Outcomes of the RILEM round robin on degree of reaction of Slag and fly ash in composite cements

Working group 2 of the RILEM TC 238-SCM organized a round robin test to compare the protocols of different laboratories to determine the degree of reaction of two slags, a calcareous and a siliceous fly ash in binary mixes with Portland cement. The techniques used were: selective dissolution, analysis of the differences in portlandite content from thermogravimetric analysis, X-ray diffraction with PONKCS (partial or no known crystal structure) refinement, and scanning electron microscopy with image analysis. As each laboratory followed their own protocols, the collective assessment of the results provided an idea of the maximum inter-laboratory variability, which should be universally valid. This study assesses the accuracy and precision of the four techniques investigated and with respect to each of the materials studied.