Masonry Magazine April 2000 Page. 32
Masonry Grout
Continued from page 30 contractor is the most comfortable method for the contractor, thereby giving the best quality grout installation.
When the contractor elects to construct the walls without using cleanouts, the walls are built to a maximum of 5 feet (1.5 m), then grouted. This is referred to as the low lift grout.
Full face shell cleanouts in a masonry wall
ing method. Immediately after completion, which is likely the following day, installation of the masonry units is continued and the grouting cycle is repeated. This sequence works very well when a separate grouting crew follows a laying crew and by the time the laying crew finishes laying the first lift, usually 4'-8" (1.4 m), the laying crew can continue to construct the next lift at the original starting point, and repeat the cycle.
The contractor may also elect to construct the masonry to the full height before grouting. This method is commonly called high lift grouting. Specification for Masonry Structures (ACI 530.1-99/ASCE 6-99/TMS 602-99), Table 7 contains certain limitations when using this method. Essentially, the grout space must be large enough so that grout flow's thoroughly, without segregation.
Low Aft grouting system
Immediately after placement in the wall, all grout lifts over 12 inches (300 mm) are vibrated by mechanical means. Electric and gas powered vibrators are made specifically for this application. The vibrator should be inserted into the cell and immediately removed. If the grout in the cell is vibrated for more than 2 or 3 seconds, there is a high risk that excessive vibration will blow the wall out. The code also provides that grout should be reconsolidated in order to minimize the voids in the grout system. With proper consolidation and reconsolidation, grout can settle as much as 1 inch (25 mm) per foot (300 mm). Reconsolidation is more of an art than a science. Grout should be reconsolidated after the initial water loss and
Low lift grouting system
before the stiffening of the grout due to the curing process. Factors that can affect the time between consolidation and reconsolidation are moisture content of the grout, water absorption by the units, ambient temperature and humidity, temperature of grout during placement and height of grout lift. If the contractor waits too long before the reconsolidation process, there may be damage done to the grout by stabbing the grout with the vibrator.
The strength of grout is recognized in masonry shortly after placement. The Uniform Building Code allows for prism tests, including the component of grout, at 3 and 7 days, providing the correlation between the 3 or 7-day tests and the 28-day tests can be established. For example, if testing of grout at 3 days gives a 60% value of the 28-day test, assuming consistent parameters, then the 3-day test may be extrapolated for a 28-day test value. This gives the designer, developer, contractor and testing agency immediate quality control results while the project is usually proceeding at a lightning pace.
The International Building Code is bringing change to the industry. The method of construction will not significantly change, but the application of the method will affect many contractors. Specifically, geographic areas of the country that did not require structural reinforcement before
ACI 530.1-99/ASCE 6-99/TMS 602-99, TABLE 7-GROUT SPACE REQUIREMENTS
| GROUT TYPE | MAXIMUM GROUT POUR HEIGHT, ft.(m) | MINIMUM WIDTH OF GROUT SPACE, in.(mm) | MINIMUM GROUT SPACE DIMENSIONS FOR GROUTING CELLS OF HOLLOW UNITS, in.x in. (mm x mm) |
| ----------- | ----------- | ----------- | ----------- |
| Fine | 1 (0.30) | 3/4 (19.1) | 11/2 x 2 (38.1 x 50.8) |
| Fine | 5 (1.52) | 2 (50.8) | 2 x 3 (50.8 x 76.2) |
| Fine | 12 (3.66) | 21/2 (63.5) | 21/2 x 3 (63.5 x 76.2) |
| Fine | 23 (7.32) | 3 (76.2) | 3 x 3 (76.2 x 76.2) |
| Course | 1 (0.30) | 11/2 (38.1) | 11/2 x 3 (38.1 x 76.2) |
| Course | 5 (1.52) | 2 (50.8) | 21/2 x 3 (63.5 x 76.2) |
| Course | 12 (3.66) | 21/2 (63.5) | 3 x 3 (76.2 x 76.2) |
| Course | 23 (7.32) | 3 (76.2) | 3 x 4 (76.2 x 102) |