Specific to synthetic microfibre reinforcement for ready-mix and precast concrete, SikaFiber PPF is supplied as a fibrillated polypropylene micro fibre. The product designation identifies a fibrillated polypropylene micro fibre supplied in pre-weighed, mixer-degradable bag units for direct addition to rotating-drum and stationary concrete mixers. The fibrillated tape geometry opens into a fine network during mixing, creating a dispersion of individual filaments with a high surface area-to-mass ratio. When batched at dosages between 0.6 kg/m³ and 1.8 kg/m³, the product is specified primarily to mitigate plastic shrinkage cracking in slabs, pavements, overlays, precast elements, and shotcrete. The base polymer is polypropylene with a density of approximately 0.91 g/cm³; the material is non-corrosive, alkali-resistant, and inert under normal concrete pH conditions. Product conformance is declared under EN 14889-2:2006 for polymer fibres and under ASTM C1116/C1116M Type III synthetic fibre-reinforced concrete. The product should not be treated as a direct replacement for structural steel reinforcement or macro synthetic fibres where post-crack residual strength is required.

What Are the Nominal Properties and Conformance Criteria?

Physical property data for fibrillated polypropylene micro fibre supplied under this product designation are controlled within manufacturing ranges typical of EN 14889-2:2006 Class I micro fibres. The equivalent fibre diameter after fibrillation is generally below 0.1 mm; standard cut lengths are commonly specified at 6 mm, 12 mm, or 19 mm depending on aggregate gradation and application. Tensile strength of the fibre is reported in typical product data using ASTM D2256 or EN 14889-2:2006 Annex A methods, usually ranging from 320 MPa to 400 MPa. Elastic modulus is approximately 3.5–4.5 GPa, which is significantly below the modulus of the surrounding cementitious matrix; this property defines the fibre as a plastic-shrinkage crack control agent rather than a load-bearing reinforcement. The melt point of polypropylene is typically 160–170 °C, limiting exposure to sustained service temperatures above 80 °C in some applications, and melt flow rate is controlled during extrusion to permit fibre fibrillation and splitting during mixing. Where published data for a specific project configuration is limited, pre-construction laboratory trials should be performed.

Mix Design Thresholds and Equipment Interaction

Dosage above 1.2 kg/m³ can reduce slump by 10–30 mm under ASTM C143/C143M and can increase air-void clustering if fibre is added too early or too late in the batching sequence. In central mixers with counter-current pan or twin-shaft geometry, the preferred addition point is after aggregate and cement, before water, at residual aggregate moisture contents below 4%. In truck-mixed concrete, fibre bags are added at the plant after batching or on site, followed by mixing at 12–18 rpm for 4–5 min per m³. Insufficient mixing time has been observed to produce fibre balls on 5–10 mm sieve retention tests; extended mixing beyond 10 min at high drum speed can cause fibre separation and non-uniform distribution in low-cement mixes. When added to truck mixers at the plant, fibre bags are introduced after the first 60–70% of batch water has been added, then mixed for the prescribed time. Site addition into ready-mix trucks should follow the concrete producer’s batching ticket; the drum must be free of washout water exceeding 30 L per 6 m³ load to avoid fibre balls. In low-water mixes with water-cement ratio below 0.40, dry fibrillated fibre has been observed to form clumps at the mixer blades; pre-wetting of fibre or splitting the bag charge into 2 additions is used on production lines to restore uniform dispersion. Because the fibrillation process increases effective fibre surface area, water demand and superplasticizer interaction should be evaluated under EN 934-2 before full-scale batching. Superplasticizer based on polycarboxylate ether should be added after fibre dispersion to avoid fibre-admixture competition for available water in the first mixing minute. Air-entrained mixes with target air above 6% may require additional trial batching because fibrillated fibres can alter bubble spacing and reduce the consistency of the air void system measured under ASTM C457. At placement, a conventional internal vibrator with head diameter 25–60 mm may be used; excessive vibration can float micro fibres near the surface but does not eliminate their crack-control function if finishing is delayed until bleed water disappears.

Because plastic shrinkage cracking occurs when bleed water evaporation exceeds bleed rate, fibrillated polypropylene micro fibre reduces crack width by bridging the weak capillary network during the first 6–12 h after placement. Under restrained cracking evaluation such as ASTM C1579-21, fibrillated micro fibres at 0.9 kg/m³ typically reduce total crack area relative to plain concrete by 40–80%; exact values vary with cement fineness, admixture package, and evaporation rate. The fibre does not significantly reduce bleeding and does not replace proper fogging, windbreaks, or evaporation retardants at evaporation rates above 1.0 kg/m²/h. Slab-on-grade specifications often include the product at 0.9–1.5 kg/m³ to control early-age random cracking before saw cutting, with saw-cut timing governed by ACI 302.1R and joint layout by ACI 360R. In overlays and repair mortars, the low fibre diameter reduces surface protrusion after trowelling compared with macro fibres; however, final burnishing should be delayed until bleed water disappears to avoid folding the fibre into the surface paste. Project-specific performance should be verified by ASTM C1579-21 and by field test panels under the same wind, temperature, and humidity conditions as the finished slab.

