Large-area ground-supported slabs placed by laser screed receive SikaFiber Monofilament-12 at a dosage between 0.6 kg/m³ and 0.9 kg/m³ before the final third of batch water is metered into a twin-shaft counter-current mixer. The charging sequence is set to avoid fibre accumulation on the underside of the mixer cover: coarse aggregate is introduced first, then the monofilament, then the cementitious binder and remaining water. At a target slump of 150 mm to 180 mm measured per ASTM C143/C143M-20, the addition of 0.9 kg/m³ is observed to reduce slump by 10 mm to 20 mm on production batches; the mix is corrected with a polycarboxylate ether superplasticizer at 0.4% to 0.6% by cement weight. Restrained shrinkage testing per ASTM C1581/C1581M-18a on companion mortar shows delayed crack onset relative to an unmodified reference, although published data for this specific configuration is limited regarding long-term curling. Power-trowel finishing after the bleed-water sheen does not produce surface fuzz at 0.6 kg/m³; at 0.9 kg/m³, delayed final trowelling can expose occasional monofilament ends. The finished element is an internal floor slab for logistics buildings, light manufacturing halls, and automotive storage facilities where early-age crack control within the first 6 h after placement is the controlling requirement. The fibre does not alter saw-cut spacing and is not a substitute for structural reinforcement or dowel load transfer at construction joints.

What Limits Early-Age Crack Width in Thin Precast Elements Without Changing Demoulding Strength?

In thin-section precast façades with wall thickness between 40 mm and 80 mm, SikaFiber Monofilament-12 is dispersed into a self-compacting concrete matrix at 0.5 kg/m³ to 0.8 kg/m³. The batching sequence in a high-energy pan mixer is reversed relative to ordinary practice: the fibre is introduced after the polycarboxylate superplasticizer has been fully dispersed in the mixing water, because early fibre charging in a low-water self-compacting mix can create agglomerates that interrupt the formwork vibration response. Slump flow measured per EN 12350-8:2019 decreases from 650 mm to 580 mm at 0.8 kg/m³; the reduction is compensated by increasing superplasticizer dosage by no more than 0.05% of cement weight. Demoulding strengths at 16 h are not significantly reduced at fibre dosages up to 0.8 kg/m³, based on cube compressive strength tested per EN 12390-3:2019. The terminal component is an architectural cladding panel, modular fence element, or precast screen wall where crack width during formwork release and early ambient curing is the critical acceptance criterion. For acid-etched or polished façade surfaces, a trial panel is required because monofilament ends can appear as surface stipple when the face is ground or polished to a depth greater than 1 mm. The fibre is supplied under EN 14889-2:2006 conformity assessment and is not intended to replace steel reinforcement in load-bearing precast elements.

Wet-Mix Shotcrete Rebound Control and In-Situ Slope Performance

Where wet-mix shotcrete is specified for rock slope stabilization and temporary tunnel starter walls, SikaFiber Monofilament-12 is batched into the carrier concrete at 1.0 kg/m³ to 1.8 kg/m³. The aggregate grading is modified to a maximum nominal size of 8 mm to prevent fibre hang-up at the nozzle body; cement content is held between 380 kg/m³ and 425 kg/m³, and the water-cement ratio is restricted to 0.42 to 0.48. The mixed material is pumped through a 50 mm flexible conveying hose at pump pressures between 30 bar and 60 bar; at fibre dosages above 2.0 kg/m³, pressure oscillations of ±5 bar are observed at the pump gauge and rebound on a vertical panel can exceed 20%. Field rebound measured on a vertical test panel remains between 8% and 15% when nozzle distance is maintained at 1.0 m to 1.5 m and air pressure is set at 4 bar to 5 bar. Compressive strength specimens are extracted from shotcrete test panels after 7 d and 28 d and tested per EN 14488-2:2006. The installed product is a temporary or permanent facing shell on rock slopes, tunnel breakout zones, and swimming pool shells where early-age crack reduction and placement speed are specified. SikaFiber Monofilament-12 does not replace welded-wire mesh in permanent load-bearing tunnel linings unless the responsible engineer has accepted an alternative design based on applicable sprayed concrete standards such as EN 14487-1.

