Masonry Magazine July 1961 Page. 16
KEYWALL
GALVANIZED MASONRY
REINFORCEMENT
Gives greater crack resistance
Adds strength at lower cost
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KEYSTONE STEEL & WIRE CO.
Peoria 7, Illinois
Lime in Masonry Mortar
(Continued from page 13) pieces of carpet, pet, burlap or rags which tend to smear the faces of the work. Such smears are most difficult to remove.
It has been found that the acid cleaning puts more water back into the walls and may be the cause of later efflorescence. When walls cannot be cleaned with simple scrubbing and washing with clear water, it is recommended that they be cleaned by light sand-blasting which is generally found to be no more expensive than acid cleaning.
QUESTION "What can be done to correct the over-use of lime?"
ANSWER-It seems to me that the problem here is not on over-use of lime, but on the under use. The answer to control of mixes is: first, a reliable contractor-second, inspection.
QUESTION "What effect does over-use of lime have on strength of mortar, and can the percentage of overage be used to prepare a graph?"
ANSWER-Use a given mix of 1: 6:46, 1:1:6, 1:2:9, or other mix. An increase in the amount of lime in these mixtures will reduce the strength of the mortar. Tests have been made and graphs have been drawn to show this relationship.
QUESTION "Should lime be as much a part of mortar as cement and sand?"
ANSWER-Definitely yes! The definition of mortar is lime and sand, to which cement may or may not be added. All building codes, including the codes of other authorities such as the California State Division of Architecture, require a minimum amount of lime in mortar. Anything else added to mortar is termed an admixture.
QUESTION "What are the advantages and disadvantages of fire clay in lieu of lime in mortar?"
ANSWER-There is no advantage -but a disadvantage in the use of fire clay in mortar for laying up unit masonry. Lime is a cementitious material, and fire clay is not. Water mixed with fire clay produces a slippery paste, but a mixture of fire clay and sand has an extremely high shrinkage coefficient. Tests have shown that mortar composed of cement, fire clay and sand have extremely low structural values. Buildings constructed years ago, in which cement, fire clay and sand were used for mortar, have become streaked with a gray film on the exteriors, due to the leaching out of the fire clay.
QUESTION "How do the masonry contractors propose to control the addition of lime to the mix? (No matter what mix is specified, either by the architect or by building codes, etc., all is to no avail unless it is follow the letter on the job.)"
ANSWER- Only by the honesty and integrity of the contractor, his superintendents and foremen. I would say that the selection of an experienced and honest contractor with a good record and reputation is probably about as important as the specifications covering a job. Both are essential to top quality work.
QUESTION "Should we not give more consideration to making certain that the proper proportions of lime-cement-aggregate are used? (What we have in mind is that the mortar man used the cement proportion for lime and the lime proportion for cement, causing a job to be torn down.)"
ANSWER-Certainly, yes. This is true of all segments of the building industry, whether masonry, plumbing, wiring, concrete, steel, wood, etc. All jobs containing structural elements for private or public safety should receive architectural or engineering supervision periodically to insure the proper performance of work in accordance with plans and specifications.
Referring specifically to mortar, it has been my experience that good contractors make a particular point of having an experienced and reliable hand tending the mixer. It is a very important job. Much depends upon having a good mortar delivered on schedule to the bricklayers.
UTILITY
Hepblo STRUCTUR
FACING TI
meets modern demands fo
MODEST COST
MAXIMUM UTIL
MINIMUM MAINTENANCE
Write for Catalog, Shape List and Dealer L
WEST VIRGINIA BRICK COMPA
Charleston 24, West Virgin
STARK
Stark Structural Glazed Tile are produced mainly in vertical core type to assure better bonding, easier-less costly cutting, and solid bed and head joints. Write for complete catalog.
STARK CERAMICS, INC., CANTON 1, OHIO
OWENS-ILLINOIS GLASS BLOCK
keep costs down
O-I Class Block arrive on the job site packed in sturdy cartons. No loose block to handle. Panels can be made to fit any size opening. No frame is necessary. Mortar-bearing surfaces pre-coated with special grit material for easy installation. Exterior faces have O-I's "magiclean" finish for easy cleaning. Available in 3 sizes and a variety of decorative and functional patterns. Wide distribution. Write Kimble Glass Company, subsidiary of Owens-Illinois, Dept. MCN, OWENS-ILLIN
Toledo 1. Ohio.
GENERAL OFFICES TOLEDO
MASONRY-JULY,