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Lime, cement and concrete
Published in Arthur Lyons, Materials for Architects and Builders, 2019
Where the depth of concrete cover over reinforcement is in doubt, it can be measured with a covermeter. If reinforcement is corroding, cathodic protection by application of a continuous direct current to the steel reinforcement may prevent further deterioration and lead to realkalisation of the carbonated concrete.
Codes and Specification Guides
Published in Mohamed Abdallah El-Reedy, Steel-Reinforced Concrete Structures, 2017
The position of reinforcement should be checked before and during concreting; particular attention should be directed at ensuring that the nominal cover is maintained within the given limits, especially in the case of cantilever sections. The importance of cover in relation to durability justifies the regular use of a cover meter to check the position of the reinforcement in the hardened concrete. Figure 5.3 shows the electromagnetic cover meter equipment, which is discussed in detail in Chapter 4.
An experimental study on the corrosion amount using a statistical analysis
Published in Corrosion Engineering, Science and Technology, 2018
Hongjun Zhu, Xin Liu, Chaolong Jia, Baisong Du, Simeng Liu, Ying Qian
The experiment was carried out on a reinforced concrete T-beam bridge when the weather was sunny and calm. Before heating, the diameter of the testing rebar and the thickness of its cover were estimated using a cover meter, as shown in Figure 6(a). The induction coil was placed on the concrete surface with the central axes of the coil and the rebar meeting at right angles (Figure 6(b), close-up illustration). Then we captured the temperature with the steps, shown in the section ‘Experimental procedure’. Note that the test points are far enough away from each other to keep out of temperature influence, heating time should be short enough to avoid high temperature damage on the bridge.
A hybrid experimental-numerical approach for load rating of reinforced concrete bridges with insufficient structural properties
Published in Structure and Infrastructure Engineering, 2019
Abdollah Bagheri, Osman E. Ozbulut, Devin K. Harris, Mohamad Alipour, Ali Zare Hosseinzadeh
However, for bridges with limited or missing structural details, only a limited number of studies related to determining bridge load rating are available in the literature. In an investigation by Huang (2007) and Huang and Shenton (2010), researchers formulated a method described as the steel area method to rate reinforced concrete bridges without as-built information. In this approach, measured strain or displacement data is used to estimate the unknown area of reinforcing steel in a bridge by solving the strain profile relationship of a cross-section for the area of steel where the depth to neutral axis is calculated from the moment-strain stiffness. A limitation of this approach is that it requires instrumentation on the riding surface of the bridge, which can impede service and also requires the knowledge of the mechanical properties of the materials used in the structure, which requires some form of destructive testing or approximation. Similarly, Aguilar et al. presented a four-step load rating procedure for prestressed concrete bridges using proof load testing (Aguilar, Jáuregui, Newtson, Weldon, & Cortez, 2015). Their method included estimating the number and eccentricity of strands using Magnel diagrams and typical details at the time of construction. They conducted a proof load test with a target proof load based on the AASHTO MBE and the results were used to calculate final load ratings. According to the MBE, proof load testing is recognized as a viable solution to determine the safe load carrying capacity of a bridge, but this approach is also potentially a destructive method as the structure is incrementally loaded until signs of distress appear. Proof load testing is considerably complicated and costly in terms of logistics and safety because of the potential for damage to the structure. In another study, Subedi (2016) employed non-destructive technologies including a concrete rebound hammer and cover meter to estimate concrete strength and rebar details, respectively. The ratio of the corresponding allowable load to the original design load was calculated as a rating factor. It should be noted that the method did not include the effects of field factors or bridge condition in load rating, and the use of deflection as the limit state does not correspond with the actual allowable capacity for load rating. These works further highlight that this challenge of bridges with missing or insufficient structural details is one of national interest, but solutions are still needed.