There are many structural testing and investigation techniques currently available to Owners, Operators, Engineers and Architects to examine and rapidly assess the condition of their structures. Many of these tests use Non-Destructive Testing or NDT techniques.
When the need for testing arises, either on a construction site or for existing structures, due to unknown structural properties, structural defects or material deterioration, we can use a variety of NDT techniques and intrusive investigations to determine material properties, assess the cause of defects and examine the extent and severity of deterioration. Structural testing and investigations can be used on single elements or can be expanded to assess the overall condition of existing structures.
Testing methods such as cover surveys, half-cell potential surveys and resistivity surveys on embedded reinforcement provide the essential data for a standard condition assessment of reinforcement.
A covermeter survey will quickly determine the depth of cover to reinforcement and with modern covermeters, we can determine reinforcement layout to depths of up to ≈160mm in the concrete. Moreover, covermeters can now generate images of the embedded reinforcement and estimate the rebar diameter for on-site review.
Cover meter surveys are restricted to the top mat of reinforcement in concrete. Hi-frequency Ground Penetration Radar (GPR) systems are now readily available for testing concrete structures and imaging to depths of ≈550mm. GPR for concrete structures is used by Infrastruct to gather information on rebar layouts, locating hidden defects, locating post-tensioning cables and in conjunction with the other test systems below confirming the integrity of concrete structures.
Half-cell potential surveys and resistivity measurements will indicate the risk of reinforcement corrosion in concrete but adopting the Linear Polarisation Resistance (LPR) technique will allow a determination of the rate of reinforcement corrosion.
The need to understand the in-situ compressive strength of concrete is a basic requirement for Engineers and Architects to push forward with their construction projects. Rebound Hammer surveys often referred to as Schmidt Hammer surveys are useful for screening concrete in advance of concrete coring operations. If a calibration curve, specific to a concrete region is prepared, a Schmidt Hammer survey can then be used to estimate the in-situ compressive strength of concrete.
Concrete quality and the integrity of placed concrete will affect the in-situ compressive strength and durability of concrete. Engineers and Architects need to have confidence that the concrete placed on their projects is of good quality and that there are no hidden defects within the concrete.
At Infrastruct, we use different techniques depending on the site conditions and information required. Ultrasonic Pulse Velocity tests, also referred to UPV surveys, are very useful to classify the quality of the in-situ concrete. UPV surveys are completely non-destructive and are useful for many structural configurations.
Ultrasonic Pulse Echo surveys and Impact Echo testing can locate and quantify the extent of hidden defects in hardened concrete. At Infrastruct we use the MIRA pulse echo tomograph and DOCter Impact Echo equipment for location of hidden defects in concrete structures.
Concrete permeability is critical to the durability of concrete in all service environments. Permeability is determined by many different techniques and on-site this can include air permeability testing and water permeation testing. At Infrastruct, we use different techniques, depending on requirements, to carry out concrete permeability surveys including the GWT permeability method from Germann Instruments. Careful surface preparation, understanding the moisture condition of the concrete and measurement of concrete resistivity are important for accurate surveys on existing structures.
Mechanisms that can cause concrete deterioration or corrosion of reinforcement are common and can, under certain conditions, rapidly affect the durability of concrete if we do not know the attack is on-going. Carbonation testing is used to determine the penetration of the carbonation front into concrete over time. The risk of carbonation-induced corrosion increases when the depth of carbonation is equal to or is greater than the depth of rebar cover. The rate of carbonation penetration can be modelled for individual structures for residual service life calculations.
The chloride content of concrete in structures is determined using shallow sampling depth increments, collecting the concrete dust samples and analysing the samples for chloride concentration and plotting a profile of chloride concentration versus depth and comparing the chloride content in the concrete to the depth of reinforcement cover. Chloride testing is essential to determine the risk of chloride induced corrosion of reinforcement in concrete. The rate of chloride ingress is important and can be modelled for individual structures for residual service life calculations.
The above concrete testing systems can provide Engineers and Architects with pertinent information on the condition of their structures. However, it is critical that the information gathered is correct, accurate and taken from specific locations on the structure. We always recommend that structural testing and investigations are carried out by competent engineers and technicians, trained and experienced in the use of structural test equipment.
If you require more information on structural testing and structural investigations, the right test equipment for your project or interpretation of test results or test information then please don’t hesitate to contact us at info@infrastruct.ie.
