They used special microfibers, rather than coarse bits of gravel and sand, to strengthen the cement.
他们用特殊的超细纤维来替代粗糙的砂石颗粒，以强化水泥。
2
For both materials (especially HD80), rough up the glue surface first with coarse sand paper, then apply a coat of cement and let it dry.
为两种材料(尤其是hd80)，粗糙了胶的表面首先与粗砂的文件，然后申请一件外套，水泥，让它干。
3
Cement concrete, formed with cement, coarse and fine aggregates and water in appropriate proportion before a period of hardening, is a sort of stone material.