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Prof. Dr. Paul Ziehl
Department of Civil and Environmental Engineering, University of South Carolina, Columbia, SC 29208, USA

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0 Acoustic Emission
0 Sustainability
0 smart structures
0 geopolymers
0 Structural Health Monitoring (SHM)

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Journal article
Published: 15 June 2021 in Nuclear Engineering and Design
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Alkali-silica reaction (ASR) is one of main damages causes in concrete structures such as nuclear power plants which may endanger structural serviceability and integrity. Acoustic emission (AE) is a passive nondestructive method for structural health monitoring. It is very sensitive and has the capability of monitoring structures continuously. This method may be an alternative for early damage detection in concrete nuclear structures affected by ASR. The innovation of this paper lies in the implementation of deep learning algorithms to evaluate the ASR progress. ASR was monitored by AE in a concrete specimen, which was cast with reactive coarse aggregates and reinforced by steel rebars. The AE signals recorded during the experiment were filtered and divided into two classes. Two deep learning algorithms of convolutional neural network (CNN) and stacked autoencoder were employed to classify the AE signals into the corresponding classes. The model based on CNN resulted in a classifier with higher accuracy than the model based on the autoencoder network.

ACS Style

Li Ai; Vafa Soltangharaei; Paul Ziehl. Evaluation of ASR in concrete using acoustic emission and deep learning. Nuclear Engineering and Design 2021, 380, 111328 .

AMA Style

Li Ai, Vafa Soltangharaei, Paul Ziehl. Evaluation of ASR in concrete using acoustic emission and deep learning. Nuclear Engineering and Design. 2021; 380 ():111328.

Chicago/Turabian Style

Li Ai; Vafa Soltangharaei; Paul Ziehl. 2021. "Evaluation of ASR in concrete using acoustic emission and deep learning." Nuclear Engineering and Design 380, no. : 111328.

Review
Published: 17 April 2021 in Journal of Building Engineering
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The incorporation of multiwalled Carbon nanotubes (MWCNTs) and their dispersion procedures such as the use of surfactant agents, functionalization, and ultrasonication have been intensively implemented to improve the mechanical and durability properties of ordinary Portland cement (OPC) mortar and paste. Many studies stated significant enhancements in the mechanical properties of OPC mortar or paste; however, others showed impairments. The review observed the preparation techniques for dispersion and mixing MWCNTs with dry materials such as cement and sand. The recent studies regarding the implementation of MWCNTs on the mechanical properties of OPC paste and mortar were reviewed. These properties include compressive, tensile, flexural strengths, and elastic modulus. A statistical approach was conducted to observe the effects of the MWCNTs' amendment on the mechanical properties of Portland cement paste and mortar. The results showed that there is no consistent preparation technique for the dispersion of MWCNT. The ultrasonication, used in most studies either alone or as a surfactant combination, was the most effective technique for dispersion when the sonication duration was between 20 and 45 min. The statistical mechanical property observations revealed that the majority of compressive strength enhancements were below 40% (approximately 91% of the data) regardless of the MWCNTs %. The improvement in strength below 40% was 74% of the data for tensile/flexural strength of mortar. For cement paste, 50% of the enhancements were equal to or below a 40% increase. However, some studies showed impairments in the mechanical properties of OPC composites when MWCNTs were incorporated. Most reduction in compressive strength was below 40% compared to mortar and cement with 0% MWCNTs.

ACS Style

Lateef Assi; Ali Alsalman; David Bianco; Paul Ziehl; Jamal El-Khatib; Mahmoud Bayat; Falah H. Hussein. Multiwall carbon nanotubes (MWCNTs) dispersion & mechanical effects in OPC mortar & paste: A review. Journal of Building Engineering 2021, 43, 102512 .

AMA Style

Lateef Assi, Ali Alsalman, David Bianco, Paul Ziehl, Jamal El-Khatib, Mahmoud Bayat, Falah H. Hussein. Multiwall carbon nanotubes (MWCNTs) dispersion & mechanical effects in OPC mortar & paste: A review. Journal of Building Engineering. 2021; 43 ():102512.

Chicago/Turabian Style

Lateef Assi; Ali Alsalman; David Bianco; Paul Ziehl; Jamal El-Khatib; Mahmoud Bayat; Falah H. Hussein. 2021. "Multiwall carbon nanotubes (MWCNTs) dispersion & mechanical effects in OPC mortar & paste: A review." Journal of Building Engineering 43, no. : 102512.

