Mechanical Properties and Microstructure of Alkali-Activated Soda Residue-Blast Furnace Slag Composite Binder

Zhaoyun Zhang (), Chuang Xie (), Zhaohu Sang and Dejun Li
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Zhaoyun Zhang: School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
Chuang Xie: School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
Zhaohu Sang: Tangshan Sanyou Alkali Chloride Co., Ltd., Tangshan 063000, China
Dejun Li: Tangshan Sanyou Alkali Chloride Co., Ltd., Tangshan 063000, China

Sustainability, 2022, vol. 14, issue 18, 1-17

Abstract: This study prepared an alkali-activated soda residue (SR)-blast furnace slag (BFS) composite binder by adding a large amount of SR to the alkali-activated material system. Considering many factors, such as the Na 2 O content, ratio of SR to BFS and the water-binder ratio, the variation patterns in the new binder’s mechanical properties and its micro-evolution mechanisms were assessed. The results show that the compressive strength first grew and then dropped with the Na 2 O content, with an optimal level at 3.0%. At this level, the strength values of the 3d and 28d samples were 10.5 and 27.8 MPa, respectively, exceeding those in the control group without Na 2 O by 337.5 and 69.5%, respectively. As the Na 2 O admixture increased from 0 to 3%, the fluidity of the mortar decreased from 156 mm to 127 mm due to the high frictional resistance caused by the faster generation of hydration products, and the high water absorption of SR also led to reduced fluidity. The new binder’s hydration process mainly generated C-(A)-S-H gel, ettringite (ET), hydrocalumite (HC), calcium hydroxide (CH), and other crystalline hydrates. A 3% Na 2 O content inhibited the ET growth but significantly promoted the formation of uniformly distributed C-(A)-S-H gel and HC. Crystals grew in the pores or were interspersed in the gel, filling microcracks and significantly increasing the structure density and strength. Excessive Na 2 O (>3%) could promote the generation of non-uniformly distributed gel, producing more macropores in the matrix and reducing its strength. Additionally, the increased SR content was not conducive to C-(A)-S-H gel formation, but significantly promoted ET formation, which would inhibit strength development. This study provides a theoretical basis for replacing cement with this new binder in pavement bricks and other unreinforced products.

Keywords: composite binder; soda residue; blast furnace slag; mechanical properties; microstructure (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2022
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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