Freeze-thaw resistance of concrete: Insight from microstructural properties

Composite cements offer low carbon alternatives to conventional CEM I. These also generally tend to perform better than CEM I in aggressive chemical environments. However, the freeze-thaw resistance, evident through surface scaling and internal damage is usually impaired. Postulated theories on freeze-thaw induced damage do not fully explain the origin of this weakness in composite cement concretes.

This contribution systematically presents the phase assemblage changes associated with the freeze-thaw of concrete specimen made from composite cements with and without limestone. The freeze-thaw test was performed on concrete according to CIF method based on CEN/TR 15177 and the corresponding cement pastes characterized by X-ray powder diffraction (XRD) and thermogravimetric analysis (TGA). In all investigated composite cements, portlandite was already depleted after the 7d capillary suction. The implications of this and other modified assemblages during the conditioning and the freeze-thaw test are consequently discussed.