CADD - Concrete Admixtures Testing

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Concrete Admixtures Testing

What are Concrete Admixtures?

Concrete admixtures are substances that are added to concrete during mixing to improve its properties. There are many different types of concrete admixtures, each with its own unique purpose. Some of the most common types of concrete admixtures include:

  • Water reducers: Water reducers are admixtures that reduce the amount of water needed to make concrete. This can improve the strength and durability of concrete.
  • Air-entraining admixtures: Air-entraining admixtures add tiny air bubbles to concrete. This makes concrete more workable and durable, and it also helps to improve its resistance to freezing and thawing.
  • Set retarders: Set retarders slow down the setting time of concrete. This can be helpful in hot weather or when concrete needs to be placed in large pours.
  • Set accelerators: Set accelerators speed up the setting time of concrete. This can be helpful in cold weather or when concrete needs to be placed quickly.
  • Corrosion inhibitors: Corrosion inhibitors help to protect concrete from the harmful effects of water and chemicals.
  • Coloring admixtures: Coloring admixtures add color to concrete. This can be used to create decorative concrete or to match the color of other materials on a project.

Concrete admixtures are a valuable tool for improving the properties of concrete. By selecting the right admixtures for the job, you can create concrete that is stronger, more durable, and more resistant to the elements.

Here are some of the benefits of using concrete admixtures:

  • Improved strength: Concrete admixtures can improve the strength of concrete by up to 25%.
  • Improved durability: Concrete admixtures can improve the durability of concrete by making it more resistant to water, chemicals, and freezing and thawing.
  • Improved workability: Concrete admixtures can improve the workability of concrete by making it easier to place and finish.
  • Reduced cost: Concrete admixtures can reduce the cost of concrete by reducing the amount of cement needed.

What is Concrete Admixtures Testing?

Concrete admixtures testing is the process of evaluating the properties of concrete admixtures to ensure that they meet the required specifications. This is done to ensure that the admixtures will perform as intended when they are used in concrete.

There are many different types of concrete admixtures testing, each designed to measure a different property of the admixture. Some of the most common concrete admixtures tests include:

  • Water reduction efficiency: This test measures the ability of the admixture to reduce the amount of water needed to make concrete.
  • Air entrainment efficiency: This test measures the ability of the admixture to entrain air bubbles in concrete.
  • Set retardation: This test measures the ability of the admixture to slow down the setting time of concrete.
  • Set acceleration: This test measures the ability of the admixture to speed up the setting time of concrete.
  • Corrosion inhibition efficiency: This test measures the ability of the admixture to protect concrete from the harmful effects of water and chemicals.
  • Colorfastness: This test measures the ability of the admixture to retain its color over time.

Concrete admixtures testing is an important part of the quality assurance process for concrete admixtures. By testing admixtures, manufacturers can ensure that their admixtures meet the required specifications and will perform as intended when they are used in concrete.

Here are some of the benefits of concrete admixtures testing:

  • Ensures that admixtures meet the required specifications: Concrete admixtures testing can help to ensure that admixtures meet the required specifications, such as water reduction efficiency, air entrainment efficiency, set retardation, set acceleration, corrosion inhibition efficiency, and colorfastness.
  • Identifies potential problems: Concrete admixtures testing can help to identify potential problems with admixtures, such as manufacturing defects or material flaws.
  • Improves quality: Concrete admixtures testing can help to improve the quality of admixtures by identifying and correcting problems early in the manufacturing process.
  • Reduces costs: Concrete admixtures testing can help to reduce costs by preventing the use of defective admixtures and by improving the quality of admixtures.

In addition to the above, concrete admixtures testing can also be used to:

  • Monitor the condition of admixtures in service
  • Identify areas where admixtures are likely to fail
  • Optimize admixture maintenance schedules
  • Develop new admixture materials and designs

Concrete admixtures testing is a valuable tool for ensuring the quality and safety of concrete admixtures. By testing admixtures, manufacturers can help to prevent defects and failures, and improve the overall performance of admixtures.

Concrete Admixtures Testing Plans

The following is a list of tests that are often included in testing plans for concrete admixtures:

PropertyMaterialASTM / MethodDetails
Standard Admixture SpecificationAdmixture for ConcreteASTM C494 / AASHTO M194

Standard Specification for Chemical Admixtures for Concrete

Standard procedure for evaluating an admixture’s effect on a concrete mix. Six batches are cast in the laboratory. Three with admixture, and three control batches. Properties are compared and evaluated for conformance with the limits set for that specific type of admixture.

