Improving the Plastic Shrinkage Cracking Resistance of Self-Consolidating Concrete with Fiber Addition

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Title: Improving the Plastic Shrinkage Cracking Resistance of Self-Consolidating Concrete with Fiber Addition

Author(s): Dean Forgeron and Jean Francois Trottier

Publication: Special Publication

Volume: 276

Issue:

Appears on pages(s): 1-14

Keywords: Plastic Shrinkage Cracking, Self-Consolidating Concrete, Self-Fibrillating Macro-Synthetic Fibers, workability.

Date: 3/1/2011

Abstract:
Self-consolidating concrete has become an important material in the concrete construction industry, however the modifications required to produce self-consolidating concrete (SCC) can significantly increase its susceptibility to cracking. This is an important durability issue when SCC is considered for use in reinforced concrete marine and highway structures. A common method of increasing the resistance of concrete to cracking is the addition of discrete monofilament macro-synthetic fiber reinforcement. However, the addition of fibers to SCC has the negative effect of reducing its self-consolidating characteristics. An experimental program was conducted to investigate the mixture modifications required to maintain the self-compactability of SCC with the addition of various rates between 0.2% and 0.4% by volume (1.8kg/m3 (3.0 lbs/yd3) - 3.6kg/m3 (6.0 lbs/yd3)) of a commercially available monofilament self-fibrillating macro-synthetic fiber. The effect of fiber addition rate on the plastic shrinkage resistance of SCC was also evaluated. The addition of fiber volume fractions ranging from 0.2% to 0.4% by volume were easily incorporated into several SCC mixtures (w/c =0.4, 0.42, 0.45) with adjustments made to the coarse/fine aggregate ratio and high range water reducer dosage rates. Interestingly, the addition of as little as 0.2% by volume of the monofilament self-fibrillating macro-synthetic fiber resulted in a 44.6% decrease in plastic shrinkage cracking area, when compared to its unreinforced counterpart, while also reducing the maximum observed crack widths by 43%. The addition of a higher fiber dosage (0.4% by volume) resulted in as much as a 70.4% reduction in cracking area and a 62% reduction in maximum crack widths for SCC mixtures with w/c ratios ranging from 0.4 to 0.45. From this study, it can be concluded that monofilament self-fibrillating macro-synthetic fiber reinforcement can be successfully incorporated into an SCC mixture to significantly increase its resistance to plastic shrinkage cracking while maintaining the workability expected from this type of concrete.