Results of Investigation

Results of Deteriorated Sealed Joints—The sealant product condition is pro­vided in terms of a qualitative assessment of the extent of damage and the clas­sification of sealed joints between ALC panels and are shown in Table 3. In buildings aged over 20 years, all sealed joint products were one component

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TABLE 1—Outline of investigation concerning ALC building.

Hokkaido, Tokyo, Kobe, Kagawa Building age: 10 years

-Structure: steel frame construction,

-Panel fixing method: Rocking panel fixing system – Sealed joint: Two-sidedadhesion joint

-Structure: steel or wood frame construction, – Panel fixing method: screw fastening system -Sealed joint: Three-sidedadhesion joint – Structure: wood frame construction,

-Panel fixing method: Fastening system by screws – Sealed joint: Three-sidedadhesion joint

Sampling of sealants from actual external wall in 4 regions

-Visual inspection on the surface of sealants with coating material (deterioration, crack condition)

Подпись: 50 JAI • STP 1545 ON DURABILITY OF BUILDING AND CONSTRUCTION-Hardness of sealants, tensile stress of sealants

Results of Investigation

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Results of Investigation

TABLE 3—Sealant inspection results.

Depth of ALC wall panel

100 mm

50 mm 35(37) mm

Two-sided adhesion joint

Three-sided adhesion joint

Sealant

typea

O b A b x b

O b Ab x b O b Ab x b Total

Elapsed

years

5-9

AC-1

1

0

0

2 | 0 | 0

2

0 | 0

5

PU-2

5

0

0

___ -———– ‘ "

_________ —

5

10-14

AC-1

__________________

9

1

0

6

2

0

18

PU-2

2

0

0

1

0

0

________ —

3

15-19

AC-l

3

0

0

3

0

0

10

(1

0

16

PU-2

3

0

0

1

1

0

_________ —

5

20-21

AC-1

5

ft

0

5

0

0

10

PU-2

_________ — ■

____________ ______

0

Total

14

ft

ft

21

2

ft

23

2

0

62

Note: A=Slight (partial) damage on sealed joint; x=Damage on sealed joint in many places.

aAC-1:1 component acrylic sealant, PU-2:2 component urethane sealant. bO: No damage on sealed joint.

acrylic sealants; inspection results are reported for acrylic sealants at four inter­vals, the first between 5 and 9 years, thereafter at 10-14 years, 15-19 years, and 20-21 years. Whereas for buildings less than 20 years of age only two compo­nent urethane sealants had been used for the sealed joints; inspection results are only reported for intervals of 5-9 years, 10-14 years, and 15-19 years. Because the amount of anticipated movement in the sealed joint between the deep ALC panels was large, a two component urethane sealant was used as a working joint given its capacity to accommodate movement.

There was no evidence of any complete damage to the sealed joint (symbol: x), regardless of the depth of the panel, however partial failure (sym­bol: A) of the sealed joint was observed (4 damages out of 62 total) in four loca­tions in thin panels, specifically, the ALC panel having a 50 mm depth had partial damage (symbol: A) evident for one acrylic (1 damage out of 20) and one urethane sealant (1 damage out of 3), and the ALC panels with 35 (37) mm wall depth had partial damage for two acrylic joints (2 damages out of 25).

Crack Conditions of Sealed Joint—Examples of damaged sealant products applied to joints of ALC panels are shown in Fig. 1. All damaged sealed joints (symbol: A) were those occurring in thin ALC panels and for joints having three­sided adhesion. Of those joints having three-sided adhesion, 2 damaged joints were evident for 50 mm deep panels and another 2 damaged joints for 35 mm deep panels. In both instances, cohesive failure occurred at the center of the

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Results of Investigation

FIG. 1—Crack condition of sealed joints.

sealed joint and where cracks were observed. In 47 of the 62 sealed joints inspected cracks were evident on the surface coating material (i. e., damage evi­dent to 47/62); these cracks did not depend on the movement of the structure or the type of sealant to which they were applied. The coating material has, in fact, a reduced performance in accommodating deformation as compared to that of sealants. It was also evident that the sealed joints along the short side of the panel have significantly more cracks than joints along the longer side of the panel. It is thought that the degree of expansion and contraction of the joint along the short side of the panel is greater than that along the longer side of the panel.

