TB-0702 — The Use of FORCE 10,000D® for Sulfate Resistance Concrete Technical Bulletin

In areas where soils and ground water have high sulfate contents, or structures in a marine environment, concrete must be designed to resist sulfate attack. Solid sulfate salts do not attack concrete, but when present in solution they can react with hardened cement paste. When sulfates permeate concrete, expansive reactions occur with the cement hydration products: Ca(OH)2 (calcium hydroxide) and calcium aluminate and silicate hydrates. Rapid disintegration of the concrete can result. Three common forms of sulfates are calcium, sodium and magnesium. Calcium sulfate attacks only calcium aluminate hydrate, while sodium sulfate attacks the calcium aluminate hydrate and the Ca(OH)2. Magnesium sulfate attacks the calcium aluminate and silicate hydrates and the Ca(OH)2. Under certain conditions, attack by magnesium sulfate is more severe than by other sulfates. Concrete can be designed for a long service life in an aggressive sulfate environment with the incorporation of silica fume. Silica fume protects against sulfate attack in two ways. First, it decreases concrete permeability, which prevents the ingress of the sulfate solution. Secondly, silica fume chemically binds some of the free Ca(OH)2 in the paste preventing future reaction with sulfates. ACI 234 states that silica fume concrete has good resistance to sodium sulfate attack but does not work as well against magnesium sulfate.

Common preventive measures also include reducing the water/cement ratio to decrease permeability and providing air entrainment to allow room for expansive reaction by-products. The use of Type V cement, which is low in C3A (tricalcium aluminate), as a replacement for a higher C3A Type I cement, greatly increases sulfate resistance. However, the availability of Type V can be a problem. In addition, chloride resistance may be sacrificed when Type V cement is used. C3A chemically binds chloride ions leaving fewer ions available to attack embedded steel. In a concrete produced with Type V cement, less C3A is present to bind chloride ions than in Type I cement, and the potential for corrosion of reinforcing steel is increased. There are several references available showing superior sulfate resistance with the inclusion of silica fume in concrete. Research conducted by Rasheeduzzafar et. al., published in the ACI Materials Journal, March–April 1990, shows that Type I cement used with 20% silica fume provides more sulfate resistance than Type V cement. In these tests, cement paste cubes were immersed in a 5% sodium sulfate solution and tested for compressive strength at various ages over a 300-day period. Strength decreases measured the degree of sulfate attack. The conclusion of the work is that the use of Type I cement with silica fume can offer maximum protection against sulfate attack.

gcpat.com | North America Customer Service: 1 877-4AD-MIX1 (1 877-423-6491)

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.

FORCE 10000D 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.

© Copyright 2018 GCP Applied Technologies Inc. All rights reserved.

GCP Applied Technologies Inc., 62 Whittemore Avenue, Cambridge, MA 02140 USA.

In Canada, 294 Clements Road, West, Ajax, Ontario, Canada L1S 3C6.

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: 2018-11-29