No further reproductions authorized. Masonry Prism Construction 5. Recording the location of the structure that corresponds to a set of prisms allows the test results to be attributed to a particular portion of the structure. Construct prisms in a location where they will remain undisturbed until transported for testing. Orient units in the prism as in the corresponding construction.
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Significance and Use 4. Decisions made in preparing such field-removed prisms for testing, determining the net area, and interpreting the results of compression tests require professional judgment. No further reproductions authorized.
C 11a deviations from this test method shall be reported. Such research prisms shall not be used to verify compliance with a specified compressive strength of masonry. Masonry Prism Construction 5. If units have flutes or ribs that project 12 in. When prisms are used for field quality control or assurance, record the location in the structure that corresponds to the set of prisms constructed.
NOTE 2Building codes or project specifications may require a set of prisms for a given square footage of construction. Recording the location of the structure that corresponds to a set of prisms allows the test results to be attributed to a particular portion of the structure.
Construct prisms on a flat, level base. Construct prisms in a location where they will remain undisturbed until transported for testing. Orient units in the prism as in the corresponding construction. At the time of prism construction, the surfaces of the units shall be free of moisture.
Where the corresponding construction is of multi-wythe masonry having wythes composed of different units or mortar, build prisms representative of each different wythe and test separately. Any required saw cutting shall be performed on units prior to prism construction. The moisture content s of units used to construct prisms shall be representative of those used in construction. Prisms composed of units that contain closed cells shall have at least one complete cell with one full-width cross web on either end see Fig.
Prisms composed of units without closed cells shall have as symmetrical a cross section as possible. The minimum length of prisms shall be 4 in. Thus, these reduced length unit prisms are less likely to be damaged and are more likely to be properly capped and tested.
Also, the smaller prism will be less likely to be affected by plate bending effects during testing, as described in Note 9, and will therefore provide a more accurate assessment of the strength of the materials in the masonry prism.
For these reasons, the use of reduced length prisms is encouraged. Use mortar representative of that used in the corresponding construction. Use mortar joint thickness and a method of positioning and aligning units, that are representative of the corresponding construction. Use mortar joints that are cut flush. For prisms to be grouted, remove mortar fins that protrude into the grout space. When prisms are used for other FIG. C 11a purposes, grout prisms not less than 4 h nor more than 48 h following the construction of the prisms.
NOTE 4Testing of prisms may be part of a projects field quality control or assurance program. These prisms are intended to be representative of a constructed masonry element such as a wall, column, pilaster, or beam. They are built as companions to the masonry element at a jobsite where the masonry element is site-constructed, or within a factory or shop where the element is shop-built. Prisms may also be fabricated in a laboratory for research purposes.
Use grout representative of that used in the corresponding construction. Before placing grout, remove mortar droppings from the grout space. Use grout consolidation and reconsolidation procedures representative of those used in the construction. Place additional grout into the prisms as necessary after each consolidation.
Screed off excess and finish the grout so that it is level with the top of the prism and in contact with the units at the perimeter of the grout space. Grouted prisms shall contain no reinforcement. Brace forms to prevent displacement during grouting.
Grout as described in 5. Do not disturb or move prisms for the first 48 h after construction and grouting. Keep prisms in the moisture-tight bags until 48 h prior to testing. Obtaining and Transporting Masonry Prisms 6. Secure prisms and specimens to prevent jarring, bouncing, or tipping over during transporting. Extend storage time as needed to ensure dry surface conditions of the prisms at the time of testing.
Test a set of prisms at each age. Prism age shall be determined from the time of laying units for ungrouted prisms, and from the time of grouting for grouted prisms.
Measurements and Determination of Net Area 8. Determine the length and width by averaging the four measurements of each dimension. Measure the height of the prism at the center of each face to the nearest 0. Determine the height by averaging the four measurements.
NOTE 5Prisms obtained from field-removed masonry specimens will have many different sizes, shapes, and configurations. These variations are a result of differing bonding arrangements, mortaring or joining practices, presence of reinforcement and other accessories in conjunction with the masonry in service, and of techniques used to remove the specimens from wall assemblies.
