Education

Research Description

Dr. Pour-Ghaz studies the durability of reinforced concrete materials and structures, the long-term durability Fiber Reinforced Polymer (FRP) composites for civil infrastructure, and electromagnetic sensors and sensing techniques. The overall goal of his research program is to contribute to the development of mechanistic service life prediction models that integrate measurement techniques (structural health monitoring and nondestructive testing) for model updating.

Publications

Abrasion Resistance of Concrete Exposed to Organic Acids

Park, S., Castellano, L., Barlaz, M. A., & Pour-Ghaz, M. (2020), JOURNAL OF MATERIALS IN CIVIL ENGINEERING, 32(8). https://doi.org/10.1061/(ASCE)MT.1943-5533.0003251

Degradation Model for the Tensile Strength of PVC and Rubber Gasket Materials Exposed to Benzene and PCE-Saturated Aqueous Solutions

Hosseini, P., Alhomair, S., Faeli, Z., Pour-Ghaz, M., Gabr, M., Knappe, D., & Parker, C. (2020), TRANSPORTATION RESEARCH RECORD. https://doi.org/10.1177/0361198120906126

Quantifying moisture damage in asphalt concrete using axisymmetric flexural vibration technique

Rashetnia, R., Kusam, A., Yadav, S., Pour-Ghaz, M., & Tayebali, A. (2020), INTERNATIONAL JOURNAL OF PAVEMENT ENGINEERING. https://doi.org/10.1080/10298436.2020.1757671

Retrieval of the saturated hydraulic conductivity of cement-based materials using electrical capacitance tomography

Voss, A., Pour-Ghaz, M., Vauhkonen, M., & Seppanen, A. (2020), CEMENT & CONCRETE COMPOSITES, 112. https://doi.org/10.1016/j.cemconcomp.2020.103639

The Effect of Gas Solubility on the Secondary Sorption in a Portland Cement Mortar Observed by X-ray CT

Dalton, L. E., Jarvis, K., & Pour-Ghaz, M. (2020), TRANSPORT IN POROUS MEDIA. https://doi.org/10.1007/s11242-020-01429-6

Another Look at the Abrasion Resistance of Concrete

Park, S., & Pour-Ghaz, M. (2019), ADVANCES IN CIVIL ENGINEERING MATERIALS, 8(1), 423–434. https://doi.org/10.1520/ACEM20180159

Durability of CFRP strands used for prestressing of concrete structural members

Khalafalla, O., Pour-Ghaz, M., ElSafty, A., & Rizkalla, S. (2019), CONSTRUCTION AND BUILDING MATERIALS, 228. https://doi.org/10.1016/j.conbuildmat.2019.116756

Numerical simulation and experimental corroboration of galvanic corrosion of mild steel in synthetic concrete pore solution

Mohammadian, A., Rashetnia, R., Lucier, G., Seracino, R., & Pour-Ghaz, M. (2019), CEMENT & CONCRETE COMPOSITES, 103, 263–278. https://doi.org/10.1016/j.cemconcomp.2019.04.027

Three-dimensional electrical capacitance tomography - A tool for characterizing moisture transport properties of cement-based materials

Voss, A., Hosseini, P., Pour-Ghaz, M., Vauhkonen, M., & Seppanen, A. (2019), MATERIALS & DESIGN, 181. https://doi.org/10.1016/j.matdes.2019.107967

Detection and reconstruction of complex structural cracking patterns with electrical imaging

Smyl, D., Pour-Ghaz, M., & Seppanen, A. (2018), NDT & E INTERNATIONAL, 99, 123–133. https://doi.org/10.1016/j.ndteint.2018.06.004

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Grants

Repair Strategies for Waste Transfer Station Concrete Overlays

Environmental Research & Education Foundation(3/01/20 - 9/30/22)

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Repair Strategies for Waste Transfer Station Concrete Overlays