Journal article
Published: 15 February 2021 in Nuclear Engineering and Design
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The dry cask storage system (DCSS) canisters have been used for the storage of high-level nuclear for decades. The inspections are needed to ensure that structural integrity is maintained. One mechanism of degradation on DCSS canisters that is of interest is stress corrosion cracking (SCC). Acoustic emission (AE) is a nondestructive technique that can be employed as an inspection approach since it can offer real-time degradation detection. This paper presents the approaches that can localize SCC sources by minimal acoustic emission (AE) sensor. To achieve this goal, three machine learning techniques (artificial neural network, random forest, stacked autoencoders) were adopted to improve the conventional source localization approach. In this paper, source localization is treated as a classification problem. The testing specimen was divided into multiple zones and located the AE signals to their corresponding zones. The AE signals were processed to create two datasets: a dataset consisting of AE parametric features and a dataset consisting of AE waveforms. Source localization approaches using artificial neural networks, random forest, and stacked autoencoders were trained and tested based on the datasets. The results show all three machine learning techniques can learn to map AE signals to their sources. Among them, stacked autoencoders have the best performance (97.8% accuracy of stacked autoencoders versus 91.5% of random forest, and 80.0% of ANN), demonstrating that it could be a potential approach to localize SCC events on DCSS canister.

ACS Style

Li Ai; Vafa Soltangharaei; Mahmoud Bayat; Bruce Greer; Paul Ziehl. Source localization on large-scale canisters for used nuclear fuel storage using optimal number of acoustic emission sensors. Nuclear Engineering and Design 2021, 375, 111097 .

AMA Style

Li Ai, Vafa Soltangharaei, Mahmoud Bayat, Bruce Greer, Paul Ziehl. Source localization on large-scale canisters for used nuclear fuel storage using optimal number of acoustic emission sensors. Nuclear Engineering and Design. 2021; 375 ():111097.

Chicago/Turabian Style

Li Ai; Vafa Soltangharaei; Mahmoud Bayat; Bruce Greer; Paul Ziehl. 2021. "Source localization on large-scale canisters for used nuclear fuel storage using optimal number of acoustic emission sensors." Nuclear Engineering and Design 375, no. : 111097.

Journal article
Published: 08 October 2020 in Construction and Building Materials
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The focus of this research is the identification of cracking mechanisms for cement paste using acoustic emission data, recorded from compression and notched four-point bending tests. A procedure is developed for analyzing the data by employing an agglomerative hierarchical clustering method, an artificial neural network, and a ray-tracing source location algorithm. An agglomerative hierarchical clustering method is utilized to cluster the AE data from a compression test using frequency-dependent features. A neural network is trained using the compression test data and applied to the AE data emitted during the four-point bending test. The clustered data from the four-point bending test is localized using a ray-tracing algorithm. Based on the occurrence and locations of the clustered events and signal feature analyses, potential cracking mechanisms are identified and assigned.

ACS Style

V. Soltangharaei; R. Anay; L. Assi; M. Bayat; J.R. Rose; P. Ziehl. Analyzing acoustic emission data to identify cracking modes in cement paste using an artificial neural network. Construction and Building Materials 2020, 267, 121047 .

AMA Style

V. Soltangharaei, R. Anay, L. Assi, M. Bayat, J.R. Rose, P. Ziehl. Analyzing acoustic emission data to identify cracking modes in cement paste using an artificial neural network. Construction and Building Materials. 2020; 267 ():121047.

Chicago/Turabian Style

V. Soltangharaei; R. Anay; L. Assi; M. Bayat; J.R. Rose; P. Ziehl. 2020. "Analyzing acoustic emission data to identify cracking modes in cement paste using an artificial neural network." Construction and Building Materials 267, no. : 121047.

Journal article
Published: 01 October 2020 in Journal of Materials in Civil Engineering
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The effect of steel reinforcement on the distribution of alkali-silica reaction (ASR) damage in concrete blocks is studied by leveraging acoustic emission sensing with a data-driven approach. The innovation lies in deriving damage contours caused by ASR based on a minimal sensor array. Through this approach, damage progression can be traced in time and event distribution can be visualized. A gap in the current literature, namely evaluating ASR progress in concrete structures with different internal restraint using acoustic emission (AE), is addressed. Unsupervised pattern recognition is utilized to study the effect of the temporal damage condition. In the confined specimen, the distribution of AE events in the midwidth region of the specimen is concentrated and close to the normal distribution. The surface cracks are mostly oriented along the specimen length and in the midwidth region. However, in the unconfined specimen, the distribution of AE events is more uniform, and cracks are randomly distributed.

ACS Style

Vafa Soltangharaei; Rafal Anay; Li Ai; Eric R. Giannini; Jinying Zhu; Paul Ziehl. Temporal Evaluation of ASR Cracking in Concrete Specimens Using Acoustic Emission. Journal of Materials in Civil Engineering 2020, 32, 04020285 .

AMA Style

Vafa Soltangharaei, Rafal Anay, Li Ai, Eric R. Giannini, Jinying Zhu, Paul Ziehl. Temporal Evaluation of ASR Cracking in Concrete Specimens Using Acoustic Emission. Journal of Materials in Civil Engineering. 2020; 32 (10):04020285.

