Fiber Reinforced Concrete Research Paper

CHAPTER 3

Project Description

3.1 THEORITICAL CONCEPTS ABOUT FIBER REINFORCED CONCRETE

Concrete being a brittle building material and having low tensile strength is unfit to resist tension until duly reinforced. The concept of using fibers to reinforce building materials is not a nascent concept this method has been old and been run by intuition. Hoarse hairs and straws had been used in old times to prevent plaster material from cracking. More recently when Portland cement started evolving, attempts were made to enhance the properties of the cement by adding fibers. The concept of adding fibers to overcome the inherent behavior of concrete of showing brittle failure under tensile load. After the year 1970 rapid innovation in the field of fiber reinforced concrete started unfolding and

The effects on both are defined below

PLASTIC SHRINKAGE

Plastic shrinkage takes place while the concrete is still in the plastic state due to loss of water by evaporation from the surface of the concrete, which leads to surface cracking. Adding polypropylene fibers to concrete has been reported to be very effective in reducing the plastic shrinkage cracking. It has been reported that there is unexpected reduction in plastic shrinkage and bleed water migration to the surface of the polypropylene fiber reinforced concrete specimens compared to that of the plain concrete specimens.

HARDENED SHRINKAGE

Dry shrinkage can be controlled to some extent by use of polypropylene fibers. But researchers couldn’t lead to credible agreeable result in this aspect. Some of the reports showed high reduction in shrinkage by using polypropylene fibers, while others indicated small differences shrinkage between fibrous concrete and plain concrete. A pilot study reported in 1982 indicated that polypropylene fibers reduced shrinkage of plain concrete specimens by about 75 percent. However, more recent test results do not agree with these