Browsing by Author "Behravan, Amir"
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- Analysis of the Physiochemical Interactions of Recycled Materials in ConcreteLowry, Michael Donovan (Virginia Tech, 2023-01-18)This thesis broadly addresses the issue of materials sustainability in the production of Portland cement concrete. Two methods are presented, both aimed at achieving more sustainable concrete through the use of waste and recycled materials. The first method involves utilizing reclaimed asphalt pavement (RAP) as an aggregate in structural concrete, and the second method involves utilizing waste quarry fines as partial replacement of Portland cement in concrete mixes. Many efforts have been made in recent years to justify the use of RAP aggregates in concrete. All previous efforts appear to unanimously report a reduction in concrete performance with varying proportions of RAP usage. The poor performance of RAP aggregates in concrete is attributed mainly to a larger, more porous interfacial transition zone (ITZ) and to the cohesive failure of the asphalt. It is hypothesized that the detrimental impact on the ITZ is attributable to organic compounds leached from the asphalt in the high pH pore solution. This study proves the presence of organic compounds in the pore solution and demonstrates that there is an apparent retardation of cement hydration. This study also attempted to pretreat the RAP in a sodium hydroxide (NaOH) solution to pre-leach the organic compounds. The pretreatment demonstrated that organic compounds were leached and that NaOH modified the asphalt surface chemistry. However, only a marginal improvement in compressive strength was observed by completing the pretreatment. Replacement of Portland cement by filler products is a practice aimed at reducing the carbon footprint of concrete, such as is common with Type IL Portland limestone cement. This study investigates the impact of replacing cement with seven different quarry fines materials. The quarry fines were used to replace cement at 5% to 20% by volume in either cement paste or mortar samples that were then analyzed for various physicochemical properties. It was found that all the quarry fines had detrimental impact on the hydration kinetics of cement pastes. The inclusion of quarry fines was also found to cause varying degrees of reduction in mortar compressive strength. While further analyses of the quarry fines are required, quarry fines 2, 5 and 7 did display encouraging signs to suggest the potential for use as a filler material in blended cements.
- Field Inspection of High-Density Polyethylene (HDPE) Storage Tanks Using Infrared Thermography and Ultrasonic MethodsBehravan, Amir; Tran, Thien Q.; Li, Yuhao; Davis, Mitchell; Shaikh, Mohammad Shadab; DeJong, Matthew M.; Hernandez, Alan; Brand, Alexander S. (MDPI, 2023-01-20)High-density polyethylene (HDPE) is widely used for above-ground storage tanks (ASTs). However, there are currently no guidelines for the non-destructive testing (NDT) and evaluation (NDE) of HDPE ASTs. Moreover, the feasibility, limitations, and challenges of using NDT techniques for the field inspection of HDPE ASTs have not been well established. This study used both infrared thermography (IRT) and ultrasonic testing (UT) for the field inspection of HDPE ASTs. Highlighting the implementation challenges in the field, this study determined that: (1) ambient environmental parameters can affect IRT accuracy; (2) there is an ideal time during the day to perform IRT; (3) the heating source and infrared camera orientation can affect IRT accuracy; and (4) with proper measures taken, IRT is a promising method for flaw detection in HDPE ASTs. Additionally, UT can be used following IRT for detailed investigation to quantify the size and depth of defects. The manuscript concludes with a discussion of the limitations and best practices for the implementing of IRT and UT for HDPE AST inspections in the field.
- Laboratory Study on Non-Destructive Evaluation of Polyethylene Liquid Storage Tanks by Thermographic and Ultrasonic MethodsBehravan, Amir; deJong, Matthew M.; Brand, Alexander S. (MDPI, 2021-09-28)High-density polyethylene (HDPE) above-ground storage tanks (AST) are used by highway agencies to store liquid deicing chemicals for the purpose of road maintenance in the winter. A sudden AST failure can cause significant economic and environmental impacts. While ASTs are routinely inspected to identify signs of aging and damage, current methods may not adequately capture all defects, particularly if they are subsurface or too small to be seen during visual inspection. Therefore, to improve the ability to identify potential durability issues with HDPE ASTs, additional non-destructive evaluation (NDE) techniques need to be considered and assessed for applicability. Specifically, this study investigates the efficiency of using infrared thermography (IRT) as a rapid method to simultaneously examine large areas of the tank exterior, which will be followed by closer inspections with conventional and phased array ultrasonic testing (UT) methods. Results show that IRT can help to detect defects that are shallow, specifically located within half of the tank’s wall thickness from the surface. UT has the ability to detect all defects at any depth. Moreover, phased array UT helps to identify stacked defects and characterize each defect more precisely than IRT.
- Performance Evaluation of Silane in Concrete Bridge Decks Using Transmission X-ray MicroscopyBehravan, Amir; Aqib, Syed Muhammad; Delatte, Norbert J.; Ley, M. Tyler; Rywelski, Anna (MDPI, 2022-02-28)The corrosion of steel reinforcement in concrete structures is a most widespread problem. Silane is commonly used as a surface treatment material to reduce the entry of moisture containing harmful chemicals into the concrete matrix, thereby restricting corrosion. There is not a standard test method to evaluate the long-term performance of such sealers when applied on concrete. Moreover, the literature does not have a definitive conclusion on the performance of silanes. In this work, transmission X-ray microscopy (TXM) and optical imaging were used to investigate the mass transport properties and silane thickness of field samples treated with silane to gain insight into the performance of silane coatings. Quantitative measurements using optical staining techniques showed that the average measured silane thickness for all 14 projects was 2.5 mm. The TXM results revealed that, on average, the samples with silane coatings exhibited 8.5 times less penetration of outside chemicals, at a depth of 2 mm, as compared to uncracked samples without silane coatings. This work shows that silanes are a useful and practical tool to significantly reduce the permeability of in-service concrete and resist corrosion.