Fiber-Reinforced Concrete (FRC)

Fiber-Reinforced Concrete (FRC) is concrete with discrete steel, glass, or polymer fibres added to control crack widths, improve toughness, and provide secondary reinforcement. Per IS 456:2000 + IS 16707:2017 (test methods for FRC), fibres are typically 25-65 mm long with aspect ratio 50-100. Used for: (1) Industrial floors — load-bearing slabs subject to point loading and impact. (2) Tunnel linings — primary support during excavation. (3) Pre-cast concrete — improving impact resistance. (4) Slabs-on-grade — replacing distribution mesh. (5) Specialty applications — earthquake-resistant elements, blast-resistant structures.

Main fibre types: (1) Steel fibres — most effective for structural toughness; typical 30-50 mm length, 1.0% by volume. Cost ₹35,000-65,000/tonne. (2) Polypropylene fibres — for plastic shrinkage control; typical 12 mm length, 0.1% by volume. Cost ₹60,000-90,000/tonne. (3) Glass fibres — alkali-resistant for cement environment; typical 12-25 mm. (4) Synthetic macro fibres — heavy-duty alternative to steel. Effects on concrete: (a) Toughness increased 2-5×; (b) Crack widths reduced 30-50% under service load; (c) Impact resistance increased 2-3×; (d) Flexural strength increased 10-25%.

Mix design: (a) Add fibres at 0.5-2% by volume of concrete. (b) Adjust aggregate maximum size to ≤ 40% of fibre length. (c) Use PCE superplasticisers — fibres reduce workability significantly. (d) Trial mixes mandatory. The most-overlooked aspect of Indian FRC: dispersion. Fibres tend to clump in mixers; thorough mixing essential. Industrial flooring contractors specialising in FRC ensure proper dispersion via specific mixing protocols.