Concrete Performance, Production and Compliance Criteria

A- Standards pertaining to Concrete and Constituents of Concrete

EN 206 provides standards and guidelines for concrete and its constituents used in construction across Europe. Below is a summary of the relevant EN standards that govern the constituents of concrete based on EN 206:2013+A1:2016.

1. Cement

• EN 197-1: Common cements (includes Portland, composite, blast-furnace, and pozzolanic cements)
• EN 197-2: Assessment and verification of consistency of performance for cement
• EN 413-1: Masonry cement
• EN 15167-1: Ground granulated blast-furnace slag (for use with Portland cement)

2. Aggregates

• EN 12620: Aggregates for concrete

Defines requirements for grading, shape, density, and durability.

• EN 13055: Lightweight aggregates
• EN 13242: Aggregates for unbound and hydraulically bound materials for civil engineering

3. Admixtures

• EN 934-2: Concrete admixtures (includes plasticizers, superplasticizers, retarders, and accelerators)
• EN 934-6: Admixtures for shotcrete

4. Water

• EN 1008: Mixing water for concrete

Specifies requirements for water quality, including criteria for water recycled from concrete production processes.

5. Additions (Supplementary Cementitious Materials)

• EN 450-1: Fly ash for concrete (Pozzolanic materials
• EN 13263-1: Silica fume for concrete

Both standards provide chemical and physical requirements, including fineness and reactivity.

Concrete

• EN 206: Concrete – Specification, performance, production, and conformity

This is the primary standard governing concrete production, specifying mix design, mechanical performance, and durability criteria.

Steel Reinforcement

• EN 10080: Steel for the reinforcement of concrete

Covers properties and performance of reinforcement steel used in structural concrete.

These standards ensure the quality, safety, and consistency of concrete used throughout the construction industry.

B- Concrete Classification

Below is a summary of the relevant concrete classification based on EN 206

1. Classification by Weight

Concrete is classified based on density:

• Lightweight Concrete (LWC):

  • Density: 800–2000 kg/m³
  • Uses lightweight aggregates (e.g., expanded clay or pumice).
  • Typically used in precast elements, insulation, or structures requiring low self-weight.

• Normal-weight Concrete (NWC):

  • Density: 2000–2600 kg/m³
  • Uses conventional natural aggregates like gravel or crushed stone.
  • Standard for most structural applications (e.g., buildings, bridges).

• Heavyweight Concrete:

  • Density: > 2600 kg/m³
  • Uses heavy aggregates (e.g., barite, hematite) or metal inclusions.
  • Commonly used in radiation shielding (e.g., nuclear plants).

  2. Classification by Strength

Concrete is classified into strength classes based on compressive strength, typically determined using standard cube or cylinder tests:

• Normal-strength Concrete:

  • Strength class: C12/15 to C50/60 (MPa)High-strength Concrete:

• Strength class: > C50/60

  • Used in demanding structural elements like high-rise buildings or bridges.

3. Classification by Exposure Class (Durability)

Concrete is also categorized by exposure conditions, which determine requirements for resistance to environmental factors:

• XO: No risk of corrosion or attack (e.g., indoor concrete with no moisture).
• XC1 to XC4: Corrosion induced by carbonation (e.g., reinforced concrete exposed to air or moisture).
• XS1 to XS3: Corrosion induced by chlorides (e.g., marine environments).
• XD1 to XD3: Corrosion induced by de-icing salts.
• XF1 to XF4: Freeze-thaw with or without de-icing agents.
• XA1 to XA3: Chemical attack (e.g., from acidic soils or industrial chemicals).

4. Classification by Consistency (Workability)

Workability of fresh concrete is measured using the slump test or flow test and categorized into classes:

• S1 to S5: Slump class (ranging from stiff to highly fluid)
• F1 to F6: Flow class (measuring flow spread for self-compacting concrete)

5. Special Types of Concrete

• Self-compacting Concrete (SCC):

  • Highly fluid, flows under its own weight without vibration.
  • Used in densely reinforced sections and complex formworks.

• High-performance Concrete (HPC):

  • Designed to meet specific properties like high strength, durability, or low permeability.

• Fibre-reinforced Concrete:

  • Contains steel, glass, or polymer fibers to improve toughness and crack resistance.

• Air-entrained Concrete:

  • Contains tiny air bubbles to enhance resistance to freeze-thaw cycles.

• Shotcrete:

  • Concrete sprayed onto surfaces through a nozzle, used in tunnels or repairs.

