Topical report on leaching tests with Simuli-3 plasma slag at 40 °C and in IPM water at pH 12.5: Pre-STABSLAK tests

In order to select the best setup for the ETF project STABSLAK, in which the durability of slags with different chemical compositions will be studied, different setups were tested to investigate the durability of the Simuli-3 plasma slag in IPM water at 40 °C. Based on ASTM standards both dynamic tests and static leaching tests were carried out. The first ones allowed the determination of a dissolution rate, which was quite similar to the dissolution rate on a relatively short time frame from static leaching tests with coupons. Static leaching tests were conducted with slag coupons (10 x 5 x 2 mm), slag powder (125 – 250 µm) and slag grains (1 – 2 mm). From the Si and Al concentrations measured in the leachates, the normalised mass losses (NL) were calculated and modelled using second order polynomial regressions going through (0,0), all of them giving good R2 values. To compare the NL values calculated in tests with coupons with the ones in tests with powder and grains, factors to correct the powder and grains surface areas were established. By applying such correction factors, it was shown that all data points were in good agreement, suggesting that all tests were reliable. Because dynamic tests only provide data on a relatively short time frame, this setup was not selected for the STABSLAK project. Preliminary tests for the slag production showed that the slags will not be homogeneous, so in agreement with ONDRAF/NIRAS, it was decided that the best setup is the one using slag grains (1 – 2 mm).