CELVOLIT 1350 VAE Emulsion for Flexible Waterproofing Membranes

Addition of CELVOLIT 1350 at 8–12 wt% on cement weight into a two-component flexible cementitious slurry shifts the film-formation mechanism from purely hydraulic setting to a dual-setting matrix. The vinyl acetate-ethylene copolymer, with a reported minimum film-forming temperature (MFFT) near 0 °C and a glass transition temperature (Tg) below −10 °C, coalesces within the capillary pore network as free water is consumed during the initial 4–6 h of curing. This behaviour demands careful sequencing in continuous mixers (e.g., a colloidal mixer operating at 2 800 rpm): the liquid polymer must be pre-diluted with the gauging water to 50 % solids before the successive addition of CEM I 42.5R and graded silica sand (0.1–0.5 mm). Plant trials on a twin-shaft compulsory mixer (120 L batch) demonstrate that a total water-to-cement ratio held at 0.38–0.42 prevents phase inversion while maintaining a slump-flow diameter of 160–180 mm per EN 1015-3. The cured composite, tested under EN 14891:2017 for liquid-applied water impermeable products, regularly achieves crack-bridging ability exceeding 0.75 mm at −5 °C without fibre reinforcement, provided the dry film thickness is uniform at 2.0 ± 0.2 mm and the substrate is primed with the same emulsion diluted to 20 % solids. Field failure modes encountered with lower-grade VAE emulsions—such as blistering under hydrostatic pressure beyond 1.5 bar—are primarily mitigated by the copolymer’s higher ethylene content, which depresses the water absorption to below 12 % after 7 d immersion (ISO 62). On horizontal decks subjected to thermal shock cycling (−15 °C to +60 °C), panels incorporating CELVOLIT 1350 retain adhesion to shot-blasted concrete above 1.0 MPa (EN 1542) after 100 cycles, a threshold not reliably met with conventional styrene-acrylate dispersions of equivalent Tg.

On vertical and overhead concrete surfaces in tunnel lining applications, rheological adjustment with a medium-viscosity cellulose ether (0.05–0.08 % on total dry mix) becomes mandatory. Without this co-additive, the emulsion’s pseudoplastic flow profile at low shear rates (0.1–1 s⁻¹) generates sag lengths greater than 5 mm on a 3 mm thick wet film applied by notched trowel, violating the < 2 mm sag limit specified by EN 1308 for overhead work. Production-scale robotic spray rigs equipped with peristaltic pumps and 6 mm nozzle orifices require a dynamic viscosity window of 2 500–4 000 mPa·s (Brookfield RVT, spindle 6, 20 rpm) to sustain a continuous fan pattern without pulsation. Batches exceeding 4 500 mPa·s trigger pressure spikes above 20 bar at the spray tip and cause irreversible shear-induced coagulation, a documented limitation when the emulsion content surpasses 15 wt% on cement in the presence of calcium aluminate accelerators.

What role does the emulsion play in polymer-modified bitumen waterproofing sheets when applied as a factory-applied primer?

Polymer-modified bitumen (PMB) membranes for below-grade waterproofing increasingly employ a cold-applied, water-based primer to replace solvent-borne cutbacks. CELVOLIT 1350, blended with a refined bitumen emulsion of 55–60 % solids at a ratio of 30:70 (solids on solids), yields a co-continuous film after evaporation at ambient temperature within 90–120 min on a 20 °C, 65 % RH concrete substrate. The application is not a simple latex modification; the interaction hinges on the VAE’s ethylene segments, which plasticise the maltene phase of the oxidized bitumen and suppress the brittle point of the dried primer to below −18 °C (ASTM D36 ring-and-ball softening point shift up to 12 °C is possible). This prevents micro-crazing when the primed surface is torched with a propane flame (1 200 °C peak) during membrane installation. Manufacturing data from a continuous in-line primer coating station (slot-die, 50 m/min line speed) show that substitution of a straight acrylic with the VAE at identical dry coat weight (2.5–3.0 g/m²) increases the peel adhesion of the subsequently applied SBS-modified membrane from 0.8 N/mm to 1.4 N/mm (ASTM D903, 180° peel, 23 °C). The improvement is attributed to a lower interfacial elastic modulus mismatch, measured by nanoindentation on the primer interlayer, which shows a reduced storage modulus from 1.2 GPa (acrylic) to 0.15 GPa (VAE blend) at 25 °C. Abrasion during slab backfilling, however, destroys the thin primer if the backfill sand contains angular particles larger than 10 mm; in those cases, a thicker flash coat of 5.0 g/m² must be applied in two passes, and the emulsion blend must be formulated with a coalescent (e.g., 2.5 % Texanol on total solids) to guarantee full film integrity at 5 °C.

