Overview
Applying hot mastic asphalt on concrete bridge decks with flexible polymer-bitumen waterproofing sheets may negatively affect the bond between concrete base and waterproofing sheet due to formation of blisters. These bonding imperfections are not initially visible thanks to the leveling effect of mastic asphalt. They present, however, weak areas promoting horizontal water penetration and therefore putting at risk durability and functionality of the system at a later stage of life time.
The objectives of the project are as follows:
- Evaluation and ranking of test methods and procedures for assessing the formation of Blisters between concrete base and flexible polymerbitumen sheets for waterproofing on mastic asphalt
- Development of a simulation test for the assessment of the resistance against building of blisters which can appear between the concrete base and the flexible polymer-bitumen sheets for waterproofing after the application of mastic asphalt. The following parameters will be taken into account: the blister pressure (simulating the influence the humidity of the base), the initial temperature of the mastic asphalt, the pavement course thickness, and the kind of the blister seeds (single blister, blister assembly).
- Experimental and numerical modelling of the growth of blisters as a basis for the assessment of different bridge pavement constructions and for the possible future investigations.
- Elaboration of scientific basics for better understanding of the blistering phenomena of dense pavements within the frame of a PhD thesis at KTH under the supervision of the project leader who has the position of associate Professor at KTH. This point includes a theoretical parameter study.
The procedure set for the project can be described as provisional. Depending on the progress and findings of the work is to be expected that the Centre has to amend the procedure for optimal achievement of objectives in our own technical-scientific responsibility for informative consultation, respecting the financial constraints.
For example, must not be forgotten that one of the main problems of the project will be the reproducible uniform Labware application of hot mastic asphalt in a model system. Experiences were collected by the EMPA in connection with the development of the SIA 281/1 or EN 14693. This experience is support in the development of a suitable refined method. However, should not prove practical application, will be to go through another the mastic asphalt layer simulating, which proves in heat transfer, weight, reproducibility as advantageous.
Funding
Results
The project generates scientific basic know-how for advanced fundamental understanding of the blister formation with dense pavements.
In this study a model system of practical relevance and as close to reality as possible is experimentally and numerically investigated with respect to the influence of four parameters (1. blister pressure simulating the influence of the humidity of the base; 2. initial temperature of the mastic asphalt; 3. pavement thickness; 4. kind of the blister seeds) on the growth of blisters under a flexible polymer-bitumen sheet for waterproofing during and immediately after the casting of hot mastic asphalt.
From that investigation, a simulation test was carried out that was suitable for the assessment of the resistance of bridge deck waterproofing systems against blister formation. The project generates scientific basic know-how for advanced fundamental understanding of the blister formation with dense pavements.