Masonry Magazine August 1976 Page. 16
Value of fm Interpolated
Value of fm interpolated from the values in Table 4. Since only Types M, S and N mortars are permitted for engineered brick masonry, Type O mortar is not included in this table.
Table 4
Assumed Compressive Strength of Brick Masonry
Assumed Compressive Strength of Brick Masonry, fm. psi
| Compressive Strength of Units, psi | Without Inspection | With Inspection |
|---|---|---|
| | Type N Mortar | Type S Mortar | Type M Mortar | Type N Mortar | Type S Mortar | Type M Mortar |
| 14,000 plus | 2140 | 2600 | 3070 | 3200 | 3900 | 4600 |
| 12,000 | 1870 | 2270 | 2670 | 2800 | 3400 | 4000 |
| 10,000 | 1600 | 1930 | 2270 | 2400 | 2900 | 3400 |
| 8,000 | 1340 | 1600 | 1870 | 2000 | 2400 | 2800 |
| 6,000 | 1070 | 1270 | 1470 | 1600 | 1900 | 2200 |
| 4,000 | 800 | 930 | 1070 | 1200 | 1400 | 1600 |
| 2,000 | 530 | 600 | 670 | 800 | 900 | 1000 |
From Building Code Requirements for Engineered Brick Masonry, SCPI, 1969.
Color
Colored mortars may be obtained through the use of colored aggregates or suitable pigments. When the desired colors can be obtained with colored aggregates, their use is preferable. White sand, ground granite, marble or stone, etc. usually have permanent color and do not weaken the mortar. For white joints, use white sand, ground limestone or ground marble with white portland cement and lime.
Mortar pigments must be sufficiently fine to disperse throughout the mix, must be capable of imparting the desired color when used in permissible quantities, and must not react with other ingredients to the detriment of the mortar. These requirements are generally met by metallic oxides. Iron, manganese and chromium oxides, carbon black and ultramarine blue have been used successfully as mortar colors. Avoid using organic colors and, in particular, those colors containing Prussian blue, cadmium lithopone, and zinc and lead chromates. Paint pigments may not be suitable for mortars.
Use the mimimum quantity of pigments that will produce the desired results; an excess may seriously impair strength and durability. The maximum permissible quantity of most metallic oxide pigments is in the order of 10 to 15 percent of the cement content by weight. Exercise this caution when using carbon black, a popular pigment: limit it to 2 to 3 percent of the cement by weight. Although carbon black is a very effective coloring agent, it will seriously impair mortar strength when used in greater amounts.
For best results, premix color with portland cement in large, controlled quantities. Premixing large quantities will assure more uniform color than can be obtained by mixing smaller batches at the job. Color also depends upon the color of other mortar constituents, particularly aggregates and cements. Color permanence depends upon quality of pigments, and weathering and efflorescing qualities of the mortar.
Recommended Mortar Uses
General. Selection of a particular mortar type is usually a function of the needs of the finished structural element. Where high winds are expected, high lateral strength is required and, hence, mortar with high tensile bond strength is chosen. For load-bearing walls, high compressive strength may be the governing factor, or considerations of durability, color, flexibility, etc. may be of utmost concern. Factors which improve one property of mortar often do so at the expense of others. For this reason, when selecting a mortar, evaluate properties of each type and choose that mortar which will best meet particular end-use requirements. No single type of mortar is best for all purposes. Recommended general uses for mortars are discussed in the following paragraphs.
Type N Mortar
Type N mortar is a medium strength mortar suitable for general use in exposed masonry above grade. It is specifically recommended for parapet walls, chimneys and exterior walls wherever these are subject to severe exposure.
Type S Mortar
Type S Mortar. Tests indicate that the tensile bond strength between brick and Type S mortar approaches the maximum obtainable with cement-lime mortars. Type S mortar also has reasonably high compressive strength. It is recommended for use in reinforced masonry, for unreinforced masonry where maximum flexural strength is required, and for use where mortar adhesion is the sole bonding agent between facing and backing.
Type M Mortar
Type M mortar has high compressive strength and somewhat greater durability than other mortar types. It is specifically recommended for unreinforced masonry below grade and in contact with earth such as foundations, retaining walls, walks, sewers and manholes.
Type O Mortar
Type O mortar is a low strength mortar suitable for general interior use in non-loadbearing masonry. It may be used for load-bearing walls of solid masonry where compressive stresses do not exceed 100 psi, provided that exposures are not severe. In general, do not use Type O mortar where it will be subject to freezing action.
Cavity Walls
Where wind velocities will exceed 80 mph, use Type S mortars. For locations where lesser winds are expected, use Type S or Type N.
Tuck-Pointing Mortar
Use only prehydrated mortars. To prehydrate mortars, thoroughly mix