Ability of the R3 test to evaluate differences in early age reactivity of 16 industrial ground granulated blast furnace slags (GGBS)

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.

Effect of TiO2 and 11 minor elements on the reactivity of ground‐granulated blast‐furnace slag in blended cements

“…However, when a 2 × RSD range is considered as the method error, ranges from the latter two samples and the reference overlap. 8 Additions of SnO 2 (1.2 wt%), SrO (1.8 wt%), Cs 2 O (0.2 wt%), and BaO (2.0 wt%) had slight positive effects on GGBS reactivity but were all within the 2 x RSD range of the reference samples. The addition of 1.2 wt% K 2 O had a significant positive effect on GGBS reactivity with a heat release of 233 J/g.…”

“…Concentrations of TiO 2 additions were chosen to reflect contents of modern day GGBS (0.2-3.0 wt%). 8,39 MnO additions were set to 3 wt%, V 2 O 5 and Cr 2 O 3 to about 1 wt%, which were our estimates for maximum concentration that could occur in a modern industrial setting. Network modifier additions of Sr and Ba were chosen to be close to 2 wt%, a compromise between economic viability for a potential application on industrial scale and amount necessary to observe an effect.…”

“…The resulting fritted granules were then ground using a Retsch RS100 disk mill (15 g of slag in a 50 mL tungsten carbide bowl for 1 minute at 1400 rpm) to give about 4200 cm 2 /g Blaine fineness. 8 X-ray fluorescence measurements were carried out on a S8 Tiger device by Brucker. The samples were prepared using a mix of lithium meta-and tetraborate, results are displayed in Table 2.…”

“…Details of the method were published elsewhere. 8 In brief, 1.5 g of GGBS together with 4.5 g of laboratory grade Ca(OH) 2 were placed in a polypropylene recipient. Then a solution of 0.3 M K (from KOH and K 2 SO 4 (1:5 w/w)) was added in a s/l ratio of 0.8.…”

“…Slag reactivity was then screened using a modified calorimetric R3 protocol. 8,37 This test is based on a model system approach that imitates concrete pore solution using only pure components. 37,38 To validate the calorimetric protocol four different levels of Ti-modified slags were prepared and their compressive strength tested on 2 × 2 × 2 cm 3 mortar cubes.…”