Effect of chlorides on moisture content and sorption isotherms

Author(s): M. Leivo, H. Kuosa, E. Holt, E. Vesikari, R.M. Ferreira
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: 130 – 131
Total Pages: 2
Language: English

Abstract: 
Moisture in concrete is an influential factor in the transport mechanism of aggressive species and therefore directly related to concrete durability. The presence of salts in the pore structure of concrete is known to have a negative influence due to their hygroscopic nature. Despite the well-known thermodynamic behaviour of pure salts, it is not sufficient to explain the effects salts have on certain properties of concrete. In this research the effect salt (NaCl) has on the moisture content and sorption isotherm of concrete was studied.
Six different concrete mixes with varying binder and air content were used for this purpose. To introduce chlorides into the concrete pore structure, specimens (10 × 100 × 100 mm3 and 25 × 100 × 100 mm3) were subject to 16 immersion-drying cycles (5 days immersed/2 days drying). Three different mediums were used: water, 3% NaCl solution and 10% NaCl solution. This was followed by determining the sorption isotherms of the concrete specimens by finding the moisture equilibrium at 95%, 65% and 50% relative humidity at 20°C.
Results include, among other tests, the porosity, moisture content, chloride content and the mentioned sorption/desorption isotherms. Moisture uptake and the degree of saturation were also measured.
Experimental results showed that the presence of salt strongly influences the sorption and moisture characteristics of concrete. At each level of relative humidity studied, an increase in the moisture content was observed—in some cases up to 30% higher. As the moisture content of concrete had an influence, this parameter should be considered when evaluating other deterioration attacks such as frost salt resistance and reinforcement corrosion.

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