Masonry Magazine April 1997 Page. 38
Mortar Handling
• Always pre-wet mortar containers before filling with fresh mortar.
• Control mortar temperatures (that is, cool materials if needed in hot weather, and heat mortar materials as required in cold weather).
• Mix mortar to keep pace with construction (don't let mortar set in mixer or mortar box for excessive periods of time).
Testing
Requirements for testing of mortar or mortar materials will vary from project to project. The contract documents should indicate who is responsible for retaining testing agencies and what tests are required. Whether or not the mason contractor has any obligation to provide test reports, he should know what mortar tests will be required on the project. Since improper mortar testing and improper interpretation of mortar test reports often result in unwarranted delay of masonry construction, the prudent mason contractor will also know how mortar should be tested and what test results indicate.
Mortar testing should be performed by reliable testing agencies that employ trained, experienced technicians. The agency should be able to provide an accreditation document indicating their conformance to ASTM C 1093, the Standard Practice for Accreditation of Testing Agencies for Unit Masonry. It should also identify the personnel who will conduct the required procedures and list their qualifications. The Cement and Concrete Reference Laboratory (CCRL) of the National Institute of Standards and Technology (NIST) now provides a proficiency sample program for mortar in which participating laboratories can compare their test results on mortar materials distributed by CCRL to those obtained by other laboratories across the country. Testing agencies that are committed to providing reliable mortar test results will participate in these programs.
Testing may be required to qualify mortar materials or for quality control of mortar production at the job site. It is important to distinguish between the two, since the procedures used to qualify mortar materials are different from those used in quality control testing. As previously indicated, ASTM C-270 is typically used for acceptance of mortars. While on most projects, the test reports initially submitted for approval of mortar materials are sufficient, additional tests may be required to verify conformance of materials to specifications during the project. For example, on projects involving multiple shipments of mortar materials over an extended time span, such testing may be required. When mortar is qualified under the property specifications of ASTM C 270, verification of mortar materials' conformance to specifications during construction must be performed in accordance with the procedures outlined in ASTM C 270. Since 28 day compressive strengths are required, coordination in advance between the contractor and the testing laboratory is important to avoid construction delays.
Sometimes field testing of mortar is specified as a quality control measure. ASTM C 780 should be referenced for such test procedures. ASTM C 780 defines procedures for measuring properties of plastic mor-
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38 MASONRY-MARCH/APRIL, 1997