Microstructural Analysis of Silica Fume Concrete with Scanning Electron Microscopy and X-Ray Diffraction

B Uzbas,A C Aydin

doi:10.48084/etasr.3288

Abstract

The effects of using different ratios of silica fume on the mechanical and microstructural properties of hardened cement paste and concrete were investigated in this study. Portland cement was replaced with 5%, 10%, 15%, and 20% silica fume (SF) by weight. Microstructural properties of obtained samples were investigated by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The XRD analysis showed that the ratio of calcium hydroxide (CH), which is produced by hydration, decreases depending on the concrete age and the amount of silica fume. The SEM analysis showed that the use of silica fume decreases gaps and calcium silicate hydrate (C-S-H) which is also a hydration production. Silica fume content of up to 15% improved the observed mechanical and microstructural properties of concrete. At the optimum value of 15%, improvement in the paste was observed due to the filler effect and the reaction between the silica fume and calcium hydroxide, leading to a reduction in calcium hydroxide in the concrete.

Highlights

Strong pressure has been placed on natural resources due to the rapid economic development and the growth of the global population
Silica fume has been shown to improve the microstructure of cement paste in concrete by densifying the cement paste matrix and the porous paste aggregate interfacial zone
It was observed that the porosity of silica fume concrete decreased as the silica fume content increased up to 15%, after which the porosity increased as the silica fume content increased

Summary

Introduction

Strong pressure has been placed on natural resources due to the rapid economic development and the growth of the global population. From the economic point of view, cement and fine aggregates contribute the bigger portion of cost in the production of concrete, to have them replaced by waste material of similar characteristics has a major economic gain, while being more environmentally friendly [2]. Most of the increase in cement demand will be met by the use of supplementary cementing materials, in order to reduce the green gas emission. Industrial waste, such as blast furnace slag, fly ash, and silica fume are being used as supplementary cement replacement materials and, recently, agricultural waste is being used as pozzolanic material in concrete [3]. Reduction in the permeability of concrete decreases the deterioration caused by several factors such as alkali-aggregate reaction, carbonation, chloride attack, freezing and thawing, sulfate attack, etc. [4]

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Results

Conclusion