Effect of the activator on the performance of alkali-activated slag mortars with pottery sand as fine aggregate. (10th February 2019)

• Record Type: Journal Article
• Authors: Jiao, Zhenzhen; Wang, Ying; Zheng, Wenzhong; Huang, Wenxuan
• Is Part Of: Construction & building materials. Volume 197(2019)
• Page Start: 83
• Page End: 90
• Publication Date: 2019-02-10
• Subjects: Alkali-activated slag -- Pottery sand -- Sodium carbonate -- Sodium hydroxide -- Mechanical properties -- Microstructure; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2018.11.178
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: A mixture of Na2 CO3 and NaOH was used as alkaline activator for AAS mortars. Properties and microstructural characteristics of AAS mortars were investigated. Characteristics of AAS mortar depend on Na2 CO3 -to-NaOH ratios and Na2 O contents. Na2 CO3 can prolong the setting time and improve compressive strength of AAS mortar. Both Na2 CO3 -to-NaOH ratio and Na2 O content obviously affected drying shrinkage. Abstract: Recently, alkali-activated slag mortars have attracted considerable attention as environmentally friendly materials. The objective of this paper was to explore the influence of an alkaline activator (NaOH or NaOH/Na2 CO3 solutions) on the performance of alkali-activated slag (AAS) mortars with pottery sand as fine aggregate. Five Na2 CO3 -to-NaOH ratios of 0/100, 20/80, 40/60, 60/40, and 80/20, and three Na2 O contents of 4%, 6%, and 8%, were used to prepare AAS mortars. The water-to-slag ratio and slag-to-aggregate ratio were kept constant, at 0.38 and 0.8, respectively. The setting time, fluidity, compressive strength, and drying shrinkage were measured. The reaction hydrates were analyzed using microscopy and elemental analysis, while the pore structures were characterized using mercury intrusion porosimetry. The experimental results showed that both the Na2 CO3 -to-NaOH ratio and Na2 O content had a significant effect on the fresh and hardened properties of AAS mortars. A high Na2 CO3 -to-NaOH ratio and low Na2 O content resulted in AAS mortars with longer initial and final setting times. The higher Na2 CO3 -to-NaOH ratios led to a higher late compressive strength of AAS mortars, where the 6% Na2 O samples showed the best performance with Na2 O contents of 4–8%. In addition, the drying shrinkage behavior of AAS mortars as a function of Na2 CO3 -to-NaOH ratio was dependent on the Na2 O content. Moreover, the compressive strength and drying shrinkage have a direct relationship with the microstructure of AAS mortars.