Chicago/Turabian Style

Vafa Soltangharaei; Rafal Anay; Li Ai; Eric R. Giannini; Jinying Zhu; Paul Ziehl. 2020. "Temporal Evaluation of ASR Cracking in Concrete Specimens Using Acoustic Emission." Journal of Materials in Civil Engineering 32, no. 10: 04020285.

Review
Published: 13 April 2020 in Journal of Cleaner Production
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Previous research has not sufficiently addressed the availability of geopolymer concrete raw materials, which influences adoption for infrastructure constructions. The overview herein assesses the supply, demand, and cost of these raw materials, including fly ash, slag cement, metakaolin, sodium hydroxide, sodium silicate, and silica fume. The results suggest that geopolymer concrete is a viable partial replacement for ordinary Portland cement (OPC) in the United States and Europe. Limitations exist in the rest of world, specifically China. Fly ash-based geopolymer concrete represents an opportunity due to low cost along with significant global production and reserves. Additionally, an activating solution composed of sodium hydroxide and silica fume with 25% Portland cement as a partial replacement appears to be most desirable. However, approximately only 7% replacement of OPC with geopolymer concrete is currently feasible globally due to limitations in sodium hydroxide supply. The analysis reveals a need for continued research to reduce the use of sodium hydroxide to improve availability and reduce cost of geopolymer concrete.

ACS Style

Lateef N. Assi; Kealy Carter; Edward Deaver; Paul Ziehl. Review of availability of source materials for geopolymer/sustainable concrete. Journal of Cleaner Production 2020, 263, 121477 .

AMA Style

Lateef N. Assi, Kealy Carter, Edward Deaver, Paul Ziehl. Review of availability of source materials for geopolymer/sustainable concrete. Journal of Cleaner Production. 2020; 263 ():121477.

Chicago/Turabian Style

Lateef N. Assi; Kealy Carter; Edward Deaver; Paul Ziehl. 2020. "Review of availability of source materials for geopolymer/sustainable concrete." Journal of Cleaner Production 263, no. : 121477.

Journal article
Published: 09 March 2020 in Construction and Building Materials
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The quality and performance of concrete is improved by the introduction of multi-walled nanotubes (MWCNTs). However, some research has shown negligible improvement. This paper investigates the effect of sonicated water and sonicated water plus MWCNTs on the properties of Portland cement concrete and paste. Changes are expected in the areas of compressive strength, load versus displacement, absorption, void space (ASTM C642) ratio, and microstructure. Deionized water (DI), sonicated deionized water (SDI), and sonicated deionized water with 0.01% MWCNTs concentration (SDI + MWCNTs) were used in preparing three batches. Compressive strength was improved by 18% for samples made with SDI and 21% SDI + MWCNTs in comparison with samples made with DI water. The load versus displacement, absorption, and permeable void ratio were improved for SDI and SDI + MWCNT samples. Results revealed the main effects are related to the sonication of water rather than incorporation of untreated MWCNTs. The scanning electron microscopy observations showed that cement paste samples made with SDI and SDI + MWCNT water have the same distinctive microstructure with more ettringite needles than paste samples made with deionized water. The hypothesis explaining those effects is that the sonication process produces a salt-calcium peroxide (CaO2), which enhances the early mechanical and microstructural properties of Portland cement.

ACS Style

Lateef N. Assi; Yasir A.J. Al-Hamadani; Edward (Eddie) Deaver; Vafa Soltangharaei; Paul Ziehl; Yeomin Yoon. Effect of Sonicated Deionized Water on The Early Age Behavior of Portland Cement-Based Concrete and Paste. Construction and Building Materials 2020, 247, 118571 .

AMA Style

Lateef N. Assi, Yasir A.J. Al-Hamadani, Edward (Eddie) Deaver, Vafa Soltangharaei, Paul Ziehl, Yeomin Yoon. Effect of Sonicated Deionized Water on The Early Age Behavior of Portland Cement-Based Concrete and Paste. Construction and Building Materials. 2020; 247 ():118571.

Chicago/Turabian Style

Lateef N. Assi; Yasir A.J. Al-Hamadani; Edward (Eddie) Deaver; Vafa Soltangharaei; Paul Ziehl; Yeomin Yoon. 2020. "Effect of Sonicated Deionized Water on The Early Age Behavior of Portland Cement-Based Concrete and Paste." Construction and Building Materials 247, no. : 118571.

