This article looks at the latest findings of the American Concrete Institute (ACI) and the implications for waterproof concrete construction.
Kevin Yuers | Kryton International Inc., Vancouver Canada
Though the benefits of integral crystal-line waterproofing in concrete structures are well-documented, some North American builders have been slower to adopt it than their international counterparts. The traditional choice, namely external membrane waterproofing, meets existing North American building codes and appears on the surface to be more cost-effective. However, integral crystalline waterproofing has experienced a surge in popularity since the ACI published its report on permeability-reducing admixtures for concrete, ACI 212.3R•10{‘}.
The report goes a step further than endorsing integral crystal- crystalline waterproofing: it separates the chemical admixture into two categories. The report provided much—needed classification for permeability reducing admixtures by replacing outdated and unclear terminology such as ‘waterproof` and ‘damp-proof“ with PRAH (permeability reducing admixture – hydrostatic conditions) and PRAN Leer- meability-reducing admixture – non-hydro- static conditions). The new classifications revealed that not all admixtures are created equally: only those designated as PRAH are suited to watertight construction. While the clarification was welcome, it has resulted in some concrete manufacturers claiming that their product is PRAH when in tact it only meets PRAN standards.
Case study: Sekolah Sukan Sabah
The Government of Malaysia takes its Olympic programme very seriously and would settle for less than PRAH Standards when it built Sekolah Sukan Sabah, the latest of its modern integrated academic and sports schools designed to produce the nation’s Olympic contenders. The concrete used to create the Olympic-sized swimming and diving pools needed to withstand hydro• static pressure, chlorine and heavy usage. The complex houses facilities for every sport imaginable.
The owners of the project wanted to be sure the building solution they selected would withstand the demands of heavy usage, the humid tropical climate and proximity to the sea. With several solutions providers vying for the project, the owners needed demonstrable proof that their water- proofing system would be reliable.
Kryton had recently finished work on the neighbouring Marina Bay Sands project in Singapore, an immense resort complex built on reclaimed land surrounded by seawater, the deepest point being 25m below grade. The engineer behind the project could attest to the effectiveness of the PRAH Standard integral crystalline waterproofing of the concrete: even if cracks should form in the future, the incoming moisture reactswith the concrete admixture to produce more crystals and preserve the watertight seal.
The Marina Bay Sands project also demonstrated the efficiency of construction with crystalline admixtures, which allowed the formidable project to be completed to the highest safety standards on a tight timeline. Over 6o,ooom3 of concrete were water- proofed in the Marina Bay Sands project; and 11oom3 in the Sekolah Sukan Sabah project.
After construction, the design engineer performed tests and reported that the PRAH admixture used, Krystol Internal Membrane [KIM], performed exactly as the data sheets indicated it would.
Case study: Royal Mills 
Where waterproofing is carefully considered in new concrete construction, restoration projects require a different kind of finesse.
The Royal Mills Riverpoint Apartments project on Rhode Island was a reclaimed 19th Century cotton mill whose structure had been weakened by a century of industrial use, neglect, a fire and exposure to river water. In order to preserve the character of the building’s original facade, the structure needed to be waterproofed from the inside out. In addition to repairing existing cracks and leaks with a crystalline crack repair sys- tem, KIM was mixed into several slabs of concrete used to strengthen the structure and to repair rubble and elevator pits.
Thanks to the extensive waterproofing and restoration, the developer was able to reclaim several units that had previously been deemed uninhabitable.
New England Dry Concrete, Kryton’s East Coast distributor, was awarded the 2o1o New England International Concrete Repair Institute (ICRI) Project of the Year for its work on Royal Mills.
Ensuring PRAH standard
Although traditional membrane waterproofing is still a common practice and may be appropriate for certain projects, the wide- spread adaptation of crystalline integral waterproofing has resulted in a higher concrete construction standard to which many developers adhere.
The further classification of crystalline waterproofing admixtures by ACI 212,3R-1o demonstrates a clear, singular choice for a watertight building solution — one that con tains permeability reducing admixture for hydrostatic conditions. As a result, water-proofing costs are lower, reliability and quality control are increased and weeks are shaved from the construction schedule.
Ensuring your waterproof building solu tion meets PRAH standards involves a little effort, but the legwork will prove worthwhile for years to come. One step is to request case studies as points of refer ence, which any reputable distributor will be happy to provide, Another involves sim ply asking your building solutions provider to show you the proof in the form of a permeability test.
