?????? ??? ?? ????? ?? ????

2018-08-14

?????：?????? ??? ??? ?? ?? ??????? ?? ????? ? ???? ??? ?????? ??? ?? ?? ?? ????? ????? ??? ??? ???? ??? ?????? ??? ??? ???? ??? ??? ???? ???? ??? ?????? ?? ??? ?? ???? ????? ???? ???? ??? ???? ????? ?? ????????? ???????? ?? ??? ??? ??? ?? ?????? ???? ??? ????? ?? ??? ??? ?? ??? ?? ???? ????? ??? ?? ????? ?? ????? ?? ??? ?? ???? ??? ?? ????

?????? ??? ??? ?? ?? ??????? ?? ????? ? ???? ??? ?????? ??? ?? ?? ?? ????? ????? ??? ??? ???? ??? ?????? ??? ??? ???? ??? ??? ???? ???? ??? ?????? ?? ??? ?? ???? ????? ???? ???? ??? ???? ????? ?? ????????? ???????? ?? ??? ??? ??? ?? ?????? ???? ??? ????? ?? ??? ??? ?? ??? ?? ???? ????? ??? ?? ????? ?? ????? ?? ??? ?? ???? ??? ?? ???? of the crushing and screening process. In modern time, due mainly to environmental constraints, the focus is shifting to the deliberate manufacture of sand to fill demand that natural sand deposits cannot continue to supply.

?????? ??? ?? ??

????? ??? ?????? ??? ????? ???? ?????

????? ????? ????? ???? ?????? ???? ??? ????? ??? ?????? ?????? ?? ????? ?? ??? ????? ?? ????? ?????? ??? ????? ???? ????? ?? ??? ???? ???

??? ???? ????????? ??????? ??????? ?? ????? ??????? ?? ??????? ??? ??????? ???? ??????? ?? ???? ????? ????? ??? ?? ????? ??? ???? ?? ???? ?? ??? ?? ?????? ????? ???? ???

??? ????? ???? ???? ????????? ??? ?????? ????? ??? ????? ??? ??? ???? ??? ?? ??? ???? ?? ?????? ?? ????? ???