Effect of brine on long-term performance of four HDPE geomembranes

The performance of four 1.5 mm thick high-density polyethylene (HDPE) geomembranes (GMBs) (denoted MxA-15, MxC-15, MyE-15, and MyEW-15) immersed in a brine solution with 200,000 ppm total dissolved solids and a pH = 8.7 is presented for 4 years. Accelerated ageing experiments were conducted at 40, 65, 75, and 85 degrees C for 4 years. It is shown that neither the Std-OIT nor HP-OIT had reached a residual value before physical degradation was observed, suggesting that the traditional three-stage concept for degradation did not apply when based on the values obtained (as is usual) through the entire GMB thickness. The time to nominal failure, based on a reduction of 50% of the initial value, was less than 4 years for all GMBs at temperatures >= 65 degrees C. However, using the time at which the stress crack resistance (SCR), obtained from the single point notched constant tensile load (SP-NCTL) test, decreased to 50% of the minimum requirements of GRI-GM13, the times to nominal failure are greater than 20 years for at T <= 65 degrees C for MyE-15.