Modern construction relies heavily on TMT (thermomechanically treated) bars, particularly in RCC (reinforced cement concrete) constructions. They offer the tensile strength needed to resist environmental stressors and structural loads. However, if they are not handled, positioned, or used appropriately during construction, even premium TMT bars cannot guarantee structural integrity. Unknowingly, a lot of homeowners, contractors, and builders commit errors that impair RCC constructions’ functionality.
In this article, we highlight some common mistakes to avoid while using TMT bars in RCC work, helping ensure safety, durability, and cost-effectiveness in construction projects.
1. Improper Storage of TMT Bars
One of the first and often overlooked steps is how TMT bars are stored on-site. Leaving them exposed to moisture, rain, or direct contact with the ground can lead to rusting and corrosion, even before construction begins.
Tip:
Store TMT bars in a dry area, elevated off the ground using wooden planks or supports, and cover them with plastic sheets or tarpaulin to protect them from water and dust.
2. Using Rusted or Damaged Bars
Sometimes, rusted TMT bars are still used in construction, especially when left exposed during storage. While surface rust might seem harmless, it can weaken the bond between steel and concrete, ultimately reducing the structure’s strength.
Tip:
Always inspect bars for rust. Minor surface rust can be cleaned, but deeply corroded bars should be avoided. Use only clean and anti rust bars in RCC work.
3. Incorrect Cutting and Bending
TMT bars are designed to withstand stress in a specific orientation. Incorrect cutting or bending, especially using flame torches, can damage the microstructure of the steel and reduce its strength.
Tip:
Use mechanical bending and cutting tools instead of heating methods. Ensure all bends follow the recommended diameters and angles as per IS codes.
4. Not Following Bar Placement Guidelines
Improper placement of TMT bars in slabs, beams, and columns can result in weak zones in the RCC structure. This includes incorrect spacing, alignment, or orientation.
Tip:
Follow structural drawings and design specifications provided by the structural engineer. Use proper chairs, spacers, and stirrups to maintain bar positions during concreting.
5. Inadequate Lapping and Anchorage Lengths
In RCC work, when bars are joined by overlapping (lapping), improper lengths or techniques can cause joint failure under load. Similarly, insufficient anchorage lengths can cause bars to slip from concrete.
Tip:
Maintain minimum lapping lengths as per IS 456 standards (typically 50 times the diameter of the bar). Use proper tying techniques and anchorage hooks as recommended.
6. Ignoring the Use of Stirrups and Ties
Stirrups (closed loops) in beams and columns provide shear strength and hold the main bars in position. Often, stirrups are incorrectly spaced or loosely tied, affecting overall structural performance.
Tip:
Use stirrups of the right diameter, spacing, and shape. Secure them tightly using binding wire to hold the entire rebar cage firmly in place.
7. Poor Binding Wire Usage
Loose or insufficient use of binding wire can cause displacement of TMT bars while pouring concrete. This leads to uneven load distribution and weak bonding between steel and concrete.
Tip:
Ensure all joints and intersections of bars are tightly tied with binding wire. Avoid over-tightening which might damage the bar coating.
8. Skipping Cover Blocks
Cover blocks ensure the right concrete cover over TMT bars, protecting them from environmental exposure and fire. Many sites either skip using cover blocks or use stones or wood pieces instead.
Tip:
Always use concrete or plastic cover blocks of the correct thickness (as per design) to maintain required concrete cover around the bars.
9. Mixing Different Grades of TMT Bars
Using different grades of TMT bars (e.g., Fe 415 and Fe 500) in the same structural element can result in uneven stress distribution and may lead to cracks or failure.
Tip:
Use uniform TMT bar grades throughout a structural member. If changing grades is necessary, consult the structural engineer and adjust design accordingly.
10. Neglecting Supervision and Quality Checks
Even if all materials and designs are perfect, poor workmanship can lead to disastrous consequences. Lack of supervision during bar placement and concreting often results in undetected mistakes.
Tip:
Ensure that all TMT bar work is supervised by experienced engineers or site supervisors. Conduct periodic checks and follow construction codes and safety standards.
Final Thoughts
Using TMT bars in RCC work is not just about sourcing the right material—it’s about using it correctly. Avoiding the common mistakes listed above can make a significant difference in the structural safety, longevity, and overall cost of your project.
