EDS Microanalysis of Unhydrated Blast Furnace Slag Grains in Field Concrete with Different Service Life

Abstract

Because the essential quality metrics of blast furnace slag are based on its oxide composition, the determination of chemical compositions of unhydrated slag grains in an aged concrete could be useful for understanding its past performance and in predicting the remaining service life of existing slag-bearing concrete. In this research, the authors explored the feasibility of using standard-based energy-dispersive X-ray spectroscopy (EDS) microanalysis, in tandem with electron imaging, as a tool for quantitative measurement of the chemical composition of blast furnace slag grains in cement/concrete. In the experimental study, seven concrete samples representing various service life durations were collected in the Netherlands. The microanalysis results of the samples revealed that the change in slag chemistry is insignificant for samples B (1985) to F (2006); however, elevated CaO and SiO2 contents are found in slag used for sample G (2015), opposite to that of Al2O3 and MgO. After discussing compositional characterization, the paper discusses favorable microanalysis protocols for acceptable elemental quantification accuracy. It was concluded that quantitative EDS microanalysis is a strong tool to characterize the chemical composition of unhydrated slag used in field concrete, which could potentially contribute to understanding the correlations between composition and long-term performance in slag concrete structures.

Role of the grain size on the hydration characteristics of slag in an aged field concrete

“…At the same time, it was estimated that nearly half of the Al ions enter into the matrix and are incorporated into C-S(A)-H gel phase. (The Mg/Al atomic ratio of raw slag was just a little <1 [21] and all magnesium is fixed into hydrotalcite-like phase with a Mg/Al ratio ≈ 2.0.) Meanwhile, there were still large quantities of calcium and silicon entrapped inside the core, playing a role in the formation of C-S-H gel phase (Fig.…”

Recycling of Aluminosilicate-Based Solid Wastes through Alkali-Activation: Preparation, Characterization, and Challenges

“…The higher the accelerating voltage, the larger the interaction volume [61]. When analyzing the elemental compositions of phases with a small size, e.g., the rim around unhydrated slag grain, a high accelerating voltage can contribute to the formation of a large interaction volume including interference of surrounding phases, leading to the generation of inaccurate information [56].…”

Some Critical Reflections on the SEM-EDS Microanalysis of the Hydrotalcite-like Phase in Slag Cement Paste

“…All microa performed at a working distance of 10 mm. For other instrumentally related the readers can refer to [27]. Hydrates in the rim of the slag were characterize standard-based (quantitative) and standardless (semi-quantitative) mi Because the current research concentrated on the precipitations within the s hydrotalcite-like phase in the particle), only four elements were involved, i.e and Mg.…”

“…Additionally, oxygen was stoichiometrically. As for standardless microanalysis, it relied on the interna provided by the commercial software Pathfinder (Thermo Fisher Scientif detailed introduction to the quantitative microanalysis process, the readers ca to [27]. It is worthwhile to mention here that the results of the std.-based m As for the H 2 O and CO 2 MS curves, the mass loss before 300 • C was mainly due to the evaporation of H 2 O.…”

“…All microanalysis was performed at a working distance of 10 mm. For other instrumentally related parameters, the readers can refer to [27]. Hydrates in the rim of the slag were characterized with both standard-based (quantitative) and standardless (semi-quantitative) microanalysis.…”