Cryo-FIB-nanotomography for quantitative analysis of particle structures in cement suspensions.

Cryo-FIB-nanotomography is a novel high-resolution 3D-microscopy technique, which opens new possibilities for the quantitative microstructural analysis of complex suspensions. In this paper, we describe the microstructural changes associated with dissolution and precipitation processes occurring in a fresh cement paste, which has high alumina and sulphate contents. During the first 6 min, precipitation of ettringite leads to a general decrease of the particle size distribution. In the unhydrated cement paste almost no particles smaller than 500 nm are present, whereas after 6 min this size class already represents 9 vol%. The precipitation of ettringite also leads to a significant increase of the particle number density from 0.29410(9)/mm(3) at t(0min) to 20.5510(9)/mm(3) at t(6min). Correspondingly the surface area increases from 0.75 m(2)/g at t(0min) to 2.13 m(2)/g at t(6min). The small ettringite particles tend to form agglomerates, which strongly influence the rheological properties. The particular strength of cryo-FIB-nt is the potential to quantify particle structures in suspension and thereby also to describe higher-order topological features such as the particle-particle interfaces, which is important for the study of agglomeration processes.