Concrete Structure Inspection

In accordance with EN 206 and EN 13670, the concrete must conform to the strength class specified in the structural design. NTC 2018 (Chapter 4.1 and Chapter 11.2) defines the permitted strength classes and site acceptance procedures. Transport documents (DDT) must indicate the exposure class (UNI EN 206), maximum water/cement ratio and consistency class.

1. Check transport documents (DDT) for each concrete load, verifying strength class (e.g. C25/30), exposure class and consistency class

2. Compare DDT data against structural design specifications and materials report

3. Verify that cube or cylinder specimens are taken in accordance with UNI EN 12390-2 and at the frequency required by NTC 2018 (Chapter 11.2.5)

4. Check compressive strength test results (UNI EN 12390-3) and verify compliance with NTC 2018 acceptance criteria

5. Carry out in-situ tests with rebound hammer (UNI EN 12504-2) or core sampling (UNI EN 12504-1) if required by the Works Director

- Missing or incomplete DDT preventing concrete traceability

- Unauthorised water addition on site altering the water/cement ratio

- Specimens not taken at the frequency required by NTC 2018

- Concrete supplied with consistency class different from specification

- Strength results below the characteristic values required by design

In accordance with EN 1992-1-1 (Eurocode 2, Section 4) and NTC 2018 (Chapter 4.1.6), reinforcement must be placed in accordance with execution drawings, with cover appropriate to the exposure class. EN 13670 specifies placement tolerances. Nominal cover must include the tolerance margin (cnom = cmin + Dcdev) per UNI EN 1992-1-1 Table 4.1.

1. Verify steel test certificates (qualification per NTC 2018 Chapter 11.3.2) and compliance with design specifications (B450C or B450A)

2. Check bar diameter, spacing and position against approved execution drawings

3. Measure cover with appropriate spacers before casting, verifying compliance with the specified nominal value

4. After casting, verify actual cover with covermeter (UNI EN 12504-4)

5. Check lap lengths (anchorage length) per EN 1992-1-1 Section 8 and permitted lap zones

6. Verify adequate number and positioning of spacers

- Insufficient cover, especially at corners and edges

- Bars displaced or stepped on during casting, not conforming to drawings

- Missing or incorrectly sized spacers

- Bar laps in zones not permitted by design

- Steel without ministerial qualification certificate or with non-conforming properties

In accordance with EN 13670 (Section 5) and NTC 2018, formwork must be designed to withstand casting loads, ensure geometric tolerances and produce surfaces with the required finish. EN 13670 defines tolerance classes (1, 2, 3) and surface finish classes.

1. Verify that formwork is clean, stable and adequately propped before casting

2. Check dimensions and alignment against execution drawings, with tolerances per EN 13670 Table 1

3. Verify formwork joint tightness to prevent grout loss

4. Check release agent application and its compatibility with subsequent finishes

5. After stripping, inspect the concrete surface for honeycombing, blow holes, early cracking or geometric defects

6. Verify stripping times in accordance with designer's instructions and EN 13670 based on maturity

- Deformed formwork causing out-of-plumb or out-of-square structural elements

- Grout loss from joints resulting in honeycombing

- Premature stripping before concrete reaches the required minimum strength

- Surface defects unacceptable for fair-faced concrete

- Insufficient propping causing excessive deformation during casting

In accordance with EN 13670 (Section 8.5) and NTC 2018, concrete must be properly protected and cured after casting to ensure cement hydration and achieve the design strength and durability. Curing method and duration depend on the exposure class (UNI EN 206), cement type and climatic conditions.

1. Verify that the curing plan is defined and compliant with EN 13670 Table 1 for the exposure class

2. Check that concrete surfaces are kept moist or covered immediately after casting (polyethylene sheets, anti-evaporation compounds, continuous wetting)

3. Verify minimum curing duration based on ambient temperature and cement type

4. In freezing conditions (temperature < 5 degrees C), verify thermal protection measures (insulating blankets, heating) per NTC 2018

5. In hot conditions (temperature > 30 degrees C), verify measures against rapid evaporation and plastic shrinkage cracking

6. Record ambient and concrete temperatures during the curing period

- Curing omitted or interrupted prematurely, resulting in shrinkage cracking

- Casting carried out at temperatures below 5 degrees C without adequate thermal protection

- Failure to wet exposed surfaces in hot and windy weather

- Plastic shrinkage cracking in the first hours after casting

- Lack of curing condition documentation in the site diary