<li>Maximum abrasion of 10% for 100 revolutions and maximum of 50% for 500 revolutions.</li>
<li>Maximum abrasion of 10% for 100 revolutions and maximum of 50% for 500 revolutions.</li>
</ul></p>
</ul></p>
<p>Granular material for underdrains should be clear crushed 50 mm diameter stone graded in accordance with ASTM D 2940. The void space ratio shall be 0.4 .</p>
Granular material for underdrains should be clear crushed 50 mm diameter stone graded in accordance with ASTM D 2940. The void space ratio shall be 0.4 .</p>