Concrete Structure Inspection

Per CSA A23.1, concrete must be specified by exposure class and compressive strength. The five exposure classes (C-1, C-2, C-3, C-4, C-XL) define durability requirements including maximum water-to-cemite ratio and minimum air content. Compressive strength is specified at 28 days on standard 150 mm cylinders per CSA A23.2-9C. Delivery tickets must state all mix parameters.

1. Verify delivery tickets state specified compressive strength (e.g., 25 MPa, 30 MPa) matching structural drawings

2. Confirm exposure class on ticket matches design requirements (C-1 for non-exposed, C-XL for severe exposure)

3. Check that test cylinders are cast per CSA A23.2-3C during each pour

4. Review 28-day cylinder break results against specified strength per CSA A23.1 Table 7

5. Verify air content meets CSA A23.1 Table 2 requirements for the exposure class (typically 5-8% for freeze-thaw)

- Concrete delivered with incorrect exposure class for the application

- Test cylinders not cast or improperly stored before testing

- Water added on site reducing strength and increasing water-cement ratio

- Air content outside specified range for freeze-thaw exposure classes

Per CSA A23.3 Clause 7, reinforcing bars must be placed within specified tolerances and with minimum concrete cover per CSA A23.1 Table 17. Cover varies from 20 mm (interior slabs) to 75 mm (concrete cast against soil). Bars must be securely tied and supported on chairs. Lap splice lengths must conform to CSA A23.3 Clause 12.

1. Verify bar sizes, spacing, and placement match structural drawings

2. Measure concrete cover with a cover meter — compare to CSA A23.1 Table 17 minimums

3. Check lap splice lengths per CSA A23.3 Clause 12 requirements

4. Confirm bars are securely tied at intersections and supported on proper chairs

5. Verify that reinforcement is free from loose rust, oil, or other contaminants

- Insufficient concrete cover leading to corrosion in Canadian freeze-thaw conditions

- Lap splices shorter than required or placed at points of maximum stress

- Reinforcement displaced during concrete placement

- Missing or inadequate bar chairs allowing bars to rest on formwork

Per CSA S269.1 (Falsework for Construction Purposes) and CSA A23.1 Clause 7, formwork must be designed to support all dead and live loads during construction. Forms must be tight to prevent mortar leakage, properly braced, and constructed to produce the required shape and dimensions within CSA A23.1 tolerances.

1. Verify formwork is plumb, level, and aligned to design dimensions within CSA A23.1 tolerances

2. Check that shoring and falsework are designed per CSA S269.1 with adequate bearing capacity

3. Confirm form ties are properly spaced and forms are tight against mortar loss

4. Verify re-shoring schedule for multi-storey construction per engineer's requirements

5. Check that form release agents are applied and compatible with subsequent finishes

- Formwork not plumb or level causing dimensional non-compliance

- Inadequate shoring leading to deflection or failure during pour

- Form joints not sealed resulting in mortar leakage and honeycombing

- Premature form stripping before concrete reaches required strength

Per CSA A23.1 Clause 21, concrete must be cured for a minimum of 3 days (normal conditions) to 7 days (mass concrete or severe exposure) to achieve design strength. In cold weather (below 5°C), heated enclosures or insulated blankets must maintain concrete temperature above 10°C per CSA A23.1 Clause 21.3. Hot weather concreting above 27°C requires special precautions per Clause 21.4.

1. Verify curing method is appropriate — water curing, curing compounds, or wet coverings per CSA A23.1

2. Check that cold weather protection maintains concrete temperature above 10°C for the required period

3. Confirm curing duration meets CSA A23.1 minimums (3 days standard, 7 days for severe exposure)

4. Verify hot weather precautions are in place when ambient temperature exceeds 27°C

5. Check that curing compound is applied at the rate specified by the manufacturer

- Premature termination of curing in cold Canadian winters

- Concrete freezing before reaching 3.5 MPa strength threshold

- Inadequate cold weather protection leading to freeze damage

- Surface drying too quickly in summer causing plastic shrinkage cracking

Per CSA A23.1 Clause 19, concrete must be placed within 90 minutes of batching (or less in hot weather). Free-fall drop height must not exceed 1.5 m to prevent segregation. Concrete must be consolidated using internal vibrators per CSA A23.1 Clause 19.3, with vibrator insertions at 450 mm spacing and duration of 5-15 seconds per insertion.

1. Verify concrete is placed within time limits from batching per CSA A23.1 Clause 19

2. Check that free-fall height does not exceed 1.5 m — use tremie or elephant trunk for deeper pours

3. Confirm vibration is systematic with 450 mm spacing between insertions

4. Verify cold joints are avoided by maintaining continuous pour within initial set time

5. Check that concrete is placed in lifts not exceeding 600 mm in height

- Concrete placed beyond time limits causing cold joints or reduced workability

- Excessive free-fall height causing segregation of aggregates

- Inadequate vibration leading to honeycombing and air voids

- Cold joints formed between lifts due to delays during placement

Per CSA A23.1 Table 19, dimensional tolerances for formed concrete range from +/-6 mm for walls to +/-12 mm for footings. Floor flatness must meet specified F-numbers per CSA A23.1. Surface finish classes are defined from rough-formed (Class D) to rubbed finish (Class A). Defects such as honeycombing, bug holes, and form marks must be repaired per CSA A23.1 Clause 23.

1. Check formed surfaces against CSA A23.1 Table 19 tolerances using straightedge and tape measure

2. Measure floor flatness using F-number testing equipment per CSA A23.1 requirements

3. Verify surface finish meets the specified class (A through D) for the element

4. Inspect for honeycombing, cold joints, and excessive bug holes requiring repair

5. Confirm any repairs are completed per approved repair procedures

- Walls or columns out of plumb beyond CSA A23.1 Table 19 tolerances

- Floor surfaces not meeting specified flatness requirements

- Honeycombing at congested reinforcement areas

- Surface defects repaired with inappropriate materials or methods