A slab-on-grade floor placed in an enclosed building with air movement above the finished surface develops plastic shrinkage cracking when surface evaporation exceeds the bleed rate. The evaporation regime is evaluated with the nomograph in ACI 305R-20. SikaFiber 1218 PPM is charged at 0.9 kg/m³ as the default addition rate for slab placements. The product is a polypropylene monofilament fiber with nominal length 12 mm and equivalent diameter 0.018 mm. It falls under EN 14889-2:2006 Class II polymer microfibre. The fiber is introduced with coarse aggregate at the batch plant conveyor or through automated fiber dosing equipment. Mixing continues for 4 minutes to 5 minutes after fiber addition at a truck mixer speed of 12 rpm to 15 rpm. The dose may be reduced to 0.6 kg/m³ where exterior conditions are mild and finishing windows are short. A dose above 1.8 kg/m³ is not recommended for slab-on-grade mixes because surface finish workability decreases and fiber clumping may occur under ride-on trowel machines. The fiber controls plastic shrinkage cracking by increasing early-age strain capacity of the mortar fraction before initial set. Crack reduction under restrained drying is assessed by ASTM C1579-21. Fiber-reinforced concrete is specified under ASTM C1116/C1116M-23 Type III synthetic fiber. After strike-off, a laser screed or vibratory screed is used. Final troweling is performed with a power trowel using pan blades followed by steel blades. The fibers are not a substitute for controlled curing. A curing compound meeting ASTM C309-20 is applied after final finishing. The hardened slab may be densified with lithium silicate and polished. End products include warehouse floors, distribution center floor slabs, and concrete floors with high-frequency forklift traffic.

When Precast Facade Elements Are Demolded at 16–20 MPa Cylinder Strength

Demolding thin architectural cladding at the lowest permissible cylinder strength reduces form inventory and accelerates panel turnover. Edge spalling, corner breakage, and microcracks at lifting anchor recesses are the limiting defects. SikaFiber 1218 PPM is dosed at 0.6 kg/m³ to 0.9 kg/m³ in self-compacting and stiff precast mixes. The addition takes place in a planetary countercurrent mixer after fine aggregate charging and before cement slurry injection. The dry distribution phase lasts 90 seconds before water addition. Demolding at 16 MPa to 20 MPa requires green tensile capacity across narrow ribs and return edges. The fiber mitigates plastic shrinkage cracks that form before curing compound application. It is not a structural macrofiber and does not replace reinforcement required by EN 13369:2018 or the project-specific design basis. Concrete strength development is verified by cylinder tests in accordance with EN 12390-3:2019. Surface quality is inspected for fiber protrusion after acid etching or light abrasive blasting. Panels with visible fiber groups are acceptable only if covered by architectural finish. The fiber dose is reduced when panels are polished or acid-washed to expose aggregate. Vibration-induced fiber orientation at rib intersections can produce localized weak zones if the mix is over-vibrated. End products include architectural cladding, sandwich facade panels, and spandrel elements.

For wet-mix shotcrete sprayed on freshly excavated rock, the usable open time after alkali-free accelerator addition determines whether the batch can be pumped and sprayed without surging. The mix is designed with 4% to 6% entrained air measured by ASTM C231-22 after pumping. SikaFiber 1218 PPM is dosed at 0.9 kg/m³ to 1.2 kg/m³ at the batching plant. The fiber is added after aggregate charging and before the truck mixer reaches 60 revolutions. The monofilament polypropylene fiber increases cohesion of the fresh shotcrete layer. It reduces rebound during spraying. It does not provide post-crack flexural toughness equivalent to steel fiber or macrosynthetic fiber under EN 14488-3:2006. Spray execution follows EN 14487-2:2006 and ACI 506R-16. The material is sprayed in layers not exceeding 150 mm per pass when no accelerator delay is specified. Nozzle distance is kept between 0.5 m and 1.5 m from the receiving surface. The fiber is incompatible with dry-mix gunite processes because the product cannot be uniformly fed through a dry-mix nozzle without fiber segregation. Shotcrete pump blockages are observed when fiber dose exceeds 1.5 kg/m³ and accelerator dosing is pulsed. End products include temporary rock slope support shells, tunnel transition sections, and erosion protection layers on cut slopes.

