2.1.4. Grain Size

The particle size distribution for the fraction ≤1 mm was determined with a laser diffraction particle size analyser LS13 320 by Beckman-Coulter (Brea, California, USA). The samples were sieved with a 1-mm sieve and bi-distilled water together with about 0.5 g Na4P2O<sup>7</sup> as an anti-coagulation agent. The samples were placed in an overhead shaker for 24 h and ultrasonic treated for 5 min directly before the measurement. The prepared samples were put into a liquid sample divider and two subsamples were measured with three independent runs each. The six measurements per sample were averaged to obtain the sample's grain size distribution [42]. Particle sizes are defined according to [40] and reported in vol%.
