Pe Pp Composite Waterproof Membrane For Civil Air‑defense Project

Construction Method of Polyethylene‑Polypropylene Membrane for Basement Floor

Process Flow

Base cushion acceptance → cement‑sand leveling layer → ground‑water lowering → substrate cleaning → detail additional layers → marking‑out & pre‑laying → prepare polymer‑cement adhesive → double‑sided adhesive coating → membrane laying & air expelling → lap joint treatment & edge sealing → end‑lap protection → inspection & repair → fine aggregate concrete protective layer → curing

Key Operation Points

1. Substrate & Ground‑water Control Construct solid flat cement‑sand leveling layer, free of sanding, sharp corners and pits. Make R≥50 mm rounded corners. Lower ground‑water level ≥300 mm below cushion base and keep dewatering during construction. Damp substrate is acceptable, no standing water allowed.
2. Detail Additional Layers Install same‑material additional layers (width ≥500 mm) at corners, post‑pouring belts, construction joints, pile heads and pipe sleeves. Bond tightly without hollowing.
3. Marking‑out & Pre‑laying Snap reference lines and lap lines. Unroll and pre‑relax membrane. Lay floor plane first, then leave overlap laps for vertical wall. Membrane turn‑up from floor to wall ≥300 mm, protect temporary end laps.
4. Adhesive Preparation Use special matching polymer‑cement adhesive for polyethylene‑polypropylene membrane. Mix mechanically, use‑on‑site within 2 hours. Do not reuse after initial setting.
5. Membrane Laying (Full‑bond Method) Coat adhesive on both substrate and membrane back. Cured adhesive thickness ≥1.3 mm, bonding area ≥90%. Lay membrane naturally, squeeze air out from center outward. Do not stretch membrane. Long‑side lap ≥100 mm, short‑side lap ≥150 mm. Stagger adjacent short‑side joints ≥500 mm. Fill adhesive fully in laps, reinforce joint edge with 50 mm wide adhesive sealing.
6. End‑lap Protection Protect floor‑to‑wall overlap ends from contamination and damage for later connection with wall membrane.
7. Protective Layer Construction (Critical) Cast fine‑aggregate concrete protective layer ≥50 mm thick immediately after waterproof layer acceptance. Start steel‑bar work only after protective layer fully cured.

Construction Notes

1. Only use special polymer‑cement adhesive. Plain cement or glue is not permitted as substitute.
2. Working temperature: 5‑35℃. Stop work under rain, ponding or dew.
3. No walking or material stacking before adhesive fully cured to prevent membrane damage.
4. Membrane shall not be exposed under sunlight; must be fully covered by protective layer.
5. Additional reinforcement shall not be omitted at weak positions such as pile heads and post‑pouring belts.
6. Fully inspect finished waterproofing, repair all hollowing, curling and damage.