Sponsor: Environmental Research & Education Foundation

Start Date: 3/01/20

End Date: 9/30/22

Abstract

Recently, it has been shown that the premature deterioration of concrete overlays in waste transfer stations is a result of simultaneous exposure to leachate (organic acids) and mechanical abrasion by waste handling equipment. In our previous research, we developed a material design guide and specification that owners can use for design or bidding. There are however, important limitations to the developed guide in that it: (1) does not address repair strategies and repair material selection, (2) is limited to portland cement concrete, (3) does not cover the use of unconventional concretes such as iron aggregate and epoxy matrix, (4) applies to slabs with a minimum of 6-inch thickness and does not cover thin precast and prestressed overlays, and (5) does not include provisions for the use chemical or mineral admixtures that can increase the acid resistance of concrete. The industry is in need of low cost and effective repair strategies for existing concrete overlays. The goal of the proposed research is to develop a guideline for repair strategies and repair material selection that can be (1) used by owners and operators of waste transfer stations and (2) adopted and implemented by contractors without the need for specialized equipment and labor.

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Understanding the FOG deposit adhesion mechanism on different sewer line surfaces

NCSU Water Resources Research Institute(3/01/20 - 12/31/21)

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Understanding the FOG deposit adhesion mechanism on different sewer line surfaces

Sponsor: NCSU Water Resources Research Institute

Start Date: 3/01/20

End Date: 12/31/21

Abstract

According to the US Environmental Protection Agency (USEPA), around 23,000 to 75,000 Sanitary Sewer Overflows (SSOs) occur annually and approximately 25% of these SSOs are due to sewer line blockages related to the deposition of insoluble calcium salts of fat, oil and grease (FOG). Prior research studies have quantified the chemical and rheological properties of the FOG deposits along with its formation mechanism (Keener et al. 2008; He et al. 2011, 2013; Williams et al. 2012; Gross et al. 2017). Research performed by the PI and Co-PI on the project entitled “Evaluation of Alternative Binder Material to Reduce Sewer Collection System Infrastructure Maintenance and Enhance Sustainability” funded by WRRI, investigated the substitution of Fly Ash (FA) in concrete to reduce the formation and adhesion of FOG deposit on sewer line surfaces. Although exciting results from this project revealed a significant reduction in FOG formation and adhesion on FA replaced concrete surfaces, its mechanism for reduced FOG deposition at the interface is unknown. An interesting observation from these prior adhesion studies is that FOG deposits do not form or adhere on the concrete coarse aggregate (granite) surface. Understanding this unique and previously unknown phenomenon could lead to new strategies on treating pipe surfaces that would not allow any FOG deposit adhesion. The objectives of this proposed research are to: 1) understand the FOG adhesion mechanism on different sewer pipe surfaces and 2) evaluate the factors affecting FOG adhesion on different sewer surfaces. Successful completion of this project will help to determine the adhesion mechanism of FOG deposits on sewer collection system and develop new strategies during construction or the maintenance of sewer pipes that will change the surface characteristics to reduce the adhesion of FOG deposits. We anticipate that results will eliminate or significantly retard the accumulation of FOG deposits in sewer lines leading to a reduction in the maintenance cost and the occurrence of FOG related SSOs especially in “Hot Spot” regions known for the persistent accumulation of these solids.

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Field Evaluation of Hardening Methods for Subsurface Utilities and Drainage Pipes

NC Department of Transportation(8/01/19 - 7/31/21)

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Field Evaluation of Hardening Methods for Subsurface Utilities and Drainage Pipes

Sponsor: NC Department of Transportation

Start Date: 8/01/19

End Date: 7/31/21

Abstract

The North Carolina Department of Transportation (NCDOT) routinely performs road improvement projects where a portion of the right-of-way might be contaminated. Based on the field evaluations carried out by NCDOT, at times subsurface utilities including water and/or drainage pipes are present, or need to be installed, in environments where soil and groundwater contamination exists. The currently funded project (RP 2017-08 with end date on July 31, 2019), is focused on the laboratory evaluation of contaminant migration through concrete pipes, as well as evaluation of the effect of contaminants on the mechanical performance of PVC pipe and three gasket materials (Neoprene, Buna-N, and Viton) when exposed to contaminated water. In addition, modeling of hardening methods and evaluating their efficacy is conducted as a part of the ongoing project.

