| HS Code | 165782 |
| Product Name | RDP for Exterior Waterproofing Renders |
| Polymer Type | Vinyl acetate ethylene (VAE) copolymer |
| Appearance | White free-flowing powder |
| Bulk Density | 400-600 g/L |
| Ash Content | 10-15% |
| Ph Value | 6.0-8.0 |
| Minimum Film Formation Temperature | 0-5 °C |
| Water Resistance | Excellent water repellency and reduced water absorption |
| Tensile Adhesion Strength | ≥ 1.0 MPa on concrete substrate |
| Flexibility | High flexibility and crack-bridging ability |
| Cement Compatibility | Compatible with Portland cement and other hydraulic binders |
| Storage Stability | Stable for 12 months in original sealed packaging below 30 °C |
As an accredited RDP for Exterior Waterproofing Renders factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 20 kg kraft paper bag with inner polyethylene liner, containing redispersible polymer powder for exterior waterproofing render formulations. |
| Container Loading (20′ FCL) | RDP for exterior waterproofing renders is packed in 25 kg bags, palletized, and loaded as 20′ FCL for safe transport. |
| Shipping | RDP for Exterior Waterproofing Renders is shipped as a fine, dry powder in sealed multi-layer paper bags or 25kg cartons, palletized and shrink-wrapped. It should be transported in dry, ventilated containers, protected from moisture, humidity, and direct sunlight. Standard non-hazardous freight applies with proper labeling. |
| Storage | Store RDP in a cool, dry, well-ventilated area, away from direct sunlight, heat, and moisture. Keep containers tightly sealed to prevent absorption of humidity, which can cause caking and reduce performance. Avoid contact with water and incompatible materials. Use within manufacturer’s stated shelf life to ensure optimal waterproofing properties. |
| Shelf Life | Shelf life: 12 months from production date when stored unopened in a cool, dry place away from moisture. |
For two-component flexible cementitious slurries applied as exterior waterproofing membranes over concrete and masonry, a dry mix containing 3.0–5.0 wt% redispersible polymer powder is blended with water on site at a controlled low-shear input. The RDP is based on a vinyl acetate–ethylene copolymer with film coalescence possible at substrate temperatures of 5–35 °C. Mixing is carried out with a paddle mixer at 400–600 rpm; rotor speeds above 800 rpm entrain air and produce pinholes after curing. A batch size of 25 kg is common for vertical work, and pot life at 23 °C and 50% RH falls between 45 min and 60 min. The mixed slurry is applied in two passes to a total wet film thickness of 1.5–2.0 mm, with the second pass applied wet-on-wet after the first pass has begun to set but before surface skin formation. On a prepared concrete substrate with a minimum pull-off strength of 1.5 MPa, the cured membrane exhibits tensile adhesion values in the range of 0.8–1.2 MPa under EN 1542 direct pull-off conditions. Crack bridging is evaluated under EN 14891; formulations in this class are tested at the specified crack opening width before and after water immersion. The water-cement ratio of the mixed slurry should remain below 0.45 because excess free water delays polymer film formation and lowers early cohesive strength. Curing requires 24 h at 23 °C and 50% RH before water exposure, followed by 7 days of dry hardening for complete film formation. Adding RDP before water and mixing for 30 s before adding the remaining dry components reduces lump formation in production-scale batches. A defoamer at 0.05–0.15 wt% of dry mix is generally required to keep fresh air content below 8%. Without defoamer, air voids larger than 0.5 mm form at the bond line and become leakage paths.
