Signs of a good quality TMT bar include a smooth, rust-free surface, a consistent and uniform rib pattern, the presence of ISI/BIS marks, a clear brand name and grade marking, and its ability to bend and re-bend without cracking. A quality bar will also demonstrate high ductility, corrosion resistance, and the ability to return to its original shape. 

Physical & Visual Checks

• Surface:
  A good quality TMT bar has a smooth, uniform, and clean surface, free from rust, cracks, dents, or other defects. 

• Ribs:
  Look for a consistent, uniform, and well-defined rib pattern, which ensures a strong bond with concrete and prevents slippage. 

• Dimensions:
  Ensure the bar's length, diameter, and weight are consistent and match the manufacturer's specifications. 

Tests

• Bend & Re-bend Test:
  A quality TMT bar should be flexible enough to bend to 180 degrees and then return to its original shape without breaking or developing cracks. 

• Scratch Test:
  When a bar is scratched, it should not flake or show signs of rust, indicating proper manufacturing and resistance. 

Markings & Certification

• Brand & Grade Marks:
  Look for clearly embossed brand names and grade markings (e.g., Fe 500D, CRS 550D) on the bar. 

• BIS/ISI Mark:
  The presence of the Bureau of Indian Standards (BIS) or the Indian Standards Institute (ISI) mark ensures the bar meets necessary quality standards. 

• Manufacturer's Certificate:
  Request a certificate guaranteeing the bar's chemical and mechanical properties from the manufacturer. 

Performance Characteristics

• Ductility:
  A quality bar should be highly ductile, meaning it can stretch and deform without breaking, absorbing energy during seismic events. 

• Corrosion Resistance:
  Proper manufacturing processes make high-quality TMT bars resistant to rust and corrosion, ensuring a longer lifespan. 

• Weldability:
  Top-quality bars have excellent weldability, allowing for seamless integration into the structure without compromising its integrity