About MC-Bauchemie MC-Fibre PP

MC-Fibre PP is MC-Bauchemie’s polypropylene monofilament fibre for controlling plastic shrinkage and settlement cracking in concrete and cementitious mortars. Each cubic metre of concrete carries millions of individual fibres, roughly 18 to 22 microns thick and cut to either 12 mm or 19 mm, that spread through the matrix in every direction. Because polypropylene is chemically inert in the high-alkaline pore water of fresh concrete, the fibres neither corrode nor degrade over the life of the structure, which is a genuine advantage over the light steel mesh they often replace for crack-control duty. This is secondary reinforcement, not structural steel: it manages the young, plastic phase where conventional bar and mesh contribute nothing.

For a distributor’s audience of site engineers and contractors, the appeal of MC-Fibre PP is that it solves an expensive, hard-to-repair problem cheaply and without changing the way concrete is batched or placed. Plastic shrinkage cracks that open up on a fresh slab surface become permanent defects, dust traps and water paths that no amount of curing fixes afterwards. A dose of well under a kilo and a half per cubic metre, added at the mixer, cuts that risk sharply. It suits ready-mix and site-batched work alike and rides through the normal pumping, screeding and power-floating sequence without special handling.

The technical insight

In the first few hours after placing, concrete has effectively zero tensile strength while the surface loses water to evaporation faster than bleed water rises to replace it. The drying surface tries to contract, the wetter concrete below restrains it, and the resulting tensile stress tears the plastic surface into the familiar map of shrinkage cracks. MC-Fibre PP works by putting a dense, uniformly dispersed three-dimensional web of monofilaments into that zone. Each fibre bridges the micro-crack as it tries to form and carries a small share of the tensile stress, so instead of a few wide cracks the mix distributes the strain across countless harmless micro-cracks that never fully open. Because the fibres are fine and numerous rather than few and thick, the crack-arresting action begins at the very earliest age, exactly when the concrete is most vulnerable and mesh has not yet engaged. Once the concrete gains its own tensile strength the fibres continue to add a modest toughness and impact resistance, and the same PP network is known to reduce explosive spalling under fire by giving trapped steam escape channels as the fibres melt.

Where it is used

• Industrial, warehouse and factory ground-floor slabs where a crack-free, dust-free wearing surface matters
• Roof and terrace slabs exposed to sun and wind, where evaporation-driven plastic cracking is worst
• Cement-sand floor screeds and toppings prone to surface crazing
• Cement renders and plaster on masonry and concrete walls
• Precast concrete, including thin panels and sections where mesh is impractical
• Concrete and cementitious repair mortars for spalled or patched areas
• Pavements, hardstandings and external paving slabs
• Shotcrete and sprayed mortar linings needing early-age crack control

Key advantages

• Controls plastic shrinkage and settlement cracking from the earliest age, before mesh can contribute
• Alkali-resistant and chemically inert, so it never corrodes and lasts the life of the concrete
• Very low dose of 0.6-1.0 kg/m3 delivers three-dimensional crack control at low cost
• Reinforces uniformly in all directions, unlike a single plane of mesh
• No special equipment or change to normal batching, placing or finishing
• Compatible with PCE superplasticisers, retarders and integral waterproofing admixtures
• Reduces surface permeability and improves abrasion and impact resistance
• Contributes to fire performance by lowering the risk of explosive spalling

Limitations & considerations

• Secondary reinforcement only, it does not replace structural steel bar or mesh for load-carrying
• Does not stop long-term drying shrinkage or thermal cracking in hardened concrete
• Must be mixed long enough to fully separate and disperse, or fibres ball up and leave dry clumps
• Slightly reduces workability, so a compatible superplasticiser is usually needed to hold slump
• A few stray fibres can show at the finished surface and may need light burning-off on exposed work
• Good curing is still essential, the fibre is not a substitute for proper moist curing

Selection & best practice

Specifications

Industry use cases

How we position MC-Bauchemie MC-Fibre PP

MC-Fibre PP sits in the MC-Bauchemie fibre range alongside the finer MC-Fibre Poly Micro grades for very fine crack control and structural macro-fibres where load-bearing fibre reinforcement is specified. It pairs naturally with MC-Bauchemie PCE superplasticisers to hold workability at dose, and with the company’s curing compounds and integral waterproofing admixtures on the same slab. Where a project is standardised on another supplier, we also stock equivalent monofilament PP fibres such as Fosroc Structuro and Sika’s polypropylene fibre lines, so specifiers can match an approved vendor without changing the crack-control approach. For a full slab package, talk to us about combining the fibre with a joint sealant and surface hardener from our flooring range.

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