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July/August 2008
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Concrete Committee at Work on Proposed New Standards for Calcium Nitrite, High-Reactivity Supplementary Cementitious Materials

Two proposed new standards are currently among the activities being pursued by ASTM International Committee C09 on Concrete and Concrete Aggregates.

Testing Calcium Nitrite in Concrete

A proposed new ASTM International standard will be used to ensure that the correct dose of calcium nitrite has been added to act as a corrosion inhibitor for concrete in chloride-containing corrosive environments. The proposed standard, WK17639, Test Method for the Analysis of Water-Soluble Nitrite in Hardened Concrete, is being developed by Subcommittee C09.69 on Miscellaneous Tests.

Calcium nitrite is most often added to concrete in structures built in or around the ocean, as well as structures such as bridges and parking garages that are salted during the winter. “Testing of concrete is often required to ensure that the specified amount of calcium nitrite corrosion inhibitor has been added to the concrete,” says Rachael Barbour, principal scientist, BASF Construction Chemicals, and C09.69 member. “Although there are published methods, notably the North Carolina Department of Transportation method and the Michigan Department of Transportation method for plastic concrete, none are standardized with a formal round-robin to establish precision and bias under defined conditions.”

In addition to departments of transportation, Barbour notes that independent laboratories hired by specifiers and anyone involved in supplying or specifying concrete subject to chloride-induced corrosion will be able to use WK17639.

According to Barbour, there are two commonly used methods of sampling hardened concrete and three commonly used chemical methods of analysis. “These need to be compared and evaluated for their absolute and relative accuracy and precision,” says Barbour. “In particular, the method of sampling the concrete is known to have a strong correlation to both the accuracy and the precision of chemical measurements.“ In addition, different laboratories may have different equipment, so Barbour says that it is important to know how different methods of analysis compare.

Subcommittee C09.69 encourages participation in the development of WK17369. “Once we have the proposed standard written, we will need laboratories willing to participate in a round-robin study to establish precision and bias of the methods,” says Barbour. “Anyone with any interest, whether or not they are involved with laboratory testing, is welcome.”

High-Reactivity Supplementary Cementitious Materials Covered in Proposed Specification

While supplementary cementitious materials have been used successfully in the concrete industry for many years, the applications and benefits of a more recently developed class of the materials, high-reactivity supplementary cementitious materials, are not fully addressed in current standards. Subcommittee C09.24 on Supplementary Cementitious Materials is currently developing a proposed new standard, WK18326, Specification for High-Reactivity Supplementary Cementitious Materials (HRSCMs), to fill this urgent need.

“When approved, WK18326 will allow engineers, ready mix concrete producers and departments of transportation to correctly specify HRSCMs when high performance concrete or mortar is required,” says Zhaozhou Zhang, director, research and laboratory services, Boral Material Technologies Inc. Ultra fine fly ash, silica fume and high grade slag cement are good examples of HRSCMs. The proposed specification will help users select the right materials in mix designs when high strength and good durability are required in projects.

CONTACT

Technical Information:

(WK17639) Rachael Barbour, BASF Construction Materials, Cleveland, Ohio

Phone: 216-839-7238

(WK18326) Zhaozhou Zhang, Boral Material Technologies Inc., San Antonio, Texas

Phone: 210-349-4069, ext. 191

ASTM Staff: W. Scott Orthey

Phone: 610-832-9730