6. Classification by Production and Delivery Method

• Ready-mixed Concrete:

  • Delivered fresh from a batching plant in transit mixers.

• Site-mixed Concrete:

  • Mixed directly on the construction site.

• Precast Concrete:

  • Cast and cured in a controlled environment, then transported to the site.

These classifications help define the suitability of concrete for various structural, environmental, and aesthetic purposes.

C. Standards Governing Concrete Properties Testing

Testing the properties of concrete is essential to ensure it meets design specifications and performance requirements. Here’s an overview of key concrete properties tests based on EN 206 standards, along with the typical methods used.

1. Fresh Concrete Testing

These tests assess the workability, air content, and other fresh-state properties.

1.1. Workability (Slump Test) – EN 12350-2

• Purpose: Measures the consistency (flow) of concrete.
• Method: A cone is filled with fresh concrete, lifted, and the slump (decrease in height) is measured.
• Result: Classified into slump classes (S1 to S5).

1.2. Flowability (Flow Table Test) – EN 12350-5

• Purpose: Assesses the ability of concrete to flow freely.
• Used for: Self-compacting concrete (SCC).
• Method: Fresh concrete is spread on a flow table, and the diameter of the spread is measured.

1.3. Air Content – EN 12350-7

• Purpose: Measures the amount of air in the concrete mix, essential for freeze-thaw resistance.
• Method: Uses a pressure gauge or volumetric method to determine the air content.

1.4. Temperature and Density – EN 12350-6

• Purpose: Monitors the temperature and density of fresh concrete.
• Method: Samples are taken, and density is measured to confirm mix design compliance.

2. Hardened Concrete Testing

These tests ensure that hardened concrete meets strength, durability, and dimensional stability requirements.

2.1. Compressive Strength – EN 12390-3

• Purpose: Measures the compressive strength of concrete, a critical parameter for structural performance.
• Method: Concrete cubes (150mm) or cylinders (150x300mm) are cured and tested under compression.
• Result: Classified into strength classes (e.g., C30/37).

2.2. Flexural Strength – EN 12390-5

• Purpose: Determines the bending (tensile) strength of concrete.
• Method: A beam of concrete is subjected to a three- or four-point loading test.

2.3. Tensile Splitting Strength – EN 12390-6

• Purpose: Measures the indirect tensile strength to evaluate crack resistance.
• Method: A concrete cylinder is placed horizontally under a compression testing machine.

2.4. Modulus of Elasticity – EN 12390-13

• Purpose: Determines the stiffness (elastic behavior) of concrete.
• Method: A cylindrical specimen is subjected to compressive stress, and strain is measured.

3. Durability Testing

Durability tests help ensure the concrete can withstand environmental conditions.

3.1. Water Absorption – EN 12390-8

• Purpose: Measures the amount of water absorbed, which indicates permeability and porosity.
• Method: Concrete specimens are immersed in water, and the increase in weight is recorded.

3.2. Freeze-Thaw Resistance – EN 12390-9

• Purpose: Tests concrete’s ability to resist cracking and scaling under freeze-thaw cycles.
• Method: Specimens are subjected to repeated cycles of freezing and thawing in water.

3.3. Chloride Penetration Test – EN 12390-11

• Purpose: Assesses resistance to chloride ingress, which can cause steel reinforcement corrosion.
• Method: Concrete samples are exposed to chloride solutions, and penetration depth is measured.

4. Dimensional Stability Testing

These tests focus on shrinkage, creep, and deformation properties over time.

4.1. Drying Shrinkage – EN 1367-4

• Purpose: Measures the reduction in size due to moisture loss.
• Method: Concrete prisms are air-dried, and changes in length are recorded.

4.2. Creep Testing – EN 12390-5 (with modifications)

• Purpose: Evaluates long-term deformation under sustained load.
• Method: Specimens are subjected to a constant load for an extended period, and deformation is measured.

5. Chemical Testing

These tests detect harmful substances that could affect durability or structural integrity.

5.1. Sulfate Attack Resistance – EN 196-2

• Purpose: Assesses concrete’s resistance to sulfate-rich environments.
• Method: Specimens are exposed to sulfate solutions, and changes in strength or mass are recorded.

5.2. Alkali-Silica Reaction (ASR) Testing – ASTM C1260 / EN 12620

• Purpose: Detects the potential for ASR, which can cause expansion and cracking.
• Method: Aggregate samples are tested for reactivity with alkalis present in cement.

These testing methods help ensure that the concrete performs as required for specific applications, environments, and design lifespans.