Journal article
Published: 24 January 2019 in Mechanical Systems and Signal Processing
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Robust identification of the most accurate observed input data among a pool of observations is key in modeling and decision making. A statistically biased observed measurement deteriorates the predictive power of a model and affects decision-making ability based on the prediction of the model. When two competing methods of measurement are available, such as methods which identify arrival times in acoustic emission (AE) signals, a principal question is whether one of the two obtained datasets, or a combination of the two, should be used later on, for example, to localize an AE source. This question becomes more important when collecting not repeatable data such as AE signals created by a propagating crack. This paper considers an inverse source location problem in a concrete block to address the mentioned issue, a proposed methodology which also has wider application in competitive data selection. Elastic energy released by an AE event, such as a propagating crack, is recorded by acoustic emission data acquisition system. The onset time of AE signals is often used to locate the source of the event, and its accuracy directly affects the precision of source identification. This research proposes an innovative approach to select the most probable onset time obtained from two automatic picker methods. The proposed method selects the most probable onset times, which are observed by each picker for each sensor, in a probabilistic fashion. To validate the proposed method, the most accurate onset time observed by each picker is identified by visual inspection and is compared with the one is selected by the proposed method. Finally, the dataset is used for source location identification. Results show that picked onset times determined by the proposed method generate more accurate source identification when compared with coordinates obtained using each dataset individually.

ACS Style

Ramin Madarshahian; Paul Ziehl; Juan M. Caicedo. Acoustic emission Bayesian source location: Onset time challenge. Mechanical Systems and Signal Processing 2019, 123, 483 -495.

AMA Style

Ramin Madarshahian, Paul Ziehl, Juan M. Caicedo. Acoustic emission Bayesian source location: Onset time challenge. Mechanical Systems and Signal Processing. 2019; 123 ():483-495.

Chicago/Turabian Style

Ramin Madarshahian; Paul Ziehl; Juan M. Caicedo. 2019. "Acoustic emission Bayesian source location: Onset time challenge." Mechanical Systems and Signal Processing 123, no. : 483-495.

Conference paper
Published: 01 January 2019
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ACS Style

Lateef Assi; Rafal Anay; Vafa Soltangharaei; Paul Ziehl. Effect of partial Portland cement replacement on properties of fly ash based geopolymer concrete. 2019, 1 .

AMA Style

Lateef Assi, Rafal Anay, Vafa Soltangharaei, Paul Ziehl. Effect of partial Portland cement replacement on properties of fly ash based geopolymer concrete. . 2019; ():1.

Chicago/Turabian Style

Lateef Assi; Rafal Anay; Vafa Soltangharaei; Paul Ziehl. 2019. "Effect of partial Portland cement replacement on properties of fly ash based geopolymer concrete." , no. : 1.

Journal article
Published: 03 November 2018 in Applied Sciences
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Alkali-silica reaction has caused damage to concrete structures, endangering structural serviceability and integrity. This is of concern in sensitive structures such as nuclear power plants. In this study, acoustic emission (AE) was employed as a structural health monitoring strategy in large-scale, reinforced concrete specimens affected by alkali-silica reaction with differing boundary conditions resembling the common conditions found in nuclear containments. An agglomerative hierarchical algorithm was utilized to classify the AE data based on energy-frequency based features. The AE signals were transferred into the frequency domain and the energies in several frequency bands were calculated and normalized to the total energy of signals. Principle component analysis was used to reduce feature redundancy. Then the selected principal components were considered as features in an input of the pattern recognition algorithm. The sensor located in the center of the confined specimen registered the largest portion of AE energy release, while in the unconfined specimen the energy is distributed more uniformly. This confirms the results of the volumetric strain, which shows that the expansion in the confined specimen is oriented along the thickness of the specimen.

ACS Style

Vafa Soltangharaei; Rafal Anay; Nolan W. Hayes; Lateef Assi; Yann Le Pape; Zhongguo John Ma; Paul Ziehl. Damage Mechanism Evaluation of Large-Scale Concrete Structures Affected by Alkali-Silica Reaction Using Acoustic Emission. Applied Sciences 2018, 8, 2148 .

AMA Style

Vafa Soltangharaei, Rafal Anay, Nolan W. Hayes, Lateef Assi, Yann Le Pape, Zhongguo John Ma, Paul Ziehl. Damage Mechanism Evaluation of Large-Scale Concrete Structures Affected by Alkali-Silica Reaction Using Acoustic Emission. Applied Sciences. 2018; 8 (11):2148.

Chicago/Turabian Style

Vafa Soltangharaei; Rafal Anay; Nolan W. Hayes; Lateef Assi; Yann Le Pape; Zhongguo John Ma; Paul Ziehl. 2018. "Damage Mechanism Evaluation of Large-Scale Concrete Structures Affected by Alkali-Silica Reaction Using Acoustic Emission." Applied Sciences 8, no. 11: 2148.

