ASTM C780-07a

5.1 During preconstruction and construction evaluations, use of these test methods establishes specific and overall performance characteristics for the mortar system.

5.2 Preconstruction testing of mortars prebatched by weight provides information for the selection of the individual mortar system best suited for the masonry to be constructed. The recommended tests and their significance are as follows:

5.2.1 Consistency determinations by cone penetration allow gaging the water additions for all mortars included in the preconstruction test series. Even if the mortar consistency as measured at the construction site is at a different penetration value than those measured during the preconstruction tests, the cone preparation test serves to standardize water additions for mortars being considered as alternatives before construction. Additional testing of mortar water content-consistency relationships (Annex A4) will allow relating these two factors to batch-to-batch variations at the construction site.

5.2.2 Consistency retention by cone penetration using disturbed or undisturbed mortar samples provides a means of establishing the early-age setting and stiffening characteristics of the mortars. Because laboratory testing is conducted under static climatic conditions, consistency retention test results reflect the relative performance of the mortar systems under test. The same general relationships are expected to hold during testing at the construction project, except as they are influenced by jobsite weather conditions.

5.2.3 Mortar water-content determinations (Annex A4) allow measurement of the water content of the mortar mixture. Mortars prebatched using moist masonry sand may be mathematically analyzed for mortar water content; however, this test, when used for preconstruction evaluation, establishes the effectiveness of the test method and serves as the control or base for tests performed at the construction site.

5.2.4 Mortar aggregate ratio testing provides a method for determining the ratio of aggregate-to-cementitious materials. The sieving operation employed during this test is incapable of separating an individual cementitious material when more than one such material is used, but can accurately establish the aggregate-to-cementitious materials ratio of the mixture.

5.2.5 Mortar air-content testing is useful in establishing the value of this component of the mortar. This test is of particular importance in evaluating mortars that contain air-entraining portland cement, air-entraining lime, masonry cement or any combination thereof.

5.2.6 Compressive strength testing of molded mortar cylinders and cubes allows establishment of the strength developing characteristics of the mortar. The measured strength is dependent upon the mortar water content at the time of set, along with other factors, and reflects the general strength that would be attained by the mortar in the masonry. The measured value shall not, however, be construed as being representative of the actual strength of the mortar in the masonry. Due to specimen shapes—cylinders versus cubes—the strength results between the two different-shaped specimens of identical mortar will vary.

Note 3—When cube and cylinder test specimens from like mixtures are to be compared, the cylinder compressive strength may be considered to be equal to 85 % of the cube compressive strength.

5.2.7 Splitting tensile strength of molded mortar cylinders provides a method for determining the splitting tensile strength developing characteristics of the mortar. The measured strength is dependent upon the mortar water content at the time of set, along with other factors, and reflects the general strength attainable by the mortar in the masonry. The measured value, however, is not representative of the actual strength of the mortar in the masonry.

5.3 Testing during the actual construction may employ one or more of the test methods described in 4.2. Repetitive testing using these test methods on consecutive or intermittent batches provides a method for measurement of batch-to-batch variations in the mortar production. Testing during actual construction may be referenced to laboratory testing and used to predict later age mortar characteristics. In addition to the comments in 5.2, the following test meanings may be obtained from construction project testing:

5.3.1 Consistency by cone penetration is used as a quick reference for indicating batch-to-batch variations in mix ingredients and mixing time. Erratic consistency readings indicate poor control during batching and mixing, but they do not indicate if cement, sand, or water additions are improper. Other test methods must be used to isolate and identify the unsatisfactory proportioning or mixing procedure, for example, cement to aggregate, mortar water, or air content tests.

5.3.2 Consistency retention by cone penetration tests establishes the early-age setting and stiffening characteristics of the mortar. These properties are influenced by mix proportions and ingredients, weather conditions, effects of chemical additives, and mixing time.

5.3.3 Individual and repeated evaluations of mortar water content (Annex A4) show the ability of the mixer operator to properly and consistently add water to the mixer.

5.3.4 Individual and repeated tests for mortar aggregate ratio show the ability of the mixer operator to properly and consistently add the cementitious material and sand to the mixer, and will establish batch-to-batch variations in the composition of the mortar.

5.3.5 Individual and repetitive tests for mortar air content show the changes caused by variations in mixing time, mixing efficiency and other factors.

5.3.6 Compressive strength tests of molded cylinders and cubes stored in accordance with the test method reflect approximate mortar strengths because lower water-cement ratio mortars are found in the wall than are typically measured for mortars from the mixer.

5.3.7 Splitting tensile strengths of molded cylinders stored in accordance with the test method reflect the approximate strength of the masonry mortar because lower water-cement ratio mortars are found in the wall than are typically measured for mortars from the mixer.

1.1 This test method covers procedures for the sampling and testing of mortars for composition and for their plastic and hardened properties, either before or during their actual use in construction.

Note 1—Guide C 1586 provides guidance on evaluating mortar and clarifies the purpose of both this test method and Specification C 270.

Note 2—The testing agency performing this test method should be evaluated in accordance with Practice C 1093.

1.2 Preconstruction Evaluation- This test method permits comparisons of mortars made from different materials under simulated field conditions. It is also used to establish baseline values for comparative evaluation of field mortars.

1.3Construction Evaluation- Use of this method in the field provides a means for quality assurance of field-mixed mortar. It includes methods for verifying the mortar mix proportions, comparing test results for field mortars to preconstruction testing, and determining batch-to-batch uniformity of the mortar.

1.4 The test results obtained under this test method are not required to meet the minimum compressive values in accordance with the property specifications in Specification C 270.

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 and health practices and determine the applicability of regulatory limitations prior to use. For specific hazards statements, see Section 8.