Methodology for including the age effect of concrete with SCMs in results from accelerated testing

Author(s): E. Gruyaert, N. De Belie
Paper category: Conference
Book title: Concrete Repair, Rehabilitation and Retrofitting III (ICCRRR)
Editor(s): M.G. Alexander, H.-D. Beushausen, F. Dehn, P. Moyo
Print ISBN: 978-0-415-89952-9
Publisher: Taylor & Francis Group
Pages: 164 – 165
Total Pages: 2
Language: English

Abstract: 
Concrete containing Supplementary Cementitious Materials (SCMs) such as Fly-Ash(FA) or Blast-Furnace Slag (BFS) shows a slower development of its microstructure when compared to mixes with Ordinary Portland Cement (OPC). However, concrete properties are mostly evaluated at the age of 28 days and also accelerated durability tests may start at that age. Therefore, it may be questioned whether the durability of concrete with SCMs is not underestimated when the attack in an accelerated test is concentrated in the initial stage of its lifetime, when its properties have not yet fully developed. On the other hand, when tests are started at later age, e.g. 6 months, one may criticize that in reality the concrete may undergo some degradation already before that age. Therefore, an alternative approach is suggested, in which degradation curves from accelerated tests starting at various ages are first converted to those corresponding with a real environment. Then, the degradation kinetics at different ages are combined into one final degradation curve. This principle is illustrated with data from accelerated carbonation tests in a 10 vol% CO₂ atmosphere, carried out after 1, 3, 6 or 18 months of curing. The results are used to judge whether carbonation-initiated corrosion is a risk for the structure within its life span.
In another approach to compare concrete with SCMs to OPC concrete, some researchers have attempted to determine k-values for fly ash, silica fume and slag with regard to different degradation mechanisms (mainly chloride ingress and carbonation). These k-values may also be time-dependent. An attempt was made to calculate k-values for slag with regard to chloride migration based on experimental test results using a graphical method. The obtained k-values are critically discussed.

Online publication: 2014
Publication Type: abstract_only
Public price (Euros): 0.00