An Attempt at Finding a Correlation Between Environmental and Accelerated RILEM TC 139-DBS Weathering for One-Component Polyurethane Sealants Applied on Mortar

摘要

Two sets of butt joint test specimens (ISO 8339 type) with mortar substrate (ISO 13640, Method 1) were prepared without primer using eight one-component polyurethane sealants; four of low modulus (LM) type showing a movement capability of 25 % and four of high modulus (HM) type showing a movement capability of less than 12.5 % (nomenclature HM according to ISO 11600 as they show a secant modulus >0.4 MPa at 23℃ and >0.6 MPa at -20℃, but the movement capability of these sealants does not comply with any of the HM classes stated by ISO 11600). All specimens were conditioned according to ISO 8339 Conditioning Method B. Afterwards the specimens were divided into two sets: the first set was exposed for 24 months in static conditions to the outdoor environment in the urban area of Milan, facing southeast at an angle of 45°. Periodically, i.e., every four months, they were evaluated by visual inspection of their exposed surface. The second set of joints was subjected to accelerated weathering according to RILEM TC 139 DBS in a light-exposure apparatus (xenon-arc type) with water spray. At the end of each RILEM cycle (eight weeks weathering plus one week thermo-mechanical cycling according to ISO 9047) the specimens were visually inspected. The authors found a good correlation between the results obtained in outdoor exposure and those observed after the RILEM durability cycling. In addition to tabulating the findings for crack density and size, the results are also presented as photographic documentation.