Journal article
Published: 09 October 2018 in Construction and Building Materials
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This study investigates the initial and final setting times of fly ash-based geopolymer concrete using an activating solution that was a mixture of silica fume, sodium hydroxide, and water. The addition of sucrose (sugar) was implemented to improve the initial and final setting times. The effects of including sucrose on the mechanical, microstructure, and potential durability properties were observed. Sucrose was considered a viable solution to extending hardening times because it is readily available and affordable. Three different percentages were observed: 3%, 6%, and 9%. In order to eliminate the need for external heat, 10% of the fly ash was replaced by Portland cement. The results showed that when 10% of the fly ash weight was replaced by Portland cement, the initial and final setting times were 10 min and 25 min. The final and initial setting times were enhanced by more than 100% to reach more than 60 min when 3%, 6%, and 9% of sucrose were included. For instance, the final setting time reached 65 min when 3% of sucrose was added, 320 min for 6%, and 755 min for 9%. The reason for the delay is because the sucrose increased the viscosity leading to a postponement in the initiation of the geopolymerization process. The results showed that when sucrose was included in the mixtures, the compressive strength was not affected, and absorption and permeable void ratios were reduced.

ACS Style

Lateef N. Assi; Edward (Eddie) Deaver; Paul Ziehl. Using sucrose for improvement of initial and final setting times of silica fume-based activating solution of fly ash geopolymer concrete. Construction and Building Materials 2018, 191, 47 -55.

AMA Style

Lateef N. Assi, Edward (Eddie) Deaver, Paul Ziehl. Using sucrose for improvement of initial and final setting times of silica fume-based activating solution of fly ash geopolymer concrete. Construction and Building Materials. 2018; 191 ():47-55.

Chicago/Turabian Style

Lateef N. Assi; Edward (Eddie) Deaver; Paul Ziehl. 2018. "Using sucrose for improvement of initial and final setting times of silica fume-based activating solution of fly ash geopolymer concrete." Construction and Building Materials 191, no. : 47-55.

Journal article
Published: 14 September 2018 in Applied Sciences
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Reinforced concrete systems used in the construction of nuclear reactor buildings, spent fuel pools, and related nuclear facilities are subject to degradation over time. Corrosion of steel reinforcement and thermal cracking are potential degradation mechanisms that adversely affect durability. Remote monitoring of such degradation can be used to enable informed decision making for facility maintenance operations and projecting remaining service life. Acoustic emission (AE) monitoring has been successfully employed for the detection and evaluation of damage related to cracking and material degradation in laboratory settings. This paper describes the use of AE sensing systems for remote monitoring of active corrosion regions in a decommissioned reactor facility for a period of approximately one year. In parallel, a representative block was cut from a wall at a similar nuclear facility and monitored during an accelerated corrosion test in the laboratory. Electrochemical measurements were recorded periodically during the test to correlate AE activity to quantifiable corrosion measurements. The results of both investigations demonstrate the feasibility of using AE for corrosion damage detection and classification as well as its potential as a remote monitoring technique for structural condition assessment and prognosis of aging structures.

ACS Style

Marwa Abdelrahman; Mohamed ElBatanouny; Kenneth Dixon; Michael Serrato; Paul Ziehl. Remote Monitoring and Evaluation of Damage at a Decommissioned Nuclear Facility Using Acoustic Emission. Applied Sciences 2018, 8, 1663 .

AMA Style

Marwa Abdelrahman, Mohamed ElBatanouny, Kenneth Dixon, Michael Serrato, Paul Ziehl. Remote Monitoring and Evaluation of Damage at a Decommissioned Nuclear Facility Using Acoustic Emission. Applied Sciences. 2018; 8 (9):1663.

Chicago/Turabian Style

Marwa Abdelrahman; Mohamed ElBatanouny; Kenneth Dixon; Michael Serrato; Paul Ziehl. 2018. "Remote Monitoring and Evaluation of Damage at a Decommissioned Nuclear Facility Using Acoustic Emission." Applied Sciences 8, no. 9: 1663.

Journal article
Published: 17 July 2018 in Journal of Cleaner Production
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In an effort to reduce waste and engage in more sustainable construction, this research focuses on the development of a cost-competitive, environmentally-friendly geopolymer concrete mixture that offers structural benefits relative to ordinary Portland cement (OPC), uses fly ash, a toxic waste byproduct as a raw material, and reduces the amount of CO2 emitted during production of the concrete. The production of OPC, the current standard in concrete, relies on a high amount of energy, and as a result accounts for 7% of CO2 emissions worldwide. Production of OPC is expected to increase 4-fold over the next 30 years, posing significant environmental risk. While numerous studies have examined the use of geopolymer concrete as a more sustainable construction material, concerns about the cost and environmental impact are obstacles against widespread production and market adoption. The new mix designs proposed herein result in up to a 50% decrease in the cost of geopolymer concrete, making this sustainable alternative a viable option relative to traditional concrete. In addition, the production of the proposed mixtures requires less than 50% of the fuel usage (thermal energy) required for OPC, decreasing CO2 emissions. The proposed mixtures not only reduce environmental impact, but they also offer improved performance, which may appeal to many concrete manufacturers. While the proposed alternative to Portland cement is suitable for most applications, it is posited that those firms interested in pursuing sustainable construction may be most inclined to adopt the proposed mixture in order to meet their sustainability goals.