Where a trowel-applied waterproofing render is specified for exterior basement walls, the dry formulation is commonly built around a cement-to-sand ratio of 1:2.5 to 1:3 with RDP added at 2.5–4.0 wt% of total dry batch. The mixed mortar carries a water dosage of 16–19 wt%, which must be held within ±0.5 wt% because the capillary water absorption coefficient measured under EN 1015-18 rises sharply when the mixture is overdosed with free water. For a cured render of 8–12 mm thickness, capillary water absorption falls into the W1 class at or below 0.40 kg/(m²·min^0.5); unmodified reference mortars of the same cement-sand ratio exceed that threshold within 24 h of immersion. Direct pull-off adhesion on concrete, measured under EN 1542, is maintained between 0.8 MPa and 1.5 MPa. The RDP film reduces the dynamic elastic modulus and permits microcrack dissipation across shrinkage fissures smaller than 0.2 mm. Application is carried out by steel trowel over a saturated-surface-dry substrate, but standing water must be removed to avoid polymer dilution at the bond line. Wet curing is limited to 48 h; prolonged water saturation prevents film coalescence and leaves a weak surface layer. Full water impermeability develops after a subsequent 7-day air cure at 23 °C and 50–60% RH. On vertical wall areas, a first pass of 4–6 mm is followed by a second pass to the full design thickness once the first has reached initial set. If the first pass is allowed to dry completely, the second pass debonds under shrinkage stress and the pull-off value drops below 0.5 MPa.
Spray application of an RDP-modified waterproofing render on vertical retaining walls introduces rheological constraints not present in trowel work. The dry mix is fed through a screw-conveyor continuous machine with a rotor-stator pumping unit and a variable water flow meter set to a water-to-dry-material ratio of 0.15–0.19. Spray nozzle orifice diameters of 6–8 mm and air pressures of 4–6 bar are used for a two-coat build. The RDP dosage is set at 3.0–5.0 wt% of the dry mortar; at the lower end, rebound on vertical substrates can exceed 20%, while at the upper end the material becomes prone to slumping after 10 mm single-pass thickness. Coarse aggregate is retained at a maximum particle size of 2.5 mm, because larger particles block the spray tip and produce uneven polymer dispersion. The principal processing failure is pulsating material output caused by inconsistent water flow; this disturbance entrains air at the nozzle and creates shadow areas with lower compaction. A second failure mode is blocking of the dry mix in the conveyor when the residual moisture of the RDP-containing powder exceeds 0.3 wt%, causing polymer caking on the screw. The spray-applied render is built in two passes of 5–8 mm each with the second pass applied only after the first has lost surface tack. Capillary water absorption is evaluated under EN 1015-18; spray-compacted specimens typically meet the W1 class limit of 0.40 kg/(m²·min^0.5) only if the wet density exceeds 1,900 kg/m³ after spraying. Bond strength to a clean, sound concrete substrate, tested under EN 1542, is controlled in the range 0.7–1.1 MPa. Equipment cleanup is not a cosmetic step; cured polymer-cement paste in the rotor-stator assembly reduces output by more than 30% in the next production run.
Terrace and balcony waterproofing systems combine an RDP-modified slurry underlayment with a polymer-modified tile adhesive. The adhesive is classified under EN 12004; a C2 adhesive must achieve a tensile adhesion strength of at least 1.0 MPa after standard conditioning, while an S1 deformability classification requires a transverse deformation of at least 2.5 mm. Addition of 4.0–6.0 wt% RDP to a cementitious tile adhesive can elevate a C1 formulation into the C2S1 range, but the conversion is not linear. Above 6.0 wt%, early shear strength falls markedly, and large-format porcelain tiles may show lateral movement during setting. The waterproofing underlayment itself is tested under EN 14891, with tensile adhesion after water immersion retained at ≥0.5 MPa. In a balcony assembly, the adhesive layer is loaded by thermal expansion and foot traffic; the RDP film reduces cracking in the cement-rich layer and improves wet adhesion to the membrane. Mixing for site batches of 25–50 kg is carried out with a low-speed drill at 400–600 rpm for 2–3 min, followed by a 5 min rest and a 30 s remix. Overtwisting accelerates drying on the trowel and disrupts coalescing polymer particles. The notched trowel size is typically 6 mm × 6 mm for flat-back ceramic tiles and 8 mm × 8 mm for gauged porcelain. Choosing a smaller notch on uneven terraces reduces contact area and lowers pull-off results under EN 12004.
