The effects of water to binder ratio and polyethylene(PE)fiber content on the compressive and flexural strength,bending toughness and early shrinkage properties of ultra-high toughness cementitious composites(UHTCC)were investigated,and analyzed the microstructure of UHTCC with scanning electron microscopy(SEM).The results showed that with the increase of water to binder ratio,the compressive and flexural strength of UHTCC decreases,and its bending toughness shows a trend of decreasing and then increasing.The in-crease of PE fiber content could significantly improve the flexural strength and bending toughness of UHTCC,but will reduce its 3 d com-pressive strength and increase its 7 d and 28 d compressive strength.In terms of early shrinkage performance,the increase of water to binder ratio would reduce the early autogenous shrinkage of UHTCC,but its early drying shrinkage increased.The early autogenous shrinkage and early drying shrinkage of UHTCC decreased with the increase of PE fiber content.The microstructure analysis showed that the increase of PE fiber content was easy to lead to fiber agglomeration.The increase of water to binder ratio would reduce the compactness of UHTCC matrix and the interfacial adhesion between fiber and matrix,which was not conducive to the development of mechanical properties of UHTCC.
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