Скачать или смотреть How to maintain proper clear cover and spacing between two layer rebar in slab.

Maintaining proper clear cover and spacing between two layers of rebar in a slab is essential to ensure durability, structural integrity, and compliance with design codes. Here's how to do it:


1. Slab Bottom Clear Cover

The clear cover is the distance between the surface of the concrete and the nearest reinforcement bar. This is crucial to protect the reinforcement from corrosion and ensure fire resistance.

Steps to Maintain Clear Cover:

Use Cover Blocks:

Place concrete or plastic cover blocks at regular intervals (600–900 mm apart) beneath the bottom layer of rebar.

The thickness of the cover block should match the specified clear cover in the design (usually 20–50 mm, depending on the exposure conditions and code requirements).

Ensure Uniform Placement:

Ensure the cover blocks are of the same thickness and are firmly placed to prevent displacement during concreting.

Secure Rebars:

Tie the bottom reinforcement to the cover blocks using binding wire to prevent movement during construction.


2. Spacing Between Two Layers of Rebar

Proper spacing ensures effective load distribution, prevents congestion, and allows proper concrete flow during casting.

Steps to Maintain Rebar Spacing:

Use Rebar Spacers or Chairs:

Use spacers, bar supports, or chairs made of steel or plastic to maintain a uniform distance between the top and bottom layers of reinforcement.

The height of the spacer should be equal to the specified spacing between the two layers.

Tie Rebars Firmly:

Use binding wire to tie the intersection points of the rebar layers securely to prevent displacement.

Ensure Proper Alignment:

Check the alignment of rebar using a level or straight edge to ensure it remains within the required spacing tolerances.

Follow Design Drawings:

Refer to the structural drawings for the exact spacing and overlap requirements, and ensure compliance with relevant codes (e.g., IS 456, ACI 318).


3. Quality Checks

Check During Construction:

Inspect the clear cover and rebar spacing before and during concreting.

Use tools like cover meters to verify the clear cover after placing concrete.

Correct Issues Immediately:

Rectify any misalignment or displacement of rebar before pouring concrete.

By adhering to these steps, you can maintain the required slab bottom clear cover and proper spacing between rebar layers, ensuring a durable and well-performing structure.