Autogenous shrinkage behavior of ultra-high performance concrete

摘要

This study presents experimental results on the shrinkage behavior of ultra-high performance concrete (UHPC), including the shrinkage development pattern, the calculation of autogenous shrinkage strain and the steel fiber restraining effect. UHPC is found to exhibit a multi-stage shrinkage characteristic. During the first two dormant stages, shrinkage is mainly composed of thermal contraction when limited hydration reaction occurs. Rapid shrinkage development commences once hydration is accelerated, leading to pore moisture depletion and pore refinement. In the later stage, shrinkage gradually levels off due to the decreasing hydration reactivity and the stiffening matrix. Autogenous shrinkage is separated by the removal of thermal strain based on the knowledge of coefficient of thermal deformation (CTD). This leads to the appearance of a transient swelling segment which may be attributed to the formation of Ca(OH)(2) and ettringite crystals generating expansive stresses. Addition of steel fibers is found to reduce the shrinkage strain significantly. Its shrinkage restraining effect is a result of the matrix-fiber interfacing bonding and is numerically characterized by a mathematical model with the volume fraction and geometrical features of steel fibers as the major variables. (C) 2019 Elsevier Ltd. All rights reserved.