The paste is more sensitive to the number of scanning repetitions that are averaged together (Fig. 9) than is the mortar (Fig. 10). At intensity A with a horizontal resolution of 2 mm, the NMRSE for the paste is 2.2 % for one repetition and 1.2 % for four repetitions (Fig. 9a). Under these same conditions, the NRMSEs for the mortar are 2.0 % and 1.9 % (Fig. 10a). The larger small-scale variability due to the aggregates and the uncertainty in the positioning of the x-ray beam/detector combine to maintain a high NRMSE for the mortar even after averaging over four scans.
For both the paste and mortar, the dependence of the NRMSE on the number of repetitions decreases as the x-ray intensity increases (Figs. 9 and 10). For example, the range of NRMSE for the paste at intensity C with a 2 mm horizontal resolution is 0.3 % to 0.25 % from one to four scans (Fig. 9c), compared to 2.2 % to 1.2 % at intensity A (Fig. 9a). By increasing the x-ray intensity, more accurate data are obtained with fewer scans.