The particle size distributions of CCRL cements 135 and 136 were determined using laser diffraction techniques at the laboratories of Dyckerhoff Zement in Germany. For the measurements, a HELOS instrument type RODOS T4.1 from SYMPATEC GmbH, Germany 1 was used.
For the measurements, a 100 g sample of each cement was divided into 10 equal subsamples, each of which was evaluated separately. The focal distance of the HELOS instrument was set at 87.5 µm, allowing the measurement of particles with diameters between 0.25 µm and 87.5 µm. The sample feeding was adjusted in such a way that the so-called "optical" concentration of the cement particles in the measuring cell ranged from 7.5 % to 14.6 % for cement 135 and from 5.6 % to 14.1 % for cement 136. The measuring time varied between 10 s and 30 s per subsample. The average PSD curves computed by averaging the results obtained for the 10 subsamples of each cement are shown in Figure 1. The PSDs measured for the two cements are seen to be quite similar, as are their Blaine finenesses (cement 135: 394 m2/kg and cement 136: 390 m 2/kg) measured via the standard ASTM C204 technique  in the CCRL testing program .