Published literature data on the reaction degree of slag
Although it is somewhat difficult to measure the reaction degree of slag in slag blended cement comparing with the case in Portland cement, many researchers performed experiments on this field. A large body of literature can be found on the kinetics of Portland cement/slag blends.
Based on the modification of Takashima’s salicylic acid extraction method, Taylor collected some researchers’ data on the reaction degree of slag, as is showed in Table 1.
Table 1. Data on reaction degree of slag in blended cement from literature
Other researchers using EDTA or DTA also reported data on this issue under different hydration conditions; Table 2 is an uncompleted collection of these data.
Table 2. Uncompleted data collection of reaction degree of slag blended cement
By means of EDTA extraction method, the work of Lumley et al. focused on the effect of water to solid ratios and the proportions of slag on the degrees of reaction of slag blending with Portland cement. It is reported that at water to solids ratios of 0.4-0.6 and 20 °C 30-55% of the slag reacts in 28 days and 45-75% in 1-2 years, for blends containing 92% slag and w/s=0.3, the hydration degree of slag is probably limited to 30%.
They also found that at water/solid ratio 0.3 the composition of Portland cement, even with an inclusion of 5% gypsum, has no significant effect on the degrees of slag reaction in the blend at ages of 28 days to 1 year.
Luke and Glasser reported that approximate 40% of the slag in a 30%/70% ratio of slag to Portland cement blend reacted in one month with little change up to 6 months, but over 60% of slag was reacted at the age of 12 months. Their latter study showed similar results with data at 25 °C, 40 °C and 50 °C for times of 0.5 to 24 months.