Investigation on the utilization of spent waterglass foundry sand into Ca (OH)2-activated slag materials considering the coating layer of dried waterglass

Utilization of spent foundry sand (SFS) into concrete as a source of fine aggregates has become a hot topic in recent years. However, researchers rarely concerned the binder of SFS and its effects on the performance of concrete. To this regard, this paper investigated the feasibility of incorporating spent waterglass foundry sand (SwFS) into Ca(OH)(2)-activated slag material (CASM) as a source of fine aggregates towards practical application. Two kinds of SwFS suffered to 100 degrees C and 900 degrees C were prepared to reveal the role of the dried waterglass coating of SwFS on the performance of CASM. Experimental results showed that the soluble properities of SwFS determined its properities and performance in CASM. SwFS suffered to 100 degrees C released SiO32- quickly, causing side reactions with the activator Ca(OH)(2), bringing about quick loss of the flow value and obvious reduction of compressive strength of CASM mortars. On the contrast, SwFS suffered to 900 degrees C release SiO(3)(2-)in slow speeds and can be an auxiliary activator for CASM. In addition, CASM mortars with SwFS suffered to 900 degrees C possessed similar 3d and 7d compressive strengths to that of the blank mixture, and got slight decreases of 8.38% to 18.42% at 28d.