Study of Weatherability of Construction Sealants with Novel Testing Method

ABSTRACT: Although construction sealants are used for all kinds of construction joints such as static joints with little movement, dynamic joints with thermal or seismically induced movement, and so on, the general test methods employed in the evaluation of the weatherability of construction joint are based on weathering test without movement. In November of 2000, AIJ (Architectural Institute of Japan) established a subcom­mittee chartered with developing an accelerated weathering test method, which enables the determination of the durability of waterproofing materials and sealants. In this activity, we evaluated the weatherability of sealants with a new test method using newly developed test specimens, which enable exposing the cured sealants to compression and extension at the same time in a single test specimen. In this paper, we report the interim test results, which cover twelve months of natural weathering and 3500 hours artificial weath­ering with xenon lamp and carbon flame weathering device. In this evaluation, we confirm that the surface degradation of sealants is accelerated by the additional movement cycles, and the differences in the degradation among the sealants are becoming observable.

KEYWORDS: sealant, weatherability, joint movement, out-door exposure, accelerated exposure Introduction

In November of 2000, AIJ (Architectural Institute of Japan) established a subcommittee chartered with developing an accelerated weathering test method, which enables the determination of the durability of waterproofing materials and sealants. Sealants are used in a variety of applications. While some sealants are used in static joints with little movement, the majority of sealants are applied in dynamic joints, which are exposed to thermally, seismically, psychrometrically, or otherwise induced movement. Despite this fact, the majority of weatherability tests on sealants are carried out without exposing them to any move­ment [,2]. In this study on the durability of sealants, initiated by AIJ, newly developed test specimens have been employed, which enable exposing the cured sealant to compression and extension at the same time within a single test specimen. The magnitude of the movement can be adjusted to allow for the simulation of actual sealed joint conditions. This is the first interim report about this study.

Experimental Procedures

Test Specimen

A newly developed test specimen as shown in Figs. 1 and 2 was used in this study. By expanding one end of this joint test specimen, the other end gets compressed; thus, the test specimen can be exposed simul­taneously to various degrees of extension and compression in a single movement.

I. shaped anodized aluminum bar I urnahle biage

Sealant

Pin Bond breaker

Size of sealant: wide" depth * length -20 * 15 • 100 (mm)

Sealant joint exposed to movement (transformation) and weathering after enre

Spacer for fixation

IS»

( ompression

FIG. 1—Outline of test specimen.