Influence of Concrete Type and Acidic Environment on the Behaviour of Concrete Filled Steel and FRP Tubes

In this study, the experimental and numerical investigation of concrete filled steel and GFRP (Glass fiber reinforced polymer) tube columns subjected to axial compressive load is investigated. Variables considered in this study are concrete type and curing environment. The parameters such as load carrying capacity, load to weight ratio, ductility index and strength index are determined for columns filled with different types of concrete and exposure conditions. The influence of normal concrete (NC), special concrete (SC) (Fine aggregate is a combination of 60% river sand and 40% ferro chrome slag) and fiber reinforced special concrete (FSC) (Fine aggregate is a combination of 60% river sand and 40% ferro chrome slag and 2% of crimped steel fibers with aspect ratio of 60 is added by weight of cement) on the behaviour of concrete filled steel tube (CFST) and concrete filled GFRP tube columns (CFFT) are studied experimentally and numerically subjected to normal curing (28 days curing) and acidic environment (28 days normal curing and 28 days curing with 5% weight/volume of standard H₂SO₄ solution) for durability studies. In this study 18 concrete cylinders, 6 empty steel tubes, 6 empty GFRP tubes 18 CFST columns and 18 CFFT columns are cast, tested and analyzed. Failure modes, load vs axial deformation and load vs lateral displacement obtained from experimental and numerical studies are compared. In the present study optimum number of GFRP layers required for CFFT columns to get the same axial load carrying capacity as that of CFST columns filled with NC, SC and FSC subjected to normal curing and acidic environment is found. It is noticed that load/weight ratio of CFFT columns is 15% more than the load/weight ratio of CFST columns. The strength index of CFFT columns is observed to be 30% more than the strength index of CFST columns. The ductility index of CFST columns is found to be 6% more than the ductility index of CFFT columns.