Paste backfill of high-sulphide mill tailings using alkali-activated blast furnace slag: Effect of activator nature, concentration and slag properties

CİHANGİR F., ERÇIKDI B., KESİMAL A., DEVECİ H., ERDEMİR F.

MINERALS ENGINEERING, vol.83, pp.117-127, 2015 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 83
  • Publication Date: 2015
  • Doi Number: 10.1016/j.mineng.2015.08.022
  • Journal Name: MINERALS ENGINEERING
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.117-127
  • Keywords: Alkali-activated slag, Activator nature, Activator concentration, Slag composition, Paste backfill, Pozzolanic activity, COMPRESSIVE STRENGTH, PORTLAND-CEMENT, PART II, HYDRATION, ACID, DURABILITY, CHEMISTRY, CONCRETE, DOSAGE, GGBS
  • Karadeniz Technical University Affiliated: Yes

Abstract

The effect of activator type, concentration and slag composition on the strength and stability properties of paste backfill (CPB) of high-sulphide tailings using alkali-activated slag (AAS) as binder (7 wt.%) were investigated in this study. Acidic and neutral (AS-NS) slags were activated with liquid sodium silicate (LSS) and sodium hydroxide (SH) at 6-10 wt.% concentrations. Ordinary Portland cement (OPC) results were used for comparison. The strength development was found to remarkably improve with increasing the concentration from 6 to 8 wt.%. Further increase in concentration did not enhance the strength. SH was determined to produce higher early-age strength whilst LSS produced higher long-term strengths as an indication of slag selectivity for activators. More extensive gypsum formation was observed at lower concentrations in SEM/EDS studies. An increase in Na2O concentration raised the activator consumption. High concentrations also led to poorly crystallized C-S-H gel, loose structure and drying shrinkage cracks especially in NS-SH samples. A reduction in total porosity up to 20% was obtained in AAS samples compared to OPC. Amorphous structure, chemical modulus ratio and/or basicity index (BI) values were seen to control the pozzolanic reactivity, and therefore, the alkali-activation and hardening process. (C) 2015 Elsevier Ltd. All rights reserved.