This project is a continuation of a previous IDEA project (NCHRP-199) that developed a prototype device to determine the permeability of hardened concrete using X-rays to measure the penetration of a tracer. In this follow-on project, the current instrument sample holder was improved so that larger samples could be scanned. This new sample holder is also able to find the locations of previous scans to allow the investigation of various sample orientations, saving operator time and making the device easier to use. The software for the device was also improved to make it easier and faster for the user. The use of the developed technology was evaluated through three case studies. The first case study focused on the effectiveness of wet curing and how different curing lengths impacted the diffusion coefficient (Dic) of the concrete. Next, the performance of the silane sealers was evaluated in field cores. Finally, the long-term change in Dic was measured with mixtures that contained different amounts and types of fly ash. The reliability of the technique was further improved by increasing the number of orientation to evaluate the sample and the width of the analysis area. Finally, work was done to decrease the testing time from 28 days to roughly 6 hours. The test can be accelerated by using electric current to drive the tracer through the concrete. Further research is needed to make this technique applicable to a wide range of materials. An overview of the test method is provided with the suggested language that may be helpful in developing a testing standard.
The Final Report is available.
