AbstractDuring recent years, the rapid growth of shale gas exploration nationwide has resulted in a large number of overweight truck trips on roadways in areas with shale gas development. The ...Louisiana Department of Transportation and Development (DOTD) has seen a rapid decline in roadway serviceability within the Haynesville Shale area, presumably due to shale-gas-related traffic. The objective of this case study was to estimate roadway damage costs resulting from shale gas-related overweight trucks in Louisiana. In this study, the permit data for shale-gas-related overweight truck trips from 2006 to 2016 were extracted from DOTD’s oversize/overweight database using R language. The extracted overweight truck trips were subsequently assigned to the roadway network based on the shortest path method using ArcGIS. In total, it was found out that there were approximately 9.7 million shale-gas-related overweight vehicle miles traveled on Louisiana roadways between 2008 and 2016. This can be translated into a roadway damage cost of $17 million because of the shortening of roadway serviceable lives. On average, the estimated damage cost due to a single shale gas well was approximately $5,242. The damage costs per overweight mile and per equivalent single axis load were $1.74 and $0.27, respectively. However, it was estimated that only $14.5 million was recovered through permit fees. Therefore, it may be concluded that the current permit fee schedule for overweight truck trips in Louisiana cannot fully recover the damage costs resulting from overweight truck trips related to shale gas development. In general, this case study quantified the damage costs of one specific traffic type (i.e., shale-gas-related overweight truck traffic) on the roadway network using a combination of R Language, ArcGIS version 10.41, and pavement damage estimation analysis. The adopted method can also be applied to quantify the impact of other traffic types (e.g., that related to seasonal agricultural activities) on roadways or bridges. The results of the average damage costs estimated in this study may serve as a reference for future damage cost recovery due to shale gas exploration in other regions.
The use of titanium dioxide (TiO
2) ultrafine particles as coating for concrete pavement have received considerable attention in recent years as these particles can trap and decompose organic and ...inorganic air pollutants by a photocatalytic process. In spite of these promising benefits, the durability and resistance to wear of TiO
2 surface coating has not been evaluated. The objective of this study was to determine the abrasion and wear resistance properties of TiO
2 coatings and its effect on the coating’s environmental performance. To achieve this objective, an experimental program was conducted to measure and compare the environmental performance of titanium dioxide coating before and after laboratory-simulated abrasion and wearing. The environmental efficiency of the coating to remove nitrogen oxides (NO
x
) from the atmosphere was measured using a newly developed laboratory setup. Microscopic analysis was conducted using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) to determine the distribution of TiO
2 particles on the surface before and after wearing. The measured rut depth using the Loaded-Wheel Tester (LWT) was minimal indicating that the use of the coating did not appear to affect the wear resistance of the surface. Wearing of the specimens with 5% TiO
2 resulted in a small decrease in the coating NO removal efficiency. In contrast, the wearing of the samples with 3% TiO
2 slightly improved the NO removal efficiency. Results presented in this paper support that the use of TiO
2 coating as a photocatalytic compound would provide acceptable durability and wear resistance.
AbstractConsiderable interest has been directed in recent years toward the use of self-healing materials in concrete. The concept of microcapsule healing is based on a healing agent being ...encapsulated and embedded in the concrete. The objective of this study was to evaluate the effects of preparation parameters, namely, temperature, agitation rate, and pH on the shell thickness and size (diameter) of the microcapsules as well as to evaluate the self-healing mechanism in concrete through experimental testing performed in laboratory. Two healing agents were evaluated in this study, i.e., dicyclopentadiene (DCPD) and sodium silicate. Based on the results of the experimental program, it was determined that, as the pH was increased from 3.0 to 3.7, the shell thickness increased for sodium silicate, while the shell thickness reached a minimum at a pH value of 3.4 for DCPD. Sodium silicate shell thickness was almost twice the shell thickness for DCPD. The most uniform and coherent microcapsules were produced at a temperature of 55°C for both sodium silicate and DCPD. For the DCPD microcapsules and up to 49°C, the solution remained an emulsion and no encapsulation took place. An increase in agitation rate resulted in a decrease in the average diameter of the microcapsules for DCPD. On the other hand, the diameter of the microcapsules remained constant for sodium silicate microencapsulation as the agitation rate was increased from 250 to 550 rpm. Testing of concrete specimens modified with the two healing agents (DCPD and sodium silicate microcapsules) was conducted. For sodium silicate, an improvement of 11% in the modulus of elasticity of the concrete was observed after healing for the microcapsules prepared at a pH value of 3.1 and at a content of 5.0%. At other pH values, the effect of the sodium silicate microcapsules on the concrete performance was negligible. For DCPD microcapsules, the healing agent was effective in increasing the modulus of elasticity of concrete after cracking by as much as 30% for the microcapsules prepared at a pH value of 3.1 and at a content of 0.25%.
