The influence of a new metal silicate hydrate additive on concrete strength and durability

A new, highly effective accelerating additive, based on copper silicate hydrates, has been developed to promote the early hydration of portland cement. Different cement paste samples, with and without the additive, were investigated at different times of hydration by a number of techniques, including electron microscopy and synchrotron-based diffraction enhanced computed micro-tomography. The latter advanced technique allows to visualize the 3D crystal phase evolution in the cement paste, thus enabling the direct analysis of the nucleation mechanisms and the microstructural developments. The data confirmed that the new silicate hydrates truly enhance the silicate network by inducing homogeneous nucleation and the rapid development of a diffuse interconnection between the hydration products. The resulting microstructure reflects into improved mechanical and durability properties, as shown by the development of compressive strength and reduced water permeability of concrete mixtures containing the new additive.