Recycle option for metallurgical sludge waste as a partial replacement for natural sand in mortars containing CSA cement to save the environment and natural resources

• Published in: Journal of hazardous materials 2020-11, Vol.398, p.123101-123101, Article 123101
• Main Authors: Alwaeli, Mohamed, Gołaszewski, Jacek, Niesler, Marian, Pizoń, Jan, Gołaszewska, Małgorzata
• Format: Article
• Language: English
• Subjects: Calcium sulphoaluminate cement (CSA); Cement properties; Metallurgical sludge waste; Mortar properties; Sand replacement
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2020.123101

[Display omitted] •Metallurgical sludge waste may be utilized as a partial sand replacement.•Delayed initial setting time and increased water-demand are main issues.•Superplasticizer for better cosistency of mortars with metallurgical sludge waste.•Calcium sulphoaluminate cement efficient for shortening of initial setting time. The utilization of metallurgical sludge waste as a 10–30 % replacement of natural sand has been investigated in this paper for its effect on the initial setting time and hydration heat evolution of cement and the mechanical properties of mortars. The results revealed that the addition of metallurgical sludge waste increased the water demand by up to 30 %, delayed the initial setting time by 3 h for 10 %, to over 25 h for 30 % sand replacement, decreased the hydration heat evolution rate by 30 % for 30 % sand replacement, and negatively affected the mortars’ mechanical properties from 5 to 40 % for 20 % sand replacement, and from 30 to 50 % for 30 % sand replacement. For 10 % of sand replacement compressive strength was similar to the reference mortar. In order to obtain a shorter initial setting time, decrease the shrinkage and accelerate hydration heat evolution, part of the Portland cement (CEM I) was replaced by calcium sulphoaluminate cement (CSA). It was found that this method was effective for 20–30 % of CEM I replacement by 10 % of CSA and 10–30 % of CEM I replacement by 20–30 % of CSA in the case of setting acceleration, and for 10 % replacement in case of hydration heat evolution.