Masonry Magazine June 1989 Page. 13
TABLE 7.0-3
Comparison of Results: 16" Long Vs. 24" Long Masonry Units
| UNIT | | | LINE | TIME/COURSE | TIME/UNIT | NO. BLK. | RATE | RATE |
|---|---|---|---|---|---|---|---|---|
| Size | Type | COURSE | PLACEMENT | (Min:Sec) | (Sec) | (Hr.) | (Sq. Ft/Hr.) | (% Change) |
| 8×8×16 | H.W. | 3 | Outside | 16:26 | 47.0 | 76.6 | 68.6 | |
| 8×8×24 | H.W. | | | 10:49 | 46.4 | 77.6 | 104.2 | +51.9 |
| 8×8×16 | L.W. | 3 | Outside | 15:12 | 43.4 | 82.9 | 74.1 | |
| 8×8×24 | L.W. | | | 10:16 | 44.0 | 81.8 | 109.8 | +48.2 |
| 8×8×16 | H.W. | 5 | Inside | 16:08 | 46.1 | 78.1 | 69.8 | |
| 8x8x24 | H.W. | | | 12:57 | 55.5 | 64.9 | 87.0 | +24.6 |
| 8×8×16 | L.W. | 5 | Inside | 14:40 | 41.9 | 85.9 | 76.8 | |
| 8×8×24 | L.W. | | | 11:28 | 49.1 | 73.3 | 98.3 | +28.0 |
TABLE 7.0-4
Comparison of Results: Line Placement-Outside Vs. Inside
| UNIT | | | LINE | TIME/COURSE | TIME/UNIT | NO. BLK. | RATE | RATE |
|---|---|---|---|---|---|---|---|---|
| Size | Type | COURSE | PLACEMENT | (Min:Sec) | (Sec) | (Hr.) | (Sq. Ft./Hr.) | (% Change) |
| 4×8×24 | H.W. | 2 | Outside | 13:07 | 56.2 | 64.1 | 85.9 | |
| | H.W. | | Inside | 11:36 | 49.7 | 72.4 | 97.1 | +13.0 |
| 4×8×24 | L.W. | 2 | Outside | 9:41 | 41.5 | 86.7 | 116.4 | |
| | L.W. | | Inside | 9:03 | 38.8 | 92.8 | 124.5 | + 7.0 |
| 4×8×24 | H.W. | 2 | Outside | 13:07 | 56.2 | 64.1 | 85.9 | |
| | L.W. | | Inside | 9:03 | 38.8 | 92.8 | 124.5 | +44.9 |
| 4x8x24 | H.W. | 2 | Inside | 11:36 | 49.7 | 72.4 | 97.1 | |
| | L.W. | | Outside | 9:41 | 41.5 | 86.7 | 116.4 | (+19.9) |
| 4×8×24 | H.W. | 4 | Outside | 11:36 | 49.7 | 72.4 | 97.1 | |
| | H.W. | | Inside | 10:52 | 46.6 | 77.3 | 103.7 | +6.8 |
| 4×8×24 | L.W. | 4 | Outside | 9:49 | 42.1 | 85.5 | 114.8 | |
| | L.W. | | Inside | 9:34 | 41.0 | 87.8 | 117.8 | + 2.6 |
| 4×8×24 | H.W. | 4 | Outside | 11:36 | 49.7 | 72.4 | 97.1 | |
| | L.W. | | Inside | 9:34 | 41.0 | 87.8 | 117.8 | +21.3 |
| 4×8×24 | H.W. | 4 | Inside | 10:52 | 46.6 | 77.3 | 103.7 | |
| | L.W. | | Outside | 9:49 | 42.1 | 85.5 | 114.8 | (+10.7) |
| 6×8×16 | H.W. | 2 | Outside | 15:04 | 43.1 | 83.5 | 74.8 | (+1.2) |
| | H.W. | | Inside | 15:15 | 43.6 | 82.6 | 73.9 | |
| 6×8×16 | L.W. | 2 | Outside | 14:32 | 41.5 | 86.7 | 77.5 | |
| | L.W. | | Inside | 14:01 | 40.1 | 89.8 | 80.4 | +3.7 |
| 6×8×16 | H.W. | 2 | Outside | 15:04 | 43.1 | 83.5 | 74.8 | |
| | H.W. | | Inside | 14:01 | 40.1 | 89.8 | 80.4 | + 7.5 |
| 6×8×16 | H.W. | 2 | Inside | 15:15 | 43.6 | 82.6 | 73.9 | |
| | L.W. | | Outside | 14:32 | 41.5 | 86.7 | 77.5 | (+4.9) |
8.0 Conclusions
When evaluating the results from Tables 7.0-1 and 7.0-2, it becomes quite evident that significant increases in productivity can be realized when lightweight concrete masonry units are used in lieu of heavyweight units.
Further, a review of Table 7.0-3 indicates that the use of 24" long units can increase productivity by approximately 25-50% over 16" long units, depending upon the height of the lift.
Table 7.0-4 illustrates that there is a distinct advantage to laying facing the line as opposed to laying overhand; the exception being that it is more productive to lay lightweight units over- hand than to lay heavyweight units facing the line.
As noted in Section 3.0, Material Properties, the unit weight of the concretes from which the units were manufactured varied from that specified. As a result, the differences in weight between the heavyweight and lightweight units was less than anticipated. The assumption can be made that had the proper density units been provided, the increases in productivity noted in the tables would be more substantial.
Although, as indicated in the results, productivity doubled when two men were used to place the top course of 24" long units (8"x8"x24"), it has not been established whether this was due to the weight of the unit or height of the lift. Undoubtedly, it was a combination of the two. Nevertheless, it is apparent that 24" long units placed at heights of 4'-0" or above should be handled by 2 masons.
9.0 Recommendations
If it is determined that this investigation be repeated, the following recommendations are herewith presented:
1. The widths of all walls should be the same.
2. Layout of courses should be the same (i.e. single units in the same course, multiple units in the same course).
3. A fatigue factor should be included by constructing walls of predetermined length using 12"x8"x16" units on the same day and following construction of the walls consisting of 24" long units.
4. Additional tests be conducted at one or more different locations under the same conditions and supervision to determine the reproducibility of test results.
Mason's Comments
"I felt that I accomplished more after laying the 24" long units. I like them. Masons like to feel that they're accomplishing something regardless what others might think. You know, with these long units, you have fewer joints to fool with and fewer joints to leak."
MASONRY-MAY/JUNE, 1989 13