Acrylate GroutA two-component water-soluble grout based on acrylate chemistry. Offers tunable gel time, balanced strength and flexibility, and excellent penetration — used for large-area continuous water-stop work and tunnel curtain grouting. See Acrylate Grout. Active LeakageA crack or joint with water actively flowing or dripping through it. Active leakage typically requires hydrophobic polyurethane for immediate stoppage before any elastic or structural treatment.Cement Grouting (vs Chemical Grouting)Cement grouting uses cement-based slurries to fill large voids — it cannot penetrate fine cracks or stop active leaks. Chemical grouting (PU, epoxy, acrylate) uses low-viscosity polymer systems for fine-crack injection and water-reactive sealing.Closed-Cell FoamA foam structure where individual gas cells are sealed off from each other. Closed-cell PU foam is impermeable to water and provides structural compression resistance — characteristic of hydrophobic polyurethane grout.Curtain GroutingA continuous waterproofing barrier formed by injecting grout in a planned grid pattern behind a structure (e.g., behind a tunnel lining). Often uses acrylate grout for its even penetration and gel-time control.Diaphragm WallA reinforced concrete retaining wall constructed in a slurry trench, used in deep excavations and underground stations. Joints between panels are common waterproofing failure points sealed with chemical grouting.ElastomerA polymeric material with elastic (rubber-like) behavior. Hydrophilic polyurethane, polyurea, and certain acrylate systems cure as elastomers, enabling them to accommodate substrate movement without cracking.Epoxy ResinA two-component thermosetting polymer that cures into a high-strength rigid solid. Used for structural crack repair, where restored tensile strength matters. See Epoxy Injection Grout. Expansion RatioThe volumetric increase of a foam grout from liquid to fully expanded foam. Hydrophobic polyurethane typically achieves 8–15× expansion in field conditions. Higher expansion fills more void per kg of material.Gel TimeThe interval between mixing and the point at which a two-component grout becomes too viscous to flow. For acrylate grouts, gel time is precisely tunable — a key parameter for matching pump speed to crack depth.HydrophilicWater-attracting. A hydrophilic polyurethane prepolymer absorbs water and cross-links into an elastic gel. Suited to long-term seepage and movement joints. See Hydrophilic vs Hydrophobic guide. HydrophobicWater-repelling. A hydrophobic polyurethane prepolymer reacts with water but does not absorb it — instead, it expands rapidly into a rigid closed-cell foam, ideal for stopping active leaks.Hydrostatic PressurePressure exerted by static water against a structure. In underground engineering, hydrostatic pressure can drive water through any crack or joint — making active sealing essential below the water table.Injection PackerA mechanical or hydraulic device installed in a drilled hole intersecting a crack. It seals the hole and provides a one-way valve for grout injection. See Injection Packers. ISO 9001International standard for quality management systems. ISO 9001 certification verifies that a manufacturer operates documented processes for production, inspection, and traceability.Movement Joint (Expansion Joint)A deliberate gap in a structure that accommodates thermal, settlement, or load-induced movement. Sealed with elastic systems — hydrophilic polyurethane, polyurea, or specialized waterstops — never with rigid materials.OEM / ODMOEM (Original Equipment Manufacturer): producing under a buyer's brand and packaging. ODM (Original Design Manufacturer): the manufacturer designs/formulates the product and the buyer brands it. Both are common in foreign-trade waterproofing supply.PolyureaUltra-fast-cure two-component elastomer with high elongation and toughness. Used as an elastomeric grouting / sealing material for dynamic structures (tunnels, vibrating decks). See Polyurea. Polyurethane (PU)Polymer family used in chemical grouting. Reacts with water on injection, foaming (hydrophobic) or gelling (hydrophilic). The most widely used chemistry for active leak repair.Pot LifeThe working time after a two-component material is mixed before it becomes too viscous to use. Distinct from gel time — pot life refers to material in the bucket; gel time refers to material after injection.PrepolymerA partially polymerized intermediate that is reactive but not yet fully cured. Polyurethane grouts are prepolymers that complete polymerization on water contact at the injection site.Reaction TimeFor PU grouts, the interval between water contact and the start of foaming or gelling. Hydrophobic systems react in seconds; hydrophilic systems in 1–3 minutes.Service LifeExpected functional duration of an installed grout system. Properly applied PU grouts commonly achieve 20–30+ year service lives in stable, water-saturated environments.ShrinkageVolumetric reduction during cure. Most chemical grouts are formulated to be non-shrinking so the cured plug remains in tight contact with the crack walls. Shrinkage is a common cause of post-cure leakage in inferior products.Tunnel LiningThe interior structural surface of a tunnel — typically segmental precast concrete or cast-in-place concrete. Joints between segments and through-cracks are primary waterproofing targets for chemical grouting.Two-Component (2K)A material supplied in two reactive components (A + B) that cure when mixed. Epoxy injection grouts and many acrylate systems are 2K. Single-component PU grouts react with ambient water rather than a B-side.ViscosityResistance to flow. Low-viscosity grouts (e.g., epoxy injection resin at ~200–400 cP) penetrate hairline cracks; high-viscosity grouts fill larger voids without bleeding through. Viscosity also varies with temperature.Water StopAny system that prevents water passage through a joint or crack. PVC waterstops (cast into joints), bentonite strips, and chemical grout injection are the three primary categories.Water-ReactiveMaterial chemistry that initiates cure on contact with water. Polyurethane chemical grouts are water-reactive — making them ideal for wet, real-world site conditions.