When Fibrillated Polypropylene Microfibre Replaces Crack-Control Reinforcement

Although the product is often specified as a replacement for light-gauge welded wire mesh in slab-on-ground applications, the replacement is valid only for crack width control, not for structural moment capacity or joint stability. Welded wire mesh provides continuous steel area across a cross-section, while fibrillated PP micro fibres provide a distributed three-dimensional fibre network with no defined yield strength in the cracked section. For structural slabs, a designer may reduce or eliminate mesh only where subgrade support and joint layout control curling and load transfer; the material cannot compensate for inadequate joint spacing or slab thickness. Fibre dosage for mesh replacement is typically 1.5–1.8 kg/m³, with slab thickness not less than 100 mm and joint spacing not exceeding 24–36 times slab thickness per ACI 360R. The post-crack residual strength measured under ASTM C1399/C1399M or ASTM C1609/C1609M is typically negligible for this micro fibre, confirming that it is not a macro fibre substitute. Load-transfer capacity across joints must be provided separately through dowels, tied joints, or aggregate interlock, because the distributed micro fibre network does not resist differential vertical movement after cracking.

In dry-mix shotcrete, fibrillated PP micro fibres are added to the premix hopper at 0.6–1.0 kg/m³; rotary gun equipment with a 50 mm or 65 mm hose generally handles these dosages without clogging if fibre is pre-mixed with aggregate before cement addition. Wet-mix shotcrete using piston or screw pumps may require a reduction in maximum aggregate size to 8 mm and a slump of 120–160 mm to prevent blockages at fibre dosages above 1.0 kg/m³. Rebound losses in shotcrete containing fibrillated micro fibres are normally within 2–5% of plain mix values, but fibre rebound can be visually concentrated in overspray and should be removed before applying subsequent layers. The fibre can reduce early-age cracking in tunnel linings and slope protection; however, it does not provide the post-crack toughness associated with steel or macro synthetic fibres tested under EN 14488-5 or ASTM C1550. In underground construction, polypropylene micro fibres have also been specified at higher dosages for passive fire-induced spalling reduction, but the dosage and length require hydrocarbon fire or cellulosic fire testing under ISO 834 or ASTM E119 because the mechanism depends on permeability changes after fibre melting, not on fibre tensile strength.

Comparing Fibrillated PPF with Monofilament and Steel Fibres

Across concrete reinforcement fibres, fibrillated polypropylene micro fibre occupies a narrow functional bandwidth: crack control from casting to initial hardening, with minimal influence on hardened flexural capacity. Monofilament PP micro fibre provides similar plastic shrinkage control but may disperse more readily in low-workability mixes because its lower initial surface area reduces clumping. Steel macro fibre provides post-crack residual strength and can replace some structural reinforcement, but increases dead load, corrosion risk in cracked environments, and finishing wear on screeds.

Fibrillated PPF differs from monofilament PP micro fibre primarily in geometry and dispersion behaviour. The opened network structure creates a higher specific surface and can improve early-age crack bridging at equal dosage, but may increase flocculation risk in low-workability mixes or high-shear mixers. Steel macro fibres provide measurable residual tensile and flexural strength under ASTM C1609/C1609M and EN 14488-5, whereas fibrillated PP micro fibre provides negligible residual post-crack strength. Therefore, material selection between these products should be driven by whether the design requires crack width control in plastic concrete or load transfer in cracked concrete.

Material handling and regulatory compliance are typically documented under REACH registration and RoHS declarations, and manufacturing plants are often certified to ISO 9001:2015. Fibrillated polypropylene micro fibre has a limited operating temperature window; continuous exposure above 80 °C is not recommended because polymer softening and creep can reduce crack-bridging efficiency. The fibre is hydrophobic and does not increase water absorption but can float if mixed into a matrix with excessive water or overdosed above 3.0 kg/m³. Alkali resistance in concrete at pH 12–13 is generally acceptable due to the polyolefin chemical structure, but strong oxidizing agents and some solvent-based curing compounds may degrade the surface fibres. For applications requiring fire resistance, the melting and burning behaviour of polypropylene must be considered alongside cementitious matrix spalling; some tunnel specifications specifically use polypropylene micro fibres to reduce explosive spalling, but the dosage and length require fire testing under ISO 834 or ASTM E119.