... size, make it easy to be cleaned, the back-flush strength is 12-20 l/m2.s; it can save the ... filter of 7.8-9 kg/m3;4. Great mechanical strength, less abrasion loss, and never be damaged, the ceramic sand ... -1.5-Free volume,%40-45- Abrasion resistance,%≤0.5- Compressive strength, N30-150- Water permeability,t/m2.h2-4- Gas permeability ...