This session will provide attendees with a comprehensive understanding of how advanced material characterization techniques, commonly used in academic research, can be effectively applied to real-world forensic investigations of concrete failures. The focus will be on identifying the root causes of issues in both new construction and existing concrete structures. Presentations will highlight how these techniques can uncover underlying problems; help mitigate risks and improve the long-term durability of concrete. Participants will gain valuable insights into how material science tools can diagnose concrete issues, provide actionable solutions, and ultimately prevent failure. This session is designed for professionals across multiple disciplines, including consultants, contractors, engineers, researchers & scientists, material scientists. In general, anyone involved in the design, construction, and maintenance of concrete structures will benefit from attending.
Learning Objectives:
(1) Recognize frequent issues that arise during the construction phase and in existing concrete structures;
(2) Discuss the material characterization tools used to diagnose concrete-related problems;
(3) Develop insight into which forensic methods are best suited for specific types of concrete failures and understand the data they provide;
(4) Examine how concrete deterioration manifests in hardened concrete and the long-term consequences these issues may have on structural integrity;
(5) Review practical solutions to avoid future failures and improve the quality and longevity of concrete structures through proper material selection, construction practices, and monitoring techniques.
Imaging Biological Healing in Concrete Vasculature Network Using Ground Penetrating Radar (GPR)
Presented By: Panji Darmal
Affiliation: NC State University
Description: Microbially Induced Calcium Carbonate Precipitation (MICP) is an innovative bio-based technique that has gained significant attention for its potential to enhance the healing and durability of concrete. This process utilizes specific bacteria which precipitate calcium carbonate (CaCO3) as a byproduct of their metabolic activities, filling cracks and improving structural integrity. To optimize the MICP process, we propose ground penetrating radar (GPR) to visualize the MICP process. We designed five experimental scenarios to explore the MICP process using GPR measurements: (a) a baseline with the mortar bar (7.5x7.5x35 cm) in its original state; (b) a 5 cm vertical saw cut to assess structural integrity; (c) a 1 cm fill of calcium carbonate in the saw cut to evaluate minimal infusion effects; (d) a 2 cm fill to investigate deeper infill effects on radar detection; and (e) a 3 cm fill to test GPR's ability to differentiate between varying material infills. The experimental results show that we can visualize the presence of calcium carbonate both qualitatively and quantitatively through delta electromagnetic strength ?E images by using sequential differential imaging techniques.
Keywords: Ground Penetrating Radar, MICP
Forensic Investigation of Deicer-Induced Deterioration: Mechanistic Insights into Corrosion and ASR in Concrete Pavements
Presented By: Ebenezer Fanijo
Affiliation: Georgia Institute of Technology
Description: This study investigates the deterioration mechanisms in concrete pavements caused by chloride-based deicers, which contribute to significant distress through processes involving corrosion and Alkali-Silica Reaction (ASR). Chloride ions from deicing salts chemically interact with calcium hydroxide in the pore solution and cement hydration products, leading to the formation of calcium oxychloride compounds. These compounds then disrupt the cementitious matrix and caused chloride-induced corrosion by breaking down the passive oxide layer on embedded steel rebar. Additionally, the deicers have been linked to ASR by modifying the composition of calcium-silicate-hydrate (C-S-H) gel and promoting secondary reaction products. In fact, preliminary findings suggest this reaction is primarily driven by a sudden increase in pH when the deicing solution contacts cement hydration products, enhancing silica dissolution and ASR expansion. While similar deterioration mechanisms have been proposed, there is a lack of comprehensive experimental and field data validating these reactions.
This study aims to enhance understanding of chloride-based deicer interactions with concrete by elucidating the reaction mechanisms responsible for pavement distress. The research integrates laboratory investigations of deicer effects on concrete microstructure with forensic analysis of core samples from sodium chloride-treated pavements, providing insights into degradation processes and informing mitigation strategies for improved pavement durability.
Detecting ASR Damage via Raman Imaging: Lab & Field Investigations
Presented By: Nishant Garg
Affiliation: University of Illinois at Urbana-Champaign
Description: The Alkali Silica Reaction (ASR) – also known as concrete cancer - is a significant problem in concrete deterioration. This reaction occurs between the highly alkaline cement paste and reactive silica in certain aggregates. Long term, in the presence of moisture and the aforementioned chemical constituents, the formation of the ASR gel can lead to expansion and widespread cracking in concrete structures. Detecting and understanding the ASR damage, from a spatiotemporal perspective, has been a long standing interest for forensic researchers. Here, we present early results on ASR affected samples from Raman imaging – an emerging technique for quantitative understanding of phase assemblages in cement-based materials. Lab results indicate that valuable information about the mineralogy and chemical composition of the ASR products can be obtained, including their presence within cracks in aggregates and air voids adjacent to aggregates. In addition, we will share preliminary results on samples collected from the field. Overall, these results suggest that Raman imaging can be a potential tool in the tool kit of forensic investigators studying and tracking ASR.
Keywords: Raman imaging, ASR, lab samples, field samples, ASR damage, forensics
Diagnosis of Concrete Durability Related Deterioration using Concrete Petrography and other Techniques
Presented By: Chunyu Qiao
Affiliation: Wiss, Janney, Elstner Associates, Inc.
Description: Quality concrete requires well-defined and accepted properties, such as workability, volume stability, strength, and durability. Concrete durability reflects its resistance to weathering, chemical attack, abrasion, and other service condition. Depending on the exposure conditions, long-term performance of the concrete is influenced by various durability mechanisms that involve interactions between external substances and internal materials. For instance, absorbed water in concrete can potentially cause damage due to freezing and thawing, and the penetration of some chloride-based deicers can chemically degrade and deteriorate concrete and accelerate steel reinforcement corrosion.
Concrete petrography is a method of examining hardened samples using a microscope to determine their composition and assess their conditions. In complex cases, multiple characterization techniques may be implemented together to comprehensively assess the concrete condition and distress related to different durability mechanisms. This presentation focuses on the application of concrete petrography (e.g. optical microscopy including fluorescent microscopy, and scanning electron microscopy with electron dispersive spectrometry), as well as other analytical techniques, to diagnose durability related concrete deteriorations associated with alkali-silica reaction (ASR), delayed ettringite formation (DEF), and freeze-thaw cycles (F-T).
Development of a Multi-Disciplinary Approach for Macroscale Assessment of Pyrrhotite-Affected Basements
Presented By: Patrick Dixon
Affiliation: Michigan State University
Description: Concrete in residential foundations in parts of New England, Canada, and Ireland has deteriorated due to pyrrhotite-bearing aggregates. Pyrrhotite is an iron sulfide mineral that can cause expansive reactions in concrete, leading to deterioration. To investigate this deleterious expansion, a pyrrhotite-affected basement in Connecticut was examined. A macroscale, multi-tool approach was employed to assess the structural deterioration. A high-resolution 3D model of the deteriorated walls was constructed using a low-cost camera and photogrammetry techniques. This approach helped capture the condition of the walls in a fraction of the time compared to traditional assessment techniques that quantify distress at relatively few sampled locations. Subsequently, the digital format of the models enabled the training and building of convolution neural network models to automatically detect cracks. The basement was scanned with LiDAR for potential structural distortions. Over thirty concrete cores with varying levels of visual deterioration were extracted and evaluated with resonant frequency testing. Select cores were subjected to mechanical testing and analyzed for total sulfur. These traditional and advanced methods were used complementarily to better understand the impact of pyrrhotite. The developed multi-disciplinary methodology for macroscale assessment of pyrrhotite-affected basements helps to monitor and quantify the condition of other pyrrhotite-affected structures.