Theses and Dissertations - Department of Civil, Construction & Environmental Engineering

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Crack identification through computer vision: from non-learning-based to learning-based methodologies, and from patch-level to pixel-level detections
(University of Alabama Libraries, 2020-12) Zhou, Shanglian; Song, Wei; University of Alabama Tuscaloosa
Modern society requires a sustainable, robust, and serviceable infrastructure to promote social welfare and boost economy. To support such infrastructure systems, an efficient health monitoring framework is needed which can promptly detect the presence of defects and perform associated rehabilitation and maintenance. In civil infrastructure, one of the most common types of defects is cracking, which evolves rapidly under the impacts of heavy traffic, aging of materials, and drastic environmental changes. In recent decades, image-based automated crack detection methodologies have been developed and extensively applied by professionals and researchers. Nevertheless, a few issues and challenges existing in this type of methodology are yet to be systematically investigated and properly addressed. In this study, an image-based condition assessment framework for roadway crack detection is developed. It consists of four topics: i) proposing a filter-based methodology that can address image disturbances to promote a robust image-based roadway crack detection; ii) performing a systematic study to investigate the impact from hyperparameter selection on the performance of deep convolutional neural network (DCNN) on roadway crack classification; iii) achieving pixel-level crack detection resolution on image data of real-world complexities through DCNN-based roadway crack segmentation; and iv) investigating the impact from heterogeneous image data on DCNN-based roadway crack detection and proposing heterogeneous image fusion strategies to address data uncertainties. Overall, experimental results and discussions show that the proposed crack detection framework is capable to properly address the issues under investigation and leads to improved and more robust crack detection performance than current image-based methodologies.
Enhancing quality management in highway construction using emerging methods
(University of Alabama Libraries, 2020) Ogunrinde, Olugbenro; Amirkhanian, Armen; University of Alabama Tuscaloosa
Highway systems contribute immensely to economic development and growth. However, the recent D+ rating for highway infrastructure in the US highlights the dire state of highways across the nation and the need to invest in renovating or building new roads. The cascading impact of regular highway projects creates a need to construct highways that will last longer. The adverse effect of these operations increases the economic cost for state highway agencies (SHA) and commuters. For example, congestion costs for the freight industry in 2018 exceeded $87 billion. Efficient and sustainable construction practices can increase the return on investment and provide the infrastructure that meets and possibly exceeds the design life. With respect to pavements, asphalt concrete (AC) comprises over 90% of pavement surface materials. A well-designed AC pavement can have a lifespan of over 15 years with minor maintenance; however, this design life may be reduced without strongly enforced quality management processes (i.e. quality control (QC) and quality assurance (QA) programs). In cases of exceptional QC/QA programs, SHAs have observed long AC pavement service lives. For example, there is a section of I-90 in Washington state that has been in service for 35 years with no rehabilitation except minor resurfacing. The New Jersey DOT found the same to be true on a section of I-287 with 26-year-old AC pavement. This dissertation focuses on the quality of highway construction in these aspects: 1. Effect of nighttime construction on quality of asphalt paving, 2. A review of the application of emerging technologies for highway construction quality management, 3. Quality management technologies in highway construction: stakeholders’ perception of utility, benefits, and barriers, 4. Model development for automation assessment readiness in highway construction quality management processes: a fuzzy synthetic evaluation approach. Existing literature for pavement construction practices and operations have primarily focused on cost, schedule, and safety whereas this study will examine the issues surrounding quality during construction in the context of paving operation technology and efficiency. Similarly, existing literature for pavement construction practices contains numerous studies evaluating nondestructive testing NDT technology. However, this study will evaluate the application of various technologies holistically to identify information on the current state, effectiveness, and automation readiness of some quality management technologies in the highway construction industry. Information from the study will enhance the adoption of emerging methods for quality management processes and procedures in highway construction.
Experimental Investigation of Ultra-High-Performance Concrete Panels Under Tornado Impact Loads
(University of Alabama Libraries, 2021) Kniffin, Hannah Rose; Aaleti, Sriram; University of Alabama Tuscaloosa
Tornado events pose a threat to millions of people living in the tornadic-prone areas of the United States. Although many tornado shelters and safe rooms are commercially available that satisfy the extreme loading conditions required by the International Code Council and National Storm Shelter Association, there is a need for a simple yet safe design which can be easily assembled and used for multiple purposes. New engineering materials, such as ultra-highperformance concrete (UHPC), have the potential to improve tornado shelter options and save lives. This study experimentally investigates the performance of thin UHPC panels subjected to impact of standard wood 2x4 projectiles, following the requirements of ICC/NSSA 500, the leading standard on storm shelter design. 1.25-inch-thick and 1.625-inch-thick UHPC panels were cast and impacted with 15-lb wood projectiles at speeds ranging from 50 mph to 100 mph to maintain a similar impact-energy-to-panel-mass ratio. The failure response of each panel was characterized by excessive flexural deflection or punching shear. In the case of excessive deflection, a single-degree-of-freedom dynamic displacement model describes the motion of the panel during impact and the profile of the maximum deflection. In the case of punching shear, a modified equation from ACI 318 predicts the capacity of the panel. The results of the impact testing show UHPC is a promising material for future tornado shelters: UHPC panels with half the thickness of a traditional concrete shelter can be built for a similar or lower price, creatively integrated into homes, and increase accessibility of the tornado shelter for residents.
