Method for Assessment of Changes in the Width of Cracks in Cement Composites with Use of Computer Image Processing and Analysis

Abstract

Crack width measurement is an important element of research on the progress of self-healing cement composites. Due to the nature of this research, the method of measuring the width of cracks and their changes over time must meet specific requirements. The article presents a novel method of measuring crack width based on images from a scanner with an optical resolution of 6400 dpi, subject to initial image processing in the ImageJ development environment and further processing and analysis of results. After registering a series of images of the cracks at different times using SIFT conversion (Scale-Invariant Feature Transform), a dense network of line segments is created in all images, intersecting the cracks perpendicular to the local axes. Along these line segments, brightness profiles are extracted, which are the basis for determination of crack width. The distribution and rotation of the line of intersection in a regular layout, automation of transformations, management of images and profiles of brightness, and data analysis to determine the width of cracks and their changes over time are made automatically by own code in the ImageJ and VBA environment. The article describes the method, tests on its properties, sources of measurement uncertainty. It also presents an example of application of the method in research on autogenous self-healing of concrete, specifically the ability to reduce a sample crack width and its full closure within 28 days of the self-healing process.

Self-Sealing Process Evaluation Method Using Ultrasound Technique in Cement Composites with Mineral Additives

“…To evaluate the crack geometry, the side surfaces of the samples were scanned using a high resolution Epson V600 Photo 6400 dpi scanner (Seiko Epson Corporation, Tokyo, Japan). The initial crack width was measured using a method previously described [ 34 ] using computer image processing and analysis. Multiple measurements were recorded automatically and independently of the operator along the cracks.…”

“…To examine the relationship between the ultrasonic self-sealing ratio ( and the reduction in crack width at the outer surface of the samples, computer processing and analysis of the samples’ surface image was used [ 34 ] with a total of 25,080 cracks’ width measurements (an average of 418 measurements for each of six mortars at 10 time points). The average crack widths at any time point t i and relative changes in crack widths ( ) in relation to the initial crack widths were calculated according to Equations (8) and (9), respectively: where is the crack width measurement m at time point t i ; M is the total number of crack width measurements of a given mortar, m = 1, …, M ; is the average width of the cracks in samples of a given mortar at time point t i ; and is the average width of the cracks in samples of a given mortar for the state immediately after cracks were induced.…”

“…To examine the relationship between the ultrasonic self-sealing ratio ( ) and the reduction in crack width at the outer surface of the samples, computer processing and analysis of the samples' surface image was used [34] with a total of 25,080 cracks' width measurements (an average of 418 measurements for each of six mortars at 10 time points). The average crack widths at any time point ti and relative changes in crack widths (∆ ) in relation to the initial crack widths were calculated according to Equations ( 8) and ( 9), respectively: The linear relationship between the parameters describing the internal filling of cracks and the relative change (reduction) in crack width does not necessarily have to occur in all self-sealing experiment results.…”

“…Despite the widespread use of ultrasonic techniques, sensitivity to testing conditions and the accuracy of measurements remain current problems [ 19 ]. Some other technical issues and remarks related to sample preparation, the introduction of material defects, and cracks’ geometry analysis were also considered [ 34 , 35 , 36 , 37 ]. The proposed method, including self-sealing process evaluation, the experimental groups’ composition, ultrasound measurements, and the data analysis, is presented here through tests of the autogenous self-sealing of cracks in polypropylene-fiber-reinforced mortars modified with siliceous fly ash.…”

Key Factors Determining the Self-Healing Ability of Cement-Based Composites with Mineral Additives

“…Samples from the group designated M 14-days were scanned immediately after crack induction and after 122 days of subsequent curing. The digitally captured images were subjected to computer processing and image analysis using a proprietary method that has been published [ 63 ]. This study was complemented by microscopic observations (MO) using a Delta Optical Smart 5MP PRO microscope with digital image capture and a maximum optical zoom of 300×.…”