Sabine Thomas, K. Meise-Gresch, W. Müller-Warmuth
Aug 1, 1993
Journal of the American Ceramic Society
29Si, 27Al, and 1H MAS NMR studies of partially carbonated mature ordinary Portland cement (OPC) and tricalcium silicate (C3S) pastes have been carried out. The water-to-solid ratios (W/S) have been varied between 0 and 1 at hydration temperatures of 23o and 90oC. Various Q ni units with n=0, 1,2,3, and 4, and a Q3 (1Al) group have been identified using 29Si NMR. Cross-polarization experiments, in addition, have made it possible to assign the OH groups. Two types of fourfold- and one type sixfold-coordinated aluminum have been distinguished using 27Al NMR. In C3S pastes for w/s>0.7, progressive carbonation leads to a nearly perfect three-dimensional network consisting of Q3 and Q4only. In contrast, in OPC pasted only about 40% of the highly polymerized silicate units are formed, partially copolymerized with AlO4 tetrahedra.