ACS Style

Lateef Assi; Kealy Carter; Edward (Eddie) Deaver; Rafal Anay; Paul Ziehl. Sustainable concrete: Building a greener future. Journal of Cleaner Production 2018, 198, 1641 -1651.

AMA Style

Lateef Assi, Kealy Carter, Edward (Eddie) Deaver, Rafal Anay, Paul Ziehl. Sustainable concrete: Building a greener future. Journal of Cleaner Production. 2018; 198 ():1641-1651.

Chicago/Turabian Style

Lateef Assi; Kealy Carter; Edward (Eddie) Deaver; Rafal Anay; Paul Ziehl. 2018. "Sustainable concrete: Building a greener future." Journal of Cleaner Production 198, no. : 1641-1651.

Journal article
Published: 01 June 2018 in Journal of Materials in Civil Engineering
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This study investigates the geopolymerization process of fly ash–based geopolymer paste specimens using acoustic emissions; the activating solution is a combination of silica fume and sodium hydroxide, made with two different water:solid weight ratios (w/s), 0.30 and 0.35. The specimens are cured in ambient conditions (22±3°C). The acoustic emission data are processed through pattern recognition (PR), and two clusters are identified and assigned to a specific mechanism depending on their characteristics. Results show that there is a predominant difference in the acquisition data between the two water:binder weight ratios. Pattern recognition shows that the greatest number of geopolymerization mechanisms, including dissolution of Si and Al atoms, forming bubbles, and microcrack initiation, occur at roughly the same time for the 0.3 w/s samples, whereas in 0.35 w/s samples the mechanisms occur sequentially. Final setting time of Vicat penetration tests, which assume a starting point of microcrack initiations, is 60 min after the test onset for 0.3 w/s ratio samples, whereas it occurs after approximately 600 min for 0.35 w/s samples. Microcrack initiation predicted by the pattern recognition technique coincides with the final setting times. Scanning electron microscope observations also coincide with the pattern recognition findings.

ACS Style

Lateef Assi; Rafal Anay; Davis Leaphart; Vafa Soltangharaei; Paul Ziehl. Understanding Early Geopolymerization Process of Fly Ash–Based Geopolymer Paste Using Pattern Recognition. Journal of Materials in Civil Engineering 2018, 30, 04018092 .

AMA Style

Lateef Assi, Rafal Anay, Davis Leaphart, Vafa Soltangharaei, Paul Ziehl. Understanding Early Geopolymerization Process of Fly Ash–Based Geopolymer Paste Using Pattern Recognition. Journal of Materials in Civil Engineering. 2018; 30 (6):04018092.

Chicago/Turabian Style

Lateef Assi; Rafal Anay; Davis Leaphart; Vafa Soltangharaei; Paul Ziehl. 2018. "Understanding Early Geopolymerization Process of Fly Ash–Based Geopolymer Paste Using Pattern Recognition." Journal of Materials in Civil Engineering 30, no. 6: 04018092.

Journal article
Published: 01 April 2018 in Construction and Building Materials
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Geopolymer concrete has demonstrated promising mechanical and microstructural properties in comparison with conventional concrete; however, the variability found in fly ash sources and properties may be an obstacle to implementation. To better understand this variability, this study investigates the effects of particle size distribution and fly ash source on the mechanical and microstructural properties of fly ash-based geopolymer concrete. Two fly ash sources were studied including ordinary McMeekin and Wateree Station fly ash. McMeekin fly ash has three different fly ash particle grades, including the ordinary McMeekin fly ash (38.8 µm), Spherix 50 (17.9 µm), and Spherix 15 (4.78 µm). The Wateree Station is a thermally beneficiated fly ash, while McMeekin is a STAR Processed fly ash. A mixture of silica fume, sodium hydroxide, and water was used as an activating solution. The microstructure of fly ash-based geopolymer paste was observed using SEM. The density, absorption and permeable void ratios were estimated based on ASTM C642. Test results indicate that the resulting compressive strength is linearly affected by the average particle size distribution. The compressive strength of geopolymer concrete was decreased when McMeekin fly ash was used. In addition, the permeable void ratio and absorption after immersion ratio were decreased as a smaller particle size of fly ash such as Spherix 15 (4.78 µm) was used. The fly ash source influences the permeable voids, apparent density, bulk density, and absorption after immersion ratio.

ACS Style

Lateef N. Assi; Edward Eddie Deaver; Paul Ziehl. Effect of source and particle size distribution on the mechanical and microstructural properties of fly Ash-Based geopolymer concrete. Construction and Building Materials 2018, 167, 372 -380.

AMA Style

Lateef N. Assi, Edward Eddie Deaver, Paul Ziehl. Effect of source and particle size distribution on the mechanical and microstructural properties of fly Ash-Based geopolymer concrete. Construction and Building Materials. 2018; 167 ():372-380.