Flowable cementitious underlayment formulations produced for renovation over existing concrete receive SikaFiber Monofilament-12 as a dry pre-blended component at 0.3 kg/m³ to 0.5 kg/m³. The premix is added to a continuous high-shear corundum rotor mixer before the latex or powdered acrylic redispersible polymer is introduced. Adding the fibre directly to the mixing vortex without dry pre-blending produces mat formation on the paddle shaft and can reduce discharge throughput by up to 20%. Flow characteristics are assessed on a flow table per EN 12350-5:2019 with a target spread of 240 mm to 260 mm; at 0.5 kg/m³, the spread is reduced by 10 mm to 15 mm, requiring an additional 0.5% to 1.0% mixing water by dry premix weight. The installed layer is applied from 3 mm to 15 mm over old concrete or screed substrates. The fibre functions as an early-age crack control addition under vinyl, polyurethane, and trowelled epoxy floor coverings where shrinkage stress builds at door openings and under forced ventilation. Doses above 0.8 kg/m³ are not recommended for layers thinner than 5 mm because visible monofilament ends can remain after final smoothing. Site-dosed fibre is not recommended for self-smoothing systems because continuous mixing and emplacement equipment has no secondary dispersion stage.

When Repair Mortars Are Placed Overhead Without Formwork and Crack Control Is the Acceptance Criterion

In polymer-modified cementitious repair mortars conforming to EN 1504-3 Class R3 or R4, SikaFiber Monofilament-12 is added at 0.2 kg/m³ to 0.5 kg/m³ when the repair layer is specified for a minimum thickness of 15 mm. The mortar is prepared in a low-speed paddle mixer, not in a high-shear plaster mixer, to prevent fibre rupture and excessive plastic viscosity build-up. After mixing for 3 min, the mortar is left to stand for 2 min and remixed for 30 s; this sequence is critical because the fibre network develops shear-dependent gelation that improves overhead adhesion only after the polymer phase has released entrained air. Sag resistance is evaluated on an inclined plate with a maximum vertical slip of 2 mm at 20 mm thickness. The terminal repair is applied to soffit concrete and balcony edges where carbonated or chloride-contaminated substrate has been removed by hydro-demolition. For overhead repair layers thinner than 12 mm, the fibre length approaches the placement thickness and protruding monofilament ends can appear after trowelling; in such cases a shorter fibre or no fibre is specified. The fibre does not replace corrosion inhibitors, anti-carbonation coatings, or structural reinforcement in the repaired element.

Reducing Autogenous Shrinkage Cracking in High-Strength Pumped Concrete Columns and Core Walls

When high-strength core-wall concrete is pumped at water-cement ratios below 0.40 with silica fume replacement between 5% and 10%, autogenous shrinkage strain measured per ASTM C1698-19 can exceed 400 microstrain within 7 d. SikaFiber Monofilament-12 is incorporated at 0.9 kg/m³ to 1.2 kg/m³ at the batch plant, after the silica fume slurry and before the final polycarboxylate ether dose, to prevent agglomeration in the high-shear mixer. The concrete is discharged into a trailer pump with a 125 mm delivery line and placed through a boom; pump pressure at the hopper is recorded between 80 bar and 140 bar, with occasional spikes of 10 bar at the upper fibre limit. These pressure spikes correspond to segregation zones near the piston face and are eliminated by increasing the initial superplasticizer dosage by 0.1% by binder mass rather than by adding water. Cylinder compressive strength at 28 d per EN 12390-3:2019 is unchanged at 0.9 kg/m³; at 1.2 kg/m³, a strength reduction of 3% to 5% can occur if mixing time exceeds 10 min due to air entrapment on the fibre surface. The terminal component is load-bearing pump concrete for columns, shear walls, and transfer slabs where both early-age crack reduction and pump-line stability are mandatory. SikaFiber Monofilament-12 is not a substitute for wet curing, internal curing, or shrinkage-compensating admixtures in mass concrete sections greater than 1 m thickness.