| Standard | Property | Threshold |
|---|---|---|
| EN 12004 | Tensile adhesion, C2 | ≥1.0 MPa |
| EN 12004 | Transverse deformation, S1 | ≥2.5 mm |
| EN 14891 | Adhesion after water immersion | ≥0.5 MPa |
| EN 1015-18 | Capillary water absorption coefficient | ≤0.40 kg/(m²·min^0.5) |
Before a damaged exterior concrete stair edge is levelled with a polymer-modified waterproofing repair render, the substrate must be chipped back to sound concrete and prepared to an exposed aggregate profile of 1–2 mm. A repair mortar in this application typically contains 3.0–4.0 wt% RDP to meet the requirements of an EN 1504-3 R3 class repair product: compressive strength of ≥25 MPa at 28 days and direct pull-off adhesion of ≥1.5 MPa measured under EN 1542. The polymer film is not a substitute for substrate preparation; bond failure on smooth, laitance-contaminated concrete occurs below 0.5 MPa and cannot be reversed by increasing RDP dosage. The mortar is applied in layers of 5–15 mm. On vertical surfaces, a single pass above 20 mm tends to slump unless thixotropic agents are added. Shrinkage cracks are controlled by the combination of RDP and a water-to-cement ratio below 0.45. Capillary water absorption is measured after 28 days under EN 1015-18; the W1 limit of 0.40 kg/(m²·min^0.5) is the usual exterior repair expectation. Cyclic wetting and drying under practical exposure conditions can reduce bond strength by 15–30% when the repair is not fully cured before exposure to frost. The repair render is cured with a damp cloth for the first 48 h, then allowed to dry for 5–7 days before the surface is subjected to impermeability testing or decorative coating.
Exterior thermal insulation composite systems use a base coat render as the load-bearing skin over insulation boards. Addition of 3.0–5.0 wt% RDP to a cement-rich base coat lowers capillary water absorption while retaining sufficient water vapour permeability. The water absorption coefficient determined by EN 1015-18 is typically driven into the W2 class at or below 0.20 kg/(m²·min^0.5) when the polymer dosage is combined with a dense aggregate packing and a low water-to-cement ratio near 0.38. The polymer film also raises the impact resistance of the thin coat; an unreinforced base coat without RDP fails the base-coat impact tests typical of ETICS specifications, while the RDP-modified system withstands standard impact energies of 3 J and 10 J without visible cracking. However, an RDP dosage above 6.0 wt% can reduce water vapour transmission to the point that moisture trapped behind the insulation leads to freeze-thaw damage in cold climates. For this reason, the base coat is checked both for capillary absorption and for water vapour diffusion under the relevant ETICS test sequence, not only for pull-off adhesion. Adhesion to EPS board is tested under EN 13499 or the applicable EAD; cohesive failure in the insulation at 0.08–0.12 MPa is the usual acceptance mode. The base coat is applied in one or two passes to a total thickness of 3–5 mm with a stainless-steel trowel; reinforcing mesh is embedded while the first 2–3 mm layer is still fresh. Delamination occurs if the mesh is pressed against the insulation without sufficient polymer-modified render behind it.
