Masonry Magazine October 1997 Page. 21
Union Station, Indianapolis, Indiana. Built in 1888. Photo illustrates clearly the brick and mortar deterioration pattern from water running over the face of the wall (notice roof detail above), no signs of deterioration in gable area. Buildings built during the twentieth century either rely on masonry walls as a barrier to water penetration or incorporate drainage cavities utilizing flashing and weep-holes to redirect water to the exterior. Buildings constructed before the 20th century generally rely on allowing the moisture which has been absorbed by the masonry fabric to evaporate from the surface. The thickness of the walls alone in most historic buildings may have been designed to keep the moisture out. The original lime putty mortars were vapor permeable allowing a masonry structure to breathe by absorbing moisture when damp conditions prevail and releasing the moisture when relative humidity allows, without damage.
Constituents of Mortar
# Sand
Sand is the largest constituent of mortar and the material that gives mortar its characteristic color, texture and cohesiveness. Sand must be free of impurities, such as salts or clay. The three key elements of sand are; particle shape, gradation and void ratios.
# Particle Shape
When viewed under a magnifying glass or low-power binocular microscope, particles of sand generally have either rounded edges, such as found in beach and river sand, or sharp, angular edges, found in manu-
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