The NRMSEs of the paste vertical profiles decreased with increasing intensity (Fig. 9). For example, at a horizontal resolution of 1 mm for intensity A and one scan, the NRMSE is about 1.7 % while that for intensity C is 0.3 % (Figs. 9a and 9c). For mortars, the NRMSE also decreases with increasing intensity from 0.8 % to 0.3 % from intensity A to C for one scan (Figs. 10a and 10c). These results suggest that higher x-ray intensities result in lower uncertainties, as seen above. Note that NRMSEs for all intensities, for just one scan, and for horizontal spacings of 2 mm or less are <2.2 % for both the paste and mortar.
The mortar scans produced counts that are roughly twice those for the pastes (Figs. 9 and 10). The measured density of the mortar is ≈2250 kg m−3 and the measured density of the paste is ≈1900 kg m−3. Therefore, the higher counts from the mortar specimen must be the result of changes in the composition of the material in comparison to the paste. In making the mortar, some cement was replaced by silica aggregate. By increasing the silica content and by reducing the calcium silicate content in the specimen by removing cement, the total absorption/scattering cross-section, e.g., Ref. [18] and the mass extinction coefficient of the specimen (Eq. 1) decreased. Higher counts for the mortar resulted.