What Happens When Concrete Freezes?

Now is the time to protect your concrete from cold weather! Concrete can be placed in cold weather conditions provided adequate precautions are taken to alleviate the negative impacts of low ambient temperatures. Lower temperatures can retard hydration, causing a delay in setting time and strength gain. Additionally, early freezing can result in a permanent reduction of up to 50% in the ultimate strength. All concrete must be protected from freezing until it has reached a minimum strength of 3.5 MPa (500 psi). Moreover, any time temperature differentials are developed between the exterior surface and interior body of a concrete member, there is a risk of thermal shock that can lead to cracking.

Whenever air temperature at the time of concrete placement is below 5°C (40°F) and freezing temperatures within the first 24 hours after placement are expected, the following general issues should be considered: 1) initial concrete temperature as delivered, 2) protection while the concrete is placed, and 3) curing to produce quality concrete. More information on protection and curing for cold weather concreting.

A Timeline of Concrete Innovations

Concrete's versatility, durability, and economy have made it the world's most widely used construction material. PCA’s Concrete Technology newsletter is intended for decision makers associated with design, management, and construction of projects using concrete. Its purpose 30 years ago as Concrete Technology Today is the same today as in its electronic format— to show various ways of using concrete technology to advantage and to avoid potential problems.

Many concrete events have taken place during the past 30 years and Concrete Technology has covered a lot of them. Our online timeline shows our picks of important innovations, projects, and standard developments from 1980 through the end of 2009 with direct links to articles or more information on the topics. Click here for the interactive timeline.

If there are topics you would like discussed in future issues of Concrete Technology, please contact Nathaniel Mohler.

Aggregates Improve Economy and Properties of Concrete

Aggregates are used in concrete for very specific purposes. The use of coarse and fine aggregates provides significant economic benefits for the final cost of concrete in place. Aggregates typically make up about 60% to 75% of the volume of a concrete mixture, and as they are the least expensive of the materials used in concrete, the economic impact is significant. In addition, the use of aggregates provides volume stability to the hardened concrete. More on the use of aggregates in concrete.

Learn more from an educational CD on aggregates.

Q: When should field-cured cylinders be used versus laboratory-cured cylinders?

A: Laboratory-cured cylinders produced in controlled environmental conditions address the quality of the initial concrete mixture and its adequacy for the intended use in any given structure. Field-cured cylinders are produced in environmental conditions intended to mimic the exposure conditions of the concrete in-place to provide a strength relationship with the concrete in the structure. More on when to use each type of cylinder.

Significance of Tests and Properties of Concrete and Concrete-Making Materials (STP169D)

In a very real sense, specifications are the letter of the law. But for the professional that needs to know the how and why behind certain requirements, this encyclopedic reference is the place to turn.

• Ever wonder how much strength a test cylinder will lose from rolling and bumping around in the back of a pickup truck or from being dropped from waist level?
• How about the effect of bearing strips on test cylinders used for splitting tensile strength?
• Which DOT performed the original research for strength determination using maturity?
• How much heat contribution should I expect from each of the four major cement compounds?

With information that can help avoid headaches and avert disasters, this peer-reviewed work is a must have for the cement and concrete professional producing, using, or testing materials in conformance with ASTM specifications. Purchase at the PCA Bookstore.

Find more helpful resources in the PCA Concrete Technology Catalog. Each product in this catalog is linked to the PCA Bookstore for ease in ordering. To download your copy, click here.

Make Your Opinion Count

ACI 301 - Specification for Structural Concrete is now open for public discussion. The draft document and comment form can be accessed at ACI's Web site.

The document will be open for comment from Dec. 1, 2009- Jan. 17, 2010.

Lunch and Learn

The Portland Cement Association is announcing a new webinar series for 2010. These one-hour seminars will take PCA's popular engineering bulletin, Design and Control of Concrete Mixtures (EB001), and present the topics chapter by chapter via distance learning. Registration will be available for each of the 18 chapter topicss, allowing registrants to select which to attend.

Registration is now open for the first 6 webinars in the series. All webinars will be held from 12pm-1pm Central Time.

• Fundamentals of Concrete – January 21


• Portland, Blended, and Other Hydraulic Cements – February 18


• Fly Ash, Slag, Silica Fume, and Natural Pozzolans – March 11


• Mixing Water for Concrete – April 15


• Aggregates for Concrete – May 27


• Admixtures for Concrete – June 17

For a complete schedule click here.

The Transportation Research Board (TRB) 89th Annual Meeting will be held January 11-14, 2010, in Washington, D.C., at the Connecticut Avenue Collection hotels: Marriott Wardman Park, Omni Shoreham, and Hilton Washington. This year’s theme is “Investing in Our Transportation Future – BOLD Ideas to Meet BIG Challenges.”

The 2010 International Builders’ Show will be held at the Las Vegas Convention Center from January 19-22, 2010. Builders can check out many quality products that can simplify coordination, improve energy efficiency and quality, save construction time, and boost their bottom line. PCA will host the Concrete Pavilion for the 22nd consecutive year, located in the North Hall with a theme of sustainability. More than 5,000 square feet of displays and information on forming systems for walls, for floors, decorative concrete systems, pavers, masonry, and manufactured stone, will all be within easy access from the PCA booth.

Get Free Admission to World of Concrete 2010
Exhibits: February 2-5, 2010
Seminars: February 1-5, 2010
Once again, PCA offers free registration and a discount on seminars to the World of Concrete in Las Vegas, Nev. You can save as much as $65 on exhibit hall entry fees and $30 on each course you sign up for.

2010 Concrete Bridge Conference sponsored by the National Concrete Bridge Council will be held from February 24-26, 2010 at the Hyatt Regency in Phoenix, Arizona. The theme for the conference is “Achieving Safe, Smart, and Sustainable Bridges.”

Complete listing of industry conferences.