Words: Brian Carney
Over the past 10 years, the masonry industry has experienced a significant level of change by embracing new information and innovations that empower mason contractors to cut costs while increasing safety and productivity. However, the same cannot be said about the material testing industry. When it comes to masonry mortar, whether it’s test methods, material standards, or the interpretation of a test report, improper testing can have a great impact on all contractors.
Sadly, this is not a case of the saying, “if it ain’t broke don’t fix it,” because when these tests are conducted, and the material allegedly fails the field test, the result is often an unfortunate, ongoing setback putting mason contractors in a real pickle. Whether justified or not, this often leads to the shutting down of masonry crews and other trades on the job until the matter is resolved.
How big of a challenge are improper field testing and negative reports? Ask any SPEC MIX® Market Representative, or “Mudslinger,” and they will agree it’s very common. Most of the calls they receive from Masonry Foremen or Superintendents entail a request to help them unravel a failed mortar or grout field test. For some Mudslingers, 3 to 4 times each month they’re on a site working with the contractor’s team to evaluate a field-test report stating: “The masonry mortar did not meet the specified compressive strength.”
Thankfully for the contractor, the 60-plus-person team of SPEC MIX reps are technically trained and skilled at solving these problems. Additionally, they are supported by a state-of-the-art laboratory staffed with engineers who work collectively to resolve the issue to get the job site active. In addition to being a great [human] resource for its customers, the data and documentation available in SPEC MIX’s arsenal assist in proving its mortar and grout consistently meet specifications helping to frequently overturn failed tests. Furthermore, over the past 30 years, Mudslingers continually partnered with mason contractors to educate them on overcoming improperly utilized testing methods and invalid test reports to avoid a project shutdown. If you’re a contractor that hasn’t tapped into the benefits of the SPEC MIX® technical support squad, keep reading and you’ll gain a wealth of knowledge in the realm of field-testing materials and the proactive steps needed to take when a testing agency steps on your job site.
Focusing on masonry mortar, this article intends to help mason contractors by breaking down the fundamental points of ASTM Standards and Test Methods for mortar, as well as the relevant information they need to understand, interpret, and take action if a failed field-test report is received. Getting up to speed and learning how to maneuver through these situations effectively and efficiently will greatly benefit mason contractors and ultimately position masonry as a leading, responsible means of construction.
Let’s get started! It’s important to know and understand there are three specific ASTM Standards and Test Methods that apply to how masonry mortar is selected, produced, and tested.
– ASTM C270, “Standard Specification for Mortar for Unit Masonry”
– ASTM C780, “Standard Test Methods for Preconstruction and Construction Evaluation of Mortars for Plain and Reinforced Unit Masonry
– ASTM C1586, “Standard Guide for the Quality Assurance of Mortars”
A typical field-test scenario: To set the table for mason contractors to realize the time to take and interrupt a potential issue, action, below are the steps of how a failed mortar field-test commonly occurs.
- The project’s masonry mortar specification states the masonry mortar shall be Type M, S, or N based on ASTM C270 compressive strength values.
- The project calls for field-testing the masonry mortar during construction.
- The project starts and the mason contractor makes the specified mortar.
- The field-testing agency field-tests the mortar as commissioned and later reports that the mortar does not meet the compressive strength as specified.
- The field test report goes to an authority for the project.
- The authority sends the report to the mason contractor stating the mortar does not meet the specification and requires the masonry work must cease.
ASTM technical information—A contractor’s best friend: To stand on solid ground and be able to contest a failed test report, there is a specific, technical language that mason contractors need to know and intimately understand. The following three sections of ASTM C270 and C780 directly relate to a field-test report claiming the mortar strengths “do not meet the specified strengths.”
- ASTM C780 Annex A6.1.1: “Strength values for mortars obtained through these (C780) testing procedures are not required, nor expected to meet strength requirements of laboratory Specification C270 mortars or necessarily represent the strength of the mortar in the wall.” (Mandatory Language)
- ASTM C780 Scope 1.4: “The test results obtained under these test methods are not required to meet the minimum compressive strength values by the property specifications in Specification C270.”
