Comparative study on the resistance of concrete against chloride ingress (AGB1998/097)
Overview
Background & policy context:
The chloride induced corrosion is one of main causes of damages of the road infrastructure. The tightness of the cover concrete and the thickness of the cover of the rebars have an extraordinary importance.
Because of the premature failure of concrete structures one tries to increase the durability of new structures by using higher (denser) concrete qualities and thicker concrete covers. High performance concrete may be used to increase the tightness of concrete. Standardised and accepted methods for the assessment of the resistance of concrete against the chloride ingress (chloride resistance) are still missing.
Objectives:
The goal of this project is to test different techniques for determination of the chloride resistance of various concrete qualities (normal and high performance concrete) and to compare the results of the different techniques as well as to compare them with the gas permeability and with the results of the measurement of the water conduction, a widely used method in Switzerland (SIA 162/1, test No. 5).
Based on the results of this study the requirements for concrete for durable concrete structures exposed to chloride containing environments should be formulated, the appropriate tests evaluated and the corresponding criteria deduced. Based on this information a SIA-guide for "Concrete for durable concrete structures exposed to chloride" should be elaborated.
Within this research project the chloride resistance of concrete mixes with and without mineral admixtures (fly ash, silica fume, ground granulated blast furnace slag) and of concrete from older Swiss concrete structures has been evaluated. For this work different test methods have been used to characterize the chloride resistance and their validity has been compared.
Methodology:
Following tests were conducted:
- ASTM-test according AASTHO T259-80 (electric charge)
- IBAC or CTH-test (chloride migration coefficient or shortly migration coefficient)
- Streicher test (electrical conductivity)
- gas permeability (permeability)
- water conductivity test according to SIA 162/1, test nr. 5 with modification VPL (water conductivity)
- water suction (chloride content or chloride enrichment)
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