| HS Code | 138542 |
| Crack Bridging Ability | Excellent, prevents micro-crack propagation |
| Flexibility | High flexibility with low modulus for substrate movement |
| Elongation At Break | Typically 200-600% depending on formulation |
| Adhesion Strength | Enhanced bond to concrete and masonry substrates |
| Water Resistance | Good water repellency, reduces water ingress |
| Alkali Resistance | Stable under alkaline conditions of cementitious systems |
| Re Dispersibility | Forms stable film upon re-dispersion in water |
| Minimum Film Formation Temperature | Typically 0-5°C for easy application |
| Glass Transition Temperature | Tg range around -10°C to 5°C for flexibility |
| Bulk Density | Approximately 400-600 kg/m³ as powder |
As an accredited Crack-bridging RDP for Repair Mortars factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Supplied in 20 kg multi-layer paper bags with PE liner, ensuring moisture protection and easy handling for repair mortar applications. |
| Container Loading (20′ FCL) | 20' FCL loaded with 25 kg bags on pallets, approximately 20 metric tons, shrink-wrapped and securely stowed for safe transport. |
| Shipping | Crack-bridging RDP is shipped as free-flowing powder in moisture-proof multi-layer bags or drums, typically 25 kg net. Protect from humidity, rain, and direct sunlight during transport. Store in cool, dry conditions; handle with care to avoid bag damage and product contamination. |
| Storage | Store in a cool, dry, well-ventilated area, away from direct sunlight, heat sources, and moisture. Keep in original, unopened packaging; reseal tightly after use. Avoid exposure to humidity to prevent caking or loss of performance. Under proper conditions, shelf life is approximately 12 months from production date. |
| Shelf Life | Shelf life is typically 12 months when stored unopened in a cool, dry place, protected from moisture and humidity. |
In structural concrete repair, crack-bridging RDP is incorporated into single-component dry-mix formulations at addition ratios between 3.0 wt% and 4.5 wt% of total dry mortar mass; below 3.0 wt% the coalesced polymer network is insufficient to bridge microcracks wider than 0.05 mm under restrained shrinkage, while above 4.5 wt% the 28-day compressive strength trend approaches the 45 MPa lower boundary for EN 1504-3:2005 class R4 repair products. Compliance is evaluated against EN 1504-3:2005 with compressive strength determined by EN 12190:1998 and bond strength by EN 1542:1999; the chloride ion content of the prepared dry mortar is controlled below 0.05% to meet the same standard. The downstream production process at a dry-mix plant typically uses a twin-shaft paddle mixer with a working volume of 1,500 L to 2,500 L; silica sand and cement are pre-dried so that aggregate free moisture remains below 0.3 wt% before RDP is added in the final mixing stage at 80 rpm to 120 rpm. On the construction site, the powder is mixed with 4.0 L to 5.0 L of water per 25 kg bag using a forced-action paddle mixer at 400 rpm to 600 rpm. The terminal finished product types include trowel-applied structural repair mortar for columns, beams, and slabs; sprayable low-rebound repair mortar for vertical and overhead applications; and form-and-pour micro-concrete when the formulation is extended with 2 mm to 6 mm aggregate.
Field failure modes observed on production-scale dry-mix lines include erratic slump retention when residual moisture rises above 0.4 wt%, causing RDP particles to swell prematurely and form sieve residue on 315 µm security screens. The mixing sequence is therefore regulated: cement and sand are blended first for 60 s to 90 s, RDP is introduced only after the mixed material temperature falls below 35°C, and total dry-mix residence time is kept below 180 s to avoid polymer shear degradation. Bond strength by EN 1542:1999 after 28 days is commonly specified above 2.0 MPa for class R4 structural mortars; crack-bridging is not a primary classification requirement in EN 1504-3:2005 and is therefore qualified separately by EN 1062-7:2004 or an adapted beam test.
