Electrical conduits embedded in concrete have been marked through scanning — can we drill/core in cleared spaces near them?

Electrical conduits embedded in concrete have been marked through scanning — can we drill/core in cleared spaces near them?

The answer to the question seems to be obvious. Since the electrical conduits have been marked through scanning, why can't we drill/core in those cleared areas? We will keep a few inches away from those marked conduits, isn't it good enough? Unfortunately, it might not be. Are you telling us that the conduits are not marked accurately? Well, ground penetrating radar (GPR) can be as accurate as within an inch in finding conduits and other objects embedded in concrete. However, GPR accuracy is not the main issue here. The main issue lies in the limitations of scanning technologies. Due to the nature of scanning methods including GPR and cable/pipe locators, generally there are no guarantees that all conduits can be…
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Ghost rebar in ground penetrating radar concrete scanning

Ghost rebar in ground penetrating radar concrete scanning

Whether for embedded utility detecting or non-destructive testing (NDT) of concrete slabs, ground penetrating radar (GPR) interpretation involving rebar is often unavoidable. Understanding how GPR waves travel in reinforced concrete, and consequently what corresponding GPR profiles look like, are very important for appropriate GPR data interpretation. This article is about a "ghost rebar" phenomenon often encountered during GPR scanning of concrete slabs. These ghost rebar are not real but can show up and look real in GPR profiles. Even in theory this phenomenon can be easily understood, ghost rebar can cause confusion for data interpretation in real situations, especially when the concrete is not homogeneous or there are complex rebar patterns. Let's take a look at a GPR profile as…
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Cross-polarized GPR scanning – a useful technique for locating utilities embedded in reinforced concrete

Cross-polarized GPR scanning – a useful technique for locating utilities embedded in reinforced concrete

Above is an image showing two concrete ground penetrating radar (GPR) scanning profiles along the same line with normal and cross-polarized antenna orientations, respectively. Although the electrical conduit is visible in both profiles, it's easier to spot it in the cross-polarized profile than in the normal orientation profile. In the cross-polarized profile, the reinforcement's signature pretty much disappear; the conduit's signature also dials down, but remain very noticeable. So their differences are greatly amplified in the cross-polarized profile compared to the normal orientation profile. This tells us that the two signatures most likely represent two different objects, and it's most likely caused by the difference in their diameters. Of course, there are other possibilities such as differences in orientations or…
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GPR scanning for voids underneath concrete slabs

GPR scanning for voids underneath concrete slabs

Ground penetrating radar (GPR) is a great tool for checking potential voids beneath concrete slabs. The concrete on the ground surface may look fine, but the void might already be developing and it's just a matter of time before it collapses. If you have a large area of concern for potential underground voids, scanning with GPR and doing test holes in GPR anomaly areas might be the best option. Geophysicists in Quark Scan are highly experienced in concrete scanning and underground void locating. Give us a call!
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