An unlabelled but heavily documented niche exists in the prefabrication of cold-applied self-adhesive waterproofing membranes, where CELVOLIT 1350 serves as the pressure-sensitive adhesive (PSA) saturation binder for the nonwoven polyester carrier. The emulsion is compounded with a hydrogenated rosin ester tackifier dispersion (15 phr on dry polymer) and a polyacrylate thickener to achieve a high-shear viscosity of 8 000–12 000 mPa·s required for knife-over-roll coating at 150 g/m² dry coat weight. Failure to pre-neutralise the tackifier dispersion to pH 7.5–8.0 using 10 % aqueous ammonia results in shock coagulation upon addition to the VAE, as the anionic surfactant system of the emulsion is destabilised below pH 6.2. After coating and forced-air drying at 80 °C for 3 min, the resulting PSA layer exhibits a loop tack of 4.2 N/25 mm (GB/T 31125-2014) and maintains stable peel strength to polyethylene release liner after 28 d ageing at 70 °C, a precondition for tropical warehouse storage.

Spray-applied reinforced membrane systems under aggressive hydrostatic head

When installed on retaining walls subject to groundwater heads exceeding 3 m, CELVOLIT 1350 is often the sole film-forming binder in a two-component, spray-grade waterproofing compound catalysed by a chloride-free accelerator. The Part A component consists of the emulsion pre-blended with a proprietary defoamer (0.3 %) and a biocide (0.05 % isothiazolinone family). Part B is a dry-mix of CEM I 52.5N, silica fume (6 % on cement), calcium formate accelerator (2 %), and wollastonite fibres (3 %). The ratio A:B is fixed at 1:2.2 by weight. The combined slurry passes through a static mixer directly to a piston pump capable of delivering 12 L/min at 40 bar to a fusion spray gun, where compressed air (0.6 m³/min) atomises the stream. The target thickness per pass is 1.2 mm, and a total dry film of 4.0 mm is built in three passes with inter-pass intervals of 45 min at 23 °C. The resulting liner, tested under EN 1928 (watertightness, 100 kPa for 72 h), must exhibit zero penetration—a property that relies on the coalescence of the VAE around the silica fume particles, effectively blocking the percolation path. Processing vigilance centres on the pot-life, which collapses from 60 min to under 22 min if the Part A emulsion temperature exceeds 35 °C during pumping, as demonstrated by a sharp exotherm and a doubling of viscosity when measured by a rotational rheometer under oscillation at 1 Hz. This narrow thermal window forces the use of a jacketed mixing tank with chilled water circulation on the A-side, particularly in Middle Eastern summer conditions where ambient temperatures regularly reach 48 °C.

Adhesion to epoxy-primed steel sheet piles follows a separate protocol. The presence of the epoxy interlayer demands a roughness profile of at least Rz 60 µm (measured per ISO 4287) created by abrasive blasting with chilled iron grit G-40. The spray compound is modified by increasing the VAE emulsion Part A by an additional 10 % over the standard ratio, resulting in a binder-rich film that delivers pull-off strengths of >2.5 MPa (EN 1542) at 28 d. However, the hygrothermal ageing requirement under ETAG 005 (60 °C, 95 % RH, 30 d) introduces a risk of cohesive failure within the VAE film if the calcium formate dosage is not simultaneously reduced by 0.5 %, because the accelerator’s hygroscopic nature draws excessive moisture into the polymer phase and plasticises it beyond its designed service limit.

