CADD - Concrete Admixtures Testing

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.

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.

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 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 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, 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.

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 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.

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 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.

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 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 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)

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.

pH of Aqueous Solutions with the Glass Electrode

Calibrated electrodes are used to measure pH.

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.