In ready-mixed concrete supplied under EN 206 and assessed for fresh-fiber distribution in accordance with ASTM C1116/C1116M-23, Adfil Sinta F51 is introduced into the pan mixer during the aggregate-charging phase at a rate of 0.6–1.2 kg/m³ for residential slabs and 1.2–1.8 kg/m³ for exposed industrial pavements. The fibrillated synthetic micro-fiber must be dry-mixed for 30–60 seconds with 60–70% of the sand and all coarse aggregate before the first water contacts the bundle network; this sequence prevents the hydrophobic fibrils from agglomerating into mats that would otherwise survive the remaining mixing cycle. Total mixing time after water is extended by 45–90 seconds relative to the control mix to develop a uniform three-dimensional fibril network without over-shearing, which can reduce slump from S3 to S2 on the EN 206 consistency class. Because the synthetic micro-fiber does not contribute to structural tensile capacity, the section design remains governed by EN 1992-1-1 and the fiber is specified solely to reduce plastic settlement and early-age surface cracking; crack-width performance is evaluated by ASTM C1579-21 or by site trials under the actual evaporation rate. The terminal concrete is placed by conventional screed and power float methods into ground-bearing slabs, strip footings, and exterior pavement bays where early surface cracking has been observed in unreinforced control mixes.

What limits the addition rate of a fibrillated micro-fiber in dry-process shotcrete?

The limiting variable is the residual moisture in the pre-blended aggregate, not the fiber aspect ratio. In dry-process shotcrete placed in accordance with EFNARC and ASTM C1436/C1436M, fibers are dry-mixed with cement and sand in a paddle mixer and then conveyed through a rotary gunite machine with a 25–40 mm hose at air pressures of 250–400 kPa. Dosages above 1.8 kg/m³ tend to accumulate at the water ring when residual free moisture in the sand exceeds 0.8%, forming fiber-rich clumps that block the nozzle orifice and produce irregular pulsating spray. On-site adjustment usually includes drying the sand to 0.5% moisture or below, increasing the pre-dampening water at the nozzle collar from 0.8–1.2 L/s to disperse the fibers, and limiting the fiber feed rate to the maximum that still yields a visual absence of balling in the rebound material. The rebound in this process is typically 20–35%, but fibrillated fibers entrain more cement paste on their surface and can shift the rebound composition toward paste-rich fines; this material must be separated before reuse. Compliance for the hardened material is established using EN 14488-5 for flexural toughness, while the fiber type is assessed under ISO 13270:2013. The end uses are tunnel temporary linings, rock slope protection, and reinforced concrete repair where conventional formwork is not feasible.

Steam-cured precast lines operating on a 16-hour demoulding cycle introduce the fiber after the first 200 kg of aggregate but before the cement to avoid fiber-to-wall adhesion in the high-shear turbo-mixer. In non-structural elements such as cable troughs, transformer pits, and drainage channels produced to EN 13369:2023, the addition of 0.5–1.0 kg/m³ of Adfil Sinta F51 reduces edge blowouts during form stripping and fine surface cracks after steam curing at 55–65 °C. The thermal load in the steam chamber remains below the softening point of the synthetic fibrillation, so the fibril geometry does not collapse; however, a pre-cure ambient holding period of 2–3 hours at 30–40 °C is maintained to prevent hydration-induced temperature gradients from concentrating shrinkage on the exposed face. The concrete is cast with a water-cement ratio below 0.45 and a superplasticizer dosage adjusted to keep the slump in the S2–S3 range after fiber addition, because production logs indicate that fibrillated micro-fibers expose incompletely wetted fine aggregate particles at low workability. Surface finishing is carried out by vibratory screed or long-handled trowel before the final set, and no additional curing membrane is required beyond the existing sheet-curing system.

