2 criteria on selection of ALC panel joint sealant
Evaluation of Sealed Joint Performance for selection of ALC panel joint sealants (Autoclaved Lightweight Concrete Panels
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 their study pushed on July 2012 Journal of ASTM International 9(1):104064, the researchers carried out static and dynamic tests 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/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 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.
After decades of R&D, Kaneka Group in Japan invented MS sealant (Modified silicone sealant) AS4001S high performance sealant for construction joint and ALC panen joint with such outstanding features as:
Good Environmental Choice Australia (GECA) certified
ASTM C920 (Class 50) compliant
ISO 11600 (F Class 25 LM) compliant
Good UV resistance
Low static charge – Less dirt streaking
No silicone oil – Non-staining on adjacent substrates
No isocyanate – No air bubbling
No solvent – No shrinkage
Bonds most substrates without primer
see below for details:
Learn more about high performance for precast joint here