Volume 6, Issue 3 (March 2009)
Joint Sealing Systems for Pavements—A New Approach Towards a Performance Related Evaluation of Capability and Durability
Joint sealants influence decisively the performance and service life of pavements although they account for only a small fraction of the total investment. Motivated by the damages observed and the resulting, increasing maintenance efforts, the Federal German Government recognizes the need for performance-evaluated joint sealing systems with improved capability (fitness-for-purpose) and durability. A literature study showed that an identification of the actual mechanical system behavior under realistic loads as well as a prediction regarding the durability (fatigue, climatic effects) of joint sealing systems are either completely lacking in most of the relevant evaluation methods or have only been incompletely addressed previously. Furthermore an imbalance between commonly used test methodologies and the actual development status of modern modified sealing materials exists, i.e., the current test methods are not effective in evaluating the performance of tailor-made products. In this paper, the authors suggest a methodology to overcome the present situation. In contrast to the existing, predominantly empirical evaluation and selection of joint sealing materials and systems for pavements, the new approach is defined by verified performance under relevant and superimposed loads. This new approach is expected to allow a more engineered joint design. In addition to the adaptation of performance-oriented material identification tests, a special focus was placed on the development and installation of a complex test facility for the investigation of the service capability and durability of joint sealing systems in building constructions in general. This paper presents an attempt at the realization of this approach for pavement joints with the help of our new joint sealant test equipment utilizing a specific, adapted load function, which comprises cyclic movements (slow and fast acting), as well as crucial climatic exposures. The test data and its interpretation are discussed. For example, the actual mechanical behavior of the various joint sealing systems as well as the relevant maximum loading of cohesive and adhesive bonds can be deduced and used to differentiate between systems. Furthermore, information gained allows discrimination of products within the various joint sealing systems. The test results will also enable numerical simulations, e.g., of different joint designs or materials by finite element analysis. The fatigue behavior is detected by analysis of cycle-dependent changes of the mechanical system characteristics. The evaluation methodology further allows investigation of the degradation mechanisms of specific system failures and, thus, enables service life prediction by reproducing the performance of the complete system under realistic conditions. Constructional defects and material flaws can be activated and detected by the performance-related test methodology, thus identifying possible corrections to material selection and application procedures. The potential of the proposed evaluation methodology is discussed for several thermoplastic and reactive joint sealing systems.