Reinforced Concrete Structure Inspection

In accordance with EN 206, DIN EN 206-1 and EN 13670, the concrete must conform to the specified strength class (e.g. C25/30, C30/37). Conformity assessment is performed on standardised cube or cylinder specimens tested at 28 days in accordance with EN 12390-3. The delivery note must state the concrete strength class, exposure class and consistency class. In Germany, DIN 1045-3 additionally governs site execution.

1. Check delivery notes — correct strength class (e.g. C25/30) in accordance with the structural design

2. Verify that test cubes/cylinders were produced during concreting in accordance with EN 12390-1

3. Evaluate 28-day test results — mean strength must exceed fck + margin in accordance with EN 206 Table 14

4. Check exposure class for compliance with environmental conditions (XC, XD, XS, XF, XA classes)

5. Verify consistency class (S1-S5 slump or F1-F6 flow) at delivery

- Concrete delivered with incorrect strength class

- Test specimens not taken or improperly cured

- Water addition on site leads to reduction of strength class

- Exposure class does not match actual conditions (e.g. missing XF class for freeze-thaw with de-icing salt exposure)

In accordance with EN 1992-1-1 Section 4.4.1 and DIN EN 1992-1-1/NA, the minimum concrete cover (cnom) depends on the exposure class, structural class and bar diameter. Typical cnom values range from 25 mm (XC1) to 55 mm (XS3). Reinforcement must be placed in accordance with the reinforcement drawings with tolerances per EN 13670 Table 11 and DIN 1045-3.

1. Measure concrete cover with covermeter — must comply with cnom as designed (typically 25-55 mm)

2. Verify bar diameters against reinforcement drawings

3. Check bar spacing in accordance with design — use tape measure between bars

4. Check lap lengths (per EN 1992-1-1 Section 8.7, typically 40-60 bar diameters)

5. Ensure spacers maintain correct cover during concreting

- Insufficient concrete cover leads to corrosion risk

- Incorrect bar diameters or missing reinforcement bars

- Lap lengths too short at critical locations

- Spacers displaced during concreting

In accordance with EN 13670 Section 8 and DIN 1045-3, formwork must be sufficiently rigid to maintain its shape during concreting. Fair-faced concrete classes range from SB1 (basic) to SB4 (special) per the DBV Fair-Faced Concrete Guide. Tolerances for finished elements are given in EN 13670 Table 10 — e.g. columns: plumbness +/-h/300 (min. 15 mm), beams: +/-L/500.

1. Check dimensional accuracy of finished elements in accordance with EN 13670 Table 10

2. Verify plumbness of columns using plumb bob or spirit level — tolerance +/-h/300

3. Inspect surfaces for honeycombing, blow holes or cold joints

4. Assess fair-faced concrete class against specification

5. Ensure formwork tie holes and cast-in items are properly sealed or removed

- Honeycombing due to inadequate compaction or overly stiff concrete mix

- Cold joints due to interrupted concreting

- Formwork deformation under hydrostatic pressure of fresh concrete

- Visible formwork tie holes not properly sealed

In accordance with EN 13670 Section 8.5 and DIN 1045-3, concrete must be cured for a minimum duration depending on ambient temperature and cement type. For CEM I at 15 degrees C, the minimum curing duration is 3 days for exposure class XC1, 7 days for XC2-XC4. Early-age thermal cracking must be controlled in accordance with EN 1992-1-1 Section 7.3 and DIN EN 1992-1-1/NA.

1. Verify curing method (wet curing, curing compound or covering)

2. Ensure curing commenced immediately after finishing (within approximately 1 hour)

3. Check curing duration for compliance with exposure class and ambient temperature

4. In cold weather (<5 degrees C), verify protective measures such as thermal insulation or heating

5. For mass concrete elements, check for early-age thermal cracking

- No curing carried out — rapid surface drying causes shrinkage cracking

- Curing terminated too early

- Concreting in cold weather without frost protection measures (frost damage)

- Thermal cracking in mass concrete pours (>500 mm) without cooling measures