In ready-mix production for high-tolerance industrial floor slabs, SikaFiber 12 AE—a monofilament polypropylene fibre for concrete—is batched at 0.9 kg/m³ as a plastic shrinkage and plastic settlement control additive. The 12 mm monofilament geometry is introduced into the truck mixer at 12–18 rpm for 70–90 s after fibre addition; batch-to-batch variance is minimised when the fibre is introduced with aggregate at the weigh hopper rather than after batching or during discharge. The product is supplied in water-soluble bags, allowing direct addition to the mixer drum, but plant operations that feed the bags directly onto the aggregate belt before the mixer gate record fewer fibre agglomerations at the chute. Compliance is verified against ASTM C1116/C1116M-23, EN 14889-2:2006, and ACI 302.1R-15; restrained shrinkage cracking is assessed under ASTM C1581/C1581M-18a. Placement uses a laser screed with a 6–8 m screed span followed by a single float pass and power trowel passes at 10–15 rpm under low blade angle. End products include distribution centre floor slabs, logistics hub aprons, automated racking facility slabs, and airside apron pavements where floor flatness tolerances of FF 35/FL 25 or tighter are specified. The fibre reduces bleed water transmission, so trowelling is initiated when the surface sheen disappears, not before; early trowelling causes blade drag and exposed fibre matting, while delayed trowelling leaves a fibre-rich surface crust that can tear. Over-trowelling at ambient relative humidity below 30% may delaminate the fibre-rich surface layer, so finishing crews adjust the number of power float passes based on visual bleed transition rather than fixed time intervals.

Published data for this specific configuration across all local aggregate and cement combinations is limited; before any pour larger than 1,000 m³, a site trial is run using the production mixer, job aggregate moisture, and the planned transit time. The trial includes ASTM C1581/C1581M-18a ring specimens cast from the delivery truck and crack monitoring at 7, 14, and 28 days with a 20× portable microscope. The operational boundary of 0.9 kg/m³ should not be exceeded unless plant trials confirm uniform dispersion; higher dosages under water-to-cement ratios below 0.42 increase the risk of dry fibre balls behind the mixer chute. The fibre is not a primary tensile reinforcement, so welded wire mesh or reinforcing bar remains mandatory for load-induced tensile stress distribution.

How Does the Fibre Disperse Under Low-Frequency Vibration in Wet-Cast Precast Elements?

Wet-cast precast drainage channels, cable troughs, retaining wall blocks, and utility vaults require a fibre addition of 0.6–0.9 kg/m³. The fibre is introduced into a planetary counter-current or pan mixer after coarse and fine aggregate, followed by 30 s dry mixing; cement and water are then added with wet mixing for 90 s at 20–25 rpm. At water-to-cement ratios below 0.30 and dosages above 1.0 kg/m³, balling may occur at the mixer blades. This is a known process limitation, so the dosage is reduced or the fibre addition point is moved to the aggregate belt rather than the weighed water. Compliance in the European Economic Area is established under EN 14889-2:2006 for the polymer fibre itself and EN 13369:2023 for common rules covering precast concrete products; drainage products intended for vehicular areas are additionally tested to EN 1433:2020 for load classes D400 or E600. Mould filling uses bench vibrators at 50 Hz for 45–60 s; the low-density fibre does not segregate under normal vibration but may align parallel to mould faces when vibration energy is excessive. After 16–24 h steam curing at 55–65°C, the polypropylene matrix is unaffected because its melting point begins around 160°C and polyolefins do not undergo alkaline hydrolysis in portland cement pore solution. Terminal products include linear drainage channels, railway cable troughs, dry-stack retaining wall blocks, inspection chamber riser sections, and non-structural precast panels. If post-crack flexural capacity is required, the mix must include macro synthetic or steel fibre; the monofilament product is specified for crack-width control and handling durability, not as primary tensile reinforcement.

When zero-slump dry-cast production is used, the addition point is moved to the aggregate belt rather than the mixer water, because the dry mix lacks free water to dissolve the bag film and disperse the fibre. At 0.6 kg/m³ in dry-cast mixes, edge chipping during demoulding is reduced when compaction energy is limited to 30–45 s of external vibration; prolonged vibration drives the low-density fibres toward the mould face and creates fibre-rich surface patches that are visible after curing. For wet-cast elements, the dosage can be maintained at 0.9 kg/m³ without measurable effect on entrained air when the air content is maintained below 6% by volume.

When Rebound Losses Are Contractually Capped at 15 Percent in NATM Tunnelling

Wet-mix shotcrete containing SikaFiber 12 AE is batched at 0.9–1.8 kg/m³ for temporary tunnel linings, slope stabilisation skin coats, and mine drift linings. The concrete is proportioned with a slump of 160–200 mm and pumped through a piston-type shotcrete pump at 4–6 m³/h; compressed air at 200–350 L/min and 2.5–6.0 bar is injected at the nozzle. The fibre addition stabilises the fresh mix in the delivery line and helps reduce rebound, but the 15% cap requires a nozzle distance of 0.8–1.2 m and an angle of 80–90° to the substrate. Compliance is anchored to EN 14487-1:2022, EN 14487-2:2022, and ACI 506R-16; the fibre itself is evaluated under EN 14889-2:2006. Alkali-free fluid accelerator is dosed at the nozzle at 3–6% by weight of binder; the polypropylene does not react with the accelerator, but delivery line screens should be checked for fibre accumulation if the dosing exceeds 1.8 kg/m³. End products include temporary NATM excavation linings, shotcrete shells for rock tunnels, slope erosion control skins, canal lining repairs, and underground mine drift surfaces. For permanent linings where toughness and energy absorption classes are specified, the shotcrete must be tested under ASTM C1550-20 round panel methods with macro synthetic or steel fibre; the 12 mm monofilament product is not alone sufficient for contracted post-crack energy class requirements.

