FA 3.2 Reliable design and prolongation of service life
To establish the basis for exact control of the life time, by:
- Prevention of water suction
- Sufficiently high electric resistivity
- Exact knowledge about the chloride threshold value
- Hydrophobising agents and/or cementitious combinations and additions that reduce the capillary suction of the concrete to a minimum
|Project manager and disciplinary responsible:||Mette Geiker|
|PhD:||Karla Hornbostel, Jan Lindgård and Mahdi Kiumarsi|
|Post doc:||Klaartje De Weerdt|
|International advisor:||Professor Bernhard Elsener, ETH, Switzerland, and Professor Mike Thomas, University of New Brunswick, USA|
The vision of the project was to ensure that concrete structures & buildings remain attractive throughout their entire service life by preventing premature and uncontrolled deterioration of concrete and reinforcement.
The project included the following activities:
- Service life design
Reliability based service life predictions of concrete structures exposed to chloride induced corrosion
- Critical chloride content & corrosion process
PhD study: "Establish test methods for measuring critical chloride content"
- Electrical resistivity of concrete
Correlation between concrete resistivity and reinforcement corrosion with focus on measuring techniques and interpretation of data
- Alkali aggregate reactions of concrete (ASR)
PhD study: "Establish performance based testing concept for ASR"
- Improved service life modelling of reinforced concrete structures
PhD and post doc study on characterization of in-situ exposed concrete
Chloride ingress and electrical resistivity
A thorough literature review has shown that the present state of the art does not allow improving current practice. Moreover, values for theoretical chloride contents commonly used are based on experience with Portland cement; critical chloride contents for modern binder types are in general unknown. Our experimental work indicated how measuring setups for the critical chloride content can be improved so that the results are more reliable and realistic. On the basis of theoretical, probabilistic considerations it is suggested how laboratory results might be transferred to practice. A correlation could be expected between the corrosion process of steel embedded in concrete and the electrical resistivity of concrete. A literature review shows however, that the dependency varies between studies of different concretes, and one single relationship cannot be established between corrosion rate and conductivity.
COIN has aimed to evaluate whether concrete prism tests (CPTs) developed for assessment of alkalisilica reactivity of aggregates, might be suitable for general ASR performance testing of concrete. Focus has been on the internal moisture state in the test prisms and extent of alkalis leaching out from the prisms during the ASR exposure. Our work has continuously given important input to the work in RILEM TC219 ACSP (20072012), where the objective is to develop a reliable performance testing concept. Based on our preliminary results, the RILEM committee immediately withdrew two of the three RILEM methods.