Characterization of Cement Alteration Process by Transmission Electron Microscopy with High Spatial Resolution

Application tests for advanced TEM analysis techniques were carried out to study the cement alteration processes associated with water penetration at high spatial resolution. Prior to TEM analysis, we measured the changes in the penetration coefficient and determined the characteristics of the penetrating water in order to gain a fuller understanding of the overall process. These experiments revealed that the process begins with the preferential dissolution of Ca(OH)2. After most of the Ca(OH)2 is dissolved out, the penetration coefficient increases, while the pH value of the water decreases. It has been demonstrated that scanning transmission electron microscope (STEM) techniques are quite useful for determining local structures and compositions in the cement at sub-micron meter spatial resolution. The preferential dissolution of Ca ions results in refinement of cement grains. When the Ca/Si ratio decreases to 1.05, most grains have a round shape in the sub-micron range. X-ray mapping suggests the format...