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Abstract

Both polymeric fiber and water soluble polymer (WSP) have been reported effective in reducing early-age shrinkage cracking. The synergistic effect of cellulose based WSP and fiber on reducing early-age shrinkage cracking of cementitious composite exposed to a constant evaporation rate of 1 kg/(h.m2) environment was investigated in this paper. A fixed ratio of WSP was employed in the poly-acrylic fiber reinforced cementitious composites with various fiber content and aspect ratios. Results indicate that the addition of polymeric fibers reduced plastic shrinkage cracking, such as the total crack area, the average crack width and cracks wider than 1.5 mm. Further reductions on both the crack width and the total crack area were achieved when WSP was used in combination with fibers with an aspect ratio of less than 420. The synergistic reduction on the early-age shrinkage cracking may be attributed to the improvement of the fiber-matrix bond strength and polymer film formation on the drying front. Nevertheless, when fibers with an aspect ratio greater than 420 the synergistic effect provided by the WSP might be masked by the decreased fiber spacing or stronger crackbridging capability. In practical terms, preventing early-age shrinkage cracking by adding WSP not only can reduce fiber requirement but may also keep mixture workable.

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