Polyurethane sealant for bridges is a highly elastic, aging resistant, and strong adhesive material designed specifically for waterproof sealing of bridge expansion joints and seams. It is divided into two types: single component (wet curing) and two-component (reaction curing). The core implementation is JC/T 482-2022, and low modulus (LM) superior products are preferred for bridges.
1、 Core types and selection
Two component (mainstream, preferred for bridges): A material (prepolymer)+B material (curing agent), with a common ratio of 10:1/5:1; Reaction curing, synchronous surface and interior, no collapse of deep seams, adjustable curing speed; Suitable for dynamic and deep joint scenarios such as expansion joints, settlement joints, and pipe galleries.
Single component (convenient type): moisture curing, directly applied with a glue gun; Fast surface drying, slow deep solidification, and easy foaming in deep seams; Suitable for shallow seams, maintenance, and non sagging facades.
Modulus selection (key):
Low modulus LM (mandatory for bridges): Tensile modulus<0.4MPa, elastic recovery rate ≥ 95%, suitable for displacement of * * ± 25% to ± 50% * *, crack resistance and fatigue resistance.
High modulus HM: High strength, poor elasticity, only used for static joints.
2、 Core Performance (Premium Product, JC/T 482-2022)
Elasticity: elongation rate ≥ 800%, recovery rate ≥ 95%, fixed elongation rate of 200% without damage.
Bonding: Concrete/steel * * ≥ 0.6MPa * *, no need for primer (can be applied on damp surfaces).
Temperature resistance: -40 ℃~80 ℃ (long-term), -50 ℃~150 ℃ (intermittent), low temperature not brittle, high temperature not flowing.
Durability: water resistance, salt fog resistance, ozone resistance, anti-aging, outdoor life of 15-20 years.
Waterproof: ≥ 0.6MPa water tightness, blocking rainwater from corroding the beam and steel bars.
3、 Typical application scenarios
Bridge expansion joints (core): waterproofing of steel joints, modular joints, and TST joints, absorbing temperature/vehicle vibration displacement.
Beam slab joints/settlement joints: Bridge deck continuous joints, flange slab joints, and bridge abutment settlement joints are sealed.
Steel bridge deck/pavement joint: bonding waterproofing between steel box girder and pavement layer (refer to JT/T 1131.5-2025).
Surrounding/anti-collision wall joints of supports: waterproof and anti-seepage, and prevent aging and rusting of supports.
4、 Key points of construction (taking two-component as an example)
Grassroots treatment: Clean and dry the joints (damp surfaces can be constructed without water accumulation), and there is no floating ash or oil stains.
Ingredient mixing: Mix in proportion (e.g. 10:1) for 3-5 minutes until uniform and particle free; Low temperature can slightly increase the acceleration of curing of B material.
Construction:
Facade/steep slope: Use non sagging type, glue gun to inject glue, scrape and trim.
Flat/Deep Seam: Use self leveling type, natural leveling, dense without bubbles.
Maintenance: The surface dries for about 2-6 hours and fully solidifies for 24-48 hours (adjusted with temperature/humidity); Avoid rain and trampling before curing.
Quality control: The adhesive layer is full, without bubbles/cracks/debonding; The bonding test showed no peeling or cohesive damage.