Air Entraining Admixture SpecificationAir-Entraining AdmixturesASTM C260 / AASHTO M154

Standard Specification for Air-Entraining Admixtures for Concrete

Standard procedure for evaluating an air-entraining admixture’s effect on a concrete mix. Six batches are cast in the laboratory. Three with admixture, and three control batches. Properties are evaluated for conformance with the limits set for in the specification.

Air Entraining Admixture Test MethodsAir-Entraining AdmixturesASTM C233

Test Method for Air-Entraining Admixtures for Concrete

Describes the materials to be used, and the modifications to the methods listed below, as set forth in ASTM C260/AASHTO M154. Test methods are used to evaluate relative performance between control batches and test batches.

Compressive StrengthConcrete CylindersASTM C39

Compressive Strength of Cylinderical Concrete Specimens

Molded or cored concrete specimens are tested in compression and the strength is reported on a pounds/square inch basis.

Flexural Strength (Modulus of Rupture)Concrete BeamsASTM C78

Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading)

Concrete beams are cast or sawn from hardened specimens. Specimens are placed on the third-point loading appatus with an appropriate span, and are subsequently loaded to failure. The load, fracture location, and specimen dimensions are evaluated to determine the flexural strength (modulus of rupture) is reported on a pounds/square inch basis.

Density (Unit Weight), Yield, Air ContentFresh ConcreteASTM C138

Density (Unit Weight), Yield, and Air Content (Gravimetric) of Concrete

Performed on freshly cast material only. Wet concrete is consolidated in a calibrated unit weight container and weighed to determine the actual unit weight per volume of the material vs the theoretical properties.

Consistency (Slump)Fresh ConcreteASTM C143

Slump of Hydraulic Cement Concrete

Performed on freshly cast material only. Wet concrete is consolidated in a calibrated “slump cone”. The cone is removed, and the consistency (slump) of the material is determined by measuring the change in height of the cone of concrete.

Length ChangeConcrete BeamsASTM C157

Length Change of Hardened Hydraulic-Cement Mortar and Concrete

Mortar or concrete is cast into beams and cured per ASTM C157 procedures. The lengths of the beams are measured, and the beams are allowed to cure in standard conditions (either lime water or laboratory air) for a period of up to 64 weeks. Intermetent readings are taken to determine the length change of the material.

BleedingFresh ConcreteASTM C232

Bleeding of Concrete

Fresh concrete is consolidated in an appropriate container. The sample is kept in standard laboratory conditions, with the bleed water periodically removed per ASTM C232 methods. The total bleed water is expressed as a percent of the net mixing water in the test specimen.

Time of SettingFresh ConcreteASTM C403

Time of Setting of Concrete Mixtures by Penetration Resistance

Performed on freshly cast material only. The coarse material in fresh concrete is removed, with the remaining material collected in an appropriate container. Material is allowed to cure, and is periodically penetrated with a calibrated concrete penetrometer. A curve of penetration resistance over time is used to calculate initial and final setting times of the material.

Freeze Thaw Resistance (Durability Factor)ConcreteASTM C666

Resistance of Concrete Beams to Rapid Freezing and Thawing.

Concrete prisms are exposed to 300 cycles of rapid freezing and thawing. The fundamental transverse frequency is determined at 30 cycle intervals, and this is used to determine the durability factor rating (out of 100).

Infrared Spectrography Analysis (Fourier Transform Infrared Spectroscopy – FTIR)AdmixtureASTM C494 Section 18.1 / ASTM E1252

Infrared Analysis of Admixture for Concrete

Analysis is performed to generate the infrared absorption spectrum, which is then used for qualitative analysis when compared to previous tests run on the same admixture.

Residue ContentAdmixtureASTM C494 Section 18.2 / 18.3

Residue Content by Oven Drying

Admixture is dispersed in an appropriate container and oven dried per the methods described for liquid or non-liquid admixtures. The mass of residue remaining after a standard drying time is the residue content.

Relative Density (Specific Gravity)Liquid AdmixtureASTM C494 Section 18.4

Relative Density (Specific Gravity)

For liquid admixtures, samples are brought to the test temperature and a set of NIST traceable calibrated hydrometers are used to evaluate the specific gravity of the material.

pHLiquid AdmixtureASTM E70

pH of Aqueous Solutions with the Glass Electrode

Calibrated electrodes are used to measure pH.

Chloride ContentAdmixturesBS-EN 480-10

Water-Soluble Chloride Content

Sample is dispersed with chemicals per standard procedures, depending on the specific type of admixture being tested. A titration is then performed using sodium chloride and silver nitrate solutions to determine the chloride content of the admixture.

Concrete Admixtures Testing Standards

Standards and acceptance criteria related to concrete admixtures testing:

More Information on Concrete Admixtures Testing

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