Chicago/Turabian Style

Lateef N. Assi; Edward Eddie Deaver; Paul Ziehl. 2018. "Effect of source and particle size distribution on the mechanical and microstructural properties of fly Ash-Based geopolymer concrete." Construction and Building Materials 167, no. : 372-380.

Journal article
Published: 01 March 2018 in Construction and Building Materials
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Acoustic emission (AE) monitoring during compressive loading was employed to investigate micro-crack formation and coalescence in cement paste specimens. To establish a correlation between damage and AE activity, the data was categorized on the basis of amplitude and cumulative signal strength (CSS). Three distinct stages of crack behavior, illuminated by changes in the slope of the cumulative signal strength versus time relationship, were identified. Micro-crack initiation, crack extension, and unstable crack growth (crack coalescence) were assigned to these stages. An unsupervised pattern recognition approach was employed to separate the data into signal subsets which were then classified and assigned to differing mechanisms. To gain further insight into the crack growth network and behavior, specimens were loaded to varying levels of ultimate capacity and micro-CT scanning was employed to investigate the dimensional extent of micro-cracking and to correlate the images with AE data.

ACS Style

Rafal Anay; Vafa Soltangharaei; Lateef Assi; Timothy DeVol; Paul Ziehl. Identification of damage mechanisms in cement paste based on acoustic emission. Construction and Building Materials 2018, 164, 286 -296.

AMA Style

Rafal Anay, Vafa Soltangharaei, Lateef Assi, Timothy DeVol, Paul Ziehl. Identification of damage mechanisms in cement paste based on acoustic emission. Construction and Building Materials. 2018; 164 ():286-296.

Chicago/Turabian Style

Rafal Anay; Vafa Soltangharaei; Lateef Assi; Timothy DeVol; Paul Ziehl. 2018. "Identification of damage mechanisms in cement paste based on acoustic emission." Construction and Building Materials 164, no. : 286-296.

Conference paper
Published: 01 January 2018 in AIP Conference Proceedings
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Cement-based composites have been used as reliable materials in building and civil engineering infrastructure for many decades. Although there are several advantages, some drawbacks such as premature cracking may be problematic for sensitive applications such as those found in nuclear power plants or associated waste storage facilities. In this study, acoustic emission monitoring was employed to detect stress waves associated with damage progression during uniaxial compressive loading. Acoustic emission data resulting from loading of plain cement paste prisms and cement paste prisms amended with carbon nanotubes are compared. Unsupervised pattern recognition is employed to categorize the data. Results indicate that increased acoustic emission activity was recorded for the plain cement paste prisms when compared to prisms amended with carbon nanotubes.

ACS Style

Vafa Soltangharaei; Rafal Anay; Lateef Assi; Paul Ziehl; Fabio Matta. Damage identification in cement paste amended with carbon nanotubes. AIP Conference Proceedings 2018, 1949, 030006 .

AMA Style

Vafa Soltangharaei, Rafal Anay, Lateef Assi, Paul Ziehl, Fabio Matta. Damage identification in cement paste amended with carbon nanotubes. AIP Conference Proceedings. 2018; 1949 (1):030006.

Chicago/Turabian Style

Vafa Soltangharaei; Rafal Anay; Lateef Assi; Paul Ziehl; Fabio Matta. 2018. "Damage identification in cement paste amended with carbon nanotubes." AIP Conference Proceedings 1949, no. 1: 030006.

Journal article
Published: 01 November 2017 in Ultrasonics Sonochemistry
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We examined the feasibility of using two types of fly ash (an industrial waste from thermal power plants) as a low-cost catalyst to enhance the ultrasonic (US) degradation of ibuprofen (IBP) and sulfamethoxazole (SMX). Two fly ashes, Belews Creek fly ash (BFA), from a power station in North Carolina, and Wateree Station fly ash (WFA), from a power station in South Carolina, were used. The results showed that >99% removal of IBP and SMX was achieved within 30 and 60min of sonication, respectively, at 580kHz and pH 3.5. Furthermore, the removal of IBP and SMX achieved, in terms of frequency, was in the order 580kHz>1000kHz>28kHz, and in terms of pH, was in the order of pH 3.5>pH 7>pH 9.5. WFA showed significant enhancement in the removal of IBP and SMX, which reached >99% removal within 20 and 50min, respectively, at 580kHz and pH 3.5. This was presumably because WFA contains more silicon dioxide than BFA, which can enhance the formation of OH radicals during sonication. Additionally, WFA has finer particles than BFA, which can increase the adsorption capacity in removing IBP and SMX. The sonocatalytic degradation of IBP and SMX fitted pseudo first-order rate kinetics and the synergistic indices of all the reactions were determined to compare the efficiency of the fly ashes. Overall, the findings have showed that WFA combined with US has potential for treating organic pollutants, such as IBP and SMX, in water and wastewater.