ASTM C1202 tests were conducted at various ages with the corresponding surface resistivity test, and the results were compared. Samples tested included field- and laboratory-prepared samples. The ...laboratory test matrix tested several mixtures common to Louisiana at a wide range of ratios of water to cementitious materials (w/cm) to evaluate the range of the surface resistivity meter. The surface resistivity measurements correlated well with rapid chloride permeability measurements across a wide range of permeability values and sample testing ages. Suitable correlations were found between both the 14-day and the 28-day surface resistivity values and the 56-day rapid chloride permeability values. The variability of the surface resistivity test results is usually less than the variability of the rapid chloride permeability test results. The surface resistivity meter was also able to identify great differences in w/cm ratios for the same mixtures. The surface resistivity meter was determined to be user friendly. The preliminary cost–benefit analysis showed that implementation of the device would save the department about $101,000 in personnel costs in the first year. It is estimated that contractors would save about $1.5 million in quality control costs. The cost–benefit ratio for this project is estimated to be about 15. A Louisiana Department of Transportation and Development test requirements procedure, TR 233, has been developed and implementation of the surface resistivity device has begun.
Self-cleaning, air-purifying pervious concrete pavement is a promising technology that can be constructed with air-cleaning agents with superhydrophilic photocatalyst capabilities, such as titanium ...dioxide. Although this technology has the potential of supporting environment-friendly road infrastructure, its effectiveness depends on a number of design and operational parameters that need to be evaluated. The objective of this study was to evaluate the mechanical, environmental, and mix design parameters that influence the performance and effectiveness of photocatalytic pervious concrete pavement. To achieve this objective, an experimental program was conducted in which the effects of relative humidity level, pollutants' flow rate, and mix design parameters, including void ratio and depth of the photocatalytic layer, were investigated. Mechanical performance tests included porosity, unit weight, permeability, and compressive strength. The environmental efficiency of the samples to remove nitrogen oxides (NOx) from the atmosphere was measured in the laboratory. Results of the experimental program showed that increasing the depth of the photocatalytic layer increased NOx reduction efficiency. In addition, NOx removal efficiency decreased with the increase in the pollutant flow rate and increased with the increase in ultraviolet light intensity.
AbstractThe objective of this study was to evaluate the self-healing effectiveness of urea-formaldehyde microcapsules with calcium nitrate as a healing agent in cement mortar. Calcium nitrate was ...selected as a healing agent because of its ability to react with available unhydrated cement particles in crack surfaces contributing to the formation of new hydration products that may potentially heal the crack. Self-healing capability of cement mortar with different microcapsule contents was evaluated under dry and wet healing conditions. Cracks ranging from 27.0 to 386.5 μm on average were created by three-point bending and indirect tensile tests. Cracks were observed by light microscopy over a 28-day healing period. Analysis of captured images showed signs of healing in the form of small crystallike features on the edge of the cracks on water-cured specimens after 7 days of healing. Furthermore, an improvement in self-healing efficiency was reported in specimens with microcapsule contents of 0.85 and 1.0% compared to the control after 14 days of the healing period. Environmental scanning electron microscopy (ESEM) coupled with energy dispersive spectroscopy (EDS) was utilized to investigate the morphology and chemical nature of the healing products. Crystallike and gellike healing products were found with the majority being crystallike. Crystallike healing products were likely calcium carbonate in the form of calcite crystals, whereas gellike healing product’s chemical nature was presumably calcium silicate hydrate (CSH).
