Masonry Magazine June 1989 Page. 12
7.0 Test Procedure (Continued)
The placement of these units was not considered a part of the test and was not timed.
Previous to laying the courses consisting of multiple units, hardware cloth was placed on top of the preceding course. This served to provide a setting bed for the mortar forming the bedding for the face shells located along or near the enter of the wythe. This screen also prevented mortar from falling into the cores and allowed for some absorption of water into the crosswebs of the units below. This absorption is necessary to activate the setting mechanism of the extended life plastic mortar being used.
Throughout the test, mortar was applied to the head (vertical) joints of the unit previously placed as well as the unit to be laid. This method of forming head joints was arbitrarily determined prior to the start of the test and was not intended to be an integral part of the investigation.
The test walls were not struck or tooled, the determination for completion of each course being that all joints be full and ready to be finished.
The investigation took place inside the facility of the National Concrete Masonry Association's Research and Development Laboratory under controlled climate and temperature conditions. This was done to exclude such variables as may be encountered under outside weather conditions and to make the investigation more easily reproducible.
The mason performed the timed portions of the test without interruptions or distractions. Talking and smoking was discouraged, although not prohibited. During the placement of course 6A in the walls constructed of 24" long units, talking was necessary in order to assure coordination between the two masons.
7.0 Test Results
A tabulation of test results is presented in Tables 7.0-1 through 7.0-4.
Tables 7.0-1 and 7.0-2 illustrate the relative increases in number of concrete masonry units placed per hour and subsequent increased square footage of wall per hour which can be expected when lightweight units are used in lieu of heavyweight units. This comparison is made for 4", 6", 8" and 12" units, 16 inches in length; and for 4" and 8" units, 24 inches in length.
Table 7.0-3 provides a direct comparison of measured production rates between 8"x8"x16" and 8"x8"x24" heavyweight units, as well as lightweight units.
Table 7.0-4 illustrates the effect of unit weight and line placement on productivity.
Although not indicated in the tables, productivity doubled when two men were used to place course 6A as compared to one man placing course 6.
TABLE 7.0-1
Comparison of Results:
16" Long Heavyweight Vs. Lightweight Units
UNIT
LINE
Size
Type COURSE
PLACEMENT
TIME/COURSE
(Min:Sec)
TIME/UNIT
(Sec)
NO. BLK.
(Hr.)
RATE
(Sq. Ft/Hr.)
RATE
(% Change)
4×8×16 H.W.
3
Inside
15:28
44.2
81.4
72.9
L.W.
13:21
38.1
86.7
86.7
+18.9
4×8×16 H.W.
5
Outside
19:16
55.1
65.3
58.5
L.W.
15:36
44.6
80.7
72.2
+23.4
6×8×16 H.W.
2
Outside
15:04
43.1
83.5
74.8
L.W.
14:32
41.5
86.7
77.5
+ 3.6
6×8×16 H.W.
2
Inside
15:15
43.6
82.6
73.9
L.W.
14:01
40.1
89.8
80.4
+ 8.8
8×8×16 H.W.
3
Outside
16:26
47.0
76.6
68.6
L.W.
15:12
43.4
82.9
74.1
+8.0
8×8×16 H.W.
5
Inside
16:08
46.1
78.1
69.8
L.W.
14:40
41.9
85.9
76.8
+10.0
12×8×16 H.W.
1
Inside
16:08
46.1
78.1
69.8
L.W.
13:21
38.1
94.5
84.4
+20.9
12×8×16 H.W.
4
Outside
16:09
46.1
78.1
69.8
L.W.
14:51
42.3
85.1
75.9
+8.7
12×8×16 H.W.
6
Inside
20:36
58.9
61.1
54.7
L.W.
15:35
44.5
80.9
72.3
+32.1
TABLE 7.0-2
Comparison of Results:
24" Long Heavyweight Vs. Lightweight Units
UNIT
LINE
Size Type COURSE
PLACEMENT
TIME/COURSE
(Min:Sec)
TIME/UNIT
(Sec)
NO. BLK.
(Hr.)
RATE
RATE
(Sq. Ft./Hr.)
(% Change)
4×8×24 H.W.
2
Outside
13:07
56.2
64.1
85.9
L.W.
9:41
41.5
86.7
116.4
+35.5
4x8x24
H.W.
2
Inside
11:36
49.7
72.4
97.1
L.W.
9:03
38.8
92.8
124.5
+28.2
4×8×24 H.W.
4
Outside
11:36
49.7
72.4
97.1
L.W.
9:49
42.1
85.5
114.8
+18.2
4x8x24
H.W.
4
Inside
10:52
46.6
77.3
103.7
L.W.
9:34
41.0
87.8
117.8
13.6
8x8x24 H.W.
1
Inside
11:52
48.7
73.9
95.0
L.W.
9:52
40.1
89.8
114.2
+20.2
8×8×24 H.W.
3
Outside
10:49
46.4
77.6
104.2
L.W.
10:16
44.0
81.8
109.8
+ 5.4
8x8x24 H.W.
5
Inside
12:57
55.5
64.9
87.0
L.W.
11:28
49.1
73.3
98.3
+13.0
8×8×24 H.W.
6
Outside
13:57
59.8
60.2
80.8
L.W.
11:57
51.2
70.3
94.3
+16.7