Abstract
Previous studies of alkali-activated slag cement (AASC) using nano-silica have mentioned mostly powdered nano-silica and binder weight replacement methods, which have a rapid decrease in fluidity, a short setting time and a low nano-silica replacement rate (< 5%). In this study, colloidal nano-silica (CNS) was used and the mixing-water weight substitution method was applied. The substitution method was newly applied to improve the dispersibility of nano-silica and to increase the substitution rate. In the experiment, the CNS was replaced by 0, 10, 20, 30, 40, and 50% of the mixing-water weight. As a result, as the substitution rate of CNS increased, the fluidity decreased, and the setting time decreased. High compressive strength values and increased rates were also observed, and the diameter and volume of pores decreased rapidly. In particular, the increase of CNS replacement rate had the greatest effect on decrease of medium capillary pores (50–10 nm) and increase of gel pores (< 10 nm). The new displacement method was able to replace up to 50% of the mixing water. As shown in the experimental results, despite the high substitution rate of 50%, the minimum fluidity of the mixture was secured, and a high-strength and compact matrix could be formed.
Highlights
Many studies on the effect of nano-particles on the properties of cement and concrete have been reported [1,2]
The purpose of this study is to investigate the properties of the new nano-silica substitution method in activated cement (AAC) based on slag experimentally
The mixture was able to secure the minimum fluidity and working time required for compaction and molding
Summary
Many studies on the effect of nano-particles on the properties of cement and concrete have been reported [1,2]. Studies using nano-particles in the OPC base have shown improved mechanical properties and durability [6,7,8]. The research results of nano-particles based on OPC have pointed to a drastic decrease in fluidity as a major disadvantage [12,13]. The reason for the abrupt decrease in fluidity is the lack of mixing-water due to the surface area of high nano-particles [14,15]. This sudden drop in fluidity limits the use of nano-particles and limits the scope of nano-particle and OPC research
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