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March/April 2010
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Dry Mortar Mix

The majority of mortar used in construction today is preblended dry mortar designed to meet the requirements of C270, Specification for Mortar for Unit Masonry. However, certain aspects of using preblended dry mortar are not covered by C270. Now, a new standard developed by ASTM International Committee C12 on Mortars and Grouts for Unit Masonry addresses specific issues related to preblended dry mortar.

The standard, C1714/C1714M, Specification for Preblended Dry Mortar Mix for Unit Masonry, is under the jurisdiction of Subcommittee C12.03 on Specifications for Mortars.

According to Jeffrey Thompson, quality control manager, dry mix plant, Mutual-Target, and a member of Committee C12, preblended dry mortar offers the ability to directly compare the test results from mortar mix sampled at the manufacturing facility to mortar mix sampled at the job site.

“The preblended mortar mix is delivered to the job site dry and therefore can be sampled dry and taken back to the lab to be tested alongside mortar sampled from the plant, using the exact same laboratory test methods,” says Thompson. “On the other hand, with mortars batched at the job site, where the sand already contains moisture, the mortar mix is wet as soon as the sand is added, which starts the mortar setting process and therefore requires different test methods.”

There are five main components to C1714:

  • Traceability of mortar mix ingredients;
  • Ingredient blending consistency;
  • Testing frequency;
  • Allowance of additives based on performance; and
  • Dryness of all included ingredients.

In addition, C1714 provides guidance on the use of admixtures that is specific to preblended dry mortar and not included in C270 or C1384, Specification for Admixtures for Masonry Mortars.

“C1714 as published provides a solid foundation for specifying preblended mortar and serves the needs of the industry well,” says Thompson, who also notes that all interested parties are invited to participate in ongoing revisions to the standard and in other standards developing activities of Committee C12.

CONTACT

Technical Information: Jeffrey Thompson, Mutual-Target, Tumwater, Wash.

Phone: 360-705-6508

ASTM Staff: Kevin Shanahan

Phone: 610-832-9737