Alkali-silica Reaction In Concrete Structures Research Articles

ASR crack identification in bridges using deep learning and texture analysis

Alkali-Silica Reaction (ASR), commonly known as ‘concrete cancer,’ is an expansive reaction occurring over time between aggregate constituents and alkaline hydroxides from cement. As a destructive phenomenon, the need to detect the onset of ASR in concrete structures to ensure their long-term durability and structural integrity is thus evidenced. In the structural health monitoring field, vision-based approaches have been found to be viable, fast, and cost-effective in diagnosing numerous types of cracks using physical attributes and surface patterns. However, achieving high accuracy in detecting ASR cracks using traditional visual inspection techniques is challenging and time-consuming. Inspired by artificial intelligence technology, this paper proposes and evaluates a two-phase computer vision procedure for detecting and classifying ASR cracks utilizing a collection of ASR images recorded from several bridges in Queensland, Australia. In the first phase, the procedure compares common pre-trained CNN models to investigate their capability in classifying ASR cracks and to select the best-performed model. In the second phase, a novel Feature Enhancement Process (FEP) was first proposed to increase the contrast between ASR cracks and the heavily textured backgrounds within the images. Next, to better highlight the ASR crack features, the feature-adjusted images are processed further through different texture analysis algorithms including: (i) Texture Morphology, (ii) Adaptive thresholding, and (iii) Local range filtering. The study shows that the proposed FEP can improve the ASR crack classification accuracy of InceptionV3, which is the best CNN model selected from Phase 1, from 90.9% to 92.48%. Furthermore, by combining FEP with texture morphology, a robust two-stage tool for assessing ASR cracks can be made with an impressive validation accuracy of 94.07%. This research contributes towards the application of novel AI deep learning technology in providing cost-effective autonomous ASR crack classification tools to support the owners and managers of civil public works assets and other constructed infrastructures.

Alkali-silica reaction (ASR) in concrete structures: Mechanisms, effects and evaluation test methods adopted in the United States

Alkali-silica reaction (ASR) and its associated deformation are major durability problems in concrete structures and was reported as far back as the 1940s by Stanton (2008) [1]. This deleterious reaction causes excessive expansion and cracks that can lead to severe degradation of the concrete structures. Despite the age-long discovery and numerous ASR studies, understanding the ASR mechanism remains challenging due to complex processes and reactions. This paper presents a review of ASR in concrete structures and details the factors associated with ASR, the reaction mechanism and chemistry, and its adverse effect on concrete structures. The alkalis in the pore solution, the reactive amorphous silica present in aggregates, and the presence of moisture (with other external climatic inputs) are the key factors responsible for ASR. The study also provides a critical assessment of the various test methods for ASR evaluation in the United States. A case study correlating the results (from the literature) of three prominent test methods was also carried out. From this review, the new miniature concrete prism test (MCPT) method was concluded to be rapid, reliable, and capable of determining the influence of aggregate reactivity, alkali availability, and exposure conditions as compared to other methods.

Optimising an expansion test for the assessment of alkali-silica reaction in concrete structures

This work is part of an overall project for the reassessment of concrete structures damaged by alkali-silica reaction (ASR). The paper focuses on developing a laboratory method for expansion tests since the usual tests appear to be difficult to use in expert assessment. The development involves optimising the storage conditions and the sizes of the specimen and aggregate. A combined effect of the aggregate and specimen sizes on ASR expansion is thus pointed out: for a given mortar, the expansion is lower in small specimens than in large specimens. Therefore, the ratio ‘specimen size/aggregate size’ has to be sufficiently high to decrease this scale effect and obtain relevant measurements. The discussion proposes a method for always using comparable conditions during the expansion tests and finally suggests how this test can be optimised to provide fast and relevant results for use in structure reassessment.

Measurement of alkali–silica reaction progression by ultrasonic waves attenuation

Development of non-destructive methods, developed specifically for assessing the damage induced by alkali–silica reaction (ASR) in concrete structures, is needed in order to carry out a systematic evaluation of the concrete condition. The aim of this study is to monitor the evolution of the ASR-damage in laboratory with concrete samples with ultrasonic pulse velocity and attenuation of ultrasonic waves methods. For this study, results of both methods were compared with expansion and mass variation.One reactive concrete mixture was made with reactive aggregate, and one other mixture, incorporating non-reactive aggregate, was made as a control. Specimens were kept at 38 °C in a 1 mol l−1 NaOH solution to accelerate the reaction. Attenuation of transmitted ultrasonic waves appeared to be more appropriate for the evaluation of ASR-damage compared with pulse velocity. The attenuation of accelerated reactive concrete cylinders increased by 90% after 1 year while it increased by 40% for the non-reactive concrete used as a control. Major part of the attenuation increase in the non-reactive concrete is due to liquid absorption.This work suggests that in-situ non-destructive techniques based on ultrasonic wave attenuation, like ultrasonic attenuation tomography, should be developed in order to evaluate the development of ASR in concrete structures. Petrographic examination confirmed that damage to concrete is associated with ASR.