Mapei FoamJet T

Mapei FoamJet T is TRSC's default polyurethane injection specification for active water cut-off in below-grade concrete substrates where structural epoxy injection is inappropriate either because the crack is active (continuing to move) or because the substrate is wet at the time of intervention. The product is selected over alternative polyurethane injection systems on three grounds: rapid reaction time (initial expansion within 30 seconds permits sealing of high-flow leaks that would wash out slower-reacting products), high expansion ratio (~25-30× injected volume produces effective sealing volume from minimal injection mass), and hydrophobic chemistry (the cured foam is moisture-stable and does not absorb water in service). The most common specification pitfalls TRSC encounters in the field are: (1) confusing water cut-off with structural restoration — FoamJet T provides no structural contribution; cracks that require structural restoration must be addressed by epoxy injection (Sikadur-52 LP or equivalent) after the FoamJet T water cut-off has stopped the leak; the typical TRSC sequence on active leaks in structural elements is FoamJet T water cut-off followed by Sikadur-52 LP structural injection once the substrate is dry and the crack is dormant; (2) injection pressure — FoamJet T expands rapidly under low pressure; high-pressure injection forces the unreacted resin past the leak point and produces over-injection without effective sealing; the injection pressure must be controlled to permit progressive seal formation along the leak path; (3) post-injection inspection — the cured polyurethane foam is visible at the substrate surface as a yellow-orange residue around the injection ports; field installations that achieve apparent leak cut-off without visible foam residue typically have unreacted resin in the substrate that will not provide durable sealing and the leak will re-establish within weeks; visible foam residue at every port is a witness hold point on the injection acceptance. The product was used on the Waterfront Place basement remediation where active leaks at construction joints required immediate water cut-off before structural repair work could begin.