Flexural response of reinforced concrete beams with full and partial depth of steel fiber-reinforced layer at severe conditions

Abstract

The investigation aims at studying the behavior of reinforced concrete (RC) beams under flexure, with varying amount of steel fiber; variation in depth of fiber layer; and extreme environmental conditions. The test beams were exposed to artificial saline environment prepared from 3.5% NaCl solution. A total of three exposure conditions namely normal (NCC– normal casting and normal curing), mild (NSC- normal casting and saline curing) and extreme (NSC- saline casting and saline curing) were taken. In addition to the conventional reinforcement, the steel fibers were provided across full thickness, half tension zone and quarter tension zone thickness of the beam. The chopped steel fibers dose of 0.6% and 0.8% was used for each of the above-mentioned depth. In all a total of 63 beam specimens, corresponding to 21 groups of beams with 3 replications each, were prepared. For all the exposure conditions, the load and deflection values decrease as the depth of fiber layer decreases to bottom half tension zone. With further reduction in fiber layer depth i.e., to bottom quarter tension zone, the first crack load almost remains same. For all the beam specimens, the load carrying capacity and deflection decreases as the level of salinity is increases from mild to extreme exposure. The beam specimen, with 0.6% fiber content provided in the bottom quarter depth of tension zone, exhibits excellent ductility, load carrying capacity and ensuing deflection. About 20% savings in the unit cost is attained for almost same level of structural integrity as obtained when fibers are provided across the full thickness of the beam. The present investigation validates the effectiveness of additional fiber reinforcement provided in the bottom quarter tension zone of the flexural members. An analytical model is suggested for predicting the flexural behavior of reinforced concrete beams with steel fibers under saline exposure conditions. The model is in good agreement with the observed values and the mid span deflection is predicted well.