It is critical that waterproofing membranes perform not only during construction but throughout the life of the structure, resisting lateral water migration even in instances where the membrane could be punctured.

Current standard testing of hydrostatic pressure resistance of a waterproofing membrane is based on ASTM D 5385, which tests a fresh specimen, with no water immersion or aging, at water pressure up to 231 feet (100 psi). However, below-grade waterproofing needs to maintain an intimate bond to concrete and prevent lateral water migration after constant exposure to water, a result of groundwater in the soil, throughout the life of the structure. Standard bond to concrete and hydrostatic tests may not represent the real-life situation a waterproofing membrane must withstand to be effective.

Several decades ago, GCP modified the ASTM D 5385 test method to evaluate the hydrostatic pressure resistance performance of a pre-applied waterproofing membrane with a breach in the membrane. This test method has become an industry standard and is called the Lateral Water Migration Resistance test.

Lateral Water Migration Resistance

Lateral Water Migration Resistance is the ability of a pre-applied waterproofing membrane system to prevent and restrict the passage of water between the waterproofing membrane and structural concrete in the event of a breach. For this to be achieved, the membrane must be intimately and continuously bonded to the structural concrete slab.

If a waterproofing membrane without this performance characteristic is punctured or improperly installed, water that bypasses the membrane would not be confined to the breached location. Under hydrostatic pressure, this water can migrate between the waterproofing membrane and the structure. Once water has entered the structure, migration around and within concrete can result in significant leaks, and the source can be difficult to find. Repair and remediation of such circumstances is expensive, often requiring continuous grouting and/or costly alternatives.

The LWMR of a waterproofing membrane can be correlated directly to the technology used to provide bond to concrete performance. All bonded membranes are not equal in this respect and a closer examination of the bond mechanism is needed.

For example, the PREPRUFE membrane adhesive interacts with the proprietary protective coating to form an intimate adhesive bond with the concrete cast against the membrane. If a breach occurs in the membrane, the adhesive prevents water under hydrostatic pressure from migrating between the membrane and the concrete, limiting the risk of waterproofing failure. This bond is continuous and was developed to provide lasting performance. Independent testing shows the PREPRUFE waterproofing membrane can resist lateral water migration at 231 feet of hydrostatic pressure even after long term immersion in water.

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