ACS Style

Yasir A.J. Al-Hamadani; Chang Min Park; Lateef N. Assi; Kyoung Hoon Chu; Shamia Hoque; Min Jang; Yeomin Yoon; Paul Ziehl. Sonocatalytic removal of ibuprofen and sulfamethoxazole in the presence of different fly ash sources. Ultrasonics Sonochemistry 2017, 39, 354 -362.

AMA Style

Yasir A.J. Al-Hamadani, Chang Min Park, Lateef N. Assi, Kyoung Hoon Chu, Shamia Hoque, Min Jang, Yeomin Yoon, Paul Ziehl. Sonocatalytic removal of ibuprofen and sulfamethoxazole in the presence of different fly ash sources. Ultrasonics Sonochemistry. 2017; 39 ():354-362.

Chicago/Turabian Style

Yasir A.J. Al-Hamadani; Chang Min Park; Lateef N. Assi; Kyoung Hoon Chu; Shamia Hoque; Min Jang; Yeomin Yoon; Paul Ziehl. 2017. "Sonocatalytic removal of ibuprofen and sulfamethoxazole in the presence of different fly ash sources." Ultrasonics Sonochemistry 39, no. : 354-362.

Proceedings article
Published: 28 September 2017 in Structural Health Monitoring 2017
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This paper reports on a project aimed at understanding whether acoustic emission (AE) data can be used to detect and classify corrosion in PC piles exposed to saltwater, ranging from steel depassivation to concrete cracking caused by the formation of expansive surface oxides. Experimental results are presented from three specimens representing portions of PC piles, which were directly exposed to saltwater through wet/dry cycles mimicking tidal action for up to 790 days. Corrosion activity was monitored continuously using AE sensors. Half-cell potential and polarization resistance were measured periodically to serve as benchmarks to detect steel depassivation and corrosion. Visual evidence of naturally-occurring corrosion at different stages was collected from strands that were extracted from decommissioned specimens.

ACS Style

William Vélez; Mohamed ElBatanouny; Fabio Matta; Paul Ziehl. Two-year Acoustic Emission Monitoring of Natural Corrosion in Prestressed Concrete Exposed to Saltwater. Structural Health Monitoring 2017 2017, 1 .

AMA Style

William Vélez, Mohamed ElBatanouny, Fabio Matta, Paul Ziehl. Two-year Acoustic Emission Monitoring of Natural Corrosion in Prestressed Concrete Exposed to Saltwater. Structural Health Monitoring 2017. 2017; ():1.

Chicago/Turabian Style

William Vélez; Mohamed ElBatanouny; Fabio Matta; Paul Ziehl. 2017. "Two-year Acoustic Emission Monitoring of Natural Corrosion in Prestressed Concrete Exposed to Saltwater." Structural Health Monitoring 2017 , no. : 1.

Conference paper
Published: 01 January 2017 in 43RD ANNUAL REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION, VOLUME 36
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Nuclear structures are designed to withstand severe loading events under various stresses. Over time, aging of structural systems constructed with concrete and steel will occur. This deterioration may reduce service life of nuclear facilities and/or lead to unnecessary or untimely repairs. Therefore, online monitoring of structures in nuclear power plants and waste storage has drawn significant attention in recent years. Of many existing non-destructive evaluation and structural monitoring approaches, acoustic emission is promising for assessment of structural damage because it is non-intrusive and is sensitive to corrosion and crack growth in reinforced concrete elements. To provide a rapid, actionable, and graphical means for interpretation Intensity Analysis plots have been developed. This approach provides a means for classification of damage. Since the acoustic emission measurement is only an indirect indicator of structural damage, potentially corrupted by non-genuine data, it is more suitable to estimate the states of corrosion and cracking in a Bayesian estimation framework. In this paper, we will utilize the accelerated corrosion data from a specimen at the University of South Carolina to develop a particle filtering-based diagnosis and prognosis algorithm. Promising features of the proposed algorithm are described in terms of corrosion state estimation and prediction of degradation over time to a predefined threshold.

ACS Style

Wuzhao Yan; Marwa Abdelrahman; Bin Zhang; Paul Ziehl. Particle filtering based structural assessment with acoustic emission sensing. 43RD ANNUAL REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION, VOLUME 36 2017, 1 .

AMA Style

Wuzhao Yan, Marwa Abdelrahman, Bin Zhang, Paul Ziehl. Particle filtering based structural assessment with acoustic emission sensing. 43RD ANNUAL REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION, VOLUME 36. 2017; ():1.

Chicago/Turabian Style

Wuzhao Yan; Marwa Abdelrahman; Bin Zhang; Paul Ziehl. 2017. "Particle filtering based structural assessment with acoustic emission sensing." 43RD ANNUAL REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION, VOLUME 36 , no. : 1.