Characterization of Reinforcing Steel Bars in the Nigerian Construction Industry

Characterization of Reinforcing Steel Bars in the Nigerian Construction Industry

ABSTRACT

This research entitled “Characterization of Reinforcing Steel Bars in The Nigerian Construction Industry” was undertaken to find out the physical and chemical properties of the reinforcing steel bars used in the Nigerian Construction Industry. The study investigated the tensile, bending and chemical composition parameters of the steel bars in relation to their level of conformity with the standards. Samples from 418 pieces of bars from 19 companies were used in the experiment and 1520 test results were obtained. It was found that all the samples tested short of expectations of BS4449:1997 in at least one parameter tested. Eighty five percent (11/13) of the local bars tested did not comply with the characteristic strength provisions while the corresponding ductility figures are satisfactory for eighty five percent (11/13) of the bars. It was further established that the foreign bars, despite complying with the code in characteristic strength, have performed below expectations in ductility implying they can fail without warning. It was also noted that the tested reinforcing steel bars have not reasonably agreed in terms of chemical concentrations and percentage composition. There seems to be a lot of impurities in the samples as evidenced by the uncontrolled presence of sulphur, phosphorus and nitrogen. Although, the Carbon equivalent (C.eqv.) values are within acceptable range, there is a conspicuous absence of some critical elements such as Vanadium and Molybdenum that are supposed to be important determinants of strength and ductility.