Construction World – December, 2007
Leo Connell on waterproofing for the Al Mashfa Hospital by the Red Sea.
The Al Mashfa Group, a respected medical company in the Middle East, built a 10-storey full-service private hospital in Jeddah, just 1 km from the shore of the Red Sea.
The builders excavated a 12-metre (39.4 feet) pit (for a two-level parking garage beneath the hospital) in a mixture of soil and sand that had a high concentration of sulphates due to the proximity to sea. Salt water corroding stell and compromising the integrity of the structure was a key concern for the cold joints, as was extreme head pressure – up to 92 m (301.8 ft)!
An underground lake too large to pump out was another problem; a waterproofing solution that could be installed in wet conditions was called for. After considering a range of options, the builders chose the Integral Crystalline Waterproofing (ICW) system, with key advantage such as:
How does Integral Crystalline Waterproofing work?
When applied to existing concrete, crystalline chemicals are absorbed by capillary action and diffusion. Once inside, the chemicals begin growing crystals and filling the spaces between concrete particles. As long as there is moisture, crystals continue to grow throughout the concrete, reaching lengths of many centimeters over time. Once the concrete has cured, the chemicals sit dormant until another dose of water (through a new crack, or rising water table) causes the chemical reaction to begin again.
This reactivation in the presence of water gives crystalline-treated concrete the ability to “self-seal.” A unique feature of ICW technology, and one of the most useful, it helps cut down dramatically long-term maintenance and repair costs.
Waterproofing Joints with Integral Crystalline Waterproofing
At the Al Mashfa Hospital, extra care was taken when waterproofing construction joints (i.e. cold joints on the slab and walls), since these areas are the most vulnerable to water intrusion.
“Usual waterproofing methods would have been near impossible for our project, given the challenges we faced, like the 12-m cut-off wall and extreme head pressure,” said A Hamid Elmas, Project Manager & Architectural Consultant, Al Mashfa Group. “We required an advanced waterproofing system that could withstand all of these obstacles, especially during the casting if the matt slab.”
How is ICW applied?
ICW products are usually supplied as an easy-to-use, dry powder comprising Portland cement, silica sand and special chemicals that can simply be added to the readymix truck at the plant or jobsite to create a power moisture barrier in slabs and walls.
There is no need for any sort of surface application at the construction site – ICW can be simply added to the concrete. Such systems can also be surface-applied to existing walls and slabs and incorporated into construction joints during construction or later..
ICW products such as Kryton International’s KIM, which is certified nontoxic, are ideal for use in a wide variety of precast, shotcrete and cast-in-place applications such as bridges, dams, tunnels, swimming pools, water storage and wastewater treatment facilities, reservoirs, pipelines, parking garages, basements and foundations.
The Krystol® concrete waterproofing system provides two levels of protection for all cold joints: an ICW barriers, plus a physical grout barrier with a compressive strength greater than most structural concretes.
* Leo Connell is director of marketing at Kryton International, Vancouver, British Columbia, Canada.