Reinforcing Steel and Embedded Items

Steel Reinforcement and Embedded Items

Module Introduction

This chapter covers steel reinforcement (rebar, welded wire mesh) and embedded items (anchors, bolts, plates, sleeves) installed in concrete. For the Red Seal exam, you must master placement principles, tolerances, laps, applicable Canadian standards, and inspection procedures. This module represents a significant portion of the questions in the "Formwork and Concrete Work" competency block (task 4 of the qualification profile).

1. Roles and Responsibilities of the Construction Craft Worker

The Construction Craft Worker is responsible for the handling, shaping, installation, and inspection of reinforcement and embedded items. You must:

Key competency tested: the ability to distinguish the Construction Craft Worker's responsibilities from those of the engineer or specialized ironworker. The Construction Craft Worker never modifies the design without the engineer's approval.

2. Reinforcement Materials and Properties

2.1 Steel Reinforcing Bars

Reinforcing bars are designated by their grade and size. In Canada, the reference standard is CSA G30.18 (Steel reinforcing bars for concrete). Common grades are:

Standard Sizes (metric designation):

Memory aid: linear mass in kg/m ≈ (diameter in mm ÷ 10)² × 0.785. Example: 20M → (20/10)² × 0.785 = 4 × 0.785 = 3.14 kg/m (actual value 2.355 — note that this rule is approximate and must not be used for exact supply calculations).

2.2 Welded Wire Mesh

Welded wire mesh is manufactured to CSA G30.5 (Welded steel wire mesh for concrete). It is designated by two numbers: the mesh opening size and the wire size. Example: 152 × 152 – MW25 × MW25 means:

Mesh is delivered in sheets (typically 2.4 m × 6 m) or in rolls (for smaller wires).

2.3 Coatings and Treatments

Exam trap: epoxy-coated steel must never be cut or bent after coating without repairing the coating with an approved product. Coating damage must be repaired before placement.

3. Cutting and Bending of Reinforcement

3.1 Equipment and Methods

3.2 Standard Hooks and Bends

Bends are defined in CSA A23.1 (Concrete: constituents and execution of work) and CSA A23.3 (Design of concrete structures). Standard bends:

Development length: the straight portion of the bar beyond the hook must meet CSA A23.3 requirements. For a standard 90° hook, the development length is generally 12d (minimum 150 mm) for bars 10M to 35M.

3.3 Bending Tolerances

4. Placement and Installation of Reinforcement

4.1 Spacing and Laps

Minimum spacing between parallel bars:

Lap splice: the minimum lap length depends on:

Typical values (30 MPa concrete, 15M bars, spacing ≥ 300 mm):

General rule: top bars (those with more than 300 mm of concrete below them) require longer laps because the concrete beneath the bar compacts less effectively.

4.2 Supports and Chairs

Reinforcement supports (chairs, bolsters, spacers) hold bars in the exact position. Common types:

Concrete cover requirements according to CSA A23.1:

Exam trap: cover is measured from the outer surface of the concrete to the outer surface of the reinforcement (not the centre of the bar).

4.3 Placement Tolerances

According to CSA A23.1, reinforcement placement tolerances are:

Critical rule: the cover tolerance is asymmetrical. If the specified cover is 50 mm, the tolerance is +10 mm / -0 mm (never less than 50 mm).

4.4 Ties and Lacing

Bars are tied with tie wire — annealed steel wire, gauge 16 or 18. Tie types:

Requirement: ties must be tight enough to hold bars in place, but not so tight as to deform the steel. Wire ends must be bent inward toward the structure (not toward the formwork) to prevent corrosion points.

5. Embedded Items

5.1 Definition and Types

Embedded items are components installed in the concrete before the pour to allow for subsequent connections or specific functions. Common types:

5.2 Anchor Bolt Installation

Anchor bolts are the most common embedded items. Their installation must comply with:

Typical procedure:

Exam trap: bolts must never be welded to the reinforcement. Welding weakens the steel and creates stress concentrations.

5.3 Anchor Plates

Anchor plates (bearing plates) are fastened to the reinforcement with bolts or welded anchor bars. Requirements:

5.4 Sleeves and Conduits

Sleeves allow for the passage of conduits, pipes, or cables through concrete. Requirements:

5.5 Dowels

Dowels are reinforcing bars that protrude from one concrete pour to provide continuity with the next pour. Requirements:

6. Applicable Standards and Codes

6.1 Primary Canadian Standards

6.2 Canadian Electrical Code, Part I

The Canadian Electrical Code, Part I (CSA C22.1 standard) applies to electrical installations. For embedded items:

Rule 12-108: conduits must be supported at maximum intervals of 1.5 m (rigid metal conduits) or 1 m (PVC conduits).

6.3 National Building Code of Canada (NBC)

The National Building Code of Canada (NBC) references CSA A23.1 and A23.3 for concrete work. Cover and lap requirements are those of CSA A23.1.

7. Practical Site Calculations

7.1 Calculating Total Bar Length

To calculate the total length of a bar with hooks:

Total length = straight length + hook lengths

Example: 15M bar, 3.0 m long, with a 90° hook at each end.

7.2 Calculating the Number of Bars

For a 6.0 m × 4.0 m slab with 15M bars spaced at 300 mm in both directions:

7.3 Calculating Steel Mass

Mass = total length (m) × linear mass (kg/m)

Example: 35 bars of 15M, each 4.0 m long.

7.4 Calculating Laps

For a 40d lap with 20M bars:

Practical rule: the lap length must be increased by 50% if the bar is in the top position (more than 300 mm of concrete below the bar) or if the spacing between bars is less than 150 mm.

8. Inspection and Quality Control

8.1 Pre-Pour Checkpoints

Before authorizing the pour, the Construction Craft Worker must verify:

8.2 Inspection Tolerances

8.3 Testing and Controls

9. Site Safety

9.1 Specific Hazards

9.2 Regulations

The Canada Occupational Health and Safety Regulations (COHSR) apply to federally regulated workplaces. Provincial sites have their own regulations (which you should know for your region, but which are not tested on the interprovincial exam).

10. Pitfalls to Avoid

Here are the most frequent errors on the Red Seal exam on this topic:

11. Summary

Key points to remember for the exam:

12. Self-Assessment Questions

13. Last-Minute Exam Tips

Good luck with your Red Seal exam preparation!