Bridge deck and highway pavement overlays subject the repair layer to combined cyclic wheel loading, thermal expansion, and substrate crack movement; RDP addition in these formulations is therefore held to a narrower window of 2.0 wt% to 3.5 wt% because the required 45 MPa compressive strength under EN 1504-3:2005 class R4 must be maintained without excessive air entrainment. The governing North American specification for packaged rapid-setting repair materials is ASTM C928/C928M-20a; tensile bond strength to prepared concrete substrates is measured by ASTM C1583-13, while crack-bridging capacity in European projects is commonly evaluated by EN 1062-7:2004 using a crack-opening displacement procedure adapted for cementitious overlays. The downstream production process for bridge overlay dry mortar is based on a horizontal ribbon blender or twin-shaft paddle mixer with aggregate moisture controlled below 0.25 wt%; on the job site, the powder is fed through a continuous rotor/stator mortar mixer where water dosage is regulated by flow meter to maintain a wet density of 2,150 kg/m³ to 2,250 kg/m³. Application is performed by vibratory screed or low-speed pump, and the mortar is cured with a spray-applied curing membrane that must remain compatible with the coalesced polymer film. Terminal finished product types include bonded concrete overlay mortar, pavement spall repair material, and rapid-strength patch mortar for night-lane closures. A critical process threshold is water addition: a deviation of more than +1.5 wt% from the designed water demand produces surface bleeding and can reduce 28-day compressive strength by 12% to 20%; at RDP dosages above 4.0 wt%, the mortar shifts from a Bingham plastic response to shear-thinning behaviour, reducing build thickness on sloped bridge decks and increasing segregation risk unless a methylcellulose-based rheology modifier is added at 0.05 wt% to 0.10 wt%. Published data for heavy axle-load frequencies above 2×10⁶ cycles in this specific overlay configuration is limited.
Marine and hydraulic structures expose crack-bridging repair mortars to chloride ingress, wave action, and repeated wet-dry cycles. In splash zone repair, RDP dosage is increased to 3.0 wt% to 5.0 wt% to reduce open porosity and improve cohesive film formation; silica fume at 5 wt% to 8 wt% is typically co-formulated to maintain chloride resistance. Compliance for structural marine repair is anchored to EN 1504-3:2005 class R4, with chloride ingress resistance evaluated according to EN 13396:2004 and bond strength by EN 1542:1999. The production process at a dry-mix plant for marine-grade material uses a ploughshare mixer with liquid injection of hydrophobic admixture after the dry-solids blending phase; bagged product is then applied on site with a rotor/stator spray machine at 30 bar to 50 bar air pressure, or trowel-applied in tidal working windows. Terminal finished product types include spray-applied marine repair mortar for pile jackets, hand-applied splash zone patch mortar for quay walls, and temporary protection mortar for reinforcement corrosion repair. The operational boundary is strict: these RDP-modified mortars are not formulated for permanent immersion without additional polymer modification and crystalline waterproofing; sustained hydrostatic pressure can re-emulsify partially coalesced films and reduce adhesion. No organic solvent-based curing compound is used because solvent migration can plasticize the polymer film and lower the EN 1542:1999 pull-off strength below 2.0 MPa. Batch-to-batch variance on production-scale lines is primarily linked to residual moisture in marine-dredged sands; aggregate must be dried to below 0.2 wt% to prevent reagglomeration of the hydrophobicised RDP.
| Application scenario | Primary product standard | Key test method | Typical RDP addition |
|---|---|---|---|
| Structural concrete repair | EN 1504-3:2005 class R4 | EN 12190:1998, EN 1542:1999 | 3.0 wt% to 4.5 wt% |
| Bridge deck overlay repair | ASTM C928/C928M-20a, EN 1504-3:2005 | ASTM C1583-13, EN 1062-7:2004 | 2.0 wt% to 3.5 wt% |
| Marine splash zone repair | EN 1504-3:2005 class R4 | EN 13396:2004, EN 1542:1999 | 3.0 wt% to 5.0 wt% |
| Industrial floor patching | EN 13813:2002 | EN 13892-2:2002, EN 1542:1999 | 1.5 wt% to 3.0 wt% |
| Precast fair-faced repair | EN 1504-3:2005 class R3 | EN 12617-4:2002, EN 1542:1999 | 2.0 wt% to 4.0 wt% |
| Water-retaining structure repair | EN 1504-3:2005 class R4 | EN 12390-8:2019, EN 1542:1999 | 3.0 wt% to 5.0 wt% |
Industrial floor patching compounds formulated with crack-bridging RDP are produced as single-component dry mortars with polymer dosage between 1.5 wt% and 3.0 wt%. The governing product standard is EN 13813:2002 for screed materials; compressive strength is determined by EN 13892-2:2002 and bond strength by EN 1542:1999. The production process uses a horizontal ploughshare mixer with jacket cooling; fine silica sand moisture is held below 0.2 wt% before blending, and the powder is screened through a 315 µm security screen to remove RDP agglomerates. Terminal finished product types include pourable floor repair mortar, flowable edge-patching screed, and semi-levelling underlayment repair compound. This application remains a shallow processing zone because the crack-bridging demand is low relative to structural repair; only a single mixing step and moisture-controlled bagging sequence are required.
