Experimental Research On The Carrying Capacity Of Corroded R.C. Columns

In the design of concrete building little consideration was attached to structural durability in the past, and hence on which huge cost was spent in construction industry. Multiplex and complication of durability bring out huge difficulty to researches. A great many research revealed that reinforcement corrosion is one of the most important factors influencing structural durability. The reduction of effective diameter of reinforcement bars, the loss of bond between steel and concrete and the microcrack of concrete due to the expansion of the bars by the rust products are the principal aspects of the corrosion damage. Currently research on structural durability are amazingly brisk and especially in corrosion-induced reinforced concrete structural durability.Based on the summary of existing researches, this paper present accelerated corrosion experiment and load carrying capacity tests for 13 reinforced concrete columns and got a great deal of data and parameters. The specimens consist of 3 control uncorroded columns and 9 columns subjected to corrosion rate(1%,3%,9%). Works performed in this paper are listed in the following:(1)In this paper external impressed current was used to accelerate corrosion of reinforcing bars in predeterminate corroded columns and the corrosion process was recorded and analysed. The results showed that wet sand content with NaCl applied as the electrolyte is a ideal accelerated method. In this method adequate oxidation of Fe, uniform corrosion along the steel bar and marked pitting corrosion, are similar to real structures and worthy to further study and application.(2)In this paper eccentricity and corrosion rate are two main parameters in consideration and stirrups are also considered little. Carrying capacity tests of columns with different corrosion rate and different eccentricity were performed and after that the tests of concrete cubic strength and mass loss and tensile tests of steel bar were conducted. The tests revealed that the split of the cover concrete due to the corrosion of stirrups is the main factor for the decrease of the carrying capacity of the reinforced concrete compressive columns with little reinforcement corrosion. The decrease of carrying capacity of columns due to the corrosion-induced section loss is over 10% with corrosion rate 2%.With increase of corrosion rate the section reduction of columns are the main factor of decrease of carrying capacity. The carrying capacity had a sudden 30% decrease when corrosion rate reached 6%, due to the corrosion-induced section reduction and loss of bond between reinforcement and concrete.(3)According to corrosion damage state of specimens, the equivalent cross section and corresponding parameters were applied in the calculation of load-bearing capacity, which subsequently a comparison with experimental results of test columns was taken.