Mineral wool production waste as an additive for Portland cement

This study aims at investigating the possibility of using dust, collected in air filters during the melting of mineral wool raw materials (mineral wool cupola dust) as an additive for Portland cement. It was found that the investigated dust mainly consists of quartz, periclase, albite, dolomite, and the amorphous phase. The main impurities are halite and sylvite. The investigated additive was additionally milled and prepared as a microfiller. The results showed that the cupola dust additive increases the initial hydration of cement, yet prolongs the dormant period. It was estimated that up to 15 wt% of Portland cement can be replaced by the dust additive without impairing the strength properties of samples after 28 days of hardening. However, after 90 days of hydration, the compressive strength of all samples with the investigated additive is lower than in pure OPC samples. This phenomenon is concerned with the formation of a significant amount of Friedel's salt. The content of chlorides in the raw material was reduced from 4.901 to 0.612 wt% by washing with water, when the water-to-solid ratio was equal to 10. The results of the investigation showed that the washed and ground cupola dust had a positive effect on the compressive strength of the cement samples. When 5, 10, and 15 wt% of prepared dust additive were used, the compressive strength of samples after 28 and 90 days of hydration was greater than that of pure Portland cement sample. The findings suggest that the additionally prepared dust additive leads to the formation of a stable structure of the cement stone, accelerates the calcium silicates hydration, and promotes the formation of gismondine.