Abstract
The micromechanical properties of the steel-fiber-reinforced cementitious composites with different water-binder ratios and silica fume contents were studied by nanoindentation. The elastic modulus, indentation hardness, total input energy, and ratio of the elastic deformation energy to the total input energy were analyzed in the interfacial transition zone (ITZ) and the cement matrix. The results show that with the reduction of water-binder ratio in the range of 0.18–0.24, the elastic modulus, indentation hardness, elastic deformation capacity, and energy dissipation capacity increased in the ITZ and cement matrix, and the increase of the ITZ was greater than that of the matrix, yet the ITZ did not disappear. With the increase of silica fume content in the range of 0–30%, the weak ITZ was gradually strengthened or even disappeared. In terms of obtaining the stronger ITZ, adding silica fume is more effective than reducing the water-binder ratio. When the water-binder ratio was high at 0.24, large silica fume contents (30%) had significant effects on enhancing the micromechanical properties of the ITZ and matrix. At a low water-binder ratio of 0.18, large silica fume contents (30%) enhanced the micromechanical properties of the ITZ while degrading those of the cement matrix.
Highlights
With the development of industry and infrastructure construction, steel-fiber-reinforced cementitious composites, with excellent mechanical properties and durabilities, are gradually becoming one of the most widely used materials in civil engineering [1]
Wang et al [10] studied the mechanical properties of the interfacial transition zone (ITZ) in steel-fiber-reinforced mortar with different water-binder ratios and silica fume contents using nanoindentation and scanning electron microscopy (SEM). e mechanical properties of the steel-fibermatrix interfacial zones were higher than those of the cement matrix in specimens with water-binder ratios of 0.3 and no silica fume but were relatively poor in specimens with waterbinder ratios of 0.5. e results showed that when the ratio of water to binder was 0.3, the properties of the ITZs decreased with the addition of silica fume
Effect of Water-Binder Ratio on Elastic Modulus and Indentation Hardness. e water-binder ratio has a significant influence on the cement hydration degree and density of the cement microstructure, and it is an important factor that affects the elastic modulus and indentation hardness
Summary
With the development of industry and infrastructure construction, steel-fiber-reinforced cementitious composites, with excellent mechanical properties and durabilities, are gradually becoming one of the most widely used materials in civil engineering [1]. A study of the elastic modulus of the steel-fiber-cement matrix interfacial zones in high-performance concrete (HPC) was performed by Sorelli et al [9] using nanoindentation, which showed that the elastic moduli of ITZs with widths of 30–40 μm were higher than those of the cement matrix. Wang et al [10] studied the mechanical properties of the ITZ in steel-fiber-reinforced mortar with different water-binder ratios and silica fume contents using nanoindentation and scanning electron microscopy (SEM). Xu et al [11] performed nanoindentation testing to study the nanomechanical properties of the ITZs in steel-fiber-reinforced cementitious composites with water-binder ratios of 0.35, 0.40, and 0.45. E effects of the water-cement ratios and silica fume contents on the micromechanical properties of the steel-fiber-matrix interfacial zones in the samples were studied using nanoindentation testing. E effects of the water-cement ratios and silica fume contents on the micromechanical properties of the steel-fiber-matrix interfacial zones in the samples were studied using nanoindentation testing. ese results can provide guidance for designing HPC and establishing a multiscale constitutive model
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