Corrosion in steel can be detrimental in any steel rebar reinforced concrete as well as in the case of steel fibre reinforced concrete. The process of corrosion occurring in steel fibre incorporated concrete subjected to corrosive environment was systematically evaluated in this study. Concrete specimens were prepared with steel fibre inclusions at 1.5%(volume fraction) of concrete and were added in slag based concrete (containing manufactured sand) and replaced with cement at 20%, 40%, and 60% of total binder. Accelerated corrosion studies were carried out using alternate wetting and drying cycle accompanied with initial stress at 40% and 60% of ultimate stress. Concrete specimens were then immersed in chloride-free water and sodium chloride solution (3.5%) after subjecting to initial stress. The alternate wetting and drying process of different concrete mixes was continued for longer exposure (6 months). Later, the strength degradation during the accelerated corrosion process was then assessed in compressive and flexural tests. Test results indicated that the strength degradation was marginal in the case of steel fibre reinforced concrete containing higher slag content and for the concretes containing corrosion inhibitors. The maximum strength reduction was noticed in the case of plain concrete containing steel fibres and, with the slag addition, a considerable reduction in corrosion potential was noticed. Also, with the increase in slag replacement up to 60%, a significant increase in strength was noticed in flexural test. Experimental test results also showed that the corrosion process in steel fibre reinforced concrete can be controlled with the incorporation of corrosion inhibitors in cementitious system.
The behavior of glued steel fibres in high strength concrete with size reduction properties of concrete has been attempted. Glued steel fibres with both ends hooked having length to diameter ratio of 70 was added at a dosage level of 0.5% to 1.5% by volume fraction. The study was carried out to analyze the effects of fibre addition on the thickness reduction of concrete element. A high strength concrete mixture was designed and various thicknesses of concrete prisms were casted for different volume fraction of steel fibres. The hardened concrete properties were determined based on the mix constituents such as water to binder ratio 0.3 (w/b), superplasticizer dosage, fine to coarse aggregate ratio 0.6 (F/c), and fly ash replacement level at 25% and 50% by weight of binder content. The experimental test results showed that the flexural strength varies with respect to the depth of concrete specimen. It can be observed that the reduction in size up to 10% size containing 25% fly ash with 1.5% steel fibres showed better strength enhancement of 4.70 MPa and 6.69 MPa for 7 days and 28 days, respectively. Also, the addition of steel fibres at higher percentage of fly ash containing 50% showed better improvement in the flexural strength for the size reduction at 5%, when compared to plain concrete beam which exhibited higher stress carrying capacity of 6.08 MPa at 28 days and showed an increase of 7.99%.
Flyash based concrete poses constraint on the early strength gain and resulted in restriction for large scale utilization. The effect of accelerator on the improvement of setting properties is of much concern in recent years. In the present study the effect of calcium nitrate on setting properties of flyash concrete was investigated. Effect of accelerators on compressive, split tensile strength and flexural behavior of various concrete mixes was studied. For this purpose, four different variables of concrete mixes were considered namely F/C ratio (0.4, 0.5, 0.6 and 0.7), w/c ratio (0.3 and 0.4), replacement levels of flyash (5, 10, 15, 20, 25 and 30%), respectively and accelerator dosage (0.5 and 1%). The experimental studies showed that the effect of calcium nitrate on the setting properties was greatly improved due to increased reactivity. Further the results on the experimental investigation carried out in the laboratory on the performance indicated that high strength of concrete (52.1 MPa at 28 days) was obtained for F/C ratio of 0.6 at w/c ratio of 0.3 and an accelerator dosage of 1%. It can be also concluded that 20% of flyash with a w/c of 0.4 the strength gain results improved remarkably. Also, the water absorption test results showed a considerable reduction for the flyash based concrete specimens compared to reference concrete.
Abstract. The potential use of supplementary cementitious materials in plain cement concrete for improving concrete properties has been a growing concern in recent years. In addition, the effective strengthening of the matrix by reinforcements to avoid brittle This provided the motivation as a cement replacement material and brittleness in concrete. The r burnt raw rice husk sintered in a muffle furnace of the rice husk ash provided and thus resulted in high cementing evaluation of the mechanical properties of rice husk ash substituted concrete mixtures containing RHA as a partial cement substitute at 10% and 20% by weight of cement experimental results demons compressive properties compared to plain concrete. tensile and flexural strength concrete with steel fibre added
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