In concrete, there are voids and cracks that waterproofing systems must compress against to be functional. This is relevant, particularly regarding poorly consolidated substrates which is inherent to shotcrete. Swellable membranes such as Bentonite often do not achieve the 24 lbs. of compression per square foot required to achieve watertight functionality, when installed in conjunction with shotcrete.
When it comes to saving construction costs by using shotcrete at below grade vertical conditions, in lieu of cast-in-place concrete, we advise using some of those consequential savings towards a waterproofing system that can accommodate the inconsistencies inherent with blown concrete. Even the best nozzlemen cannot guarantee that voids will not be left behind.
A High-Density Polyethylene (HDPE) membrane with taped seams, used in conjunction with a bentonite option (that has the capacity of bridging in a watertight manner the poor compaction and consolidation areas that are acceptable structurally but inherently problematic from a waterproofing standpoint), is a predictable way to get watertight performance results with shotcrete applications.
Contact Terra-Petra today for a consultation on our waterproofing consulting, testing and inspection services.