| 摘要 |
Firstly, the stones are extensively dried by mechanical or thermal/mechanical means, usually using pressurized air. They are then crushed and finally graded. The stones are over 16 mm across, preferably over 32mm and have a moisture content of higher than 0.5% of their weight, preferably over 1% and after drying a residual moisture content of less than 0,5% of their weight. The drying process is aided by the use of active surface substances which waterproof the mineral surfaces. During or after the drying process the crushed stone is dedusted using mechanical shearing forces, such as through 'hard' sifing, an air jet or brushes. |
