Question

Please answer all four questions. Thank you!

1) How do fibers add strength to primary FRC?

2) What are typical crack widths in FRC concrete versus crack widths common in reinforced concrete?

3) What is relative resistance to deterioration vs. time of FRC with polypropylene? AR glass? Steel fibers?

4) How does continued hydration of cement similarly negatively affect Polymer, Glass, and Natural fibers?

Answer 1

Answer 1- Fibres are not added to improve strength , their principle role is to bridge across the cracks that develop in concrete when it is stressed,if fibres are well bonded in the matrix, they are sufficiently stiff and stong, they will permit the FRC to sustain significant load over relatively large deformation in the postcracking stage

Answer 2- Adding fibres to the concrete results in higher tendency for crack branching, which decreases the effective crack wridth,closed to the reinforcement bar, For SFRC and HyFRC, effective crack wridth is 40-45% smaller than total crack wridth , compared to 15-20% for plain concrete.

Answer 3-Polypropylene and glass fibres improves the electrical resistivity by around 61.9 and 11.9% respectively. Water penetration and gas permiability of steel fibre reinforced concrete are increased compared to plain concrete.Scaling resistance is also improved more for steel fiber reinforced concrete.

Answer 4- Adding glass fibre in concrete would greately increase fluxtural strength and wearing resistance of concrete, but glass fibre has great potential towards corrosion during cement hydration , which will directly effect long term performance and strengh stability.