Three full-scale roller compacted concrete (RCC) pavement sections built over a soil cement base were tested under accelerated pavement testing (APT). The RCC thicknesses varied from 102mm (4in.) to ...152mm (6in.) and to 203mm (8in.), respectively. A bi-directional loading device with a dual-tire load assembly was used for this experiment. Each test section was instrumented with multiple pressure cells and strain gages. The objective was to evaluate the structural performance and load carrying capacity of thin RCC-surfaced pavements under accelerated loading. The APT results generally indicated that all three RCC pavement sections tested in this study possessed very high load carrying capacity; an estimated pavement life in terms of equivalent single axle load (ESAL) for the thinnest RCC section (i.e., RCC thickness of 102mm) evaluated was approximately 19.2 million. It was observed that a fatigue failure would be the primary pavement distress type for a thin RCC pavement under trafficking. Specifically, the development of fatigue cracking was found to originate from a longitudinal crack at the edge or in the center of a tire print, then extended and propagated, and eventually merged with cracks of other directions. Instrumentation results were used to characterize the fatigue damage under different load magnitudes. Finally, based on the APT performance of this experiment, two fatigue models for predicting the fatigue life of thin RCC pavements were developed.
Seventeen surface resistivity meters and 17 operators participated in the round-robin testing conducted at the Louisiana Transportation Research Center over 2 days. The tests were conducted side by ...side, and the individual meter's results were compared. Eight mixtures representing multiple permeability classes were tested with two replicates for each mixture. A precision statement was developed for use with Louisiana Department of Transportation and Development's TR 233, Surface Resistivity Indication of Concrete's Ability to Resist Chloride Ion Penetration. The single operator coefficient of variation (CV) of a single test result has been found to be 2.2%. Therefore, the results of two properly conducted tests by the same operator on concrete samples from the same batch and of the same diameter should not differ by more than 6.2%. The multilaboratory CV of a single test result has been found to be 3.9%. Therefore, the results of two properly conducted tests in different laboratories on the same material should not differ by more than 11%.
The Louisiana Department of Transportation and Development has seen a rapid decline of low-volume roadway serviceability in recent years as a result of oil and gas exploration within the Fayetteville ...Shale Play near Shreveport, Louisiana. Similar results are expected on the low-volume roadway network within the Tuscaloosa Shale Play, north of Baton Rouge, Louisiana, as exploration expands. The objectives of this research were to determine appropriate proportions of roller-compacted concrete mixture for the construction of accelerated loading test lanes and to document field construction activities. Concrete samples were produced with four cement contents to determine the effect of moisture and density; the samples were tested for compressive strength at 7 and 28 days of age. The field testing included nuclear density testing, thickness measurements, and field-prepared compressive strength specimens. A walking profiler was used to determine the international roughness index (IRI). All laboratory-produced mixtures exceeded a compressive strength of 4,000 pounds per square inch (psi). When the desired surface characteristics and density were considered, 450 lb/yd3 was chosen as the minimum cementitious content for the construction of the test lanes. The field construction results showed that the speed of construction affected the density, the IRI, and the surface characteristics. An increased speed of construction yielded a rougher surface texture (an increased IRI between 360 and 620 in./mi) and slightly lower densities. The compressive strengths were still adequate and exceeded 4,500 psi at 28 days old. On the basis of the field results, IRI values in the 100- to 130-in./mi range and compressive strengths exceeding 5,000 psi may be expected in a full-scale roadway construction effort.
The objective of this study was to evaluate the feasibility of a cost-effective Engineered Cementitious Composite (ECC) with low fiber content (1.5% volume fraction) for pavement application. The ECC ...material studied was evaluated in compression, uniaxial tension and bending. In addition, flexural fatigue performance was evaluated. The cost-effective ECC material evaluated in this study exhibited a compressive strength of 37.6 MPa, a tensile ductility of 2.61%, and a flexural strength of 9.58 MPa. Moreover, the ECC material exhibited an equivalent flexural fatigue life to that of concrete at approximately two times the applied stress. Based on the experimental findings, it was shown that the cost-effective ECC materials with low fiber content can be promising for pavement application.
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