Workflow for Concrete Scanning
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Workflow for Concrete Scanning

During our training courses, we get many questions from new users about the practical side of concrete scanning. Learning to operate the equipment is fairly straight-forward and users improve their interpretation skills the more they use it. But to really be successful as a service company, it’s important to follow a suitable workflow that ensures you are delivering results that meet customer expectations, on-time and without incident. This article discusses a typical workflow that should be followed, with a focus on the concrete inspection market. However, some concepts can apply to other industries as well (for example rebar, post tension cable and utilities locating, and forensics).

Before even leaving the office, it’s important to ask the customer the right questions to determine if GPR is even feasible for the job. Sometimes people have incorrect, perhaps exaggerated, information about GPR’s capabilities. If expectations are not realistic and achievable, this not only gives GPR a bad name, but is also a waste of everyone’s time. Find out what are they trying to accomplish. Are they looking to core, trench cut, verify placement/depth or other investigative information? Some specific questions to ask:

  1. What is the problem/target feature being investigated?
  2. What is the target depth? Note that maximum GPR penetration in concrete is about 24″ (60 cm)!
  3. How old is the concrete? (new concrete can take up to 2 months to cure from a GPR point of view)
  4. Are there any obstructions or unique site conditions? Related to this, is there adequate room to move the GPR scanner?

Once you have determined that GPR is suitable, the next step is to properly estimate the job. The site should be ready and clear when you arrive otherwise you are wasting time doing on-site preparation. If the job is the typical “scan before you core”, then you probably already have a set charge for that (per grid or per hour). If not, you will want to get as much information as possible and request as-built drawings. Address the liability issue; should an accident occur, liability is always a concern and while GPR is very accurate, there is no technology that is 100%. Many companies choose to have terms and conditions in their work order form to mitigate that. Without sounding negative, it’s important that customers are clear that they are not buying insurance that will protect them from liability.

Upon arrival at the job site, take some time to look around, especially beneath a suspended slab or behind a wall. Take note of the visible construction design (beams, pan decking, surface mounted conduits underneath). Also try and talk to the project engineer or General Contractor to find out about any non-visible construction details (post-tension deck, hollow-core slab, topping slab). Knowing construction practice/layout will greatly aid during data interpretation. Also very important is to get an idea of what features may be embedded in the slab. If this is a coring job, you obviously don’t want to hit gas/electric as these can be very dangerous. Cutting telecom/network cables, while not fatal, can be financially disastrous for a company’s downtime. If there are any indications that these may be in the slab, you should be extra vigilant when analyzing the data.

Following a workflow does not mean there is a set formula for every job, but it provides a guideline. You still need to tailor how you approach the job to meet the customer’s requirements. As well, you have to be flexible on-site and adjust your scans should you find something unexpected. Companies need to be well versed in approaching the job in its entirety, not just from an equipment operation point of view. The importance of communication in understanding the customer’s needs and what exactly you are going to deliver can never be overstated.