Hybrid structures using ultra high performance concrete and normal concrete for bridge applications
(University of Alabama Libraries, 2018) Ronanki, Vidya Sagar; Aaleti, Sriram; University of Alabama Tuscaloosa
The aging transportation infrastructure problem coupled with rapidly increasing traffic volumes and tightening budgets necessitates the need for cost effective and durable bridge components which can be easily implemented using current construction techniques. These solutions must also be suitable for accelerated construction in order to ensure minimum disruption to existing traffic. In this regard, Ultra High Performance Concrete (UHPC), a highly engineered cementitious material with enhanced mechanical properties lends its self as an ideal material. UHPC cost is nearly 30 times the traditional concrete, making full UHPC structures uneconomical. Through this multipart research, the emerging UHPC material and the traditional normal concrete are optimally combined to exploit both their beneficial features and yield new economical hybrid bridge components. The rebar development length in UHPC was experimentally investigated using pull out and beam specimens with lap splices. The results from these tests add significant new data on the bond stress distribution for rebar embedded in UHPC and a simplified design equation is proposed. An embedment length of 8 db (db -diameter of rebar) in UHPC with 3db clear cover was found to be sufficient to yield a Grade 60 mild steel reinforcement. A hybrid prestressed girder concept utilizing UHPC in the end zones of the girder with normal concrete in the remainder of the girder was proposed for a long-span girder with existing shapes . The endzone and shear behavior of a deep prestressed girder was investigated experimentally and analytically using four 78 in. deep, normal concrete bulb-tee (BT-78) girders. A detailed finite element (FE) model was developed in ABAQUS and calibrated using the experimental data. UHPC-NC interface behavior under direct shear and flexural loading was also experimentally investigated using direct shear testing of small-scale interface samples and flexural testing of UHPC-NC beams. A detailed finite element model for the interface was developed in ATENA and calibrated using the experimental results. Further, a detailed 3D FE model of a 205ft. long UHPC-NC hybrid girder was developed in ATENA and used to evaluate the feasibility of the hybrid girder concept. It was found that the hybrid girder concept is not only feasible but also reduces significantly the amount of end-zone reinforcement and end-zone cracking. A hybrid bridge pier system using a precast UHPC shell as permanent formwork for traditional bridge piers or as a retrofit option for existing columns was proposed. Experimental tests were conducted on 24in. long UHPC-NC columns to quantify the effectiveness of the UHPC shell in providing the confinement to normal concrete. Results obtained from the tests indicate that UHPC-shell-confined specimens exhibit a 15 to 30 % increase in peak load carrying capacity along with a 26 to 46% increase in failure strain values.
In-situ production of calcium carbonate nanoparticles in fresh concrete using pre-carbonation method
(University of Alabama Libraries, 2017) Qian, Xin; Wang, Jialai; University of Alabama Tuscaloosa
To reduce the carbon footprint of ordinary Portland cement (OPC)-based concrete, a novel technique, pre-carbonation process, has been developed to produce CaCO3 nanoparticles in fresh concrete. In this technique, gaseous CO2 is first absorbed into a slurry of calcium-rich minerals which is then blended with other ingredients to produce mortar/concrete. The objective of this work is to obtain an in-depth understanding of the underlying scientific mechanisms associated with the enhancement of strength and durability of the concrete induced by the new method. A comprehensive research plan has been carried out to study the carbonated slaked lime slurry and the effect of carbonated slaked lime slurry on the performance of OPC-based concrete, and to evaluate the potentials of the pre-carbonation method. Experimental studies show that carbonating the calcium-rich mineral slurry with CO2 can produce CaCO3 nanoparticles and Ca(HCO3)2 in the slurry, and these carbonation products were dictated by four parameters of the pre-carbonation method: the duration and temperature of the carbonation, the concentration of the calcium source slurry, and the stirring method of the calcium source slurry during the carbonation. The mechanical properties and durability of the mortar/concrete made with the carbonated slurry were significantly improved, which can be attributed to major mechanisms induced by the pre-carbonation method: promoted hydration of the cement and denser microstructure of the mortar/concrete. Calorimetry testing showed that the hydration of OPC was greatly improved by the pre-carbonation because of the extra heterogenous nucleation sites provided by the CaCO3 nanoparticles. XRD and TGA results revealed that more ettringite was produced in the mortar/concrete with pre-carbonated slaked lime slurry. The overall volume of the hydration products of the cement was increased by the pre-carbonation, leading to denser microstructure of the mortar/concrete. It has been found that the pre-carbonation can be used to the OPC-supplementary cementitious materials (SCMs) blended cement mortar/concrete, as evidenced by the improved mechanical properties achieved by these mortars produced by using the pre-carbonation method. A preliminary study was also conducted to examine whether other calcium-rich minerals, such as Class C fly ash and limestone, can be used as calcium source in the pre-carbonation method.
