Early age autogenous shrinkage cracking risk of an ultra-high performance concrete (UHPC) wall: Modelling and experimental results

Abstract

Ultra-High Performance Concrete (UHPC) exhibits high autogenous shrinkage (AS) which significantly increases the risk of early age cracking. To predict the risks of early age shrinkage cracking of environmentally friendly CEM III-based UHPC, a numerical model originally developed for early age crack assessment of ordinary concrete, has been further developed and applied on a demonstration wall with high risk of cracking, cast on a non-deforming slab. The design of the wall was determined through numerical simulation using different parameters, resulting from specific experiments performed on the desired concrete mixture. Early age crack assessment parameters for the model were obtained through different tests performed using the Temperature-Stress Testing Machine (TSTM). Finally, this UHPC wall was built, and occurring strain deformations were recorded in real time using fiber optic (SOFO) sensors embedded in the wall, and measurements taken from demountable mechanical strain gauges (DEMEC). Restrained shrinkage measurements were obtained for the same mixture through ring tests. A comparison between the numerical simulation results and the measurements proved that the proposed model is suitable for UHPC, and the model predicts well the time of crack appearance. Finally, it has been shown that shrinkage values along the wall height are influenced by the degree of restraint.