Effect of Synthetic Fibers and Aggregate Size on Flexural Crack Widths


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Title: Effect of Synthetic Fibers and Aggregate Size on Flexural Crack Widths

Author(s): Erik Stefan Bernard

Publication: Structural Journal

Volume: 116

Issue: 3

Appears on pages(s): 19-26

Keywords: aggregate size; corrosion; crack widths; fiber-reinforced concrete (FRC); flexure; testing

Date: 5/1/2019

Cracks can lead to corrosion of steel reinforcement, so limits are placed on maximum allowable in-service crack widths to reduce the likelihood of corrosion during the design life of a reinforced concrete (RC) member. The relatively light level of reinforcement required to meet strength requirements in some applications can result in quite wide in-service crack widths, so either additional steel bar reinforcement or fibers must be included to limit maximum crack widths. The mechanism by which fibers are believed to reduce crack widths in RC flexural members relies on the tensile stress generated by the fibers across cracks. Provided post-crack performance is satisfactory, fibers of any composition should be capable of reducing crack widths in RC members. This investigation has therefore assessed the influence of several high-performance macro-synthetic fibers on flexural crack widths in RC members and has also examined the influence of maximum aggregate size. The results indicate that for a moderate dosage rate (4.0 to 4.5 kg/m3 [6.7 to 7.6 lb/yd3]), the currently examined macro-synthetic fibers reduced flexural crack widths by approximately 20% compared to plain concrete. Maximum aggregate size was also found to influence mean crack spacing but had a negligible effect on crack width.