How to choose the Perfect Waterproofing system?
Overall, a robust waterproofing membrane should exhibit a combination of crucial characteristics, including exceptional water resistance, mechanical resilience, flexibility, adhesive strength, resistance to punctures and tears, durability, and ease of installation. These fundamental attributes are imperative to ensure the membrane’s effectiveness in its intended purpose, delivering enduring water-proofing protection.
Water Resistance: The membrane must demonstrate an outstanding capacity for resisting water infiltration, effectively safeguarding the underlying structure. It should endure sustained exposure to water pressure while maintaining its waterproof integrity over an extended period. One industry-standard test, ASTM D 570, evaluates the weight gain of coating films when immersed in water. For systems that will be immersed or remain continuously wet, it’s crucial to assess the saturation weight gain (the point at which further weight gain ceases), as outlined in Paragraph 7.4 of the standard. A saturation weight gain of less than 1% indicates a high level of resistance.
A well formulated 2K Polyurethane can withstand can withstand water pressure of 100,000 N/m (equivalent to a 34-foot head) or even greater.
Mechanical Toughness: The membrane must exhibit robust mechanical properties, including impressive tensile strength, resistance to impacts and abrasions, enabling it to withstand potential damage from construction activities before the final covering, if applicable, is installed. In this regard, well formulated 2K systems shine as they are exceptionally resilient, eliminating the need for additional masonry cover, resulting in significant cost savings. This resilience is particularly valuable in applications like basement raft waterproofing, where the membrane can endure even the dragging of reinforcing steel. Tensile strength also plays a pivotal role in the membrane’s ability to span and bridge cracks, as described below.
Crack Spanning Capacity: A proficient waterproofing membrane must possess the requisite flexibility to accommodate structural movements while effectively averting the formation of cracks and water infiltration. It should withstand building settlement and expansion without compromising its waterproofing integrity.
Crack spanning capability is contingent upon a synergy between elongation and tensile strength. Elongation, in isolation, is inadequate and should not be the sole focus of specification criteria. It’s imperative to recognize that a coating with 135% elongation and 17 N/mm² tensile strength surpasses one with 500% elongation and 2N/mm² tensile strength in terms of crack spanning potential. Understanding the mechanics of crack spanning is crucial; when new cracks appear in concrete, they exhibit infinite expansion at their origin. In theory, all coatings would succumb to these cracks. However, in practice, coatings endowed with elasticity and high tensile strength apply tensile stress to the concrete surface, causing the edges of the crack to crumble while keeping the coating intact, effectively forming a bridge over the crack (refer to Figure 1).
An innovative approach to achieve a substantial enhancement in crack spanning is through the utilization of combination systems, as elaborated in 2(C), where remarkable crack spanning capabilities exceeding 10 mm are attainable.
In regions with colder climates, several specifications mandate a ‘Low Temperature Crack Bridging’ assessment, exemplified by the ASTM C 836 standard for “High Solids Content, Cold Liquid-Applied Elastomeric Waterproofing Membrane for Use with Separate Wearing Course.” This test is conducted at tem-peratures as low as (-) 26°C, necessitating high elongation coatings that excel in bridging cracks in frigid conditions, as elongation decreases while tensile strength increases at low temperatures. However, in tropical climates like India (except at higher elevations), crack spanning tests conducted at 25°C suffice.
Damp Tolerance: The inclusion of damp-tolerant primers is imperative in waterproofing applications. These primers effectively permeate the surface, fortifying the concrete substrate, and creating a seal conducive for the subsequent application of the topcoat. Systems engineered with hydrophobic raw materials exhibit remarkable tolerance in high-humidity environments, devoid of issues like blistering or foaming. Similarly, rapidly reacting spray systems exhibit comparable performance in damp conditions.
Adhesion: Exceptional adhesion to the substrate is paramount for the membrane, ensuring a robust bond that thwarts any potential water infiltration through gaps or joints. In rigorous pull-off tests conducted in accordance with ASTM D 4541, well formulated 2K systems consistently demonstrate remarkable adhesion, with 90% or more of the test dolly area experiencing tensile failure of the concrete rather than a failure at the coating-concrete interface.
Resistance to Punctures and Tears: A reliable waterproofing membrane should exhibit a superior resistance to punctures and tears, capable of withstanding the impacts and accidental damage that may occur during construction or maintenance activities. Well formulated 2K systems stand out with puncture resistance levels reaching as high as 1,500 N when evaluated per ASTM E 154. Furthermore, harder elastomeric 2K Polyurethanes exhibit zero root penetration, as confirmed through testing per DIN CEN/TS 14416.
Durability: The membrane’s durability is of paramount importance, as it must endure various environmental stressors, including exposure to UV rays, tempera-ture fluctuations, and potentially harsh chemical substances. The membrane should remain resilient and not degrade or deteriorate easily, ensuring consistent, long-term waterproofing performance. Remarkably, well formulated 2K systems fulfill all these stringent durability criteria.
Ease of Installation: A user-friendly installation process is desirable for the membrane, facilitating efficient and effective application. Well formulated 2K Polyurethanes offer versatile application options, including easy paint roller application, which minimizes costs and virtually eliminates wastage. For large surface areas, 2K spray application is an ideal choice, although it may entail significant equipment costs and a higher degree of over spray wastage.
There is never a single important factor when determining the waterproofing coating that should be chosen; there are always several factors that we need to look at. Only the system that meets these important criteria should be chosen.
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