Non-destructive air-permeability measurement: from gas-flow modelling to improved testing

Author(s): R. Torrent
Paper category: Conference
Book title: 2nd International conference on Microstructural-related Durability of Cementitious Composites
Editor(s): Guang Ye, K. Van Breugel, Wei Sun, Changwen Miao
Print ISBN: 978-2-35158-129-2
e-ISBN: 978-2-35158-123-0
Publisher: RILEM Publications SARL
Pages: 467-476
Total Pages: 9
Language: English

Abstract: 
The fundamentals of a test method to measure, non-destructively, the coefficient of airpermeability of the ‘covercrete’ were established in the 90’s leading to the development of a commercial instrument, the “Torrent Permeability Tester” (TPT).
The model and formula used today to calculate the coefficient of air-permeability kT were developed in 1995. They are based on assuming a unidirectional flow through a material regarded as homogeneous. Under such conditions, the response of the test (pressure increase) with the square root of time should be linear.
Deviations from the theoretical response were found for low permeability concretes not completely dry, and attributed to an artificial increase in pressure caused by the evaporation of moisture, present in the concrete pores, into the test chamber.
A new instrument, “PermeaTORR” (PT), has been designed and built to ensure a better fulfilment of the theoretical conditions assumed in the model, in order to get more reliable and accurate results.
The incorporated improvements led to an accentuated linearity of the test, enabling to shorten the test from 12 to 6 minutes.
The paper discusses the fundamentals of the model used to calculate kT, the different response of the two instruments (TPT and PT) and the correlation between them.
An example of non-linear behaviour, obtained with PT for a concrete cast against “Zemdrain” is presented.

Online publication: 2013
Publication Type: full_text
Public price (Euros): 0.00