When a fibrillated micro-fiber is required to control cracking in an industrial floor screed placed by long-distance pump

The decision to replace crack-control mesh in an unbonded screed requires the mix to remain pumpable through 50–80 mm steel line over distances exceeding 80 m, and this is where the fiber addition rate interacts with the water-cement ratio. At 0.9–1.2 kg/m³, the fibrillated material raises the lubricating layer viscosity enough to increase pump back-pressure by approximately 5–10% on rotor-stator pumps with DN50 outlets; contractors compensate by raising the paste volume from 0.30 m³/m³ to 0.33 m³/m³ and reducing the maximum aggregate size from 8 mm to 6 mm. The screed is pumped at a water-cement ratio of 0.42–0.48, a flow time of 8–12 seconds on the flow table referenced in EN 13813:2002, and a residual moisture content of the sand below 0.6%. If the fiber content is pushed above 1.2 kg/m³, the fibrils interlock in the hopper grate and form elongated clumps that survive the screw auger; the resulting floor surface shows raised fiber nodules after power-trowelling. The terminal layer is a 40–60 mm unbonded screed over insulation or a separating membrane, producing a crack-free surface beneath vinyl and tile finishes in commercial buildings. The screed is classified by EN 13813:2002, and the fiber is tested for alkali resistance in accordance with ISO 13270:2013.

Self-Compacting Concrete for Architectural White Cement Panels

Architectural white cement panels produced by casting in smooth moulds demand a fiber that does not produce visible surface blemishes at a dosage of 0.3–0.6 kg/m³. In this application, the fibrillated micro-fiber is dispersed in a high-shear colloidal mixer for 90 seconds before the introduction of the limestone filler and white cement, because direct addition to the prepared paste causes the hydrophobic fibrils to float and later appear as filaments on the panel face. The mix is proportioned with a water-powder ratio of 0.28–0.32, a polycarboxylate superplasticizer content of 0.6–0.9% by mass of cement, and a slump flow of 650–750 mm tested by ASTM C1611/C1611M. The fiber dosage is set below 0.6 kg/m³ because higher additions increase the plastic viscosity from 2–3 Pa·s to over 4 Pa·s at shear rates below 1 s⁻¹, which causes air release defects at the mould face. Because published data for this exact fiber designation in white cement SCC is limited, the dosage window is confirmed by trial mix and not extrapolated from conventional grey concrete. Hardened panels are inspected under EN 13748-1 for surface finish and under EN 12390-3 for compressive strength. The end components are internal and external cladding panels, vanity units, and reception desks, where crack-free cast surfaces are required before acid staining or diamond polishing.

Because flowable cementitious underlayments are placed at water-powder ratios above 0.50 and at thicknesses below 12 mm, the fibrillated micro-fiber is pre-dispersed in the dry-mix silo during packing rather than added on site to avoid irregularities in the final surface. For a ternary binder system based on ordinary Portland cement, calcium aluminate cement, and anhydrite, the dosage of 0.5–0.8 kg/m³ is blended with fillers, redispersible polymer powder, and fine silica sand before bagging. The installed mortar is mixed with a low-speed drill and paddle mixer for 120 seconds at 600 rpm to generate sufficient shear to open the fibrillar network. This increase in mixing time compensates for the fact that thin-section mortars cannot tolerate the high-energy mixing required to completely uncurl individual fibrils, and over-mixing above 4 minutes traps air and reduces compressive strength below the 25 MPa threshold required by EN 13813:2002 for self-leveling screeds. The fiber contributes to crack-bridging before initial set, reducing the visible hairline cracking that occurs at door thresholds and underfloor heating pipe runs. The hardened underlayment is then covered with sheet vinyl, LVT, or ceramic tile.

Extrusion of fibre-cement boards imposes a stricter upper dosage constraint than cast concrete.

Hatschek-process fibre-cement lines run with 5–8 wt% solids slurry containing Portland cement, ground silica, process fibers, and optionally silica fume; the fibrillated synthetic micro-fiber is added at 0.5–1.5% by mass of cement as a partial replacement for cellulose fibres in some formulations. The constraint is not mechanical strength but dewatering behaviour on the rotating sieve cylinders: fibrillated synthetic fibers reduce the average pore size of the filter cake by trapping fine cement particles, so addition above 1.5% can slow the dewatering rate to below 2 L/m²·s and force a reduction in machine speed. On a Hatschek machine with 4–6 sieve cylinders and a sheet formation zone of 5–7 seconds, the fiber must be pre-dispersed in water with a non-ionic surfactant for 30 minutes before being metered into the main slurry line; direct dry addition produces low-density clumps that later appear as soft spots in the board after autoclaving at 170–180 °C. The finished boards are tested for bending strength in accordance with ISO 8336:2018, and the fiber content is verified by ignition loss at 950 °C. The end products are exterior cladding boards, soffit panels, and wet-area backing boards.