ASTM C1860-19a

4.1 The purpose of the test methods in this standard is to measure the tensile strength or bond strength of portland cement-based plaster to its substrate. The values obtained using the test methods are not purported to be representative of the actual wind load capacity or other structural properties of a specific portland cement-based plaster installation but may be helpful in assessing such load capacities.

4.2 Because the test methods described in this standard are used for evaluation of portland cement-based plaster cured at least 28 days, load results obtained by either test method must be interpreted based on sound engineering practice, applicable building regulations, and codes having jurisdiction. The decision of whether to use the load results directly or to use the load results as modified by an appropriate safety factor to obtain acceptable working loads is left to the discretion of the test specifier. Determination of an appropriate safety factor shall be left to the discretion of the test specifier. Methods to calculate a safety factor and a maximum permitted working load are provided in the Appendix.

4.3 When the test methods contained in this standard are used on test specimens installed on existing structures, the test results shall not be generalized to a larger wall area without sufficient test sampling. Such efforts should be based on engineering experience and judgment of the test specifier.

1.1 These test methods cover procedures for determining the tensile strength of a section of portland cement-based plaster, the bond strength between portland cement-based plaster and a solid plaster base, or the fastener pull-out or lath pull-over strength for portland cement-based plaster bases over framing in either an exterior (stucco) or interior application. The test procedures are destructive in nature within the localized test areas and, after testing is concluded, require appropriate repair of the finish system as well as any underlying materials damaged during testing.

1.2 The test methods are suitable for use on portland cement-based plaster finish systems on both new and existing construction. Test methods shall be conducted a minimum of 28 days after application of the portland cement-based plaster. Mechanical Load Test Method A and Vacuum Chamber Testing shall be used to determine the tensile strength or bond strength of direct-applied portland cement-based plaster and may be useful in evaluating the efficacy of different surface preparation characteristics, bonding agents, or both. Mechanical Load Test Method B and Vacuum Chamber Testing shall be used to determine the tensile strength of portland cement-based plaster installed over mechanically attached lath.

1.3 The test methods are suitable for use in both laboratory and field samples. No correlation shall be made between laboratory and field testing.

1.4 The test methods are not intended to evaluate the performance of the underlying construction or framing members. Test results on a particular building may be variable depending on the specimen location, condition, and installation, and are subject to interpretation by the test specifier.

1.5 The test methods are not intended to evaluate the performance of coatings applied to the surface of the portland cement-based plaster.

1.6 The test methods are not intended to be a pre-construction qualifier to determine if the surfaces are appropriate for application of portland cement plaster. The test methods are intended to be used as a tool to quantitatively evaluate existing portland cement plaster cladding that is suspected of questionable bond or uncertain fastening to the substrate.

1.7 The values stated in inch-pound units are to be regarded as the standard. SI values in parentheses are provided for information only.

1.8 This standard may involve hazardous materials, operations, or equipment. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.9 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.