Specification and site control of the permeability of the cover concrete: the Swiss approach

Title: Specification and site control of the permeability of the cover concrete: the Swiss approach
Author(s): E. Denariè, F. Jacobs, A. Leemann, T. Teruzzi and R. Torrent
Paper category : conference
Book title: International RILEM Conference on Advances in Construction Materials Through Science and Engineering
Editor(s): Christopher Leung and K.T. WAN
ISBN: 978-2-35158-116-2
e-ISBN: 978-2-35158-117-9
Publisher: RILEM Publications SARL
Publication year: 2011
Pages: 478 - 485
Total Pages: 8
Nb references: 23
Language: English

Abstract: It is recognised that most damage to reinforced concrete structures is caused by insufficient durability rather than by low strength. In most cases, the quality and thickness of the cover concrete (“covercrete”) determine the service life of the structure. Further, due to the increasing use of slow reacting cementitious materials like slag and fly ash, proper curing will become much more important in the future.
Since the quality of the covercrete is influenced, not only by the mix composition, but also by the placing and curing conditions, it is appropriate to measure the achieved properties on the structure rather than just on separately cast specimens. Swiss Standard SIA 262 on “Concrete Construction” recommends checking the “impermeability” of the cover concrete on site. A nondestructive method to measure the Air-Permeability on Site has been standardized (SIA 262/1Annex E), allowing the assessment of the resistance of the concrete to the penetration of deleterious agents.
Based on the experience accumulated on over 100 construction elements examined, a team of Swiss experts was appointed by the Swiss Federal Dept. of Transportation (ASTRA) to prepare recommendations for specifying, measuring, and assessing the conformity of the Air-Permeability kT. This paper describes these recommendations covering: a) specification of limiting values of kT as function of the Exposure Class; b) sampling of the measurement points; c) testing (including suitable temperature and moisture conditions) and d) evaluation of conformity with specified values.
The growing requirements for site concrete air-permeability determination will lead to improvements in the construction process, such as eradication of the bad habit of adding water to the trucks and more care put into placement and curing and even to the application of other techniques that improve the tightness of the cover concrete (e.g. permeable formwork liners, vacuum dewatering, UHPC layers, etc.) which will result in an extended service life of the constructions.

Online publication: 2011-10-31
Publication type : full_text
Public price (Euros): 0.00