The product specified as SikaFiber Force PP-65/RAD65s is a macro-structural synthetic polypropylene fibre supplied in collated bundles for dry or automated dosing into concrete. The designation identifies a nominal fibre length of 65 mm and a macro-polymer geometry intended to contribute to post-crack residual strength after initial matrix cracking. The fibre is classified as a Class II macro-structural polymer fibre under EN 14889-2:2006 and as a Type III synthetic fibre under ASTM C1116/C1116M. The base polymer is virgin polypropylene with a published density of 0.91 g/cm³ when measured in accordance with ISO 1183-1:2019. The published equivalent fibre diameter is 0.80 mm, producing an aspect ratio of approximately 81. These dimensional parameters are the primary basis for mechanical anchorage rather than chemical bonding to the cementitious matrix.

Because the fibre is non-hygroscopic, no product pre-drying is required before batching, but the water-soluble collated bundle packaging must be kept dry until addition. The fibre is chemically inert in the highly alkaline pH range of 12 to 13 typical of concrete pore solution and does not introduce chloride-bearing corrosion agents. Published manufacturer data lists tensile strength of approximately 500 N/mm² and tensile modulus in the range 3.5 GPa to 4.5 GPa under ISO 527-2. The polypropylene melt peak is reported at 160°C to 165°C by ISO 3146. Water absorption is less than 0.1% by mass. Published data for the exact RAD65s suffix configuration is limited; the geometric and mechanical values stated here reflect the base PP-65 fibre family and should be verified against the current manufacturer’s Declaration of Performance.

Product Specification and CE Conformance Data

Table 1 summarises the core specification parameters for SikaFiber Force PP-65/RAD65s. For structural use under the Construction Products Regulation, the product is expected to carry a Declaration of Performance referencing EN 14889-2:2006; project specifications should verify the notified body certificate and declared values rather than relying on generic published tables.

In production-scale batching, the collated bundle format is intended to eliminate manual pre-dispersion. The bundles are typically introduced after aggregate charging or with the aggregate stream; addition directly into dry cement before water is not recommended because electrostatic and moisture films can promote balling. In twin-shaft batch mixers with rotating blades maintained within manufacturer wear limits, fibre dispersion is generally complete within the normal mixing cycle. Field observations associated with worn scraper blades and dead zones in pan mixers indicate an increased risk of local clumping at dosages above 6.0 kg/m³; mixer condition should be verified before production. A measurable slump reduction occurs above 3.0 kg/m³. Correction is typically achieved with a high-range water-reducing admixture complying with ASTM C494/C494M Type F, and slump should be checked under EN 12350-2. Air content should be monitored after fibre addition because fibres can alter the spacing factor of the entrained air void system measured under ASTM C457/C457M. No pre-drying is required at ambient relative humidity, but prolonged exposure of opened packaging to moisture can compromise the water-soluble bundling film.

How Does the 65-mm Anchor Geometry Influence Residual Flexural Capacity?

The macro-synthetic fibre is not specified by tensile strength alone; post-crack performance is governed by fibre length, equivalent diameter, aspect ratio, surface morphology, and fibre count. The 65 mm nominal length provides embedment depth that must exceed the critical anchorage length for pull-out resistance. With an equivalent diameter of 0.80 mm, the aspect ratio of 81 places the product in the range where pull-out work contributes to toughness without excessive workability loss. At a dosage of 4.0 kg/m³, calculated fibre count based on published geometry is approximately 130,000 fibres/m³; a hooked-end steel fibre of 60 mm length and 0.90 mm diameter at the same mass dosage yields roughly 13,000 fibres/m³. The higher count influences crack spacing but does not equal the stiffness of steel.

Residual flexural performance should be established by notched beam testing under EN 14651:2005+A1:2007 or ASTM C1609/C1609M. The EN method reports residual flexural tensile strength values at crack mouth opening displacement of 0.5 mm (fR1) and 2.5 mm (fR3); these values determine the fibre contribution in design models. Because the tensile modulus of polypropylene is between 3.5 GPa and 4.5 GPa, compared with 210 GPa for steel, the immediate post-crack load capacity at small crack openings is lower than a steel fibre of similar geometry. At larger crack openings, macro-synthetic fibres may exhibit pull-out rather than tensile rupture, and the load-deflection response becomes dependent on matrix strength and fibre surface treatment. Published data for this specific configuration is limited; project-specific beam tests are required for substitution calculations.

Placement of concrete containing the macro-synthetic fibre is generally through conventional pumping and vibrating equipment. Pump lines of 100 mm nominal diameter or larger are common in slab and tunnel applications; smaller line diameters should be trialled because the 65 mm fibre length creates a length-to-line-diameter ratio that may promote blockages in tight bends. For machine-finished industrial slabs, the fibre may reduce bleed water and shorten the trowelling window; power trowel timing and blade angle should be adjusted in trial panels. Aggregate nominal maximum size of 20 mm to 25 mm is typical for dispersion; gap-graded mixes containing aggregate larger than 32 mm require additional verification. In wet-mix sprayed concrete, the fibre is added during batching and pumped through nozzle sizes of at least 50 mm; nozzle blockage risk increases at dosages above 7.0 kg/m³ unless pump capacity and hose diameter are suitable. Published guidance for this specific RAD65s configuration is limited, so field trials with the actual mixer and pump are required before production placement.

When Steel Fibre Replacement Demands Revised Joint Layout and Corrosion Resistance

The decision to replace steel fibres with the macro-synthetic polypropylene fibre is not a mass-equivalence substitution. Because density and modulus differ, engineering comparison should use residual strength class from beam tests, not fibre weight. In corrosion-sensitive environments such as marine splash zones, parking garage decks, and external pavements, the polypropylene fibre removes the risk of surface rust staining and chloride-induced fibre corrosion at exposed surfaces. The concrete cover to conventional reinforcing steel is still governed by EN 1992-1-1 or ACI 318 and must not be reduced solely because synthetic fibre is present. In ground-supported slabs, the fibre may permit wider joint spacing if the calculated residual flexural strength supports the design; joint elimination is not automatic and requires a structural model such as the Concrete Society Technical Report 34 or equivalent.

Table 2 compares the macro-synthetic fibre with a typical hooked-end steel fibre and a micro-synthetic polypropylene fibre.

The lower tensile modulus of polypropylene relative to steel has direct consequences for long-term cracked serviceability. Polypropylene exhibits viscoelastic creep under sustained load; cracked fibre-reinforced concrete may show additional deflection over time. Published long-term creep data for this specific macro-synthetic fibre is limited, and design should not extrapolate short-term beam results without verification. The fibre is not a direct substitute for primary flexural reinforcement in beams, columns, or suspended slabs unless the design explicitly uses fibre-reinforced concrete constitutive models and the residual strength class has been determined by testing. In fire-exposed concrete, the polypropylene melts at approximately 160°C, which may create pore-pressure relief channels but simultaneously removes the post-crack reinforcement; residual capacity after fire must be assessed separately. The product should be stored below 40°C in dry conditions and kept away from prolonged direct sunlight to preserve packaging integrity. Chemical exposure to strong oxidising media or organic solvents should be evaluated by immersion testing before use. At dosages above 6.0 kg/m³, workability loss and fibre balling risk increase; mix adjustments and mixer maintenance become critical. No retardation or acceleration of cement hydration is documented. Air-entraining admixture dosage should be verified because the fibre surface can modify air void spacing. These operational boundaries define the appropriate use envelope for the fibre in structural concrete applications.