Mapping to success: a quick guide to ordering the proper mortar

Masonry Construction, Feb, 2005

Mortar is supposed to be the binding element on a masonry project. But far too often, selecting the proper mortar is a problem between engineers, contractors, and in some cases, producers. The process can become more complicated when it comes to testing on the jobsite.

Fortunately for all parties, there are two key ASTM standards to direct the mortar proportion and production process. Standard Specification of Mortar for Unit Masonry, C 270, provides the guidelines to determine the best mortar for the project. And as construction is about to commence, most job documents call for all parties to follow the specifications outlined in Standard Test Method for Preconstruction and Construction Evaluation of Mortars for Plain and Reinforced Unit Masonry, C 780.

While these two standards are supportive of each other, they serve two distinct purposes. C 270 is used in the planning process, while C 780 provides guidance during construction by providing a baseline value for comparative evaluation of field mortars, and a method for quality assurance.

It has been practically impossible to compare tests results developed using the individual standards. Thus, it is important to remember that test results obtained during construction using procedures outlined in C 780 are not required to meet the minimum compressive values outlined in the property found in C 270.

Casual users are often confused in how to use these standards. To help avoid confusion, Jeff O'Leary, quality control manager for Florida Rock and chairman of the committee monitoring C 780, created this simple decision diagram.

To download the complete ASTM documents, visit www.astm.org.