Inspection of ageing, reinforced concrete structures is a world-wide
challenge. Existing evaluation techniques in civil and structural engineering have limited penetration depth and don’t allow to precisely ascertain the configuration of reinforcement within large concrete objects. The big challenge for critical infrastructure (bridges, dams, dry
docks, nuclear bioshields etc.) is understanding the internal condition of
the concrete and steel, not just the location of the reinforcement.
Muon scattering tomography is a non-destructive and non-invasive
technique which shows great promise for high-depth 3D concrete imaging.
A method was presented to locate reinforcement placed in a large-scale
concrete object. The reinforcement was simulated as two layers of 2 m long bars,
forming a grid, placed at a fixed distance from each other inside a large concrete
block. The technique exploits the periodicity of the bars in a reinforcement grid
by considering the Fourier-transformed signal. The presence of a grid leads to
peaks in the normalized Fourier frequency spectrum. Peaks locations are determined by the grid spacing and their amplitude by the bar diameters. It is
therefore possible to estimate both bar diameter and spacing with this method.
Using only one week worth of data taking, bars with a diameter of 7 mm and
larger, could easily be detected for a 10 cm spacing. The signal for 6 mm diameter bar exceeds the background and but becomes very clear after two weeks
of data taking. Increasing the spacing to 20 cm results in a smaller amount
of iron in the scanning area, thus longer data taking is required. It has been
shown that this method enables the detection of the smallest bars in practical
use within one or two weeks of data taking time and standard spacing. This is
a very important result for non-destructive evaluation of civil structures.
|Institute||University of Bristol|
|Your name||Magdalena Dobrowolska|