SHEAR BEHAVIOR OF STEEL FIBER REINFORCED PRECAST PRESTRESSED CONCRETE BEAMS

Precast industries constantly look for better alternative solutions to reduce the secondary reinforcement to speed up the production process. Addition of fibers in concrete helps in reducing the use of secondary reinforcement. Presence of fiber reinforcement has proven to enhance the ductility and energy dissipation capacity of the concrete under flexure and shear. Shear behavior of concrete members mainly depends on the compressive strength of concrete, shear span to depth ratio (a/d), amount of stirrups, aggregate interlock and dowel action of longitudinal reinforcement. The present study focuses on the shear behavior of steel fiber reinforced PSC beams with different volume fractions i.e., 0.50% and 1.00%. Fiber reinforced prestressed concrete (FRPC) beams were cast using long line method and tested with a shear span to depth ratio of 2.4 to simulate shear dominant behavior. Strain gauges were attached to the strands at loading point and at the center of shear span (a/2) to measure strain variation at different stages such as prestressing, de-tensioning and testing. During experimentation, load-deflection and strand strain was recorded. Test results indicate that the addition of steel fibers improved the shear resistance and ductility of the prestressed concrete beams

Abrasion resistance and compressive strength of unprocessed rice husk ash concrete

This paper investigates the effects of adding natural rice husk ash collected from uncontrolled burning and without previous grinding (NRHA) as cement replacement in concrete. To obtain an adequate particle size, NRHA was mixed with coarse aggregate for a convenient period of time before adding the other components. Compressive strength, water absorption, porosity, and abrasion resistance expressed as weight loss were examined. Test results show that decreasing the particle size through mixing with coarse aggregate improved the compressive strength, reduced the permeability, and increased the abrasion resistance of concrete. By mixing NRHA with aggregate for 8 min, abrasion resistance improved by 10.35 and 23.62% over the control concrete at 28 and 91 days, respectively. Incorporating NRHA in concrete by grinding with coarse aggregate during the mixing process could be suitable for making normal-strength concrete and for applications where abrasion resistance is an important parameter. In addition, using NRHA as a partial replacement cement contributes to the reduction of CO2 emissions due to the production of cement

Implication of pore size distribution parameters on compressive strength, permeability and hydraulic diffusivity of concrete

In this study, compressive strength, permeability and hydraulic diffusivity of three different grades of concrete have been estimated through pore size distribution (PSD) parameters by using mercury intrusion porosimetry (MIP). For this purpose, cubical concrete specimens are crushed and the broken concrete chunks with aggregates are collected from different grade of concrete mixes such as M20, M30 and M40. These concrete specimens are tested at wide range of ages such as 1, 3, 7, 28, 56 and 90 days of curing. From the cumulative intruded volume versus pressure data obtained from MIP experimentation, the experimental pore size distribution parameters such as mean distribution radius (r0.5), dispersion coefficient (d) and permeable porosity (P) are calculated. The estimated PSD parameters are used to estimate the compressive strength, permeability and hydraulic diffusivity through the readily available relationships for compressive strength, permeability and hydraulic diffusivity

Flow behavior and strength for fly ash blended cement paste and mortar

In this study, compressive strength and flow behavior of fly ash incorporated cement paste and mortar were investigated. For this purpose, four water to binder ratios (w/(c + f)) such as 0.25, 0.35, 0.45 and 0.55 with three curing ages and five wide range of fly ash replacement levels (f/c ratio) namely 0, 0.1, 0.2, 0.3 and 0.4 were introduced in the experimental scheme. The workability of the mixture was ensured through Marsh cone and flow table tests for fly ash blended cement paste and mortar, respectively. The test result showed that compressive strength increases with age as expected in all cases and an empirical relationship for compressive strength of blended cement paste and mortar with mix factors such as w/(c + f) ratio, f/c ratio and age is also proposed. The estimated compressive strength versus w/(c + f) ratio curves for different curing ages and f/c ratios resembles the nature of Abrams’ strength versus w/c ratio curves

Estimation of strength, permeability and hydraulic diffusivity of Pozzolana blended concrete through pore size distribution

The compressive strength, permeability and hydraulic diffusivity of Ordinary Portland Cement (OPC) with or without pozzolana blended concrete have been estimated in this investigation by using Mercury Intrusion Porosimetry (MIP). With this in view, concrete cubical specimens were crushed and the broken chunks with aggregates were collected from different mixes such as OPC mix, OPC with silica fume (5%, 10% and 15% of replacements) mix and OPC with slag (10%, 30% and 50% of replacements) mixes. The MIP experimentation was carried out for wide range of curing ages such as 1, 3, 7, 28, 42 and 90 days. The experimental Pore Size Distribution (PSD) parameters such as mean distribution radius (r0.5), dispersion coefficient (d) and permeable porosity (P) for all mixes were calculated by using the Morgan Mercer Flodin (MMF) model. The application of experimental PSD parameters is demonstrated by estimating the com-pressive strength, permeability and hydraulic diffusivity through the readily available corresponding relationships in the literature. It is observed that the lowest r0.5 and high d values are obtained in case of OPC with silica fume mix as com-pared to other mixes owing to its better pore refinement. It is observed that the estimated permeability increases with an increase in w/c ratio and decreases with an increase in curing ages which resembles the trend of Powers’ permeability versus w/c ratio curves.Published versio