Masonry Magazine February 1994 Page. 40
The Author
JAMES E. AMRHEIN, consulting engineer and Executive Director of the Masonry Institute of America, is a founding member and Past President of The Masonry Society and is on the board of directors of the Council for Masonry Research. A professor of civil engineering at California State University, he served in the U.S. Navy as a Seabee during WWII and the Korean War. A graduate of Manhattan College with a bachelors degree in Civil Engineering, he also has a masters degree in Civil Engineering from Columbia University. He's a Licensed Professional Engineer in New York and a registered Civil and Structural Engineer in California.
Evidence of grout in the cells and bond beams is indicated by moisture on the surface through the masonry units.
Clean outs. When using the high lift method of partially grouting walls, it is necessary to provide clean outs at the location of the vertical steel. These clean outs are required so that mortar droppings can be removed from the cells to be grouted. This is to allow the grout to bond to the foundation.
What about consolidating the grout? As with concrete, it's necessary to move the grout into all the voids of the system. It's necessary to compact the grout so that there are no voids left within the system itself. Proper consolidation must be made with either a puddle stick or mechanical vibrator. If the grout lift is 12" (305 mm) or less in height, a puddle stick may be used. This is recognizing that there is very little grout and the shrinkage is minimal. If the grout lift is greater than 12" (305 mm) mechanical vibrator should be used so that proper consolidation can be obtained.
The concept about consolidation besides compacting and moving the grout is that for high slump grout, 9" to 11", (229 mm to 279 mm) there is a high water content and the excess water is absorbed into the masonry which leaves a void within the grout system. It leaves a thin film of water between the masonry unit and the grout column in the cell. This film acts as a bond breaker and does not allow adhesion of the grout to the masonry unit. Accordingly, it's necessary to vibrate, consolidate the grout and close up all voids and spaces that may be between the grout and the masonry unit. This is necessary to achieve a strong homogeneous mass of material with no separation between the grout and the masonry unit.
A homogeneous system is a united monolithic system able to transmit all forces between the masonry, grout and steel. All types of forces, vertical and lateral must be transferred between the materials to make a strong monolithic structure of reinforced grouted masonry.
Conclusion. The performance of partially grouted reinforced masonry has been well documented based upon investigations of structures that have been subjected to high loading conditions. Where the conditions are due to hurricanes, as in Hurricane Andrew in Florida, or Hurricane Iniki in Hawaii or due to the earthquakes of the Loma Prieta earthquake or the Whittier earthquake or the Sylmar earthquake of the San Fernando Valley all in California, partially grouted reinforced masonry has performed well.
REFERENCES: (1) Uniform Building Code, 1991 Edition, published by International Conference of Building Officials, Whittier, California: (2) Building Code Requirements for Masonry Structures (ACI 530-92/ASCE 5-92/TMS 402-92), Specifications for Masonry Structures (ACI 530.1-92/ASCE 6-92/TMS 602-92), American Concrete Institute, Detroit. American Society of Civil Engineers, New York, and The Masonry Society, Boulder, Colorado, 1992; (3) Performance of Masonry Structure During Extreme Lateral Loading Events by Arturo E. Schultz-Building and Fire Laboratory. National Institute of Standards and Technology, Gaithersburg, Maryland. 1993; (4) Grout the Third Ingredient by J. E. Amrhein, published by Masonry Industry, 1980: (5) Grouting Masonry by J. E. Amrhein, published by Masonry Institute of America, 1990; (6) Reinforced Concrete Masonry Construction Inspector's Handbook, by J. E. Amrhein and M. Merrigan, published by Masonry Institute of America, Los Angeles, California and International Conference of Building Officials. Whittier, California, 1989.
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40 MASONRY-JANUARY/FEBRUARY, 1994