Masonry Magazine June 2001 Page. 36
COLORED MORTAR
Normally the amount of color used in a mortar mix falls between 1% and 7% of the cementitious material weight. Generally, the 7% dosage rate is the color saturation point; additional color added will not noticeably improve the intensity of the mortar color shade.
Pigments made of carbon black have a high tint strength value and are listed under ASTM-C979, but are generally not accepted by pigment manufacturers who supply pigments to the masonry industry. Exterior masonry mortars colored with carbon black have a history of loosing color from the surface of the mortar joint within six months after installation. While carbon black itself is sunfast, it does not bond well to cement. Through weather exposure the surface of a carbon black mortar joint will result in a gradual loss of color intensity.
MASONRY PROCEDURES
As with all variables listed, mason contractors have a direct impact towards the colored mortar appearance of the masonry structure. Mortar joints should only be tooled after the mortar joint has achieved a "thumb print" consistency. Tooling the joints too soon brings excessive moisture from the mortar to the surface and creates a masonry smear lighter in color. Conversely, tooling a mortar joint that has become too dry tends to burn or scrape the joint due to lack of moisture. The result is a mortar joint darker in color.
To reduce the amount of cleaning required, deposits of colored mortar should be cleared from the masonry unit face during construction using a moist towel and stiff brush. This should be done before the mortar has a chance to cure and rigidly bond itself to the masonry unit. Cleaning of new masonry should be undertaken after the colored mortar has sufficiently cured. Generally colored mortar will be cured 7 to 14 days after masonry installation; however, curing time depends upon weather conditions. A commercially prepared "proprietary" masonry cleaner should be applied at manufacturer's suggested dilution concentration. Cleaning too quickly and/or using muriatic acid or a highly concentrated masonry cleaner will cause degradation of the colored mortar with the consequential release of color pigments from their cement bond. This will result in a porous sand surface. Insufficient or irregular washing can produce streaky or blotch areas on the masonry wall. For the well being of all involved, sample mock-up panels should be constructed and tested with job cleaning procedures and approved by the owner or architect.
WEB EQUIPMENT
SALES SERVICE PARTS
New & Used
LULL™
PARTS
• Expert Help
• No Fault Guarantee
• Overnight Delivery
800/225-3858
540/657-5855
Ext. 351
Steve or Chris (Parts Dept.)
Fax Orders 24 Hours:
540-288-9607
Order online:
www.webequipment.com
Order via e-mail:
webequip@webequipment.com
Cummins™ Engines Lull™ Parts
Bradco™ Attachments
Booms
Axle Housings &
Planetary & Brake Parts
Forks &
Carriages
Transmissions
& Torque
Converters
Heavy Duty Jibs
Work Platforms
MEET OSHA REQUIREMENTS
Discoloration
Right side of sample indicates
efflorescence; left side of sample
has been cleaned.
Discoloration by efflorescence (a white coloration film of calcium and soluble salts) on the surface of the colored mortar joint is a common problem.