|
Post by thebastidge on Aug 12, 2017 15:46:24 GMT
Periodic inspection is an important part of any safety program. Determining means and methods to make a thorough and relevant inspection of any concrete or cementitious structure intended to float is a difficult undertaking. This thread can serve as a placeholder for links and techniques. heronjournal.nl/62-1/2.pdf Moisture movement in cement-based repair systems monitored by X-ray absorption
|
|
|
Post by jeff on Aug 21, 2017 17:16:13 GMT
One of the biggest drawbacks to OPC is osmosis, drawing water into even microscopic pores, where is can react with Calcium in the slaked lime, weakening the cement, even corroding steel rebar. Often the swelling is unnoticeable until just before spalling occurs. This is why so much of the American infrastructure is so difficult to assess.
Part of the inspection problem is the Calcium, which, like bones, is dense enough to absorb X-rays.
|
|
|
Post by thebastidge on Aug 23, 2017 15:52:21 GMT
Jeff, Once again, I have to disagree. X-rays show bones because it is a different density than flesh. Any time you get a wave passing through different densities of material, you can use imaging based upon the amounts reflected and the amount absorbed, and the amounts passing through compared to the original signal strength and direction. The amount of radiation in a medical X-ray is fairly precisely calibrated to show bones. A strong enough emitter would blow right through with barely a ghost image. There are LOTS of companies advertising X-ray services for concrete. In addition to ground penetrating radar and acoustic imaging. X-ray is more expensive, undoubtedly due to the danger of long term exposure to X-ray radiation and certification requirements for both equipment and technicians, plus the requirements to evacuate or perform the scan outside of business hours. The biggest problem for X-ray of concrete is having access to both sides so the plate is exposed on the opposite side of the target from the emitter. Ground penetrating radar returns and echo, but X-Ray needs film exposure. global-gpr.com/gpr-technology/concrete-x-ray-vs-gpr.htmlwww.inspection-resources.com/x-ray/bakertesting.com/index.php/gpr-vs-radiographyOtherwise, I agree with the problems with OPC. Hygroscopy, calciucm dissolving in seatwaer, sulphur reactions eating away the concrete (and creating an environment where microorganisms actually eat the minerals in the cement) and the eventual, inevitable corrosion of the steel reinforcement, not just mild steel but even stainless steel, as not all grades of stainless are equal and they simply don't corrode as fast. One problem with stainless is welding it can create microscopic pockets where the stainless alloy doesn't meet spec- it's either got inclusions from the welding medium or it gets hot enough to separate the alloyed metals by weight and it's not exactly the uniform alloy it started out. Then galvanic action starts within the weld between the original spec alloy and the changed metal.
|
|
|
Post by jeff on Aug 24, 2017 5:05:03 GMT
Don't need film at all, these days. That's why field X-ray examination of Pipelines and other things can work, even be adapted to examine geopolymer. HOWEVER, it has limitations that can allow the Calcium content of OPC to hide fatal flaws. It's STILL too expensive, but doable, where ferrocement hulls get visual inspections because of the limitations of other methods in accurately finding problems in OPC, and the expense of doing so. Ground Penetrating Radar is even more limited in value. It will help detect things, but not tell you what kind of condition the stuff between them is in. en.wikipedia.org/wiki/Digital_radiography
|
|
|
Post by thebastidge on Aug 24, 2017 18:19:54 GMT
Eliminating the ferrous component provides even more benefit than the low calcium, form an inaction angle. The ferrous component is the most likely to fail and the fastest to fail, and it's hidden inside until spalling shatters the covering.
The crumbling of concrete due to sulphur attack or calcium interaction with seawater starts from the outside inward. So from an inspection point of view, easier to detect.
OPC with non ferrous reinforcement is a step up. Low calcium cement is a step up from there, both for inspection purposes and longevity.
|
|
|
Post by thebastidge on Aug 24, 2017 18:20:58 GMT
I still haven't found any resources specifically calling out the calcium component of OPC as a factor n radio graphic imaging.
|
|