Test Results of Basic Properties—The hardness [7] and tensile strength [3] of a 17 year old sealant product used in the joints of a wood frame constructed home were measured by a testing machine. The hardness of the sealed joint was measured with a Shore Type A hardness meter (JIS K 6253). The valuefor the hardness of the sealant was approximately 60 Shore A on both sides of the sealed joint. An unaged sealant of the same product type was estimated to be 20 Shore A when first installed (Table 6). The change in hardness of the aged pro­duced appears to confirm, therefore, the degradation of the sealants over time.

The tensile test for the sealed joint was carried out using a special jig, as shown in Fig. 2. Fourteen tensiletest specimens were evaluated; the maximum tensile stress ranged between 0.36 and 0.73 N/mm2 with the mean value being

0. 54 N/mm2. The elongation at maximum load ranged between 7 and 21 % and provided a mean value of 15 %. Most sealed joint fractures were characterized as failures in peel (or thin layercohesive failures), in which the sealant fractured at the interface between the sealant and the ALC substrate. The maximum elon­gation at fracture of the sealed joint extended from 53 to 223 % with a mean value of 117 %.

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Подпись: •100mm
Подпись: 60mm
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Tensile test jig

FIG. 2—Tensile test and sample specimen.

Outdoor Exposure Tests

Outline of Outdoor Exposure Test

As described in Table 4, the outdoor exposure tests were carried out at three dif­ferent locations in Japan over a 5 year period; each location had a different cli­mate. Control specimens were also prepared to which the sealants exposed to the different climates were compared; these were kept in indoor laboratory con­ditions, as described in Table 4. The evaluation parameters included the:

(i) effect of climate conditions (e. g., ultraviolet radiation, temperature, and moisture load), (ii) the effect of the joint type between ALC panels, and (ii) the effect of the sealant and coating material types.

Test Specimens and Test Methods

Test Specimens—The specimens are shown in Fig. 3 and the items inspected over the course of the outdoor exposure test are shown in Table 4. The joint types include: a two-sided adhesion joint (joint width: 10 mm, joint depth: 8 mm) and a three-sided adhesion joint (joint width and depth: 7 mm with a small 1 mm gap at mid-width and the base of joint). Low density (1.1 g/cm3) one com­ponent acrylic sealant commercially available Japanese products were those

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subjected to tests. The effect of coating materials was evaluated and the test specimens were prepared both with and without a coating material applied to the exterior surface of the joint. All sides of the ALC substrate, with the excep­tion of that surface on which the sealant was applied, were coated with one component silicone sealant in order to protect the substrate from water absorp­tion when exposed to the outdoors. The test specimens were cured indoors at 23 ± 2°C for 4 weeks before starting the outdoor exposure test. Three test speci­mens were used in evaluating each test parameter.

Exposure Test Method—As shown in Fig. 4, the geographical locations of the exposure testing sites for Rikubetsu, Yokohama, and Miyako Island are evi­dently quite different and consequently, the local climate conditions vary greatly from one location to another. The test specimens placed in the outdoor exposure site at these three locations were set up on testing tables inclined at 45° (Fig. 4). On the contrary, test specimens prepared as control specimens were cured in a darkroom with no sunlight and maintained at a temperature of 23 ± 2°C over the test period.

Figure 5 shows the outdoor temperature conditions at the three outdoor ex­posure sites over a selected exposure period in October. The mean value for the maximum outdoor temperature over a five year period for the warmest expo­sure site (Miyakojima Island) was 29.4°C; whereas, the mean value for the mini­mum outdoor temperature over five years for this same exposure site was 18.2°C. On the other hand, Rikubetsu is an exposure site where temperature dif­ferences are large and the mean value for the maximum temperature over five years was 18.6°C and the corresponding minimum temperature was —9.6°C. Therefore, the sequence of exposure sites in order of decreasing thermal expo­sure severity is as follows: Miyakojima Island > Yokohama > Rikubetsu.

Evaluation Method for Degradation of Sealed Joints—The degree of degrada­tion of the sealed joint is evaluated by observation of the surface of the sealed joint, with use of the hardness meter (Shore Type A), along with tensile tests. Moreover, the tensile tests were carried out by fixing the test specimen to a spe­cial jig (Fig. 2). The tensile rate of deformation was 5 mm/min and the test tem­perature was 23 ± 2°C.