Comparing ASTM and JS']JSA Sulfur Trioxide Analysis Methods for Slag Aggregates

In this study, we investigate various methods for determining the sulfur trioxide (SO3) content of slag aggregates. Proper measurement of the SO3 content is important because high levels of SO3 can result in significant loss of strength of the concrete produced from the slag aggregates. In particular, we analyze two testing methods, one from the ASTM and one from the Japanese Standard Association (JSA), and we compare them to SO3 measurements from portable x-ray fluorescence spectrometry (pXRF). The 3 testing methods are applied to 27 specimens of slag aggregates, which were composed of 5 different types: blast furnace, basic oxygen furnace, electric arc furnace, old bank, and open hearth. The results show that the ASTM measurements closely align with the pXRF measurements, whereas the JSA method produces significantly higher SO3 measurements. Owing to the complexity of performing the JSA testing method, as well as its lack of agreement with XRF measurements, we recommend the ASTM testing method for SO3 over the JSA method.