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Fiber Reinforcement for Latex Modified Concrete Overlays

NC Department of Transportation(8/01/19 - 7/31/21)

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Fiber Reinforcement for Latex Modified Concrete Overlays

Sponsor: NC Department of Transportation

Start Date: 8/01/19

End Date: 7/31/21

Abstract

A large number of bridge deck rehabilitations are performed each year in North Carolina. Latex Modified Concrete (LMC) and LMC–Very Early Strength (LMC-VES) are frequently used in these rehabilitations because these materials provide reasonable installed performance and allow for a rapid return to service. Over the last 5 years, the NCDOT has completed an average of about 25 overlays per year using LMC or LMC-VES materials. The vast majority of these projects are highly successful. However, despite comprehensive NCDOT guidelines and specifications (such as PSP003 and PSP004), substantial cracking is sometimes observed in these overlays shortly after installation. Prior research funded by NCDOT has indicated that if placement and curing follows proper construction procedures, then the primary causes of cracking (such as shrinkage and plastic shrinkage) in LMC and LMC-VES materials are unlikely to develop. However, other secondary mechanisms can potentially cause cracking, including vibration of the structure during casting and curing, temperature changes during casting, and slight differential settlement/deflection of supporting decks as overlay placement progresses across a bridge. These suspected secondary causes of cracking are difficult (or impossible) to mitigate in practice. In practice, it can also be difficult to completely enforce proper construction procedure, which can lead to some shrinkage cracking. For example, fogging above fresh LMC-VES is allowable, but allowing water to accumulate on the material during placement and finishing is not – the distinction is sometimes difficult to monitor and enforce in the field.

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Durability of Pipe Materials in Soils

NC Department of Transportation(8/01/19 - 7/31/21)

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Durability of Pipe Materials in Soils

Sponsor: NC Department of Transportation

Start Date: 8/01/19

End Date: 7/31/21

Abstract

A large number culvert pipes are installed every year in North Carolina. While the loading and structural requirements for these pipes are considered during the selection process, the exposure condition of these culverts receives less attention. Many pipe choices exist including reinforced concrete, galvanized steel, aluminum, aluminized, and various types of plastic. Choosing the right pipe for the right installation is a non-trivial task that carries significant financial impact. Factors such as structural capacity, environmental durability, anticipated life-span, required pipe size, site conditions, and available construction expertise are all important when selecting a pipe. Existing NCDOT selection tables provide some limited guidance, but often result in highly-conservative selections being made, particularly from the perspective of matching pipe materials to site environmental conditions. Selection of the wrong pipe material (or an overly-conservative pipe material) can result in significant excess cost. If materials degrade too quickly, costly re-work is required, and additional costs and risks may be incurred due to reduced performance of the degraded pipe. If high-cost and high-performance materials are selected in areas where they are not needed, then initial construction costs can increase dramatically. For example, in many situations, aluminized corrugated steel pipe can likely provide the same useful service life as corrugated aluminum pipe at a dramatically reduced cost. Aluminum pipe may be justified in regions with salt-water exposure, however, it is likely an over-conservative choice for regions where contact with salt will be incidental. Accounts from NCDOT personnel have indicated widespread use of aluminum pipe in regions where it is likely not needed (i.e., regions with limited salt exposure).

