WRDA® 20

Water-Reducing Admixture: ASTM C494 Type A

Product Description

WRDA® 20 is an aqueous solution of modified glucose polymer containing a catalyst which promotes more complete hydration of the portland cement.

WRDA® 20 is manufactured under rigid control to ensure uniform predictable performance. It is supplied as a dark brown, low viscosity liquid and is ready to use as received. WRDA® 20 weighs approximately 1.20 kg/L (10.0 lbs/gal).


WRDA® 20 is a general purpose water-reducing concrete admixture that is recommended for use in a wide variety of applications where concrete with normal setting characteristics is required. It is used in ready mix, job site, and concrete paver plants; for normal and lightweight concrete; in block, precast and prestress work ... wherever concrete is produced.


WRDA® 20 produces a mix with lower water content (typically 5%to 10% reduction) and higher compressive and flexural strengths at all ages than untreated concrete. WRDA® 20 produces plastic concrete that is easier to place and finish, and yields a stronger, less permeable and more durable concrete.


Finishers have stated that the cement paste or mortar in WRDA® 20 admixtured concrete has improved trowelability. Floating or troweling by hand or machine imparts a smooth, close tolerance surface.

Chemical Action

As a dispersing agent, WRDA® 20 lessens the natural interparticle reaction between cement grains in water. The admixture is adsorbed onto the cement particles, where it reduces their tendency to clump together and thereby reduces the amount of water needed to produce a workable mix.

As a cement catalyst, WRDA® 20 initiates a more complete hydration of the cement, beginning immediately after the cement and water come together. WRDA® 20 also adds to the water retention and internal cohesiveness of the mix, reducing bleeding and segregation as it increases workability and placeability.

Addition Rates

WRDA® 20 meets the requirements of ASTM C 494 as a Type A, Water-Reducing Admixture. Excellent results are obtained using an addition rate of 160 mL/100 kg (2.5 fl oz/100 lbs) of cementitious materials. In some cases it may be necessary to modify the addition rate due to variations in cement, aggregate and other jobsite conditions.

Compatibility with Other Admixtures

WRDA® 20 is compatible with all other GCP admixtures. When used in combination with other admixtures, each admixture should be added separately into the mix.

Dispensing Equipment

A complete line of accurate, automatic dispensing equipment is available. WRDA® 20 may be added to the concrete mix on the sand or with the mix water.


WRDA® 20 is available in bulk, delivered by metered tank trucks and 210 L (55 gallon) drums.

Architects’ Specifications

Concrete shall be designed in accordance with Standard Recommended Practice for Selecting Proportions for Concrete, ACI 211.

The water-reducing admixture shall be WRDA® 20 as manufactured by GCP Products, or its equivalent. It shall meet all the requirements of Specification for Chemical Admixtures for Concrete ASTM Designation C 494, as a Type A admixture. Certification of compliance shall be made available on request.

The admixture shall be delivered as a ready-to-use, liquid product and shall require no mixing at the batching plant or jobsite. The admixture shall not contain calcium chloride. It shall be used in strict accordance with manufacturer’s recommendations.

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We hope the information here will be helpful. It is based on data and knowledge considered to be true and accurate, and is offered for consideration, investigation and verification by the user, but we do not warrant the results to be obtained. Please read all statements, recommendations, and suggestions in conjunction with our conditions of sale, which apply to all goods supplied by us. No statement, recommendation, or suggestion is intended for any use that would infringe any patent, copyright, or other third party right.

WRDA is a trademark, which may be registered in the United States and/or other countries, of GCP Applied Technologies Inc. This trademark list has been compiled using available published information as of the publication date and may not accurately reflect current trademark ownership or status.

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This document is only current as of the last updated date stated below and is valid only for use in the United States. It is important that you always refer to the currently available information at the URL below to provide the most current product information at the time of use. Additional literature such as Contractor Manuals, Technical Bulletins, Detail Drawings and detailing recommendations and other relevant documents are also available on www.gcpat.com. Information found on other websites must not be relied upon, as they may not be up-to-date or applicable to the conditions in your location and we do not accept any responsibility for their content. If there are any conflicts or if you need more information, please contact GCP Customer Service.

Last Updated: 2022-05-06