Evolution. It’s something that every industry strives for and, in fact, needs in order to maintain their significance as the world’s demands change at a rapid pace. The Concrete Waterproofing industry is no different. With infrastructure expanding into areas that were not considered to be viable sites twenty years ago, waterproofing these structures in extreme environments is critical.
Sheet membrane systems just don’t hold up to the high hydrostatic pressure of many new buildings requiring reliable protection against leakage. As well, these membranes are not intended to last forever, and at some point will deteriorate. This was acceptable years ago, when the life expectancy of a structure was merely 50 years before it would be replaced, but now we are creating more high-risk mega structures, intended to last hundreds of year in the future as iconic symbols. These structures, such as Singapore’s Marina Bay Sands, or Dubai’s Palm Jumeirah, (both built on reclaimed land) need a permanent, reliable waterproofing system which only increases its effectiveness over time.
For over four decades now, a new type of waterproofing has been used around the globe. These integral admixture systems are added at the batching plant or onsite, and react chemically within the concrete. Instead of forming a barrier on the positive or negative side of concrete, they turn the concrete itself into a water barrier. Integral concrete waterproofing systems can be densifiers, water repellents or crystalline admixtures.
Crystalline-based systems typically come in a dry, powdered form and are hydrophilic in nature. Unlike their hydrophobic counterparts, crystalline systems actually use available water to grow crystals inside concrete, effectively closing off pathways for moisture that can damage concrete. They block water from any direction because the concrete itself becomes the water barrier. The crystalline formula can allow concrete to self-seal hairline cracks up to 0.5 mm (0.02 in.), even years after the original construction. It contains no volatile organic compounds (VOCs), and can be completely recycled when demolition occurs.
Additionally, crystalline admixtures offer installation advantages. Unlike traditional membrane waterproofing, which tends to be labor-intensive and expensive, crystalline admixtures can be shipped in dissolvable, pulpable bags that are thrown into the concrete batch during mixing. This speeds up the construction schedule and decreases labour costs by combining steps with concrete placing.
As with any new technology, until recently there has been a lack in standardized terminology across the concrete waterproofing industry. This lack of clarity on what these newer, permanent technologies could truly achieve, were contributing to the breakdown of communication when it can to actually specifying the products for new buildings.
Fortunately, the concrete waterproofing industry has since redefined their terminology. In fact, American Concrete Institute’s 212.3R-10 Report on Chemical Admixture document devoted Chapter 15 to Permeability Reducing Admixtures that outlines PRAH and PRAN classifications. Permeability Reducing Admixture – Hydrostatic Conditions or PRAH products reduce water penetration through crystalline growth or a polymer plug can perform under hydrostatic pressure and are suitable for watertight construction.
Conversely, dampproofing admixtures are now referred to as Permeability Reducing Admixture – Non-Hydrostatic Conditions or PRAN. PRAN admixtures reduce water absorption by repellent chemicals (soap, oils) or partial pore blocking (fine particle fillers). These admixtures are not suitable for concrete exposed to water under pressure and cannot protect in the presence of hydrostatic pressure. Waterproofing against hydrostatic pressure is an important distinction that set PRAHs apart from PRANs.
This only touches the surface of what the new chapter offers the industry. With new definitions, testing parameters, selection and evaluation guidelines, ACI’s 212.3R-10 document is a valuable resource to all, especially to those who would not be naturally well-versed in concrete waterproofing. Ultimately, the document’s objective is to educate stakeholders so that they are empowered to actively contribute to the construction process; be it specifiers, owners, or applicators. On a higher level, ACI’s 212.3R-10 document is representative of what an industry can achieve when an issue is identified and a collaborative solution is developed to overcome these challenges. These documents not only ensure that the parties are educated, but through specification also ensure that the right products would be used.