- ASTM C270 Specification Limitations 3.3: “Since the compressive strength values resulting from field-testing mortars do not represent the compressive strength of mortar as tested in the laboratory nor that of mortar in the wall, physical properties of field sampled mortar shall not be used to determine compliance to this specification and are not intended as criteria to determine the acceptance or rejection of the mortar.”
Taking action: Typically, any of these three ASTM stipulations will independently or collectively serve as the justification to reply to, if not reverse, a failed field-test report. As stated in #3 above, the reality is that too often the compressive strength values posted in the ASTM C270 Property Specification, such as Type S Mortar achieving 1,800psi or greater at 28 days, are incorrectly applied to an ASTM C780 mortar field test. ASTM does not publish minimum compressive strength requirements for field-prepared and tested mortars. It’s like comparing apples & oranges, ASTM C270 is a specification used to select and approve a mortar type before construction, whereas C780 is a test method used during construction to evaluate the consistency of a mortar throughout the project. So even though the contractor’s use of the claims above shows the test report is irrelevant or invalid, in some cases these three petitions may not function as the “silver bullet” solution accepted by the testing agency.
Subsequently, where does a mason contractor go from here? Take a step back and look at the facts. One, the mortar has been submitted and approved. Two, a subsequent field test has been performed and the mortar strength is in question. Three, it’s known that the verbiage and values (compressive strength) of C270 and test procedures of C780 are completely independent of each other, and do not relate to field-test compressive strength results.
Like a lawyer, the next step in a mason contractor’s line of defense is gathering information and understanding the exact purpose of ASTM C780 and its limitations. Having a working knowledge of this test method provides added ammunition that strengthens a contractor’s position of contention. The following subsections extracted from C780 and C270 are bullets to shoot down a failed mortar field test.
- ASTM C780 Summary of Test Methods 4.2: “The test results permit further verification of preconstruction testing and reflect batch-to-batch variations introduced during mortar production and use at the construction site.”
- ASTM C780 Significance and Use 5.3.6: “Comparison of compressive strength tests (Annex A6) of field-test mortars to preconstruction mortar compression tests, each conducted by this test method, can be used to identify variations in mortar mix constituents and/or proportions.”
- ASTM C270: This Specification does not state anything related to field-testing mortar other than to direct the user to ASTM C780.
This information explicitly pertains to field-testing mortar for preconstruction and construction evaluation of masonry mortars. Because the primary objective of C780 is to monitor the quality control of mortar, yes, a preconstruction mortar test should be done to establish a performance benchmark for comparing ongoing mortar test results, but this is the extent of C780.
Back to the Future: By now it’s clear that to prevent challenges with material testing, the key is knowledge and being prepared. Before starting construction, carefully review project documents and specifications, especially the mortar sections, with your masonry teams. The content may seem repetitive to that of previous projects, but knowing the particulars stated in CSI Section 042000 – Unit Masonry, Mortar Materials is invaluable to determine exactly what mortar type prerequisites are and the specific wording for any field-testing procedures. This is your golden opportunity to proactively correct any invalid requirements that could impact your project’s productivity and profitability.
Once the mortar specification meets your requirements and your mortar submittal package is approved, contact the project authority to review the documents and schedule a pre-construction evaluation of mortar as per ASTM C780 Section 4.1. This might be completely new to them, yet it establishes the perfect foundation and working relationship to avoid future, unnecessary predicaments tied to a failed mortar test.
Peace of mind: Having your mortar field-tested during the job is no reason to break a sweat, especially if you’re using a factory pre-blended mortar such as SPEC MIX®. Included with the product comes a complete submittal package, which includes material certification letters, current test reports, product data sheets, and SDS (Safety Data Sheets). What’s more, the day you start working with your SPEC MIX® representative, rest assured your company and project will have access to as much technical support, laboratory equipment, and expert personnel as needed.
Regardless of whether the mason contractor or the material supplier awarded a project, the best approach is for both organizations to form a partnership and work together from job start to finish. This includes the design community and material testing agencies. When these four teams collaborate, masonry will win every time.