Precast façade elements, architectural concrete panels, and exposed fair-faced surfaces impose strict limits on drying shrinkage because even minor differential movement becomes visually detectable. In this application, crack-bridging RDP is added at 2.0 wt% to 4.0 wt% in combination with a shrinkage-compensating cement or expansive additive; compliance is assessed under EN 1504-3:2005 class R3 for non-structural repair, with shrinkage and expansion measured according to EN 12617-4:2002 and bond strength by EN 1542:1999. The downstream production process for fair-faced repair mortars uses a low-shear planetary mixer at 40 rpm to 80 rpm to prevent excessive air entrainment and maintain uniform pigment dispersion; coloured oxide pigments, when required, are limited to below 0.8 wt% of total mix because higher loadings can interfere with polymer film coalescence and produce surface mottling. The mixed mortar is applied by trowel or filled into edge forms at a maximum layer thickness of 5 mm to 20 mm, depending on profile depth. Terminal finished product types include fair-faced patch mortar, micro-concrete for panel edge rebuilding, and pigmented repair stucco for architectural restoration. The processing window for water addition is narrow: mix water is limited to 3.8 L to 4.6 L per 25 kg bag, and overtempering beyond +1.0 wt% increases capillary porosity sufficiently to cause visible efflorescence on tinted surfaces. Published data for long-term colour stability under UV exposure in this specific RDP configuration is limited.
Repair of water-retaining concrete structures and secondary containment bunds introduces a sustained moisture state that alters the film coalescence mechanism of crack-bridging RDP. Dosage is set at 3.0 wt% to 5.0 wt% to reduce water permeability once the cement matrix has cured; the relevant product specification is EN 1504-3:2005 class R4, with water penetration resistance tested by EN 12390-8:2019 and pull-off adhesion by EN 1542:1999. The production process for water-retaining repair mortar uses a twin-shaft paddle mixer with a baghouse dust-control system; bagged powder is mixed on site with a low-speed mortar mixer at 300 rpm to 500 rpm, applied by trowel in 2 mm to 6 mm layers, and cured with a water-based curing membrane. Terminal finished product types include water-retaining structure repair mortar, secondary containment joint fillet mortar, and fillet repair material for bund wall transitions. The operational boundary is negative-side hydrostatic pressure: crack-bridging films are not rated for continuous back-side water pressure without an additional crystalline slurry or sheet membrane; published data for sustained hydrostatic pressure on RDP crack-bridging films in this configuration is limited. Aggregates with high sulfate content must be excluded, and combination with amine-based epoxy bonding agents is avoided because residual amine on the substrate can alter cement hydration at the interface.
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A crack-bridging redispersible polymer powder for repair mortars is a spray-dried vinyl acetate–ethylene (VAE) copolymer with a glass transition temperature below −10 °C, a free-film elongation at break of 250–400 % under ISO 527-3 at 23 °C, and a minimum film-forming temperature of 0–2 °C. Commercial model designations vary by supplier; the product class is defined by low-Tg VAE chemistry, alkali resistance, and redispersibility in calcium-rich mixing water, not by a single proprietary code. In EN 1504-3 class R4 structural repair mortars, the powder is dry-blended at 4.0–6.0 wt% of total dry mortar to reduce the elastic modulus of the hardened mortar while maintaining a capillary water absorption below 0.5 kg m⁻² h⁻⁰.⁵ after 28 days. The powder redisperses in the mixing water to form a continuous polymer film that interpenetrates the calcium silicate hydrate phase and bridges static and low-amplitude dynamic cracks without transferring destructive stress to the cement matrix.
Typical powder specifications include bulk density of 450–550 g/L by ISO 60, residual moisture ≤ 1.0 wt% by ISO 3251, ash content ≤ 12 % after ignition at 450 °C, and residue on a 400 µm sieve below 2 %. The pH of a 10 % redispersed dispersion is 7.0–9.0. These values are monitored at the dry-mix plant because residual moisture above 1.5 wt% can cause caking in silo storage, while elevated ash content indicates incomplete polymer separation or excessive anti-caking agent.
