TMT steel bars have applications in concrete reinforcement structures like bridges, flyovers, dams, skyscrapers, industries, roads, and tunnels due to their corrosion resistance and strength, especially in coastal areas and earthquake zones. The quality of TMT bars depends on factors like quenching time, temperature control during tempering and quenching, the quality of raw materials used, and bar diameter. Low quality TMT bars have issues like inconsistent carbon content, improper quenching methods, and unspecified temperature control during quenching.