Combating Concrete Corrosion

Steel used for reinforcement in concrete is usually in a non-corroding passive condition. However, reinforced concrete is often used in severe environments where sea water or de-icing salts are present. The chlorides can move into the concrete, disrupting the passive layer that protects the steel and leading to rusting and pitting.

When reinforced concrete is used in situations where it may be susceptible to corrosion, there are ways to help protect the reinforcement. Providing sufficient concrete cover will guard against corrosion. Also, reducing the permeability of the concrete will help keep the deleterious chlorides away from the passive layer around the steel.

"Corrosion of Embedded Metals" is an overview on the PCA Web site of corrosion that discusses the corrosion mechanisms, the role of chloride ions, carbonation, and dissimilar metals corrosion.

Q: In the design stage for a new high-rise condominium project the architect has suggested the use of aluminum railings for the balconies. I had heard that this material may have some risks in this type of application. Can you provide some guidance on this issue?

A: Aluminum is an amphoteric material, meaning it will react chemically with either an acid or an alkali. When portland cement is hydrating it releases free calcium hydroxide which is a very strong alkali. The pH of a fresh concrete mix can be more than 13. Consequently any material that reacts chemically with an alkali should be carefully considered if it is to be embedded in or placed adjacent to fresh concrete. More.

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Durability Chapter of ACI 318 Building Code Streamlined

For the 2008 edition of the Building Code Requirements for Structural Concrete, ACI Committee 318 has proposed a significant restructuring of the durability chapter. Without changing the current prescriptive requirements, the 2005 version has been modified to include an “exposure class” concept, to improve clarity and flow of the durability provisions. The adoption of such an exposure class approach could represent a first step towards a more performance-based specification in future versions of ACI 318. More.

Comments Invited

The American Concrete Institute announces that ACI Committee 318 plans to publish 318-08, Building Code Requirements for Structural Concrete, in January 2008. As an important part of finalizing revisions to ACI 318-05, ACI invites the public to review and comment on the proposed revisions during a public discussion period. The changes will be available as a download from the ACI website, no later than July 1. All comments received by August 15 will be considered by the committee.

ACI Recognizes Growing Importance of Decorative Concrete

The American Concrete Institute’s Technical Activities Committee (TAC) has established a new decorative concrete committee, ACI 310. Aptly named “Decorative Concrete,” ACI 310 expands on the existing committee structure, which includes ACI 124—Concrete Aesthetics, and ACI 303—Architectural Cast-in-Place Concrete.

Since 1985, Concrete Aesthetics has developed and reported information on the aesthetic, social, and cultural aspects of concrete, whereas Architectural Cast-in-Place Concrete, organized in 1967, has focused on the production of architectural finishes for cast-in-place concrete.

The new committee will meet for the first time at the fall 2007 convention to take place in Puerto Rico. Working in coordination with ACI 301—Specifications for Concrete, the new committee's first task is to provide an outline for the specification of architectural flatwork.

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Effect of Pervious Concrete on Potential Environmental Impacts from Animal Production Facilities (SN2993a)
This study provides information concerning the use of pervious concrete in agricultural settings. Tests were conducted on specimens to determine various hydrologic properties, solid material retention capacity, and the effluent nutrient reduction capacity of the material. The pervious concrete exhibited the potential to provide environmental benefits by reducing nutrients from compost effluent and significantly fecal coliform concentrations after only one week of rainfall simulations.

Comparison of Mortar Leaching Methods (SN2660)
Results of this research suggest that cements containing up to approximately 1,000 mg/kg of lead, cadmium, or chromium do not pose a significant environmental risk for leaching of those elements into ground water or soil. Results also suggest that cement containing less than approximately 500 mg/kg of these elements does not pose a risk when used in drinking water system components.

Fundamentals of Concrete (CD062)
Part of a series of training programs on cement and concrete technology, this CD provides an introduction to the fundamentals of concrete. Topics include: materials used in concrete mixtures, the essentials of quality concrete, and the desired fresh and hardened properties of concrete. Fully narrated, with a quiz included at the end to qualify for CEUs/LUs/PDHs.

Albert Litvin, 1917-2007: Bibliography
An annotated list of the writings of Albert J. Litvin, 1917-2007, engineer with Construction Technology Laboratories, Inc. from 1961-1986. Litvin supervised and conducted important research in shotcrete placement, structural lightweight concrete, architectural concrete methods, heat transfer development, and masonry construction. The list includes conference papers, research reports, and journal articles from 1945-2004. Mr. Litwin passed away in May.

Durability Publication at Half Price

Types and Causes of Concrete Deterioration (IS536)
This practical guide gives a clear and concise overview of each of the types and causes of concrete deterioration, including corrosion of embedded metals, freeze and thawing, chemical attack, alkali-aggregate reactivity, abrasion/erosion, fire/heat, restraint to volume changes, overload and impact, loss of support, and surface defects. Only $6 for a limited time.

PCA Skokie Fall Schedule Announced

• Kiln Process - October 1-4, 2007
• Aggregates and Chemical Admixtures for Use in Concrete - October 1-2, 2007
• Mill Grinding - October 22-24, 2007
• Concrete: Principles & Practices - October 22-25, 2007
• Cement Manufacturing for Process Engineers - November 5-8, 2007
• Troubleshooting: Solutions to Concrete Field Problems - November 5-7, 2007

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."

Pulverized Fuel Guidelines for the Cement Industry and Raw Mix Chemistry
PCA regional programs— September 18-19, 2007 in Bethlehem, Pa.

12th International Congress on the Chemistry of Cements—July 8-13
The premier cement chemistry technology transfer event takes place this year in Montreal. More than 400 presentations and technical posters will be presented on all aspects of cement chemistry. Organized by the Cement Association of Canada and the National Research Council Canada, this event promises to fulfill the tradition of excellence dating back to 1918.

This year’s Congress includes presentations based on two PCA-sponsored research projects on concrete durability: Y. Shimada will present on Ettringite Formation in Heat-Cured Mortars and Its Relationship to Expansion , while L. Graf will present on Effects of Relative Humidity on Expansion and Microstructure of Heat-Cured Mortars.

ACI Field Testing Technician Certification Open Enrollment— Sept. 21
PCA will hold its second of two ACI Concrete Field Testing Technician Grade I Certification examinations at its Skokie, Ill., headquarters. Our qualified and experienced instructors will administer the written and performance evaluations for certifying concrete testing technicians.

Complete listing of industry conferences