Suitability of impedance surface moisture meter to complement air-permeability tests

Author(s): Roberto Torrent, Veronica Bueno, Fabrizio Moro, Albert Jornet
Paper category: Proceedings
Book title: Proceedings of the International Conference on Sustainable Materials Systems and Structures (SMSS2019) Durability, Monitoring and Repair of Structures
Editor(s): Ana Baričević, Marija Jelčić Rukavina, Domagoj Damjanović, Maurizio Guadagnini
ISBN: 978-2-35158-217-6
e-ISBN: 978-2-35158-218-3
Publisher: RILEM Publications SARL
Publication year: 2019
Pages: 56-63
Total Pages: 813
Language: English

Abstract: The coefficient of air-permeability kT, measured non-destructively by the so-called "Torrent Method", has gained acceptance as a suitable durability indicator of the as-built cover concrete and has been standardized in Switzerland (Standard SIA 262/1:2013 Annex E). The standard adopted the ND electrical impedance method to control the moisture of site concrete, requiring that the latter should not exceed 5.5% for making meaningful readings of kT. This paper presents data of moisture changes, assessed gravimetrically (H) and by ND Impedance (m) of concrete cubes dried naturally in the lab (during ≈ 3 years) and in an oven at 50°C (during ≈ 5 months). The changes in H, m and air-permeability kT were monitored regularly. Data of 17 concrete mixes, made with 9 different cement types (produced from 2 clinkers), are presented and discussed. A monotonic decrease of m and increase of kT was observed along the drying process, with reasonable continuity between natural and oven dried specimens. The results confirm that the impedance-based surface moisture meter is a suitable instrument to monitor the changes in humidity of drying concrete and an essential complement when measuring kT. The results obtained are very useful for establishing a preconditioning process prior to kT tests in the lab and offer solid ground for developing a correction factor of kT as function of m, when the latter is outside the range 4.5% - 5.5%.

: Online publication :2019
Publication type : full_text
Public price (Euros) : 00