Correlation of Cement Performance Property Measurements with C3S/C2S Ratio Determined by Solid State 29Si NMR Measurements

The physicochemical and engineering performance properties of several API class G and H ordinary Portland cements (OPCs) from various foreign and domestic sources have been investigated in comparison with the tricalcium silicate/dicalcium silicate ratio (C 3 S/C 2 S) as determined by magic angle spinning (MAS) 29 Si nuclear magnetic resonance (NMR) experiments. XRF-derived oxide analysis appears to provide a lower C 3 S/C 2 S ratio than determined by NMR analysis. Furthermore, oxide analysis suggests that all the cements have a C 3 S/C 2 S ratio of 2-5, while our NMR method suggests the actual range is significantly broader. Determination of C 3 S/C 2 S ratios by NMR provides an effective method of analysis for cements, owing to NMR's direct measurement of the minerals in question. NMR C 3 S/C 2 S ratios demonstrate predictive ability for the determination of engineering performance properties. This is especially the case for prediction of strength development; in keeping with generally accepted understanding of cement hydration behavior, the strength development correlates with increasing C 3 S/C 2 S ratio, i.e., C 3 S content. The observed correlation between NMR-derived silicate ratio and strength development holds for cements in the presence of either a retarder (lignosulfonate) or a fluid loss additive (N,N-dimethylformamide/2-acrylamido-2-methylpropanesulfonic acid copolymer). No significant correlation is observed between C 3 S/C 2 S ratio and the 72 h crush strength. The lack of dependency of either thickening time or Young's modulus to the C 3 S/C 2 S ratio as determined by MAS 29 Si NMR measurements suggests that these physical properties are independent of the relative silicate composition. No correlations are observed between any physical property and the silicate ratio derived from XRF data.