Pump line pressure is monitored at the main gauge; when the dosage is increased from 0.9 kg/m³ to 1.8 kg/m³, line pressure may increase and delivery hoses should be checked for build-up at couplings. The fibre does not replace steel mesh or welded wire in temporary linings where rock loads are transferred to lattice girders; the primary support remains bolts, lattice girders, and shotcrete thickness per design. Preconstruction trials are required to verify rebound under the actual aggregate grading because published data for this specific configuration at some tunnel sites is limited.

For bonded, unbonded, and floating cementitious screeds produced under EN 13813:2019, SikaFiber 12 AE is dosed at 0.6–0.9 kg/m³, with the lower band selected when the sand aggregate is well graded and the water-to-cement ratio does not exceed 0.45. The fibre is metered into a continuous screed mixer or forced-action paddle mixer after aggregate and before binder; mixing continues for 60–90 s until distribution is visually uniform at the discharge point. The mixed screed is transported by screw pump or tailboard and compacted with a vibratory beam at 40–50 Hz, then power-floated using a 750 mm diameter pan float. Standard references include EN 13813:2019 for screed material property classes, BS 8204-1:2012 for in-situ floor finishes, and ASTM F710-22 for substrate preparation; the fibre's alkali resistance is assessed under EN 14889-2:2006. Terminal products in this application include office tower subfloors, retail centre screeds over underfloor heating pipes, renovation bonded overlays, and aircraft hangar float finishes. The operational boundary is that the fibre should not be exposed by aggressive steel-trowel burning; if a hard trowelled surface is specified, then the final pass must occur only after the surface moisture has stabilised and any visible fibre ends are pressed below the film-forming surface layer. The monofilament is not a substitute for structural reinforcement in load-transfer screeds, and project specifications must not rely on it for load distribution at movement joints.

Thermal Gradient and Settlement Crack Mitigation in Thick Mat Foundations

Mass concrete rafts, water-retaining basins, and thrust blocks receive SikaFiber 12 AE at 0.6–0.9 kg/m³ to reduce plastic settlement cracking above reinforcement and around column starter cages. The concrete plant batches the product in a twin-shaft compulsory mixer; the fibre is fed automatically after aggregate, followed by 40 s dry mixing and then wet mixing to a total of 80 s at 15 rpm. The concrete is placed in 300–500 mm lifts and compacted with 60 mm high-frequency poker vibrators at 12,000 vibrations/min for 5–10 s per insertion. The fibre reduces bleed water movement, so the timing of any re-vibration after initial settlement is shortened to avoid creating a plastic crust that would disrupt the top surface. Thermal control follows ACI 207.1R-05, with the core-to-surface temperature differential limited to 20°C, while cracking potential is compared using ASTM C1581/C1581M-18a and ACI 224R-01. The fibre material itself is specified under EN 14889-2:2006. Terminal products include raft foundations, clarifier tanks, stormwater detention basins, and transformer plinths. In these thick sections, SikaFiber 12 AE is used only for early-age crack control; the primary tensile capacity remains with conventional reinforcement, and the presence of fibre must not be used to justify a reduction in reinforcing steel area.

When concrete is placed on profiled steel decking to form a composite floor slab, SikaFiber 12 AE is dosed at 0.9 kg/m³ in the ready-mix plant and transported in truck mixers. The concrete is pumped through a 100 mm delivery line onto the deck, then struck off with a vibratory screed rail; the addition controls plastic shrinkage cracking at deck ribs and around shear stud zones where differential restraint develops. Standards used include ANSI/SDI C-2017 or EN 1994-1-1:2004 for composite steel-concrete design, and ASTM C1116/C1116M-23 or EN 14889-2:2006 for the fibre-reinforced concrete. The fibre-containing concrete is not considered in composite action calculations; shear stud capacity and deck bending resistance are determined by AISC 360-22 or EN 1994-1-1 using the normal-density concrete cylinder strength. Terminal products are office building floors, hospital deck infill slabs, and car park intermediate decks. The welding of through-deck shear studs after concrete placement does not affect the polypropylene fibres in the surrounding matrix, but the upper fibre-rich surface must be power-trowelled at a later stage than plain concrete to avoid surface tearing and drag lines. If the deck pour is subject to high wind velocities above 8 m/s and low relative humidity, additional evaporative controls should be active to prevent premature crusting before trowelling. Concrete cover requirements to metal deck and shear studs remain unchanged; fibre addition does not justify a reduction in specified cover.