Volume changes of very-high-performance cement-based composites

The autogenous shrinkage and drying shrinkage of very-high-performance cement-based composites (VHPC) as well as their potential volume change under long-term water heat treatment conditions are investigated. The relationship between drying shrinkage and autogenous shrinkage and the relationship between the self-desiccation and autogenous shrinkages are also presented in the present paper. Further, the mechanisms-related volume changes of VHPC are analysed. The results indicate that the total shrinkage (autogenous and drying shrinkage) of VHPC with water/binder ration (w/b) = 0·17 is more than 700 μm/m within considered ages. Severe self-desiccation is observed during hydration of VHPC. The value of autogenous shrinkage of VHPC is almost equal to half of total shrinkage. There is a linear relationship between autogenous shrinkage and relative humidity change caused by self-desiccation in VHPC. However, the potential volume change of VHPC under long-term water heat treatment conditions is small. A large number of chemically unstable unhydrated particles exist in VHPC, which are probably unharmful to microstructure. It follows that VHPC possesses excellent long-term volume stability. The very dense microstructure of VHPC is responsible for this.