Coastal exterior renders must address chloride ingress, sulphate exposure, and cyclic wetting by chloride-laden spray. In this context, RDP addition of 3.0–4.5 wt% is co-optimized with granulated blast-furnace slag at 20–30 wt% or metakaolin at 8–12 wt% replacement of cement. The RDP component reduces capillary absorption under EN 1015-18 to the W1 or W2 class, while the supplementary cementitious material refines pore structure and lowers chloride migration. Chloride migration testing may follow NT BUILD 492; published data for RDP-modified renders under this specific configuration are limited, so qualification should include a parallel control mix without polymer rather than relying on extrapolated values. Direct pull-off adhesion on sea-exposed concrete under EN 1542 is maintained at 0.8–1.2 MPa only when the substrate is free of salt crystallization. If the render is applied over a substrate contaminated with chloride, a salt-retardant primer or substrate removal is necessary; the polymer film will not block osmotic passage by itself. The mixed mortar is applied in two passes of 6–10 mm each. A low water-to-cement ratio below 0.45 is essential, and a curing period of 7 days before first splash exposure prevents surface leaching of the polymer film. Formulations that rely on RDP alone without slag or metakaolin show higher chloride diffusion coefficients, but numerical field correlations are not universally available.
Competitive RDP for Exterior Waterproofing Renders prices that fit your budget—flexible terms and customized quotes for every order.
For samples, pricing, or more information, please contact us at +8615380400285 or mail to sales2@liwei-chem.com.
We will respond to you as soon as possible.
Tel: +8615380400285
Email: sales2@liwei-chem.com
Flexible payment, competitive price, premium service - Inquire now!
A redispersible polymer powder for exterior waterproofing renders is a spray-dried copolymer powder designed to modify cementitious rendering mortars. The reference product described here, designated RDP-EWR 8042, is based on a carboxylated ethylene-vinyl acetate/vinyl chloride terpolymer protected by a polyvinyl alcohol colloid. The material is supplied as a free-flowing off-white powder with a non-volatile content of ≥98% (ISO 3251), a bulk density of 480–620 g/L (ISO 60), and a pH of 7.0–8.5 when measured on a 25% aqueous dispersion (ISO 1147). The ash content is 10–14% after ignition at 1000 °C (ISO 3451-1). The glass transition temperature determined by differential scanning calorimetry is −7 °C (ISO 11357-2), and the minimum film formation temperature is 0 °C (ISO 2115). In an exterior render formulated to EN 998-1:2016, the powder is introduced at 2.5–4.0 wt% of the total dry mortar weight. The function is not to form a surface-sealing paint film; it is to reduce capillary water absorption, increase adhesion to concrete and masonry, and provide controlled flexibility while leaving the hardened render sufficiently vapour-permeable to avoid trapped moisture behind the render layer.
| Parameter | Method | Typical range |
|---|---|---|
| Bulk density | ISO 60 | 480–620 g/L |
| pH, 25% dispersion | ISO 1147 | 7.0–8.5 |
| Ash content | ISO 3451-1 | 10–14% |
| Non-volatile content | ISO 3251 | ≥98% |
| Glass transition temperature | ISO 11357-2 | −7 °C |
| Minimum film formation temperature | ISO 2115 | 0 °C |
The primary waterproofing mechanism is polymer film coalescence inside capillary pores and at the paste-aggregate interface. When the dry mortar is mixed with water, the protective colloid dissolves and the polymer particles redisperse into an aqueous polymer phase. As cement hydration consumes free water, the polymer particles are progressively concentrated in the remaining capillary water. If the substrate and ambient temperature remain above the 0 °C MFFT, the particles deform under capillary pressure and coalesce into a continuous or semi-continuous polymer film. This film bridges microcracks, coats capillary walls, and reduces the continuity of the pore network. Below the MFFT, the particles remain discrete and the hardened render behaves more like an unmodified mortar; water absorption measured by EN 1015-21:2002 may be 30–50% higher after curing at 5 °C than after curing at 23 °C for the same mixing composition.
A laboratory reference mix based on 1 part CEM I 42.5 R and 3 parts 0–4 mm silica sand with 3 wt% RDP-EWR 8042 typically exhibits a capillary water absorption coefficient of 0.08–0.20 kg/(m²·min^0.5) after 28 days at 20 °C and 60% RH. The unmodified control under the same curing regime shows 0.40–0.70 kg/(m²·min^0.5). The vapour diffusion resistance factor remains moderate at 15–30 (EN ISO 12572) compared with 10–15 for the unmodified control, which allows the render to dry outward after rain wetting. The polymer film does not completely occlude the capillary system at this addition level; closed-cell film formation would produce lower water vapour permeability and increase the risk of moisture accumulation at the substrate interface during winter. Published data for this exact dry-mix composition are limited; the cited ranges are representative of laboratory trials using comparable ethylene-vinyl acetate/vinyl chloride redispersible powders in 1:3 cement-sand mortars.
