Influence of steel slag to granulated blast furnace slag ratio on the chloride binding and penetration of metallurgical slag-based binder

Abstract

The durability of concrete is significantly affected by the chloride solidification property of the binder. This study investigated the chloride-binding capacity and penetration process of metallurgical slag (MS)-based binder and mortar. It also analysed the influence of the ratio of steel slag (SS) to granulated blast furnace slag (GBFS). The results showed that the C–S–H gels and Friedel’s salt (Fs) bound more chloride ions in high- and low-concentration NaCl solutions, respectively. In a 0.1 mol/L NaCl solution, Fs captured 0.01–0.04 mmol/g Cl^–. However, in a 5 mol/L NaCl solution, the chloride bound by the C–S–H gels was 0.07–0.20 mmol/g. In addition, the increase of the SS to GBFS ratio (SGR) promoted the generation of Fs through the activity promoting of GBFS and reduced the Cl content captured by the C–S–H gels by improving calcium ions and their unstable connections with silicate chain oxygen. The increasing SGR decreased the percentage of pores smaller than 10 nm, reaching a minimum of 22.6 % at R3. However, the chloride resistance of R3 also exhibited the highest C_s of 1.01 % and the lowest D_a of 8.54 × 10^–12 m²/s among MS-based mortars due to a 0.10 % decrease in porosity. Furthermore, the chloride-binding capacity and resistance performance of MS-based binders were all better than those of ordinary Portland cement.