Master of Science (MS), Ohio University, 2019, Civil Engineering (Engineering and Technology)

This thesis evaluates natural and chemically stabilized subgrade soils from five project sites throughout Ohio. Three of the five project sites were historically known to have moderate to high sulfate concentrations in the natural soils (DEF-24-2.67-W, LAK- 2-7.76-W, MRW-71-3.17-N), while the other two sites were known to have little to no sulfate levels (CLA-70-13.98-W, CLI-73-6.52-E), and were used as controls. The main objective of the study was to compare in-situ and laboratory test results to determine if there were formations of ettringite or thaumasite in the soil, which can lead to sulfate heave and premature failure of pavement. Several field tests were performed such as PSPA, FWD, LWD, DCP, and SPT. Standard soil tests were performed on natural and chemically stabilized samples, such as gran size analysis, Atterberg limits, organic content, moisture content, and pH, as well as a chemical analysis comprising of neutralization potential, sulfate concentration, and X-ray diffraction (XRD). Analysis showed no major differences of moduli for pavement or soil layers between control and non-control. Results showed that sites where sulfates were known to exist, the chemically stabilized layers had sulfate concentrations greater than 3000 ppm and the pH was just barely greater than 10, which is an indication of concern for ettringite and thaumasite formation. However, the chemical analysis did not indicate formation of either mineral, therefore all conditions were not met.

Committee: Issam Khoury (Advisor) Subjects: Civil Engineering; Geotechnology; Soil Sciences

Doctor of Philosophy, University of Akron, 2017, Polymer Engineering

Poly(ethylene glycol)s (PEGs) are an important class of polymeric materials. In addition to standard linear PEGs, polymers synthesized from (meth)acrylated PEGs are specially versatile in modern technological applications. Comb-like copolymers derived from (meth)acrylated PEGs, such as polycarboxylate ethers (PCEs) are widely used as hydration and setting modifiers in cement while the working mechanisms in cement hydration have remained uncertain. The first part of this dissertation uncovers correlations between copolymer architecture and setting properties of cement for a range of synthesized PCEs architecture. Adsorption of PCEs on calcium silicate hydrate surfaces involves migration of Ca2+ ions in the acrylate backbone to the calcium silicate hydrate surface and subsequent ion pairing of the anionic polymer backbone with the positively charged surfaces of calcium-silicate-hydrate (C-S-H) gel. Two consistent sets of property correlations are identified as a function of copolymer design. The adsorption strength of PCEs onto cement pastes, the conductivity, and retardation of cement hydration correlate in the same order. The water-to-cement ratio necessary for processing, zeta potentials, and the fluidity of the cement pastes correlate in a different order. The adsorption set directly correlates with the density of carboxylate groups, leading to strong, flexible ionic packing of multimolecular layers for low density and short length of side chains. The fluidity increases with density and length of PEG side chains, leading to less flexible, flat-on conformation, and lower adsorbed mass. Best dispersion of cement particles and greatest water reduction require a compromise reached by low density and intermediate length of PEG side chains. The mechanisms support the design of cement materials and related particle dispersions. A new series of ultraviolet (UV) curable electrical contact stabilization materials, which contain polypropylene glycol (PPG)-block-polyeth (open full item for complete abstract)

Committee: Mark Soucek (Advisor); Sadhan Jana (Committee Chair); Miko Cakmak (Committee Member); Toshikazu Miyoshi (Committee Member); Richard Elliott (Committee Member) Subjects: Polymer Chemistry; Polymers

PhD, University of Cincinnati, 2002, Engineering : Environmental Engineering

This paper presents the study results for a novel stabilization/solidification (S/S) process for high mercury wastes (Hg > 260 ppm). A relatively low-cost powder reactivated carbon (PAC) was used to stabilize mercury in solid wastes. Then the stabilized wastes were subjected to cement solidification. To improve the mercury adsorption capacity, PAC was impregnated with sulfides to obtain sulfurized PAC (SPAC). It was found that sulfurization of PAC by both CS 2 and Na 2 S significantly improved the mercury stabilization efficiency. For a Hg(NO 3 ) 2 solution with 40 mg/L initial Hg 2+ , the equilibrium concentration of Hg 2+ was lowered to 110 μg/L by SPAC, compared with an equilibrium concentration of 4310 μg/L by PAC. The adsorption efficiency was increased by more than one order of magnitude. The mechanism of sulfurization on mercury adsorption was investigated. It is believed that formation of low solubility mercury-sulfide species was the major cause of this phenomenon. The cement-solidified wastes were subjected to TCLP leach testing and constant pH leach testing. For the constant pH leach testing, the wastes were leached at constant pH values of 2, 4, 6, 8, 10, and 12 for 14 days. From the experimental results, it was found that, once in the solidified waste form, SPAC particles retained most of the adsorbed mercury, even in the presence of high chloride concentration, possibly due to the build-up of a gel-membrane outside the carbon pores as the hydration of cement proceeded. Experimental results from constant pH leaching tests indicated that the stabilized and solidified wastes were quite stable over a wide pH range after 14 days. A model was developed to simulate mercury sorption by reactivated carbon in stirred batch reactors. The model involved the coupling of a pseudo-second order kinetic model, surface equilibrium models, including the Langmuir isotherm and the Freundlich isotherm, and a material balance equation based on batch reactors. The predicted a (open full item for complete abstract)

Committee: Dr. Paul L. Bishop (Advisor) Subjects: Engineering, Environmental