What you need to know about steel rebars

Unfortunately, production process of TMT type of rebars needs special mills with very strict control of quenching and tempering parameters. This increases their cost of production. Many companies still produce rebars without quenching and tempering treatments and market them in many countries. It is not possible to differentiate between TMT and non TMT bars just by looking from naked eye. The users unaware about the quality of such rebars use them in their construction work. As shown in the following figure 2, both TMT and normal bars (non TMT) have ribs and it is not possible for consumers to differentiate between them. It can be differentiated only after looking in to the rim formed on the cross section of rebars. TMT bars develop a circular rim around the cross section but non TMTs do not exhibit such a rim.

How to find out whether the rebars are TMT or non TMT

It is very simple. Cut a small piece of the bar. Grind its cross section area on emery paper to remove scratches. Dip the cross section in acidified solution of alcohol for 30 seconds (98 percent alcohol plus two percent nitric acid). Remove the bar from the solution and let them get dried. If a circular ring appears along the periphery of its cross section, it is TMT bar. The photograph of cross section of TMT bar after testing is shown in the above figure 2.

Part II of this series will describe the “Caribbean vis-?-vis international scenario on use of rebars for reinforcement of concrete structures”