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Development of Test Methods to Characterize Heat Production from Special Wastes Disposed in Landfills

Environmental Research & Education Foundation(9/01/18 - 9/01/21)

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Development of Test Methods to Characterize Heat Production from Special Wastes Disposed in Landfills

Sponsor: Environmental Research & Education Foundation

Start Date: 9/01/18

End Date: 9/01/21

Abstract

Recently, there have been reports of municipal solid waste (MSW) landfills that have been experiencing temperatures in excess of 80 °C. Elevated temperatures have a number of deleterious effects that are well known to landfill owners. Consequently, elevated temperature landfills often require increased monitoring and management. In recent work supported by the EREF, we developed a model of heat accumulation in a landfill. The objective of the model was to help identify and mathematically describe all sources of heat input, generation and loss in a typical Subtitle D landfill. The model simulations identified several reactions that contribute significant heat to landfills including the hydration and carbonation of calcium-containing wastes (e.g., ash) and aluminum corrosion. Model predictions however, were based on information adopted from the literature for systems other than landfills. In addition to MSW, many landfills receive non-hazardous industrial wastes including ash from both coal and MSW combustion, ash used to solidify liquid wastes, auto shredder residue (ASR) that contains Al and Fe, and perhaps other Al-containing wastes. Methods are needed to measure the heat production potential of such wastes under landfill-relevant conditions and to use the resulting heat production data to evaluate the quantity of a given waste that can be disposed without the accumulation of unacceptable heat. The objectives of the proposed research are to (1) develop laboratory methods to measure heat evolution from special wastes under landfill-relevant conditions and (2) measure rates of heat production to parameterize our heat accumulation model. The model will then be used to estimate acceptable quantities of specific heat-producing wastes for disposal. The proposal emphasizes heat release from ash and metal corrosion. However, methods will be generalized to assess the heat generation of other wastes.

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Use of Moisture-Induced Stress Test (MIST) to Determine Moisture Sensitivity of Asphalt Mixtures

NC Department of Transportation(8/01/16 - 7/31/19)

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Use of Moisture-Induced Stress Test (MIST) to Determine Moisture Sensitivity of Asphalt Mixtures

Sponsor: NC Department of Transportation

Start Date: 8/01/16

End Date: 7/31/19

Abstract

Asphalt mixtures used in pavement construction are required to meet the NCDOT moisture sensitivity specifications. The current lab procedure to test moisture sensitivity uses conditioning procedures as per modified AASHTO T283. This is a fairly lengthy procedure involving specimen preparation, sample saturation, conditioning the samples for 24 hours, and then indirect tension testing. The variability involved in TSR test results is also observed to be high. The current test method uses the ratio of indirect tensile strength of the conditioned and unconditioned specimens (TSR). The indirect tensile strength is a qualitative measure of the moisture sensitivity. There is a need for a quicker test method(s) that is quantitative and has less variability. The new test should also lend itself to measure intrinsic properties such as the dynamic modulus of asphalt concrete that will allow inferior mixtures to be eliminated even though they may pass the TSR test.

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The effects of contaminated soil and groundwater on subsurface utilities, surface water and drainage

NC Department of Transportation(8/01/16 - 7/31/19)

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The effects of contaminated soil and groundwater on subsurface utilities, surface water and drainage

Sponsor: NC Department of Transportation

Start Date: 8/01/16

End Date: 7/31/19

Abstract

The North Carolina Department of Transportation (NCDOT) routinely performs road improvement projects where a portion of the right-of-way might be contaminated. Potential sources of contamination include underground storage tanks in the vicinity of the road improvement site, old unlined landfills, or abandoned industrial and agricultural operations with practices leading to soil and/or groundwater contamination. It has been reported by NCDOT in RNS#7406 that in several situations, subsurface utilities including drainage pipes are present in environments where soil and groundwater contamination exists. The effect of the contamination on the integrity and durability of the subsurface drainage pipes and gaskets is largely unknown but such integrity is a function of the type of contamination and the physicochemical properties of pipe, gasket, and other materials forming a given subsurface utility. In addition to the variety of contaminants and concentrations that prevail at these sites, a wide variation in soil geological formation and hydrogeological conditions exist across the state. While in general the groundwater table is expected to be high in the North Carolina (NC) Coastal Plain Physicographic region, it is expected to be deep in the Mountains. On the other hand, it is more likely that groundwater will feed surface water springs and streams in the NC Mountains. Therefore, a "typical" contaminated site is difficult to define. Accordingly, the adverse effect of subsurface contamination on drainage pipes and the efficacy of hardening measures are usually developed on a site-specific basis. Objectives of this project are to (i) catalog the prevalent types of contaminants and their concentrations at sites where subsurface utilities are installed, (ii) document the typical materials used in subsurface utilities and drainage systems in NC, (iii) quantify the effect of contaminants on the long-term durability of commonly used hardened and unhardened materials that are used in construction of subsurface utilities, (iv) quantify the rate and extent of migration of common contaminants through concrete utilities, (v) recommend effective hardening methods for different materials, and (vi) provide documentation and better understanding of the effect of subsurface utility installation on the contamination of groundwater and surface water through simulation of several typical scenarios. These objectives will be achieved through a multidisciplinary effort of the research team as outlined in the project plan. Objective (i) will be achieved through examination of available data from the NC Department of Environmental Quality (DEQ). If necessary, limited sampling of groundwater and surface water will be conducted in consultation with NCDOT in areas where subsurface utilities have been installed and contamination is known to exist or expected to occur. Objectives (ii), (iii), and (iv) will be accomplished through literature review and accelerated coupon testing in our laboratory. Objective (v) will be achieved by analyzing test results and literature data. Objective (vi) will be accomplished through numerical simulations.

