건설재료시공학연구실

Building material & construction lab.

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 evaluating the expected performance of sealants applied to ALC substrates. In this study, static and dynamic tests were carried out to obtain an index 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 to understand 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 storey-to-storey drift of an external wall due to earthquake loads. Thereafter in a subsequent stage of the study, five types of 2-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 0.6-0.7 N/mm2 , the ALC substrate is more easily fractured than the sealant. In a final stage of the study the cyclic fatigue resistance of the same 2-component sealants was evaluated by 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 both a low modulus and applied in the normal fashion as a two-sided joint.

DOI:10.1520/JAI104064