These variations may create non-uniform prism dimensions along its length or in its cross-section. As such, additional measurements are often required to adequately document the condition of the prism and to communicate that condition to readers of the test report. Curing 7. If cut units are used for prism construction, determine the net cross-sectional area from additional units cut in a similar manner. Determine net cross-sectional area of fully grouted prisms by multiplying the length and width of the prism see 8.
NOTE 6Net area determined by Test Methods C for hollow concrete units is usually slightly different from the minimum net crosssectional area because unit face shells and webs are typically tapered.
Net area for prisms obtained from fieldremoved masonry specimens is considered to be minimum bearing area. If prisms are not of uniform length or width throughout the height of the specimen, or if mortared surfaces are not fully bedded, use professional judgment to determine the minimum bearing area that exists for the prism at whatever location that occurs.
NOTE 7While constructed prisms are required to be fully-bedded with mortar, prisms obtained from field-removed masonry specimens, particularly for hollow masonry, will often have only the face shells of the hollow units mortared.
For such prisms, if any mortar on the top and bottom bearing surfaces of the prisms are removed to result in full bearing across the unit cross-section, the minimum cross-section will typically occur at an intermediate mortar bed joint. For face shell bedded sections, multiplying the measured length of the prism at the bed joint location by the sum of the face shell thicknesses can be an effective method for determining minimum net bearing area. Because the face shells of hollow units are often tapered, the thickness of the face shell above the mortar bed joint and below the mortar bed joint may differ.
In such a case, use the least face shell thickness of the two in the calculation. Obtaining access to measure face shell thickness is often difficult or impossible. Measurements of similar cross-sections from representative units or other parts of the prism is an option as is performing measurements after testing is performed. Refer to Test Methods C67 and C for recommended methods of measuring face shell thickness.
Capping 9. Procedure The upper platen shall be a spherically seated, hardened metal block firmly attached at the center of the upper head of the machine. The center of the sphere shall lie at the center of the surface held in its spherical seat but shall be free to turn in any direction, and its perimeter shall have at least 14 in.
The diameter of the upper platen determined in accordance with A1. A hardened metal bearing plate used beneath the specimen is not required, but has been found to minimize wear of the lower platen of the machine. The length and width of the steel plate shall be at least 14 in. The surfaces of the platen and plate shall not depart from plane surfaces by more than 0. NOTE 8Annex A1 includes guidance on determining the required plate thicknesses based on the configurations of the test specimen and the test machine.
NOTE 9Research has shown that the thickness of bearing plates has a significant effect on the tested compressive strength of masonry prisms when the bearing area of the plate is not sufficient to cover the area of the specimen.
Plate bending results in nonuniform stress distributions that can influence the failure mechanisms of the tested specimens. The magnitude of this effect is controlled by the stiffness of the plate, the size of the specimen tested, and the strength of the specimen.
Tested compressive strengths will typically increase with increased plate thickness and with reduced distance to the furthest corner of the specimen. Some testing laboratories have machine size limitations that limit the practicality of eliminating plate bending entirely.
Therefore, the plate thickness requirements in Place the test specimen on the lower platen or bearing plate. Align both centroidal axes of the specimen with the center of thrust of the machine. As the spherically seated upper platen or plate is brought to bear on the specimen, rotate the movable portion of the upper platen gently by hand so that uniform seating is obtained.
Apply the remaining load at a uniform rate in not less than 1 nor more than 2 min. Apply the remaining load at a uniform rate in not less than 2 nor more than 4 min. Record the maximum load and note the mode of failure. Note whether failure occurred on one side or one end of the prism prior to fracture of the opposing side or end of the prism.
Identify mode of failure using Fig. C 11a FIG. Calculation Determine the correction factor from Table 1. Report
C1314 Resistencia a La Compresion de Prismas de Mamposteria
Significance and Use 4. Decisions made in preparing such field-removed prisms for testing, determining the net area, and interpreting the results of compression tests require professional judgment. No further reproductions authorized. C 11a deviations from this test method shall be reported. Such research prisms shall not be used to verify compliance with a specified compressive strength of masonry. Masonry Prism Construction 5.
ASTM C1314 - 18