No abstract

Ground granulated blast furnace slag (GGBS) is a glassy by-product of pig iron production and is commonly used in concrete industry to replace cement and thereby lower the carbon footprint of the material. Large variations in reactivity exist depending on the GGBS physical and chemical features. Here we investigate the ability of three rapid calorimetric methods to evaluate the reactivity of GGBS. On a set of 16 industrial GGBS, we show that 24h heat release, using the R3protocol, correlates well with 2d compressive strength of standard mortars using 75 wt.-% GGBS. The correlation of R3-test results (R²= 0.87) is better than for traditional reactivity indices calculated from chemical composition. Furthermore, we present data on the repeatability of the test protocol and show that the R3 protocol is very sensitive to sample fineness. Finally, XRD patterns show that slight differences in phase assemblage exist between the most and least reactive GGBS.

No abstract

For many microstructural studies it is necessary to ''stop'' cement hydration-to remove free water. This paper describes the results of a round robin test on the impact of hydration stoppage methods on the composition of hydrated cements. A regular and a fly ash blended Portland cement hydrated for 90 days were selected. Ten laboratories participated in the round robin test. Four common hydration stoppage methods were studied: (1) oven drying at 105 °C, (2) solvent exchange by isopropanol, (3) vacuum drying and (4) freeze drying. After the stoppage of hydration powder samples were studied by thermogravimetry (TG) and X-ray diffraction (XRD). Bound water and Ca(OH) 2 content were determined based on the TG data. Portlandite and ettringite content were quantified by Rietveld analysis of the XRD data. The goal was to establish interlaboratory reproducibility and to identify the best available protocols for research and standardization purposes. Based on the results of the round This report has been prepared by a working group within RILEM TC 238-SCM. The report has been reviewed and approved by all members of the TC.