Winter Weather: Optimizing the Use of Fly Ash in Concrete

Cold weather and winter conditions can be challenging when concrete contains fly ash. Especially when used at higher levels, fly ash concrete typically has extended setting times and slow strength gain, leading to low early-age strengths and construction delays. In addition, concretes containing fly ash are often reported to be more susceptible to surface scaling when exposed to deicing chemicals than portland cement concrete. It is therefore important to know how to adjust the amount of fly ash to minimize the drawbacks, while maximizing the benefits.

The architect for the Bayview high-rise apartment optimized the amount of fly ash on the basis of the requirements of the concrete specification, the construction schedule and the temperature. He limited the amount of fly ash in slabs on grade placed during winter months to 20%. If adequate curing cannot be provided or if the concrete is exposed to freezing and thawing in the presence of deicer salts, the amount of fly ash should always be less than 25%. More.

Optimizing the Use of Fly Ash in Concrete (IS548)

The optimum amount of fly ash varies not only with the application, but also with composition and proportions of all the materials in the concrete mixture (especially the fly ash), the conditions during placing (especially temperature), construction practices (for example, finishing and curing), and the exposure conditions. This document discusses issues related to using low to very high levels of fly ash in concrete and provides guidance for its use without compromising the construction process or the quality of the finished product. Case studies were selected as examples of some of the more demanding applications of fly ash concrete for ASR mitigation, chloride resistance, and green building. More.

What are the differences between Codes, Standards, and Specifications, and how are they related?

In the U.S. construction industry “Codes” typically refer to model building codes which are requirements for safety and performance of structures. These become legal requirements when adopted by state or local authorities. “Standards” are typically adopted by reference in codes. Standards cover specific details such as test methods, specifications, practices, or design provisions. This allows for simplification of the codes because technical details for defining specific products, such as portland cement, can be discussed in material specifications. “Specifications” are either material or reference specifications.

Thus, Codes, sometimes with local amendments or modifications, become the governing rules by which concrete structures (and other objects) are built. For clarity and conciseness, they refer to standards, including material specifications. More.

Click here for more cement and concrete FAQs.

Holiday Sale on Exploring The Art of Concrete CD

This CD on architectural and decorative concrete provides an extensive compilation of resources describing what it is, how to produce it, where to use it, and the advantages associated with its use. From an extensive technical manual on white cement concrete in three languages—English, Spanish, and French—to a suggested guide specification, brief fact sheets, case studies, and newsletters, these technical and promotional resources are essential references for designers, producers, builders, and other users. Various formats include: PDFs of literature, a PowerPoint presentation, an image library, and links to related organizations that provide expert information on architectural and decorative concrete.
For a limited time, save $15 on this comprehensive resource. Offer expires 1/31/08.
CD028—$20 (Regularly $35)

Click here for more about architectural and decorative concrete.

Concrete Shines as Solar Reflectance Material

Concrete does a very good job of reflecting solar energy. That is the finding from a recent PCA study which measured the solar reflectance of 135 concrete specimens from 45 mixes representing exterior concrete flatwork. In fact, all concretes tested in this study would qualify for LEED® credits for heat island effect reduction.

Solar reflectance index (SRI), a calculated value based on solar reflectance, SR, is one way to determine how much light energy a material reflects: stated another way, comparing SRI or SR of different materials tells which ones absorb less solar radiation. This is useful because darker materials absorb more heat, which is generally considered undesirable for its effect on the environment. This may have an immediate, local effect, like heat gain in urban areas (heat island). More.

Read the complete report describing test procedures, concrete mixes, materials, and other aspects of this study, Solar Reflectance of Concretes for LEED Sustainable Sites Credit: Heat Island Effect (SN2982).

New Digital Brochure Facilitates Registration to World of Concrete

As a cosponsor of the World of Concrete, PCA offers free registration and reduced costs on seminars. The annual concrete-industry trade show is scheduled for January 21-25, 2008, at the Las Vegas Convention Center.

• Click here to register online.
• Click here to download registration form.


• Digital Brochure.

Manufactured Concrete Products Expo
February 7-9, 2008, Denver, Colo.

Pervious Concrete: Hydrological Design and Resources (CD063)
Recently updated, this useful reference tool on pervious concrete is filled with technical and promotional resources. The CD includes an analysis tool on hydrological design, intended to illustrate the behavior of pervious concrete systems in relatively simple situations. Other resources included on the CD are: Pervious Concrete Pavements (EB302) and Hydrologic Design of Pervious Concrete (EB303)

Effects of Substances on Concrete and Guide to Protective Treatment (IS001)
This new edition discusses ways to improve concrete chemical resistance through choice of ingredients, proportions, mixing, construction methods, and curing. It describes strategies for dealing with attack by acids, sulfates and other salts, and corrosion of reinforcing steel and nonferrous metals. The publication gives the effects of nearly 250 substances on concrete, and lists recommended protective treatments.

PCA Archival Literature, Volume 1 (DVD024)
This compilation contains about 700 discontinued PCA documents published between 1915 and 1994. Of particular interest here are the historical editions of PCA’s best-known publication, Design and Control of Concrete Mixtures, starting with the first edition issued in 1925. All publications on this DVD are discontinued literature; however, they are still referenced today in newer publications.

Fibre Reinforced Cementitious Composites (LT306)
The use of fiber reinforced concrete (FRC) has grown steadily during the last 40 years, and extensive work has been done in recent years to optimize its properties. High performance FRC, self-consolidating FRC, pavements and slabs using FRC, are just some of the newer applications that are growing in popularity. The first part of the book addresses the mechanics of fiber reinforced brittle matrices and the implications for cementitious systems. The second part of the book describes the various types of fiber-cement composites, their production, mechanical and physical properties, durability, and applications. Published by Taylor and Francis, 2006.

Concrete: Principles and Practice
February 25-28, 2008

This industry standard has been revised this year to reflect the advances in concrete technology. We've added a new session on troubleshooting and streamlined the traditional curriculum. The result: a fast-paced, 4-day program, developed especially for ready-mix concrete personnel who need fundamental yet practical concrete knowledge. More information and registration.

Click here for a complete listing of Skokie courses for 2008.

• February 11, 2008 - Little Rock, Ark.
• February 18, 2008 - Charlotte, N.C.
• March 17, 2008 - Louisville, Ky.
• March 19, 2008 - Springfield, Mo.
• April 14, 2008 - Hartford, Conn.
• April 21, 2008 - Omaha, Neb.
• April 24, 2008 - Nashville, Tenn.
• May 1, 2008 - Philadelphia, Pa.

Complete listing of industry conferences