variety of external and exposed surfaces, and provides a maximum long term protection by forming a tough durable film.
The beginning of Britomart
LBP Certified Applicator getting the job done
“The Britomart project was challenging right from the start. We had to show that our product was superior and that is had more advantages over other specified products. We felt confident that Waterproofing Systems would always be a strong contender, but is was not always straightforward and one or two issues had to be overcome.
This was probably the most demanding waterproofing job in New Zealand for the past 10 years, so I feel confident that we can address the requirements of any other project coming up in the future.”
— John Stallard, Director, Waterproofing Systems