What Mixing Protocol Prevents Fiber Balling in Polymer-Modified Repair Mortars?

Fiber balling in polymer-modified repair mortar occurs when monofilaments are added after the wet mix has reached its polymer-coagulated state. SikaFiber 1218 PPM is dispersed into the dry powder phase before liquid polymer and water are introduced. A forced-action paddle mixer with a batch volume not exceeding 80% of rated capacity is required. The dry mixing sequence runs 120 seconds after fiber addition. Liquid addition follows over 60 seconds. Wet mixing continues for 180 seconds. Total mixing time after fiber addition is 300 seconds. The dosage is held at 0.9 kg/m³ for repair mortars placed by trowel. Lower doses below 0.6 kg/m³ show limited plastic shrinkage crack control under restrained conditions. Higher doses above 1.2 kg/m³ can increase entrapped air and reduce bond strength. The mixed mortar is applied to saturated surface-dry substrate. Bond strength is tested in accordance with EN 1542:1999. Compressive strength class is specified as R3 under EN 1504-3:2006. The fiber does not contribute to structural repair capacity. It is used in non-structural repair patches where plastic shrinkage and early drying cracks are the primary defect mode. End products include spalled balcony edge repairs, soffit repair patches, and vertical concrete surface cosmetics.

Immediately after vertical pipe demolding, the green concrete must resist core pull stresses and crane handling strains without visible surface cracking. Dry-cast concrete pipe production uses low workability mixes with water-to-cement ratios below 0.30. SikaFiber 1218 PPM is metered into the planar mixer after the first aggregate charge and before final moisture adjustment. Dosage is held at 0.9 kg/m³. The mixing cycle after fiber addition is extended by 60 seconds to 90 seconds compared with the unreinforced control batch. Compaction is completed by high-frequency external vibration on the pipe machine. The fiber distributes through the annulus between inner core and outer jacket. It limits early plastic shrinkage cracks that follow the longitudinal direction of the pipe. It is not a replacement for steel reinforcement cages required by ASTM C76/C76M-24 for load-bearing concrete pipe. Demolding is performed at the same compressive strength threshold as unreinforced pipe. A dose above 1.2 kg/m³ may reduce green compressive strength in dry-cast mixes because the monofilaments increase the void network. Published data for this specific product in dry-cast pipe applications is limited; the dosage is validated by plant trial before series production. Core pull stress cracks can appear at the top joint ring if fiber dispersion is non-uniform in stiff dry-cast mixes. End products include storm drainage pipe, sanitary sewer pipe, and manhole riser sections.

Bonded screed systems over hydronic heating circuits cannot rely on welded wire reinforcement in the 35 mm to 50 mm cover zone because the wire lies below the heating pipe and provides limited top-surface crack control. SikaFiber 1218 PPM is dosed at 0.6 kg/m³ to 0.9 kg/m³ in pump-fed cementitious screed. The fiber is batched through the dry silo agitation system before the binder and aggregate enter the mixing screw. Screed slump is controlled at 220 mm to 250 mm by the screw speed and water dosing valve. The pipe circuit is pressure-tested before screed placement. The screed is pumped at a discharge rate of 0.15 m³/min to 0.25 m³/min. The monofilament reduces plastic shrinkage cracks at the heating pipe crown where cover is thinnest. Restrained shrinkage performance is assessed by ASTM C1581/C1581M-18 or a project-specific ring test. After placement, the screed is cured with an evaporation-retardant film meeting ASTM C309-20. The fiber does not alter the thermal resistance of the screed layer to a measurable extent at doses up to 0.9 kg/m³. End products include bonded screeded floor panels over PEX and PE-RT hydronic circuits in residential and light commercial buildings.