On a dry-mix production line, the powder is introduced after the cement, graded sand, and mineral fillers have been pre-blended for 3–4 min in a horizontal paddle mixer operating at 80–120 rpm. A total dry blending time of 6–8 min for a 1-tonne batch is normally sufficient to achieve a uniform polymer distribution without destroying the polyvinyl alcohol protective colloid. High-shear ploughshare mixers are not recommended unless the jacket temperature is kept below 35 °C; local shear heating can soften the polymer particles and produce deposits on the mixer wall or dosing screws. The dry blend should be discharged at a product temperature below 30 °C and immediately sealed in moisture-resistant bags to prevent partial hydration of the cement and reduced redispersibility of the polymer.
For site mixing, the dry render blend is added to 4.8–5.5 L of water per 25 kg bag. A low-speed paddle mixer at 300–600 rpm is used for 3–5 min, followed by a 5 min slaking period and a further 30 s remix. Pot life at 20 °C is 45–90 min; at 30 °C, the working window shortens to 30–45 min and the water demand may increase by 2–3%. The substrate should be clean, sound, and pre-dampened when its absorption exceeds 20%; dry concrete with high suction will remove water from the fresh render before cement hydration and polymer coalescence are complete. The mixed render is applied by stainless steel trowel or by continuous screw pump spray equipment such as a PFT G5C or Putzmeister MP 25, with a screw pump output of 18–22 L/min and air pressure of 1.5–2.0 bar. A single pass is limited to 3–5 mm; two passes are used for total thickness up to 10 mm only when the first layer has stiffened sufficiently to support the second. Freshly applied render should be protected from rain and strong wind for 24 h. A moist curing period of 2–3 days supports cement hydration; an additional 7 days at 20 °C and 60% RH is normally required before water resistance testing is meaningful.
Wet adhesion is the main failure mode for exterior renders exposed to wind-driven rain. The adhesion loss mechanism is not solely water intrusion at the interface; it also involves plasticization of the polymer phase by absorbed water and slow alkaline saponification of the acetate comonomer units in the cement matrix. The vinyl chloride fraction in RDP-EWR 8042 reduces the diffusion of hydroxyl ions into the film and raises the wet film modulus, but it does not eliminate hydrolysis. When tested to EN 1015-12:2016, the reference 3 wt% addition usually produces 28-day dry adhesion to a pre-dampened concrete substrate of 0.70–0.95 MPa, with cohesive failure occurring in the render rather than at the interface. After 14 days immersion in water at 20 °C, the measured adhesion falls to 0.40–0.60 MPa. This remains above the common minimum of 0.3 MPa for exterior waterproofing renders, but it indicates that the product is not intended for permanently submerged conditions without additional waterproofing layers.
Two process factors accelerate wet adhesion loss. The first is overwatering: increasing the water dose from 5.0 L to 5.5 L per 25 kg can reduce wet adhesion by 15–20% due to microbleeding at the interface. The second is application to dry substrate with high capillary suction: the interface becomes depleted of water and polymer migration away from the bond line is increased. Pre-dampening is therefore not optional for dense concrete substrates. The material also has a clear lower application temperature: if the render is applied when substrate temperature is below 5 °C or is exposed to frost within 24 h, polymer film formation is incomplete and the 14-day wet adhesion can drop below 0.25 MPa in subsequent testing.
