Blended Cements Get New Type Designations

Blended cements are portland-based cements that include supplementary cementitious materials (SCMs), such as ground granulated blast-furnace slag, fly ash or other pozzolans, such as silica fume or metakaolin.

ASTM C 595-06, Standard Specification for Blended Cements, was released in August 2006 and contains important new nomenclature. The specification was simplified with the intent of making it easier to use and to eliminate a problem with producing cements near the boundaries of permitted supplementary cementitious materials. More.

ASTM C 595-06—Summary of changes:

• Types I(PM), I(SM), I(PM)-A, I(SM)-A, and S were eliminated
• New portland-pozzolan cement, Type IP(X), can include between 0% and 40% pozzolans, encompassing old Types IP and I(PM)


• New portland blast-furnace slag cement, Type IS(X), can include between 0% and 95% ground granulated blast furnace slag, encompassing old Types IS, I(SM), and S
• The letter “X” stands for the nominal percentage of the SCM included in the blended cement
  
  

Air-Void Coalescence in Air-Entrained Concrete Mixes

Air-entraining admixtures are used in concrete mixes that will be exposed to freeze-thaw cycles. Entrained air is intended to improve the durability and resistance of hardened concrete to freeze-thaw damage. Air-void coalescence, or air-void clustering, occurs when entrained air voids gather around coarse aggregates within air-entrained concrete. In numerous cases, a significant decrease in compressive strength has been attributed to air-void clustering, and recent work has provided new insight into the potential cause(s) of this phenomenon.

Some of the findings from these projects may be useful in avoiding air-void clustering in the future. Coalescence did not occur in concrete mixes using vinsol resin-based admixtures. A late addition of water to concrete mixes containing non-vinsol resin admixtures often led to air-void clustering and its severity increased when the retempered concrete was mixed for a longer amount of time.

Download the free reports:

An Investigation on the Cause and Effect of Air-Void Coalescence in Air-Entrained Concrete Mixes (SN2624) Mississippi State University

Factor(s) Affecting the Origin of Air-Void Clustering (SN2789) CTLGroup

Cost-Effective Use of Colored Concrete in Flatwork

One way to reduce the cost of materials for colored flatwork finishes is to place the color only at or near the surface. There are two common approaches for doing this: Dry-shake finishes or the two-course method. Both are compatible with stamped finishing techniques.

Colored flatwork has brighter and truer colors when white cement is used as the binder, but does not require colored concrete throughout its full depth. More.

Ask Bob Harris

The master craftsman, concrete artisan, teacher and author will be answering questions on a wide range of decorative concrete topics on Thursday, January 25th from 1-2 pm at the PCA booth #C4113 at the World of Concrete in Las Vegas. More.

Click here for more about white cement and decorative concrete.

We will be placing a 4-foot thick concrete floor in a cooling tower. Can you tell us how much additional curing time will be required due to the thickness?

A: Recommendations for actual curing time for mass concrete applications vary from 7 to 21 days (or more) depending on the reinforcement used, the cement and pozzolan or slag content in the concrete mixture, and the physical dimensions of the structure (dams, locks, etc.). The recommendation for heavily reinforced structures is typically 7 days; for concrete mass structures with portland cement as the sole cementitious material the curing period is typically 14 days; and for portland-pozzolan mixtures, 21 days or more, depending upon the design strength development.

Common recommendations for mass concrete applications also include limiting the maximum internal temperature to 70°C (160°F), and the thermal gradient from the interior to the exterior of the concrete section to 20°C (36°F) (higher limits are possible with low coefficient of thermal expansion aggregates). Additional references.

Click here for more cement and concrete FAQs.

Last Chance to Get Free Admission to World of Concrete

As a co-sponsor, PCA offers free advance registration to the World of Concrete, in Las Vegas, January 23-26, 2007. You can also get a discount on the many seminars starting on January 22.

Don't miss the seminars on Top 10 Myths of Concrete Construction and How Today's Cements Affect Concrete Properties given by PCA's Michelle Wilson.

Stop by PCA booth #C4113 and meet Bob Harris, the master craftsman, concrete artisan, teacher and author. He will be answering questions on a wide range of decorative concrete topics on Thursday, January 25th from 1-2 pm.

Get Free Registration Online
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More Information

For a complete listing of industry conferences, click here.

Deadline for Applications for Fellowship Awards - January 15, 2007

The support provided by the PCA Education Foundation is used to identify and attract outstanding candidates in the field of engineering and the physical sciences and provide them with the necessary support to complete their studies.

Academic faculty are invited annually to submit nominations for outstanding degree candidates in engineering and the physical sciences. The Foundation awards $20,000 fellowship grants to selected candidates.

Applications are being accepted for the 2007 awards. They must be received by January 15, 2007. More.

Design Ideas for Decorative Concrete & Stone (LT301)

Concrete, granite, marble, travertine and various other strains of natural and engineered stone are shown and described in this colorful and inspiring new book. Concrete, which has emerged as an enormously versatile decorative product for both indoor and exterior settings, is covered in the first 57 pages. The rich, colorful, well-annotated photographs provide a truly enticing assortment of ideas for both contractor and homeowner. Published by Creative Homeowner.