Influence of alkali addition on the setting and mechanical behavior of cement pastes and mortars with electric arc furnace dust

The use of electric arc furnace dust (EAFD) in cementitious mixtures is gaining popularity. However, an arguable retardant effect in cement setting is often observed when this dust is used in proportions higher than 3%. This problem is the principle reason why high-volume addition of EAFD is typically hindered in cementitious materials; hence, this study was undertaken to isolate the effect of alkalis addition used as set-accelerant of blended cement pastes with EAFD. Mechanical properties of mortars including 10% and 20% EAFD on cement weight and with increasing alkali contents were investigated. Results indicated that increasing the alkali content was effective on shortening the setting time of blended pastes with EAFD. Final setting time of pastes with 10% and 20% EAFD was less than 6 h, and when the EAFD content was 5%, setting time was almost the same of the cement paste. Results also showed that an increase of alkali content in EAFD mortars resulted in a noticeable increase in compressive and flexural strength at 1 and 3 days, but it led to a reduction at later ages (7 and 28 days)