MAS NMR Studies of Partially Carbonated Portland Cement and Tricalcium Silicate Pastes
Sabine Thomas, K. Meise-Gresch, W. Müller-Warmuth
Aug 1, 1993
Citations
35
Citations
Journal
Journal of the American Ceramic Society
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Key Takeaway Key Takeaway: Partially carbonated Portland cement and tricalcium silicate pastes show different carbonation processes, with C3S pastes showing a nearly perfect three-dimensional network and OPC pastes showing only 40% polymerized silicate units.
Abstract
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.