Concrete Testing Methods

• Concrete technology employs diverse testing methods for assessing concrete properties and quality at fresh and hardened stages.
• Tests are crucial to ensure concrete meets specifications and performance criteria for its intended use.

Fresh Concrete Tests

• Tests are applied to plastic state concrete.
• Determines workability, consistency and other properties before hardening.

Slump Test

• Gauges consistency and workability of fresh concrete.
• Procedure involves filling a slump cone with concrete, lifting it, and measuring slump as the height difference between the cone and the slumped concrete's highest point.
• High slump indicates high workability; low slump indicates low workability.

Compaction Factor Test

• Determines workability by measuring compaction degree from a standard work amount.
• Concrete is dropped via hopper into a mold and a ratio is calculated: the weight of partially compacted concrete vs fully compacted concrete.
• Higher compaction factor correlates with better workability.

Flow Table Test

• Assesses flow characteristics, especially in self-compacting concrete (SCC).
• Concrete is placed on flow table, which is then jolted to measure the spread.
• Flow is expressed as a percentage increase from the original diameter.

Vee-Bee Consistometer Test

• Measures workability by timing vibration needed to consolidate concrete into a cylinder.
• Concrete in a slump cone inside the apparatus is vibrated until fully consolidated, measuring the time taken.
• Lower time indicates higher workability.

Air Content Test

• Determines the amount of air entrained in fresh concrete.
• Air entrainment improves resistance to freeze-thaw cycles.
• Three main methods exist: pressure, volumetric and gravimetric.
• Pressure method measures air content by pressure change in a sealed container.
• Volumetric method washes air then measures the volume.
• Gravimetric method determines air content from the difference between theoretical and actual density.

Setting Time Test

• Determines transition time from plastic to hardened state.
• Uses penetration resistance methods like Vicat needle or Proctor penetration tests.
• Initial setting time: concrete begins to stiffen.
• Final setting time: concrete reaches specified hardness.

Density Test

• Measures mass per unit volume of fresh concrete.
• Involves weighing a known volume to calculate density.
• Density indicates the concrete’s mix proportions and quality.

Hardened Concrete Tests

• Tests are performed on hardened concrete.
• Assesses strength, durability, and other properties of hardened concrete.

Compressive Strength Test

• Finds maximum compressive stress a concrete specimen can handle prior to failure.
• Compressive load is applied to a cube or cylinder until crushed.
• Compressive strength indicates concrete quality, and informs structural design.

Flexural Strength Test

• Measures concrete's resistance to bending/flexural failure.
• A load is applied to a beam supported at two points.
• The maximum load before cracking is measured.
• Flexural strength is important for pavements, slabs, and elements under bending.

Split Tensile Strength Test

• Determines tensile strength by applying compressive load along a cylinder's diameter.
• Induces tensile stress perpendicular to the load, splitting the specimen vertically.
• Assesses tensile strength, otherwise difficult to measure directly.

Modulus of Elasticity Test

• Measures concrete stiffness/elasticity which is the capacity to deform under stress and return to its original shape once stress is removed.
• Compressive load is applied to a specimen, measuring resulting strain.
• Used for structural analysis/design.

Water Permeability Test

• Assesses resistance to water penetration.
• This indicates durability and resistance to deterioration.
• Water pressure is applied to a specimen, measuring permeation rate.
• Low water permeability indicates high durability.

Chloride Permeability Test

• Determines resistance to chloride ion penetration which is a primary cause of rebar corrosion.
• A specimen is exposed to chloride solution, measuring ion penetration over time.
• Low chloride permeability indicates high corrosion resistance.

Water Absorption Test

• Measures water absorbed when concrete is immersed in water.
• A dried specimen is weighed, immersed for a period, and weighed again.
• Water absorption is the percentage weight increase.

Shrinkage Test

• Determines shrinkage as concrete dries and hardens.
• Measures length change of a specimen over time.
• Shrinkage can cause cracking and other structural issues.

Creep Test

• Measures time-dependent deformation under sustained load.
• Constant load is applied, measuring resulting strain over time.
• Creep may cause long-term deflections and stresses.

Non-Destructive Tests (NDT)

• Assesses properties/condition without damage.
• Useful for evaluating existing structures and quality control during construction.

Ultrasonic Pulse Velocity (UPV) Test

• Measures ultrasonic pulse velocity through concrete, related to density, elasticity, and overall quality.
• Higher velocity indicates better quality.

Rebound Hammer Test (Schmidt Hammer)

• Measures spring-loaded hammer rebound off the surface.
• This is related to surface hardness/compressive strength.
• Rebound number estimates compressive strength.

Ground Penetrating Radar (GPR)

• Uses radar pulses to image the internal structure.
• Reveals rebar, voids, and other features.
• Can locate/assess rebar condition.

Infrared Thermography

• Measures surface temperature to detect defects like delaminations, cracks, and moisture.
• Temperature variations can indicate distress areas.

Core Testing

• Drills core samples for lab testing.
• Tests compressive strength, density, and other properties.
• Destructive, but provides accurate assessment of in-situ concrete properties.

Petrographic Examination

• Microscopic analysis to identify composition, microstructure, and causes of deterioration.
• Used to assess material quality, identify chemical attack, and evaluate repair material effectiveness.