Our services can be separated into two important parts, namely, Field measurement service and In-house analysis service. By Field service, our engineering team comes with a Ground Penetrating Radar device to measure the structure. The length of the service depends very much on the size of the structure. By In-house service, we process the acquired data from the clients and provide our studies in the form of graphically summarised maps and reports.
Contamination and corrosion risk
The contamination and corrosion risk maps are used to evaluate the chemical disorders of the cover concrete.
The chemical disorder analysis focuses on two elements. Firstly, we assess the vulnerability (thickness of the cover concrete) and the hazard (the contaminant concentration e.g. water and chlorides). Secondly, with this information, we can then qualify the likelihood of corrosion of the reinforcement and locate deficiencies within the waterproofing system.
Corrosion of the embedded reinforcement is the major deterioration process in reinforced concrete structures. This occurs when the chemical condition of the concrete around the rebar changes, and contamination (most often chlorides) penetrates through the cover concrete and reaches the rebar. Once initiated, its process starts and gradually reduces the rebar diameter, affecting thereby the bearing capacity of the concerned element. Therefore, early detection of the cause of chloride ingress is needed in order to avoid this risk.
With the help of our studies, our customers can evaluate the risk of corrosion of the reinforcement and take early action to prevent, slowdown or even stop the corrosion process. Thanks to our data, the repairs can be localized and applied only to the required areas.
The contamination map represents the electric conductance of the cover concrete in mS. It unveils the relative magnitude and the extent of the total chemical contamination as well as helps to identify waterproofing defects and potential water entry points. In a second step, the conductance measurement can be calibrated with the results from the chemical analysis performed on cores.
Corrosion risk map
The corrosion risk map represents the electric conductivity of the cover concrete in S/m. It highlights the areas with a higher risk of rebar corrosion.
The map is based on the corrosion risk equation ⃗
Our datasets are systematically calibrated, which consists in comparing the contamination values with the average Cl– concentration measured on cores taken from the structure.
We generally expect the correlation of the calibration to range between 75% to 85%. A correlation coefficient of 0.77 on our last 11 bridges (41 core samples) has been observed.
We also calibrate the thickness of the layers using cores whenever possible to increase our accuracy.
When possible, we ask our customers to send us some feedback to evaluate the accuracy of our measurements. The following examples show the excellent accuracy of a corrosion risk map, which helps to identify corroded and non-corroded areas of the bridge deck. Similar results were obtained on 3 major bridges in Lavaux region (Switzerland).
The GPR method was initially developed to detect features and interfaces in the ground. We use the same technique to provide detailed geometry maps of concrete structures.
With the high accuracy of our GPR equipment, we can provide the thicknesses of the various layers composing the surfacing of the bridge deck. Furthermore, in a combination with calibration using core samples, we can guarantee a +/- 1 cm accuracy.
The thickness surveys are also particularly interesting to determine the thickness of undocumented and inaccessible structures like retaining walls or base plates.
We can also provide detailed geometry of discrete elements or features such as rebar location and masonry blocks, with 3D models representing the accurate position and types of masonry stones.
Concrete cover Map
This map reveals the thickness of the cover concrete of the top layer rebars. It indicates the areas with a lack of concrete cover or potential over-thicknesses.
The removal depth and volume of material can be precisely estimated before an eventual hydrodemolition of the cover concrete.
Rebar Spacing Map
When the original blueprints are missing or incomplete, we can provide this map as a visual confirmation tool to help discover the spacing of existing structures. The same principle is also applied to the new structures.
On the concrete deck example on the right, three distinct areas are revealed: the expected 150mm spacing on the right span, a higher density rebars around 15m on the supports, and an “anti-cracking” 4mm mesh on the left span with a 200mm spacing.
Asphalt Thickness Map
With this map, we can visualize the total thickness of the asphalt. Depending on its composition, we are also able to provide the thicknesses of its different layers. Similar to the concrete cover map, this map is a valuable tool to detect potential under-thicknesses or over-thicknesses.
We have vast experience of masonry structures, ranging from retaining walls, historical bridges to ancient roman theatres.
We can provide detailed 3D models with the thickness of cladding stones, the volume of infill, and the location of potential steel reinforcement or anchor bars embedded in the walls.
Mechanical disorder maps
Generally, the typical structural disorders that can be identified in reinforced concrete and masonry structures are delamination, voids, and macro cracks. We can certainly provide our clients with those maps by using a high-resolution GPR scans in combination with our expertise.
Masonry disorder maps
Masonry Injection Maps
Masonry before and after injection
Le Grand-Chemin 73
T +41 79 297 40 54
Designed by Swiss Backstage
Le Grand-Chemin 73
T +41 79 297 40 54
Designed by Swiss Backstage | ©Bridgology 2021