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Nishi-Tokyo-shi, Japan

Miyauchi H.,Chungnam National University | Lacasse M.A.,NRC Institute for Research in Construction | Enomoto N.,Japan Sealant Industry Association | Murata S.,ALC Association | Tanaka K.,Tokyo Institute of Technology
Journal of ASTM International | Year: 2012

In Japan acrylic sealants are traditionally the sealant products of choice when specified for use between autoclaved lightweight concrete (ALC) panels. Although, in general terms, the mechanisms of the deterioration of acrylic sealants are well known its long-term durability to outdoor exposure has not, however, been fully investigated. The research described in this paper focuses on the change in the properties and deterioration of acrylic sealant products when exposed to outdoor testing. The two stage project consisted of (i) on-site investigations of deteriorated acrylic sealants that had been placed in external joints of ALC-clad buildings; and (ii) outdoor exposure testing of different types of acrylic sealant in three climate regions located in Japan. The results of the work from the first stage of the study revealed the following. Two-sided adhesion joint configurations installed in deep panel ALC cladding were more reliable than threesided adhesion joints used for thin panel ALC cladding from the viewpoint of the durability of the sealed joint installed in actual buildings. Most fractures of the sealed joint could be characterized as failure in peel (or thin layer cohesive failures), in which the sealant ruptured at the interface with the ALC substrate to which it was applied. Additionally, in 47 of 62 locations surveyed, surface cracks were apparent on the coating that had been applied to protect the sealant. The second stage of the project focused on the degree of deterioration of coated and non-coated acrylic sealants subjected to outdoor exposure testing in a cold, a warm, and a subtropical climate. Results from this stage showed that aging of the sealant, as determined by the degree of surface cracking, expectedly depended on the local temperature and the respective degree of exposure to solar radiation. It was determined that the longer the exposure period, the lower the tensile performance of the acrylic sealants. The elongation of three-sided adhesive joint configurations after 5 years exposure testing decreased remarkably and their maximum elongation was less than 50 %. A significant number of sealed joints after 5 years ofexposure had ALC substrate failure. Copyright © 2012 by ASTM International. Source

Miyauchi H.,Chungnam National University | Lacasse M.A.,NRC Institute for Research in Construction | Murata S.,ALC Association | Enomoto N.,Japan Sealant Industry Association | Tanaka K.,Tokyo Institute of Technology
Journal of ASTM International | Year: 2012

The strength of autoclaved lightweight concrete (ALC) is evidently lower than that of normal concrete. Therefore, when movement occurs at a sealed joint between ALC panels, the sealant is required to deform and remain intact without damaging the ALC substrate. However, there is currently not sufficient information to permit evaluation of the expected performance of sealants applied to ALC substrates. In this study, static and dynamic tests were carried out in order to obtain an index that could be used to select the modulus of a sealant that can be expected to provide long-term performance when applied to an ALC substrate. To develop this index, an initial study was carried out in order to clarify actual joint movement between ALC panels of buildings; the expansion and contraction at the joint were measured, and shear joint movement was calculated based on the expected story-to-story drift of an external wall due to earthquake loads. Thereafter, in a subsequent stage of the study, five types of two-component polyurethane sealant products, of different elastic modulus, were subjected to tensile and shear tests from which the relationship between stress and the type of joint fracture was determined. The results from these tests revealed that when the stress is greater than 0.6 to 0.7 N/mm 2, the ALC substrate is more easily fractured than the sealant. In a final stage of the study, the cyclic fatigue resistance of the same two-component sealants was evaluated using tensile and shear fatigue tests. Results from the fatigue tests indicated that the high modulus sealants lost adhesion from the ALC substrate at an early stage in the test. As well, the fatigue resistance of test specimens with joints having three-sided adhesion was lower than that of specimens having normally configured joints with adhesion on two sides of the sealant. Therefore, on the basis of results derived from all the studies, it was determined that a suitable sealant for use on ALC substrates is a sealant having a low modulus that is applied in the normal fashion as a two-sided joint. Copyright © 2012 by ASTM International. Source

Shiode Y.,ALC Association | Seike T.,University of Tokyo | Koyama A.,Meiji University | Tamura M.,Kogakuin University | And 3 more authors.
AIJ Journal of Technology and Design | Year: 2010

Recently, the development of proper disposal process of construction wastes has been an important subject, and it is also required to ALC panel. In this study, it is examined the emitted conditions of ALC rubbles on construction sites. As a result, ALC rubbles such the shapes as a block or powder come to occur by cutting or scraping ALC panel, and the emitted volume of ALC rubbles was grasped in the feasible study on construction site. Finally considering the results of the survey and the feasible study, the material flow model of ALC panel was clarified. Source

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