Low-cost, ubiquitous biomolecule as next generation, sustainable admixture to enhance the performance of ordinary portland cement-based concretes
(University of Alabama Libraries, 2021) Fang, Yi; Wang, Jialai; University of Alabama Tuscaloosa
The production of ordinary Portland cement (OPC) is highly energy-intensive and responsible for approximately 6% of anthropogenic greenhouse gas emissions. To reduce the carbon footprint of OPC based concrete, this research proposes to use a low-cost, ubiquitous, naturally occurring compound, tannic acid (TA) as a small-dose additive to significantly enhance the strength of OPC based concrete.This study is inspired by biosystems’ protein-based materials, which generally exhibit superior strength and toughness owing to their hierarchical structures via hydrogen-bonding assembly. With abundant reactive terminal phenolic hydroxyl groups, TA has an ability to complex or cross-link macromolecules sites through multiple interactions. Thus, TA can be used to complex or cross-link hydration products of cement at multi-binding sites so that the strength and durability of concrete can be significantly improved. A comprehensive research plan has been carried out to evaluate the potential of TA on performance enhancement of OPC-based concrete, understand how TA modifies the hydration of cement, mitigate the retardation of TA on cement’s hydration, and evaluate application potentials in concretes with SCMs. Experimental studies show that TA can strongly retard the hydration of cement and alite due to its ability to bind to various particles and chelate with calcium ions, causing less calcium hydroxide produced by the hydration. The strong interaction between the TA and hydration products leads to morphology change of the hydration products and generates nanoparticles at early age. Furthermore, addition of TA can significantly densify the nanostructure of cement pastes. Particularly, capillary pores smaller than 70nm are drastically reduced by TA. This finding is not only explaining why TA can enhance the micromechanical properties of concrete, but also opening a new approach to tune the nanoscale pores in concrete. Besides, a pre-hydration method is proposed and verified to mitigate the retarding effect of TA for widely adopted in practical application. Significant strength improvement at late age can be achieved by pre-hydration with TA without losing of strength at early age. TA is also successfully used in mortars with silica fume to achieve over 30% strength improvement, suggesting its huge potential to reduce the carbon footprint of concrete.
Synthesis and characterization of fly ash based self-dispersing, self-sensing geopolymer
(University of Alabama Libraries, 2020-12) Pan, Wei; Wang, Jialai; University of Alabama Tuscaloosa
Extensive studies have been carried out to use carbon nanotubes (CNTs) to reinforce cementitious materials because of the extraordinary strength of CNTs. More importantly, new functions such as self-sensing ability can be introduced to the materials due to the excellent electrical conductivity of CNTs. However, the application of CNTs in reinforcing materials is hampered by three major challenges: proper dispersion of the nanoscale additives, scale-up of laboratory results and implementation on larger scale, and a lowering of the cost benefit ratio. It is not easy to disperse CNTs into cementitious materials. Aiming to address all these three challenges simultaneously, this study proposes to produce CNTs reinforced cementitious materials through directly growing CNTs on fly ash particles using a novel Poptube method. Unlike any other exiting methods, Poptube method uses microwave irradiation as heating source, and a single chemical (e.g., ferrocene) to provide both the carbon source and the catalyst for CNTs’ growth. Compared with existing methods, the Poptube method is much more cost-effective and can be easily scaled-up for mass production. CNT reinforced geopolymer can be produced by mixing these CNTs grown fly ash particles with other ingredients. In this way, the time-consuming and difficult task of dispersion of CNTs is eliminated since CNTs are self-dispersed into the matrix by the fly ash particles on which CNTs were grown. To evaluate the effect of growing CNTs on the reactivity of fly ash particles, a series of tests were carried out, including dissolution testing, electric conductivity testing, and imaging with scanning electron microscopy (SEM) and Atomic Force Microscopy (AFM). Results show that growing CNTs on the surface of fly ash does not reduce the reactivity of the fly ash because of the seeding effect provided by the CNTs. The composite effect induced by the CNTs was confirmed by Raman Spectrometer, which shows that the D-band of the CNTs varies with the applied thermal stress, suggesting effectively stress transfer from the geopolymer matrix to CNTs. This finding suggests that stress in CNTs reinforced geopolymer can be sensed by a Roman Spectrometer in a non-contact fashion. The self-sensing function of the nanocomposite mortar is evaluated using a four-electrode-DC method. At early age, geopolymer mortar is piezoresistive because of its high electric conductivity. However, DC induced polarization effect is very serious at this age. This polarization effect reduces with reaction time and becomes negligible at 35d. Similar piezoresitivity was achieved by the geopolymeric nanocomposite produced by using fly ash grown with CNTs using Poptube method, which is three orders magnitude more sensitive than the geopolymer one without any CNTs.

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Browsing Theses and Dissertations - Department of Civil, Construction & Environmental Engineering by Author "Amirkhanian, Armen"

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