Measuring the Diffusion Coefficient of Paste and Concrete by Using Dental X-ray Equipment

Abstract

The penetration of ions plays an important role in the durability of concrete structures. This study aims to establish the feasibility of using dental X-ray equipment to measure the concentration and penetration of iodide within cementitious systems. This technique is known as checking ion penetration (CHIP). This test uses iodide as a tracer because it has a high electron density, and so it can be observed with X-ray imaging as it penetrates the concrete. Concentration profiles from CHIP are used to calculate the apparent diffusion coefficient (Dac). These results are similar to measurements from bulk chloride ponding tests. The Dac is used to predict the service life or evaluate the quality of an as-built concrete structure or concrete mixture. Because of the wide availability of dental equipment, CHIP shows promise to be used as a method to measure the in-place quality control of the concrete.

Measuring the Diffusion Coefficient of Concrete with Dental X-ray Equipment

“…Behravan et al [24] used inexpensive dental X-ray equipment to find results that are comparable to previous TXM measurements. This test method is known as Checking Ion Penetration (CHIP).…”

“…Next, the samples are ponded with a 0.6 mol/L potassium iodide (KI) solution for 28 days. The solution on top of the samples was changed every five days to provide samples with a constant KI concentration [22][23][24].…”

“…Behravan et al [24]radiographed paste samples from 2 sides and concrete samples from three sides. This study used radiographs from images with up to 9 sides to improve the reliability of the measurements.…”

“…Using CHIP, radiographs of these samples were collected to correlate the resulting gray value to the concentration of KI. These known concentration values were then employed to establish a calibration curve that converts attenuation values to concentrations [24].…”