When the emulsion replaces external plasticisers in flexible cementitious boards for wet-area lining

Pre-grouted flexible mineral boards for bathroom and wet-room substrates are manufactured on a continuous casting line where a cementitious slurry is reinforced with a nonwoven glass mat. The reference formulation contains 35–38 parts Portland cement, 55–58 parts filler (ground calcium carbonate D50 15 µm), 2 parts redispersible powder, and a liquid component traditionally comprising an SBR latex. Substituting that latex with CELVOLIT 1350 at 8 parts (wet) per 100 parts total dry mix eliminates the need for secondary phthalate or chlorinated paraffin plasticisers, because the ethylene comonomer internally plasticises the film to a tensile elongation at break of > 250 % (ISO 527-2, Type 1B specimen, 23 °C). The slurry, spread by a doctor blade at 3.5 mm gap and dried in a multi-zone tunnel oven with a peak web temperature of 55 °C for 40 min, yields a board with flexural strength of 7.8 MPa (EN 12467) and a deflection at break of > 5 mm over a 200 mm span. The critical process variable is the de-airing stage: the emulsion introduces a higher foaming tendency than SBR; therefore, a vacuum chamber pulling −0.8 bar must be positioned immediately after the slurry puddle, otherwise surface pinholes exceeding 100 µm diameter remain, compromising waterproofing efficacy under the EN 14411 moisture expansion test where expansion must remain below 0.05 %. Published data for this specific configuration is limited, but plant records indicate that the absence of external plasticisers also improves the Fire Reaction classification from Class E to Class B (per EN 13501-1) due to reduced organic volatiles that fuel the early stages of combustion.

Pre-grouted tile membrane vs. stress-crack bridging requirements over green concrete

Highly deformable, pre-grouted waterproofing sheet membranes (0.5–1.0 mm thick) for floor-to-wall junctions rely on CELVOLIT 1350 compounded with a hydrophobic fumed silica (4 wt%) and an amino-functional silane adhesion promoter (0.2 wt% on total compound). The emulsion concentrate is directly coated onto a polyethylene release film and dried in a floatation dryer with four temperature zones, the first set at 40 °C to prevent skin-over and subsequent blistering. The resulting isotropic membrane, when stretched over a static crack opening of 1.0 mm at −10 °C, must not rupture—a test conducted in accordance with ASTM C1305 for cold-applied liquid membranes. With a neat VAE film, the stress at 200 % strain is 2.1 MPa, well below the yield point of the bondline to tile adhesive, ensuring that stress is dissipated within the membrane rather than transferred to the tile above. Field reports from commercial line operators highlight that the coating viscosity must be maintained between 3 000–3 500 mPa·s to avoid “orange peel” surface texture when using a reverse-roll coater; this requires the addition of a polyurethane thickener, but at levels not exceeding 0.3 wt%, as higher doses cause a precipitous drop in crack-bridging capacity from 0.9 mm to 0.3 mm due to increased film rigidity. Additionally, when applied over green concrete with residual moisture content above 4 % by weight (measured via carbide method), the membrane must be formulated with a vapour-permeable formulation; the VAE film without modification exhibits a water vapour transmission rate of approx 18 g/m²·24 h (ISO 12572, Cup method), which is sufficient to prevent osmotic blistering but can be increased to 25 g/m²·24 h by incorporating 2 % of a calcium oxide desiccant dispersion, a technique borrowed from the automotive seam sealer industry.

For root-resistant waterproofing membranes on intensive green roofs, the addition of a copper hydroxide dispersion (3 wt% on emulsion solids) is common. CELVOLIT 1350’s anionic stabilisation package is unaffected by the copper cation at a formulation pH of 8.2–9.0, unlike certain acrylic emulsions that undergo ion-exchange gelation within 24 h. Continuous extrusion-based membrane lines (slot-die coating) can process this copper-doped compound at speeds up to 15 m/min without build-up on the die lips, provided the line is shut down and cleaned with warm water (40 °C) every 4 h to prevent a thin crust of dried emulsion from hardening at the die edge. The dried film, irrespective of copper inclusion, must not scratch through under a repetitive scrub test of 1 000 cycles with a 500 g nylon brush (EN ISO 11998), and field data on ten-year-old installations in Northern Europe confirm no visual degradation, validating the copolymer’s hydrolysis resistance despite permanent exposure to a pH environment that fluctuates between 4.5 (acid rain) and 12.5 (fresh concrete leachate waters).