Potential use of strain hardening ECC in permanent formwork with small scale flexural beams

Abstract

Utilizing pre-cast ECC panels as participating permanent formwork of concrete members, and the validity of using ECC to disperse the single crack in concrete into multiple ones in ECC were studied. In the process, totally two kinds of ECC with different tensile properties, 7 series of flat panels with different top surface figures and 3 U-shape panels with different inner surface forms were investigated. To evaluate the performance of the permanent formworks, small ECC-concrete composite beams were cast and tested mechanically. The 4-point bending test results show that the use of pre-cast ECC panels as permanent formwork can significantly improve the load capacity and toughness of a concrete member, effectively dispersing single widely opened crack in concrete into multiple ones in ECC. Most permanent formworks show perfect bond with the concrete cast on them, while the ones with partially debonded zone achieve the best mechanical performance. The U-shape permanent formworks show better performances than the flat ones, achieving much better improvements in both the load capacity and toughness, together with better crack width control.

Keywords

pseudo strain hardening / cementitious composites / permanent formwork / toughness / crack

References

[1] Li V. C., Wang S., Wu C. Tensile Strain-hardening Behavior of PVA-ECC[J]. ACI Materials Journal, 2001, 98(6): 483-492.

[2] Wang T. Crack Control of Engineering Structures[M], 1997 Beijing China Construction Industry Press

[3] Li V. C., Lepech M. Crack Resistant Concrete Material for Transportation Construction[C]. Transportation Research Board 83rd Annual Meeting, 2004 Washington D C Compendium of Papers CD ROM

[4] Zhang J., Li V. C. Monotonic and Fatigue Performance in Bending of Fiber Reinforced Engineered Cementitious Composite in Overlay System[J]. J. of Cement and Concrete Res., 2002, 32(3): 415-423.

[5] Giovanni MARTINOLA, Martin F BÄUML, Folker H WITTMANN. Modified ECC Applied as an Effective Chloride Barrier[C]. Proc. JCI Int. Workshop Ductile Fiber Reinforced Cementitious Composites-Application and Evaluation, Japan Concrete Institute, 2002: 171–180

[6] Wringley R G. Permanent Formwork in Construction (CIRIA C558)[C]. CIRIA/Concrete Society, 2001

[7] Nee C. Y. Investigation of Concrete Components with a Pseudo-Ductile Layer[D], 2004 Hong Kong Hong Kong University of Science and Technology 3

[8] Tsukamoto M. Tightness of Fiber Concrete[J]. Darmstadt Concrete. Annual Journal on Concrete and Concrete Structures, 1990, 5: 215-225.