Rau kev siv ntawm kev hnav cov qauv zoo xws li kev tiv thaiv kev tiv thaiv thiab vaj tse vaj tse ntawm kev tiv thaiv thiab kev sib cav sib ceg. Kev txhawb nqa lossis lub phaj txhawb nqa; Ib qho txiav ntawm lub tsheb loj lub cev. Hnav daim hlau-resistant; Kev sib xyaw thiab cov ntsiab lus, Chute trenches, cov cuab yeej, cov khoom siv criquetting presses, tuaj yeem paving abrasives thiab kev ua liaj ua teb machinery.
