10.043 Is Mortar Testing Required?

Q Can you clarify the mortar testing requirements according to the 2006 IBC and 2007 CBC? Some people in my area are still using the old UBC Standard 21-16.

— Special Inspector from Southern California

A 11/08 – Response prepared by William Wahbeh, the responsible engineer at Signet Testing Labortories, Inc. and a registered engineer in California

The UBC Standard 21-16 as referenced in previous CBC’s is no longer applicable in the 2007 CBC. The new code section for structural testing of masonry (1708.1) is adapted from the ACI 530/ASCE 5/TMS 405 reference, which does not require any field mortar testing for quality assurance. The rational of the reference is that mortar is specified based on long standing prescriptive proportioning or property testing performed in a laboratory enviroment that must meet ASTM C270. In either case, material certifications and/or test records should be provided prior to construction to confirm the materials meet the standard and the Special Inspector is responsible for verifying the proper use and proportioning of the material in the field. Per 2007 CBC, Section 2105A.5, essential facilities (schools and hospitals) still require verification testing according to ASTM C1586 for the first three successive days and once every week thereafter for strength requirements only.

11/08 – Response prepared by Jeffry Cannon, the Materials Technical Discipline Leader at Kleinfelder, Inc.

ASTM C1586 specifically states that ASTM C780 should be used to sample and test mortar from project sites (not C270), but goes on to say strength verification of field-sampled mortar should not be performed because strengths of test specimens do not equate to actual strengths of the in-place mortar (Section 5.5).

These conflicts between the CBC and the ASTM stadards that are referenced in the code have not been rectified to date. It is suggested that if field sampled mortar specimens are obtained for strength testing, specimens are fabricated and tested in accordance with C780. Some member firms are adding a statement on their reports of laboratory test results indicating that the strengths of the test specimens may not be indicative of the in-place mortar.

One side note to ASTM C780 is that after initial curing in the field, compression specimens must be cured in moist closets or moist rooms until they are tested. The use of water tanks (curing tanks) is not allowed.