New Resources for AAR Prevention

The best way to avoid deleterious alkali-aggregate reactions (AAR) is to take appropriate precautions before concrete is placed. Reducing the potential for alkali-silica reaction (ASR) requires (1) understanding the ASR mechanism; (2) properly using tests to identify potentially reactive aggregates; and, if needed, (3) taking steps to minimize the potential for expansion and related cracking.

Because different geographic regions have different needs and available materials, PCA has developed an information sheet and a guide specification for concrete subject to alkali-silica reactions. Click here for a guide specification process to determine if potential reactivity exists and to select materials to control ASR.

Diagnosis and Control of Alkali-Aggregate Reactions in Concrete (IS413) This 26-page document provides leading-edge approaches to identify and control alkali-silica reactivity and alkali-carbonate reactivity in concrete.

Guide Specification for Concrete Subject to Alkali-Silica Reactions (IS415) provides the specifier with a variety of methods to control ASR, including tests to determine if aggregates are potentially reactive and methods to demonstrate how pozzolans and blended cements can effectively control ASR. Also available as a PowerPoint® presentation (PT404).

Save 33% when you purchase both publications (XC102). Offer expires 3/31/07.

 

Q: How do you diagnose damage from alkali-silica reaction (ASR) in a concrete structure?

A: The diagnosis of alkali-silica reaction (ASR) requires recognizing a combination of the visual symptoms of ASR, appropriate testing to verify the presence of ASR gel, and deterioration of the concrete in the structure. Typical visual symptoms include unusual expansion of the concrete evidenced by longitudinal cracks, map cracking (random cracking pattern), closed joints, spalled surfaces, displacement of adjacent structural components, popouts, efflorescence, or discoloration (darkened or blotchy areas). If site inspections reveal one or more of these visual symptoms it may be appropriate to sample and test the concrete to verify the presence of ASR gel. In addition, the source of any other deterioration mechanisms should be noted and the structure should be evaluated for soundness. Appropriate testing can be performed using one of the following methods:

• Petrographic Analysis (ASTM C 856 or AASHTO T 299)


• Uranyl-Acetate Treatment (discussed in the Annex to ASTM C 856
  or AASHTO T 299)


• Los Alamos Staining Method (Powers 1999)

More on test methods for ASR.

Click here for more cement and concrete FAQs.

AASHTO and ASTM Take Three Giant Steps toward Harmonizing Standards for Portland Cement

The American Association of State Highway and Transportation Officials' (AASHTO) Subcommittee on Materials and ASTM International’s Committee C01 on Cement recently passed ballot proposals to harmonize three of five significant differences between the provisions of the standard specifications for portland cement, AASHTO M 85, and ASTM C 150. As a result, the 2007 editions of these standards will have consistent provisions for fineness, Type II C₃S content, heat of hydration–related criteria, and use of up to 5% limestone in portland cement. It is anticipated that revised standards will be published in July. More.

Sulfate Resistance of Concrete Using Blended Cements or Supplementary Cementitious Materials (SN2916a)

This literature review discusses the relationship between sulfate resistance and the chemical, physical, and mineralogical composition of SCMs. Models predicting sulfate resistance in fly ash-containing concretes have been cited and discussed. The report also reviews sulfate resistance of concrete that contains SCMs interground and optimized at the cement plant as compared to that mixed at the concrete batch plant.

From the very limited data available on the subject, use of interground SCMs with clinker has shown improved sulfate resistance for concrete, primarily attributed to finer and better particle size distributions that enhances the reactivity and reduces the permeability in concrete. The report also recommends that the optimization of sulfate should be based on 3-day strength instead of 1-day strength as in ASTM C 563. This may require a higher sulfate addition that can potentially improve sulfate resistance, as the porosity of the system would be markedly reduced. Click here for free download (PDF format, 172 KB).

New DVD Shows How Concrete Flatwork Can Be Beautiful and Sustainable

It is no secret that concrete floors and pavements are durable, cost-effective, and easy to maintain. But today, the increasing use of decorative concrete adds beautiful and environmental friendly to the list of benefits.

The Art of Decorative Concrete, a video overview of the rapidly growing field of decorative concrete, is hosted by Bob Harris, the internationally renowned concrete artisan and President of the Decorative Concrete Institute. Harris explores the processes and materials used to generate beautiful textured and colored concrete driveways, patios, walkways and interior floors. Techniques shown and discussed include stamped and stained concrete, microtoppings, polished concrete and exposed aggregate.

Click here for more about white cement and decorative concrete.

No Dusty Books in This Library

If you need information on cement or concrete, a visit to the PCA Library will reap rich rewards. The online catalog, listing more than 25,000 books, reports, journals, and electronic materials, boasts a new, flexible search interface that makes finding information easier than ever. Simple author, title, and subject searches can be performed or advanced searches combining different search fields.

Whether you are looking for published material on ASR, durability, environmental issues, or simply a list of books by a specific author, you are likely to find the sources you need. PCA’s Library has one of the most comprehensive collections of materials on cement and concrete in the world. Plus, this online resource includes more than a thousand full-text documents for you to view or download immediately.

Concrete Pavement Manual Available

Co-authored by CTLGroup, ACPA, PCA, and several other concrete experts, the Integrated Materials and Construction Practices for Concrete Pavement: A State-of-the-Practice Manual (IMCP Manual) is the new, essential resource for the concrete pavement community.

Released by the National Concrete Pavement Technology Center at Iowa State University, the 350-page manual covers the entire spectrum of concrete pavement construction. It provides information on technologies, tests, and new practices to optimize material selection, mix design, and construction practices. The focus is on concrete and concrete ingredients and how concrete performance is affected by the interaction of the material concrete with pavement construction and design. Download a free electronic manual.

Cement Chemistry Conference Comes to Canada
The 12th International Congress on the Chemistry of Cement is scheduled for July 8-13, 2007, in Montreal. This is the first time the Congress has been held in North America since 1960. As the only international conference in this field, the Congress attracts top researchers and industry representatives from around the world.

The theme of the 2007 conference is "Cement Systems: A Knowledge-Based Innovative Approach." The conference is organized by the Cement Association of Canada, the Institute for Research in Construction, and the National Research Council of Canada. Sponsorship opportunities are still available. More information.

PCA and NRMCA Present Pervious Concrete Seminars
PCA and the National Ready Mixed Concrete Association have teamed up with Land Development Today magazine to offer the seminar "Pervious Concrete—A Stormwater Solution." More. The two remaining one-day seminars are scheduled for:

• Seattle, Wash.– March 13


• Kansas City, Mo. – March 15

Concrete Technology Forum: Focus on High Performance Concrete
The 2007 Concrete Technology Forum, will bring researchers and practitioners together to discuss the latest advances, technical knowledge, continuing research, tools and solutions for high performance concrete on May 22-24, 2007 in Dallas, Texas. Forum Web site.

For a complete listing of industry conferences, click here.