Revisiting Tennis-Jennings method to quantify low-density/high-density calcium silicate hydrates in Portland cement pastes

Abstract

The Tennis-Jennings quantification method was revisited for characterizing low-density (LD) and high-density (HD) calcium silicate hydrates (C-S-H). Parameterized Portland cement pastes were prepared with different Blaine values of ordinary Portland cement and different types of cement using two water-to-cement (W/C) ratios (0.40 and 0.55). The hydration processes in these samples were examined using nitrogen sorption measurements and X-ray diffraction (Rietveld) analyses. The densities of LD and HD C-S-H were determined to be 1.19 and 1.79 (g/cm3 of dried C-S-H), respectively. Variation of the mass ratio of the LD C-S-H to the total C-S-H with hydration depended on the fineness of the original cement powder within the same Portland cement and the type of cement, especially at the later hydration for higher W/C ratios. For cement pastes with lower W/C ratios, the type of cement did not have a significant effect on the LD C-S-H precipitation at later hydration.