Environmental Health and Safety Dynamics of the Marcellus Shale in Pennsylvania

Quantifying the environmental impacts of hydraulic fracturing of the Marcellus Shale in Pennsylvania is critical for identifying high risk activities, and informing the development of engineering and policy practices aimed at risk mitigation. Environmental inspection and incident reports issued by the Pennsylvania Department of Environmental Protection (PADEP) are the most complete and consistent dataset available for analyzing trends in environmental incident rates in the Commonwealth. Overall violation and penalty rates decreased statewide between 2008 and 2011 when scaled to the number of Marcellus completions (1.08 to 14; and .43 to .03, respectively). There are regional differences in inspection practices and violation and penalty issuance between PADEP districts: Based on the assumption that intra-company environmental practices are consistent across drill sites, violation and penalty rates should generally be equivalent between PADEP districts for each driller. However, for 4 major gas companies operating in all 4 PADEP districts, the Northwest District Office issued overwhelmingly more violations and penalties than the other district offices in almost every case. Several important regulatory changes impacting Marcellus exploration activities occurred during the study period. Since many of these changes are activity specific, the overall incident rates were not affected. However, penalties for accidental discharges to stream waters declined from .04 per new completion to .01, following a regulatory change requiring a 150 foot buffer between drill sites and streams. There is generally an inverse relationship between the number of Marcellus drill site inspections, and the number of violations and fine carrying penalties issued. The number inspections increased statewide from 1195 in 2008 to 10,192 in 2011, and the rate of violations and penalties per inspection decreased from .09 to .02; and .03 to .004, respectively. This thesis shows that the relationship between incident reporting, drilling activity, inspection activity, and regulatory changes interact in a dynamic manner. It is recommended that inspection and reporting practices be centralized between PADEP districts, and that incident rates and types continue to be monitored so that regulatory and engineering practices can continue to be targeted to risk bearing activities

Equilibrium and Non-equilibrium Thermodynamic Modeling of Cement Pastes Containing Supplementary Cementitious Materials

Thermodynamic modeling of cementitious material is an established tool for predicting the hydrated phase assemblages, pore solution pH, and pore solution composition of mixtures of various chemical compositions and water-to-binder (w/b) ratios. However, traditional thermodynamic techniques have major limitations for modeling mixtures containing supplementary cementitious materials (SCM), and when modeling reactions at non-equilibrium conditions. Thermodynamic modeling using a Gibbs Energy Minimization framework computes the phase assemblages and speciation of a system based on its bulk elemental composition when the spontaneous energy of the system is at a minimum. However, cementitious systems are inherently non-equilibrium as they react. Furthermore, crystalline components of SCM generally are non-reactive in cementitious systems, so using the bulk composition of these materials in thermodynamic calculations may produce inaccurate results. Most modern-day cementitious binders contain SCM, and SCM can influence the reaction pathways and products in the binder. Because the durability and performance of cementitious mixtures depends in large part on which reaction products form, and the pore solution chemistry and pore size distribution of the mixture at different ages, there has been a clear need to develop models to incorporate SCM at equilibrium and non-equilibrium conditions into thermodynamic calculations, so that reaction products and pore solution can be accurately simulated at any age for any mixture. The work presented in this dissertation describes several models that contribute to filling these gaps in knowledge. A method to predict the pore size distribution of binders containing SCM is presented, based on an assumed equilibrium reactivity (DoR*) of the SCM (the pore partitioning model or PPM). The partitioning of pore sizes is accomplished based on the modification of a model (Powers-Brownyard) for ordinary portland cement using thermodynamic calculations. The ratio of small gel pores to larger capillary pores in binders contributes to strength gain and resistance to damaging processes in concrete. Accurate predictions from the PPM require accurate input values for DoR*. Also demonstrated in this dissertation is method to measure DoR* of pozzolanic SCM such as fly ash and silica fume. The reactivity test method combines experimental measurement of heat release and the consumption of calcium hydroxide (CH) in a simplified synthetic pore solution with thermodynamic calculations of idealized systems of silica and alumina at degrees of reaction ranging from 0% to 100%. The thermodynamic calculations provide reference lines against which the measured values can be read, providing a single numerical value for overall DoR* of a given SCM. The results of the reactivity test method confirm literature reports that SCM DoR* is highly variable, and not strictly related to the bulk elemental composition of the material. While factors contributing to the DoR* of SCM are many, the ratio of crystalline-glassy phases is known to play a major role. Also demonstrated in this dissertation is a method to determine the reactive phases in fly ash based on subtracting the ash crystalline components as measured by quantitative x-ray diffraction (QXRD) from the bulk composition of the system as measured by x-ray fluorescence (XRF). It is shown that the accuracy of thermodynamic calculations is improved when only reactive components of fly ash are modeled, particularly for ashes with high proportions of crystalline material. While accurate measurement and modeling of DoR* of SCM at equilibrium provides important information from which to determine durability-related properties of hydrated pastes, it is also important to understand the reactivity of the individual phases in the SCM at non-equilibrium conditions. Also demonstrated in this thesis is a kinetic framework for non-equilibrium thermodynamic modeling of pastes containing silica fume and fly ash. The kinetic model (MPK model) is based on a modification of the Parrot-Killoh model initially developed for ordinary portland cement. The model is an empirical model where the rate limiting step for each phase is based on the slowest of nucleation, diffusion, and reduction in ionic transport. Empirical constants for the MPK model are determined using a non-linear numerical algorithm fit from dissolution data for individual SCM phases described in literature. Using these empirical constants and a measured DoR* for each phase based on QXRD (DoRph*), the MPK model is shown to accurately predict the formation of hydration products and pore solution for mixtures containing fly ash and silica fume at different ages

Glass Fiber Waste from Wind Turbines: Its Chemistry, Properties, and End-of-life Uses

Glass fiber and glass fiber-reinforced polymers are of interest to engineers for a wide variety of applications, owing to their low weight, high relative strength, and relative low cost. However, management of glass fiber waste products is not straightforward, particularly when it is part of a composite material that cannot be easily recycled. This is especially the case for physically large structures such as wind turbine blades. This chapter deals with the challenges of managing this growing waste stream and reviews the structure and chemistry of glass fiber and glass fiber-reinforced polymers used in wind turbine blades, the separations processes for extracting the glass fiber from the thermoset resin, and end-of-life options for the materials. Thermodynamic evidence is reported and evaluated for a novel end-of-life solution for wind turbine waste: using it as a supplementary cementitious material

CALTRANS: Impact of the Use of Portland-Limestone Cement on Concrete Performance as Plain or Reinforced Material - Final Report

CALTRANS does not currently allow Portland-Limestone Cements (PLC) to replace Ordinary Portland Cement (OPC) in concrete. PLC has been proposed for consideration in CALTRANS specifications due to potential benefits in reducing greenhouse gas (GHG) emissions. This report outlines a comprehensive plan to provide both experimental and computational analysis results to address whether PLC may replace OPC without loss of mechanical and durability performance of concrete materials and mixtures specific to California. The objective of this study was to provide data for CALTRANS to make informed decisions on whether specification changes to permit use of PLC would be appropriate. Additionally, the research team was asked to assess the impact of added limestone (LS) powder as an alternative to using ASTM C 595/AASHTO M 240 cement