Increasing the RDP dosage above 5 wt% produces a more continuous and less permeable polymer film. Capillary water absorption can fall below 0.06 kg/(m²·min^0.5), and the render appears more hydrophobic in early rain exposure. The trade-off is a significant loss in compressive strength and an increase in moisture retention under the surface layer. At 28 days, a 1:3 cement-sand render with 5 wt% RDP typically loses 30–45% of the compressive strength of the unmodified control, falling from 15–18 MPa to 8–12 MPa (EN 1015-11:2019). The same mix retains more capillary water during freeze-thaw cycles because the polymer film reduces outward vapour flux; frost-related surface blistering is more likely when a saturated render freezes rapidly. For exterior waterproofing renders exposed to repeated freeze-thaw cycles, the practical addition limit is 4–5 wt% of total dry mix. Below 2 wt%, the water absorption coefficient usually remains above 0.25 kg/(m²·min^0.5), and the product does not achieve the desired waterproofing performance.
| Render system | Capillary water absorption coefficient (EN 1015-21:2002) | 28-day compressive strength (EN 1015-11:2019) | 14-day water immersion adhesion (EN 1015-12:2016) |
|---|---|---|---|
| Unmodified 1:3 cement-sand render | 0.40–0.70 kg/(m²·min^0.5) | 15–18 MPa | 0.15–0.25 MPa |
| 3 wt% EVA/VC RDP | 0.08–0.20 kg/(m²·min^0.5) | 12–15 MPa | 0.40–0.60 MPa |
| 3 wt% styrene-acrylic RDP | 0.20–0.35 kg/(m²·min^0.5) | 13–16 MPa | 0.45–0.70 MPa |
| 0.5 wt% silicone hydrophobic admixture only | 0.05–0.12 kg/(m²·min^0.5) | 14–17 MPa | 0.10–0.20 MPa |
In comparison with two-component styrene-butadiene latex admixtures, the powder provides a one-part dry-mix production route, eliminates on-site polymer dosing errors, and avoids freeze damage to the liquid polymer during winter transport. The powder also reduces the biological stabilisation workload because it contains no liquid water phase. The trade-off is that SBR latex can produce higher elongation at break in thin brush-applied waterproofing slurries; it is therefore preferred for complex positive-side waterproofing details, while the powder is better matched to trowel- or spray-applied render systems. Compared with hydrophobic silicone admixtures, RDP-EWR 8042 reduces water absorption by filling capillary pores and increasing interfacial cohesion; silicones reduce capillary water uptake by changing surface tension but do not contribute to crack bridging or adhesion. A combination of 0.2–0.5 wt% silicone admixture with 3 wt% RDP can reduce the capillary water absorption coefficient to 0.06–0.10 kg/(m²·min^0.5), but silicone dosage must remain below 0.5 wt%; higher silicone levels can interfere with polymer film coalescence and lower wet adhesion below the 0.3 MPa threshold.
Compared with styrene-acrylic RDPs, the EVA/VC product has a lower MFFT and is more tolerant of low-temperature application in early spring or late autumn. Styrene-acrylic powders often have MFFT values in the 8–20 °C range and may require coalescence aids or warm curing to develop full film strength. The styrene-acrylic polymer typically shows better resistance to alkaline saponification over very long wet exposure, but its higher film hardness can reduce crack bridging at low temperatures. Compared with PVA-only redispersible powders, the EVA/VC product is re-emulsification-resistant after drying; PVA films remain water-sensitive and are not suitable for permanent exterior waterproofing without a secondary hydrophobic system.
The product should be stored in unopened bags at 5–30 °C and relative humidity below 65%. Stacking beyond 3 pallets high can compact the powder and increase sieve retention. Under these conditions, the shelf life is 6 months. Exposure to higher humidity may cause lumping and partial irreversible agglomeration. Before use in an exterior waterproofing render, a retained sample should be checked for pH of a 25% dispersion and for redispersibility in water; any significant reduction in redispersibility indicates that the powder has absorbed moisture and should not be used for waterproofing-critical work.
