In precast segmental tunnel linings, Adfil Strux 90/40 is introduced as a dry polymer macro fibre at the batching stage, after aggregate charging and before free water enters the pan or planetary mixer, so that the individual 40 mm monofilaments are dispersed throughout the cementitious matrix rather than agglomerating at the mixer walls. The fibre is classified under EN 14889-2:2006 as a Class II polymer fibre for structural use, which places it under the harmonised CE marking route with initial type testing and factory production control verified by a notified body. Typical addition levels reported for structural macro synthetic fibres of this length in precast segments lie between 3.0 kg/m³ and 6.0 kg/m³, with the upper bound selected where early demoulding, stacking, and thrust jacking induce flexural stresses before the 28-day characteristic strength is available. The controlling laboratory parameter is residual flexural tensile strength measured according to EN 14651:2005+A1:2007, with values for fR1,t and fR3,t recorded at crack mouth opening displacements of 0.5 mm and 2.5 mm respectively. Plant-level quality control typically involves transverse sawing of witness segments or tested prisms to confirm that fibre counts per square centimetre fall within the accepted range specified in the precast producer’s factory production control procedure. Terminal products in this segment include metro tunnel rings, drainage adits, and shaft bottom units, where the fibre contribution assists in controlling demoulding cracks and spalling during ring erection and initial storage under site conditions.

What Limits Fibre Uniformity in Wet-Mix Shotcrete for Mine Drift Support?

Wet-mix shotcrete for underground mine drift support operates with a continuous feed of premixed fibre-reinforced concrete through a twin-piston concrete pump, often with an S-valve transfer tube, before the material passes through a compressed-air nozzle at 0.15 MPa to 0.35 MPa and strikes the rock surface. Adfil Strux 90/40 is dosed at 4.0 kg/m³ to 7.0 kg/m³ in wet-mix applications; the lower bound is required to obtain statistically consistent fibre counts in a single sprayed layer, while the upper bound can increase pump backpressure and rebound when alkali-free accelerator dosing exceeds 6% by mass of cementitious binder. Performance is verified using round panel tests to ASTM C1550-12a or EN 14488-5:2006, with energy absorption measured at 25 mm central deflection, and typical mine-support specifications request between 500 J and 900 J at 28 days, although published data for this specific fibre configuration is limited and must be confirmed through pre-construction spray trials. The macro synthetic fibre replaces welded wire mesh where robotic spraying is used in difficult-to-access headings, eliminating mesh installation time, rebound traps behind mesh, and the hand-arm vibration exposure associated with mesh fixing. Terminal products include temporary and permanent ground support linings in decline tunnels, drill access headings, and crusher chambers, where the fibre contributes to post-crack toughness under ground convergence without the corrosion risk associated with steel fibres in acid mine drainage conditions.

Where jointless industrial floor slabs exceed 1,000 m² of continuous pour area, the 40 mm macro synthetic monofilament is dosed at 4.0 kg/m³ to 6.0 kg/m³ in ready-mix concrete with a water-cement ratio not exceeding 0.50. The fibre is introduced either through an automated dispenser on the aggregate weigh conveyor or by adding the bags directly into the truck mixer after the initial concrete charge, provided that mixing continues for at least 90 revolutions at full mixing speed to prevent dry fibre balls in the discharge. Post-crack performance is measured to ASTM C1609/C1609M-19a, where the residual load ratios fD600,f and fD300,f at net deflections of L/600 and L/300 are compared with a plain concrete control beam. At these dosages the fibre does not replace the transverse structural steel in a slab designed to TR34 or EN 1992-1-1:2004; its technical role is to redistribute early-age shrinkage strain and to resist microcrack propagation at pour strips, column corners, and isolation joint returns. Terminal products include high-bay racking platforms, automated storage and retrieval facility floors, and freezer warehouse slabs, where crack-width control is required under exposure classes XC1 to XC4 defined in EN 206:2013+A1:2016 and where the fibre reduces edge chipping from hard-wheeled materials-handling equipment.

Precast retaining wall panels and box culverts without crack-control steel

Dosage in retaining wall panels and box culverts is generally between 2.5 kg/m³ and 4.5 kg/m³, because the dominant early-age loads are drying shrinkage restraint and demoulding handling rather than primary flexural bending. The fibre is added in a planetary mixer with a batch volume of 0.5 m³ to 2.0 m³ after the dry aggregate-carbonate filler blend has reached visual homogeneity, and the mixing water is then added gradually to avoid localised clumping at the fibre surface. Conformity is assessed under EN 13369:2018 for precast concrete products and EN 14889-2:2006 for the structural polymer fibre, while drying shrinkage is measured according to ASTM C157/C157M-17 or EN 12617-4:2002. The fibre does not substitute for lifting anchors, joint ties, or bending reinforcement in the external face, because its post-crack flexural contribution is insufficient for the ultimate limit state of panel bending under earth pressure. Terminal products are two-sided precast retaining walls, portal culvert legs, cable troughs, and stormwater U-drains with exposed aggregate finishes, where the macro synthetic fibre reduces corner pop-outs, yard storage cracks, and edge damage during lifting.

When sulphate attack controls crack-width limits in water-retaining concrete, the addition of 40 mm macro synthetic fibres alters early-age shrinkage distribution

In process water treatment basins, primary settlement tanks, and agricultural slurry stores, mix designs often contain 25% to 40% ground granulated blastfurnace slag or fly ash by binder mass to reduce sulphate ingress, and this chemical arrangement slows early strength gain while increasing restrained thermal-shrinkage cracking. Adfil Strux 90/40 is introduced at 3.0 kg/m³ to 5.0 kg/m³ specifically to control those early-age cracks, functioning as an inert tensile tie that does not corrode in sulphate-bearing water. Crack-width limits defined in EN 1992-3:2006 or ACI 350-20 are not automatically met simply by fibre addition; the structural designer must calculate crack widths using the fibre residual flexural strength measured to EN 14651:2005+A1:2007 as an additional tensile parameter in the section. Field data from water-retaining concrete generally indicate that fibre-reinforced slabs exhibit a larger number of smaller shrinkage cracks compared with unreinforced slabs of identical thickness under identical ambient conditions, but published data for this specific fibre configuration is limited and should not be extrapolated to critical storage structures without full-scale trial slab verification. Terminal products include sulphate-resistant basin linings, pump station wet wells, and sludge storage structures, where the fibre is specified to limit early-age cracking between movement joints.

For composite metal deck slabs cast over profiled steel sheeting, the fibre is dispersed at 3.0 kg/m³ to 5.0 kg/m³ in concrete with maximum aggregate size below 10 mm to avoid segregation under mechanical vibration. The concrete is placed through a boom pump rated at 30 m³/h to 60 m³/h, and the 40 mm fibre length is greater than the typical 50 mm minimum deck recess depth, which controls fibre orientation parallel to the profiled sheeting and can slightly reduce the measured flow in slump testing without affecting pumpability. Post-crack performance is checked by ASTM C1609/C1609M-19a or round panel tests, while the fire resistance of the composite slab may be assessed under EN 1365-2:2014; the fibre contribution is not included in the structural fire design unless full-scale tests validate the specific fibre deck system. Terminal products are car park decks, mezzanine floors, and high-rise composite floors, where the fibre reduces plastic shrinkage cracks in negative moment regions over steel beams and improves surface toughness at construction joints.