The quality of mortar in all masonry walls shall be determined by performing in-place shear tests in accordance with the following:
- The bed joints of the outer wythe of the masonry shall be tested in shear by laterally displacing a single brick relative to the adjacent bricks in the same wythe. The head joint opposite the loaded end of the test brick shall be carefully excavated and cleared. The brick adjacent to the loaded end of the test brick shall be carefully removed by sawing or drilling and excavating to provide space for a hydraulic ram and steel loading blocks. Steel blocks, the size of the end of the brick, shall be used on each end of the ram to distribute the load to the brick. The blocks shall not contact the mortar joints. The load shall be applied horizontally, in the plane of the wythe. The load recorded at first movement of the test brick as indicated by spalling of the face of the mortar bed joints is Vtest in Equation A1-3.
- Alternative procedures for testing shall be used where in-place testing is not practical because of crushing or other failure mode of the masonry unit (see Section A18.104.22.168).
The tensile-splitting strength of existing masonry, fsp, or the prism strength of existing masonry, f 'm may be determined in accordance with one of the following procedures:
- An alternative to material testing is estimation of the f'm of the existing masonry. This alternative should be limited to recently constructed masonry. The determination of f'm requires that the unit correspond to a specification of the unit by an ASTM standard and classification of the mortar by type.
The minimum number of tests per class shall be as follows:
- At each of both the first and top stories, not less than two tests per wall or line of wall elements providing a common line of resistance to lateral forces.
- At each of all other stories, not less than one test per wall or line of wall elements providing a common line of resistance to lateral forces.
- In any case, not less than one test per 1,500 square feet (139.4 m2) of wall surface and not less than a total of eight tests.
- Individual unreinforced masonry walls with vto consistently less than 30 pounds per square inch (207 kPa) shall be entirely pointed prior to retesting.
- The mortar shear strength, vt, is the value in pounds per square inch (kPa) that is exceeded by 80 percent of the mortar shear test values, vto.
- Unreinforced masonry with mortar shear strength, vt, less than 30 pounds per square inch (207 kPa) shall be removed, pointed and retested or shall have its structural function replaced, and shall be anchored to supporting elements in accordance with Sections A106.3.1 and A113.8. When existing mortar in any wythe is pointed to increase its shear strength and is retested, the condition of the mortar in the adjacent bed joints of the inner wythe or wythes and the opposite outer wythe shall be examined for extent of deterioration. The shear strength of any wall class shall be no greater than that of the weakest wythe of that class.
- The minimum average value of tensile-splitting strength determined by Equation A1-1 or A1-2 shall be 50 pounds per square inch (344.7 kPa). The minimum value of f'm determined by categorization of the masonry units and mortar should be 1,000 pounds per square inch (6895 kPa).
- Individual unreinforced masonry walls with average tensile-splitting strength of less than 50 pounds per square inch (344.7 kPa) shall be entirely pointed prior to retesting.
- Hollow unit unreinforced masonry walls with estimated prism compressive strength of less than 1,000 pounds per square inch (6895 kPa) shall be grouted to increase the average net area compressive strength.
Deteriorated mortar joints in unreinforced masonry walls shall be pointed in accordance with the following requirements:
- Joint preparation. The deteriorated mortar shall be cut out by means of a toothing chisel or non-impact power tool to a depth at which sound mortar is reached but not less than 3/4 inch (19.1 mm). Care shall be taken not to damage the brick edges. After cutting is complete, all loose material shall be removed with a brush, air stream or water stream.
- Mortar preparation. The mortar mix shall be proportioned as required by the registered design professional. The pointing mortar shall be prehydrated by first thoroughly mixing all ingredients dry and then mixing again, adding only enough water to produce a damp workable mix which will retain its form when pressed into a ball. The mortar shall be kept in a damp condition for 11/2 hours; then sufficient water shall be added to bring it to a consistency that is somewhat drier than conventional masonry mortar.
- Packing. The joint into which the mortar is to be packed shall be damp but without freestanding water. The mortar shall be tightly packed into the joint in layers not exceeding 1/4 inch (6.4 mm) in depth until it is filled; then it shall be tooled to a smooth surface to match the original profile.