Page 50 - ILLS Annual Report 2018

MATERIALS SCIENCE
Dorjan Dauti. Albanian
University Grenoble Alpes
Twitter account: twitter.com/DorjanDauti
‘I have a PhD in Materials Science and Civil Engineering, my research focus being the behaviour of concrete at high temperature.
In my research, I apply my knowledge to heat
and mass transfer modelling of porous construction materials, finite element simulations, neutron imaging and digital image analysis.’
Analysing 3D real-time moisture distribution in heated concrete to better understand fire spalling mechanisms
Neutron reflectometer and neutron-imaging instrument D50
The spalling of concrete, a phenomenon frequently encountered in concrete elements exposed to high temperature, can lead to structural failure. The evolution of moisture content in heated concrete is directly linked to spalling. Through this study we contribute to a better understanding of the behaviour
of concrete at high temperature, by quantitatively analysing, for the first time in the literature, the moisture migration in heated concrete using in situ neutron tomography [1].
AUTHORS
D. Dauti (University Grenoble Alpes, France and Swiss Federal Laboratories for Materials Science and Technology, Switzerland)
A. Tengattini (University Grenoble Alpes and the ILL, France)
S. Dal Pont and M. Briffaut (University Grenoble Alpes, France)
N. Toropovs (Swiss Federal Laboratories for Materials Science and Technology, Switzerland)
B. Weber (Swiss Federal Laboratories for Materials Science and Technology, Switzerland and Riga Technical University, Latvia)
ARTICLE FROM
Cement Concrete Res. (2018)—doi: 10.1016/j.cemconres.2018.06.010
REFERENCES
[1] D. Dauti, A. Tengattini, S. Dal Pont, N. Toropovs, M. Briffaut and B. Weber, Cement Concrete Res. 111 (2018) 41
[2] P. Kalifa, F.-D. Menetau and D. Quenard, Cement Concrete Res. 30 (2000) 1915
[3] N. Toropovs, F. Lo Monte, M. Wyrzykowski, B. Weber,
G. Sahmenko, P. Vontobel, R. Felicetti and P. Lura, Cement Concrete Res. 68 (2015) 166
When concrete is exposed to high temperature, a number of thermo-hydro-mechanical phenomena, which strongly interact with each other, take place. The most important among these are heat transfer due to temperature gradients, mass flow through the porous structures due
to pressure gradients, phase changes (evaporation, condensation and dehydration) and crack opening due to thermally incompatible aggregate-cement paste, etc. While existing experimental techniques provide pointwise measurements [2] or 2D moisture profiles [3], information in 3D is indispensable for taking into account the heterogeneous nature of concrete.
Neutron tomography allows access to the local moisture distribution in concrete. The experiments that we performed consisted of heating test samples to fire-like conditions while simultaneously acquiring rapid neutron tomographies, with the aim of tracking the evolution of moisture content. Cylindrical specimens with a diameter of 3 cm were tested. As one of the objectives was to estimate the influence of aggregate size, two concrete mixes were used: one with a maximum aggregate size of 4 mm
Figure 1
Example of a 3D scan acquired in 1 min with neutron tomography while the concrete is being heated. The 3D volume is cut in half to highlight the drying front around the aggregate.
ANNUAL REPORT 2018