The primary difference is the ethylene-to-vinyl acetate ratio and the resulting thermal and mechanical behaviour of the free film. Standard VAE redispersible polymer powders intended for tile adhesives and self-leveling compounds have glass transition temperatures between +5 °C and +15 °C, free-film tensile strength of 8–15 MPa, and elongation at break of 50–150 %. Crack-bridging grades shift the comonomer ratio toward higher ethylene, yielding a glass transition temperature of −15 °C to −5 °C, tensile strength of 2–5 MPa, and elongation of 200–400 %. The lower tensile strength is intentional: a soft film yields under deformation instead of transmitting crack-opening stress to the surrounding cementitious matrix. The particle architecture also differs. Crack-bridging VAE RDP is produced with higher polyvinyl alcohol protective colloid content and a finer primary particle size distribution, which supports redispersion at water addition as low as 18 wt% but can raise shear viscosity in continuous mixing equipment.
| Property | Crack-bridging VAE RDP | Standard VAE RDP | Test method |
|---|---|---|---|
| Glass transition temperature | −15 °C to −5 °C | +5 °C to +15 °C | differential scanning calorimetry, second heating |
| Free-film tensile strength | 2–5 MPa | 8–15 MPa | ISO 527-3 |
| Free-film elongation at break | 200–400 % | 50–150 % | ISO 527-3 |
| Minimum film-forming temperature | 0–2 °C | 4–8 °C | ISO 2115 |
| Bulk density | 450–550 g/L | 500–600 g/L | ISO 60 |
| Recommended addition in repair mortar | 4.0–6.0 wt% | 2.0–3.0 wt% | EN 1504-3 class R4 formulation window |
Acrylic RDPs can achieve similar elongation but generally have higher water sensitivity in long-term wet-dry cycles. Crack-bridging VAE RDP is selected when capillary absorption and crack-bridging behaviour must be met simultaneously without a site-added liquid polymer.
In production-scale dry-mix plants, low-density VAE RDP is introduced by dense-phase pneumatic conveying at 1.8–2.4 bar into twin-shaft compulsory mixers of 1000–3000 L capacity. Air velocity above 25 m s⁻¹ in dilute-phase transport can fracture the spray-dried hollow spheres and generate fines that reduce powder flow and redispersibility. Mixing time should not exceed 45 min at mixer temperatures above 50 °C; extended high-shear mixing can partially sinter the polymer particles and form blade caking when the formulation contains 0.2–0.5 wt% polycarboxylate superplasticizer and 0.05–0.15 wt% defoamer. Discharge through an inline sieve with a 1.0 mm aperture removes agglomerates; packaging into moisture-proof polyethylene-lined sacks should occur only after the blend has cooled below 35 °C to limit condensation and subsequent powder caking. Batch-to-batch variance in bulk density of the RDP should be controlled to ±20 g/L to prevent weighing errors in automated gravimetric dosing systems.
Formulation trials for EN 1504-3 class R4 repair mortars should begin with 32–36 wt% CEM I 42.5 R, 55–60 wt% silica sand with a maximum particle size of 1.0 mm, 4–6 wt% crack-bridging RDP, 0.3–0.5 wt% polycarboxylate superplasticizer, 0.05–0.10 wt% powdered defoamer, and 0.1–0.3 wt% cellulose ether to control water retention. Mixing water demand is typically 18–20 wt% of total dry mix; higher water addition to compensate for a stiff mortar lowers compressive strength and delays film coalescence. The wet mortar can be applied by trowel or spray at thicknesses from 3 mm to 20 mm; for overhead repairs, a thixotropic formulation with the RDP at the upper end of the dosage range is used. Open time at 23 °C and 50 % RH is generally 20–30 min; surface skin formation occurs earlier on absorptive concrete unless the substrate is pre-wetted to saturated-surface-dry condition.