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Durability of the Grouted Shear Stud Connection at Low Temperatures

US Dept. of Transportation (DOT)(3/01/16 - 5/15/19)

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Durability of the Grouted Shear Stud Connection at Low Temperatures

Sponsor: US Dept. of Transportation (DOT)

Start Date: 3/01/16

End Date: 5/15/19

Abstract

This research proposal addresses the design and behavior of a new, recently developed connection for steel bridge substructures. This new connection, termed the grouted shear stud connection (GSS), was shown to be an effective and improved design over current practice of directly welding hollow circular steel pipe piles to steel cap beams. In previous studies, the new connection performed well, in both quasi-static and dynamic tests at ambient (indoor) laboratory temperatures. Because this new connection relies upon the integrity of grout, a cementitious material prone to degradation from severe environmental conditions typical in Alaska, the durability of this material and the connection as a whole must be assessed. This proposed project focuses on the durability of the GSS by optimizing the grout properties through material testing, and subsequent tests of weathered and unweathered full-scale connection specimens when subjected to temperatures as low as -40° C. The outcome of this research will be a set of design recommendations to maximize the durability and hence the long term performance of the grouted shear stud connection. While developed for new bridge construction, the GSS connection is readily adapted to retrofit applications in existing steel bridge substructures with deficient pipe column to cap beam connections. The results of this study may therefore be of value in the eventual structural upgrade of Bridge No. 455, the Anchorage Port Access.

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Design of Waste Transfer Station Concrete Overlays against Premature Deterioration

Environmental Research & Education Foundation(9/15/15 - 8/14/18)

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Design of Waste Transfer Station Concrete Overlays against Premature Deterioration

Sponsor: Environmental Research & Education Foundation

Start Date: 9/15/15

End Date: 8/14/18

Abstract

The premature deterioration of concrete overlays in waste transfer stations is a major concern for the owners and operators of these facilities. Overlay replacement in these facilities has significant economic impacts including direct costs, operational delays, and planning hurdles. While the overlay deterioration is mainly attributed to the abrasion caused by scraping solid waste, anecdotal evidence suggests that other factors might equally contribute to the deterioration of the overlays. Unfortunately, published data on the contributing factors to the deterioration of concrete overlays in transfer stations and the mechanisms involved are virtually nonexistent. Some of these factors may include contact with acidic leachate from fresh waste, the type and operation of equipment used for handling waste, the amount of waste handled, and the lack of systematic structural design that accounts for concrete material deterioration. If the main contributing factors to deterioration are identified, these overlays can be designed against deterioration, resulting in better long-term performance and predictability, and consequently, reduced life cycle cost for owners and operators. The main objectives of this research are therefore (i) to identify the contributing factors to the premature deterioration of concrete overlays in transfer stations, and (ii) to establish a structural design methodology for the concrete overlay based on the observed degradation mechanism and operational conditions.

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