Flexidine HDPE PSA is a unique, high performance, flexible High-Density Polyethylene (HDPE) sheet with pre-applied pressure sensitive adhesive with a reactive inorganic fine granule layer. Flexidine HDPE PSA membrane is modified for excellent puncture resistance and mechanical properties to withstand backfill and cuts, while maintaining its integrity and continuing to provide protection from water seepage. The sheets are pre-applied with pressure sensitive adhesive and sand layer to suit pre-applied construction methods. The membrane allows poured concrete to form an integral bond with the membrane and prevent ingress or migration of water around the structure. As the mass of the structural concrete increases during the concrete pour, the adhesive is activated and forms a continuous bond with the concrete poured against it. The membrane is a cold-and preapplied waterproofing system that is installed as loosely laid, single-ply membranes onto prepared substrates before the steel reinforcement is fixed and the concrete is poured. The laps are sealed with a seam tape as required.