Crack-bridging performance is a system response that includes mortar layer thickness, polymer dosage, substrate roughness, and thermal history. A repair mortar containing 5.0 wt% crack-bridging VAE RDP is typically applied at 3.0 mm thickness over a precracked concrete substrate and conditioned for 7 days at 23 °C and 50 % RH, then subjected to crack-opening cycles at −10 °C. The relevant test method is EN 1062-7; formulations are designed to achieve class A2 or A3, corresponding to stable bridging of crack widths above 0.25 mm and 0.5 mm, respectively. Under class A3 conditions, the cracked repair layer must maintain continuity at 0.5 mm crack width for 24 h without cohesive failure of the polymer network. The high ethylene content of the VAE powder lowers the film brittle point sufficiently to maintain elongation at sub-zero temperatures, whereas a standard VAE RDP film stiffens below 0 °C and concentrates stress at the crack tip, producing adhesive debonding or brittle rupture. Thermal cycling between −10 °C and +50 °C can reduce crack-bridging capacity by 20–30 % after 50 cycles; published data for long-term durability beyond 500 cycles in aggressive chloride environments is limited.
When the crack-bridging RDP replaces styrene-butadiene rubber (SBR) latex in a dry-mix repair mortar, the production line gains a single-bag system and eliminates site dosing errors for liquid polymer. SBR latex added at 5–15 % by cement weight provides high elongation but requires on-site mixing control; dosage errors of ±1.0 % can shift the polymer-cement ratio outside the design window and alter adhesion. Crack-bridging VAE RDP is pre-dosed at the plant, leaving water addition as the main site-controlled variable. The dry powder form avoids microbial fouling and freeze-thaw coagulation that affect liquid SBR latex stored below 5 °C. In terms of mechanical performance, SBR latex films and VAE RDP films both provide elongation above 200 %; direct creep comparisons under sustained load are formulation-specific, and published data for the specific crack-bridging RDP configuration is limited. The dry-mix route also permits 25 kg prepackaged bags with a storage stability of 12 months at 5–30 °C in unopened moisture-proof packaging, provided that the bag is not exposed to relative humidity above 60 % for extended periods.
The redispersible powder is not an inert filler. The polyvinyl alcohol protective colloid and anionic surfactants that stabilize the VAE particles can retard tricalcium silicate hydration and extend initial setting time. In repair mortars containing 5 wt% crack-bridging RDP, Vicat initial setting time typically ranges from 180–240 min at 20 °C, compared with 120–150 min for an unmodified class R4 mortar. The delay is acceptable for most structural repair schedules but becomes a processing limitation below 5 °C, where early strength development may be delayed beyond 24 h. The powder is not recommended as a direct additive to calcium aluminate cement systems where rapid setting is required; the interaction with lithium carbonate accelerators is not covered by EN 1504-3 and published data is limited. Addition rates above 8 wt% can reduce compressive strength below the 45 MPa threshold for class R4 repair mortars and should be verified by EN 12190. Substrate porosity above 18 % can extract water before film coalescence; a water-based epoxy primer or continuous water curing is used to prevent premature desiccation.
The following compliance matrix summarizes the mandatory performance targets for a class R4 repair mortar modified with the crack-bridging RDP at 4.0–6.0 wt%.
| Requirement | Reference method | Target value |
|---|---|---|
| Compressive strength | EN 12190 | ≥ 45 MPa at 28 days |
| Bond strength to concrete | EN 1542 | ≥ 2.0 MPa, cohesive failure preferred |
| Capillary water absorption | EN 13057 | ≤ 0.5 kg m⁻² h⁻⁰.⁵ |
| Chloride ion content | EN 1015-17 | ≤ 0.05 % |
| Crack bridging | EN 1062-7 | Class A2 or A3 at −10 °C |
Substrate temperatures below 5 °C, air temperatures above 35 °C, and relative humidity below 50 % are outside the recommended application window for the crack-bridging RDP-modified repair mortar. Below 5 °C, polymer film formation is restricted, while above 35 °C, rapid surface water loss can produce crusting and delamination. The product is not suitable for continuously immersed repair zones, chemically aggressive sulfuric acid environments, or direct contact with strong solvents, because the VAE film swells and loses crack-bridging capacity under prolonged solvent exposure. For traffic-bearing overlays, the mortar must be covered by an abrasion-resistant topping; the unfilled crack-bridging layer alone does not provide sufficient surface wear resistance under heavy forklift traffic. Standard health and safety precautions for cementitious products apply; the powder should be handled in ventilated areas with dust extraction and personal protective equipment to limit respirable dust exposure.
