... buried, don’t need concrete cover, Can speed up the construction progress(2)Flexibility, Resistant to outside pressure and damage(3)Electric ... insulation, flame retardant, heat resistant performance is good, can be use for a long time in 130 degrees ... .(4)Resistance corrosion, long service life, can resist acid, alkali and salt corrosion; can be used more than 50 years.(5 ...