Measuring Concrete Permeability with CHIP

Project Details







Tyler Ley




Concrete, Permeability, Service life, Test procedures, Tracers (Chemistry), X-ray analysis

Project description

This project is a follow-on study 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 stage will be improved to know the locations from previous scans and to allow investigation of many different sample orientations, saving operator time and making the device easier to use. Currently, a potassium iodide solution is used as a tracer but there are other tracers that might give similar results more rapidly.  Presently, samples are ponded for 7 days for diffusion coefficient measurement.  So the measurement time may be shortened by using a different tracer and/or storing samples at an elevated temperature to speed diffusion.  Both possibilities will be explored. The previously software also needs to be made more user-friendly, as it uses several different programs to scan, analyze, and predict the service life of the concrete.  It is cumbersome to change between then programs and often confusing to the user.  The new software will also incorporate service life models that will use basic input information within already established models to predict the service life of the structure, based on the measured diffusion coefficient.  Oklahoma, Minnesota, and Illinois DOTs are collaborating to provide concrete samples during mixture design and construction and also after concrete placement and curing.  Measurement of these samples are expected to provide would allow important insights into how these different processes impact the concrete permeability.  Work in Stage 2 will develop precision and bias statement as well as an AASHTO test method. The repeatability of a single as well as multiple users to better understand the variability of the developed device will be determined by comparing the results on 20+ samples by multiple users. A rough draft for an AASHTO test method will be prepared for the developed technique.  The final report will provide all relevant  data, methods, models, and conclusions along with guidance on using the system to measure the permeability of hardened concrete.