Masonry Magazine May 1978 Page. 8
High-Lift Grouting of Masonry Walls
By Oscar Person and Leonard L. Thompson
High-lift grouting of masonry walls has now been used very successfully for over 20 years and is considered one of the better systems for masonry construction throughout California as well as other earthquake areas on the West Coast. It was developed principally for brickwork of two-wythe construction and soon was extended to block or hollow unit masonry.
The high lift grouting system consists of these 10 basic steps:
1. Building the two wythes of brick full height without grouting.
2. Having ties between the wythes.
3. Placing the reinforcing in the empty grout space, held in position by spacers or positioners.
4. Cleaning the grout space through cleanouts.
5. Inspecting and sealing the cleanout holes.
6. Pumping grout 4 feet high between control barriers.
7. Vibrating or puddling for intimate flow into position.
8. Letting the moisture leave the grout to reduce the water/cement ratio.
9. Reconsolidating due to the volume loss resulting from water loss, i.e., to reconsolidate any portions that might have settled and left voids or incipient failure of bond.
10. Repeating in 4-foot lifts until the top is reached.
The benefits gained in this procedure were many, three of which are:
1. The inspection could be much better and easier with greater assurance of adequate quality of work. For example, it is possible to look down between the wythes to verify that all the steel is in the proper locations; to see that the interior of the wall is clean, and then by watching during grouting, observe if it is placed properly. Other items that might be subject to questions, such as weakness of bond, head joints and bed joints, would be automatically tested by the 4- or 5-foot hydraulic head of grout which would subject the two wythes of masonry to more shear and bending stresses than they would ever receive under design conditions in the use of the structure.
2. The masons would lay the masonry more easily, accurately and rapidly, resulting in better and lower cost masonry after the crews are accustomed to the change in technique.
3. Better bond was developed by the wetter grout.
After several years of success in Northern California, the method was introduced to the Los Angeles area by the Masonry Institute of America, formerly known as Masonry Research, and the Brick Manufacturers Association of Southern California. It was soon discovered, however, that the procedures needed to be revised due to the different absorptive characteristics of the Southern California brick. For example, the rate of absorption was rather high, which made the timing of the reconsolidation rather critical.
In order to determine the correct procedures for the variation in absorption rates, a test program was initiated to obtain this information. Approximately 80 test panels were constructed and grouted, using brick of high, medium and low absorption rates, grouts of different water content, grouts of different admixtures, grouts of various mixes, and pours using different procedures.
A number of admixture companies were given a basic specification for an admixture performance. These were: maximum fluidity of the grout with minimum water; maximum water retention, and minimum volume loss upon loss of excess content.
It is to be noted that no emphasis was made on strength of grout; in the preliminary tests it was noted that any of the grouts were able to develop strengths far in excess of that needed to develop the masonry in accordance with the
ABOUT THE AUTHORS
Oscar Person is a Regional Vice President of the Mason Contractors Association of America and President of the mason contracting firm of Person & Western, Inc., Burlingame, Calif. Leonard L. Thompson is Executive Director of the Masonry Institute of America, Los Angeles, Calif.
The development of the high-lift grouting system began in 1955 with Person and Robert Harrington, then manager of the Clay, Brick and Tile Association of San Francisco. They started experimenting with this system and soon discovered that it had great potential.
Harrington and Person made contact with a number of prominent building officials, including those in California, and convinced them that high-lift grouting was a worthwhile system utilizing a number of new methods for masonry construction. All agreed that further research should be done.