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Corrosion of concrete sewer crowns will cost the County Sanitation Districts of Los Angeles County approximately $150 million for repairs to their deteriorating sewage system. Other parts of the country are experiencing similar problems. Crown corrosion is induced by microbial oxidation of reduced sulfur to sulfuric acid, which attacks the concrete. Bacteria, of the genus Thiobacillus are generally responsible for catalyzing these reactions. Thiobacillicollected from sewers were used to establish stoichiometry and biochemical aspects of sulfide oxidation. Metals inhibition was studied among the same cultures. Thiobacilli collected from extremely corroded sewers possess a greater tolerance for metals than those from lightly corroded areas. Acidophilic isolates grow at greater rates and oxidize sulfide more efficiently than non-acidophiles. Chemical inhibitor studies indicated that S(-II) oxidation is tightly linked to respiration by T. thiooxidans. It is doubtful that initial steps in bacterially catalyzed S(-II) oxidation are linked to oxidative phosphorylation.

Chemical inhibition of acid production by acidophilic thiobacilli was tested using a variety of metals and chelators (alone and in combination) including Hg(II), Ag(I), Co(II), Mo(VI), Cu(II), Zn(II), Cd(II), EDTA and NTA. When tested individually, Hg(II) and Ag(I) showed toxic effects at concentrations of 10-5 M and below; Cd(II), Zn(II) and NTA were noninhibitory at millimolar concentrations. Combination experiments showed both synergistic and antagonistic effects on chemical toxicities. Antagonism was apparent in experiments involving Cu(II)-EDTA, Cu(II)-Fe(III) and Cu(II)-Co(II). Synergism was apparent in experiments involving simultaneous addition of Mo(VI), Cu(II), Co(II) and Zn(II). In general, inhibitors either completely blocked or delayed the onset of acid production. In those cases where delayed reactions were observed, acid production began following an acclimation period on the order of days to weeks. Acclimation and metals speciation experiments suggest that adaptation events are due to biologically dependent changes in inhibitor speciation.

Master of Science / Department of Civil Engineering / Asad Esmaeily / Performance-based building design is a necessity in geographic locations where buildings are susceptible to large earthquakes and high winds. This design method requires an analysis of the performance of the structural system with loadings and deflections caused by earthquakes and wind. Current design codes include the load intensity in analysis procedures, but do not consider the effect of load pattern in the performance analysis of reinforced concrete columns. Because a thorough analysis must take into consideration load pattern and load intensity, computer software is ideal to analyze these systems. A computer program was originally developed by Esmaeily (USC_RC), and was revised later to be renamed (KSU_RC) in order to make the analysis of concrete column performance accurate, yet simple for design purposes. This analytical tool used analytical methods and material models, verified against experimental data, to accurately predict the performance of reinforced concrete columns under various loading conditions, including any pattern in lateral direction and independently variable axial load. However, the program was limited to circular, rectangular, hollow circular and rectangular sections and uniaxial lateral curvature and displacement. The next generation of the program, KSU RC 2.0, was developed to overcome the aforesaid limitations.

Master of Science / Department of Civil Engineering / Asadollah Esmaeily / Bridge and building construction in areas that sustain frequent seismic activity require the use of heavy lateral steel reinforcement within concrete columns to handle the lateral loads. Multi-spiral lateral reinforcement has been recently introduced to the construction field to offer an alternative to the traditional hoop and tie reinforcement. This report evaluates the experimental data observed in multiple experimental studies done on different concrete specimens. These specimens include multiple rectilinear reinforcement and several multi-spiral configurations in both rectangular and oblong columns. Due to multi-spiral reinforcement being a relatively new design, traditional computer programs have yet to include design analysis for this type of reinforcement in computer programs. Dr. Asad Esmaeily developed the program KSU RC 2.0 that can implement multiple analytical models to evaluate different multi-spiral configurations, as well as traditional hoop and tie confinement, that may be compared with experimental data. This report illustrates the comparative data from several different reinforced concrete column models. The data clearly indicates that multi-spiral reinforced columns exhibit higher compressive strength in the axial direction as well as higher ductility capabilities when compared to traditional rectilinear reinforcement of similar lateral steel reinforcement ratios. The use of multi-spiral reinforcement is also shown to lower costs for both the work time needed to install the structures as well as lowering the required steel ratio; all while maintaining the structural integrity of the columns.

Master of Science / Department of Architectural Engineering and Construction Science / Kimberly W. Kramer / This report offers a parametric study analyzing the vertical reinforcement for slender reinforced concrete walls (tilt-up panels) subject to 90 miles per hour (mph), 110 mph, 130 mph, and 150 mph three-second gust wind speeds. Wall panel heights of 32 feet (ft) and 40 ft are considered for one-story warehouse structures. First, solid tilt-up panels serve as the base design used in the comparison process. Next, square openings of 4 ft, 8 ft, 12 ft, and 16 ft centered in the wall panel, are analyzed. A total of 32 tilt-up panel designs are conducted, establishing the most economical design by the least amount of reinforcement and concrete used. In addition to lateral wind pressures, the gravity loads acting on the load bearing tilt-up panel are dead load, roof live load, and snow load. All loads for this report are determined based on a typical 24 ft by 24 ft bay. The procedure to design the tilt-up panels is the Alternative Design of Slender Walls outlined in the American Concrete Institute standard ACI 318-08 Building Code Requirements for Structural Concrete and Commentary Section 14.8 In general, an increase in panel height, lateral wind pressure, and/or panel openings, requires an increase in reinforcement to meet strength and serviceability. Typical vertical reinforcement in tilt-up panels is #4, #5, and #6 size reinforcement bars. A double-mat reinforcement scheme is utilized when the section requires an increase in reinforcement provided by use of a single-layer of reinforcement. A thicker tilt-up panel may be needed to ensure tension-controlled behavior. Panel thicknesses of 7.25 inches (in), 9.25 in, and 11.25 in are considered in design.

Call number: LD2668 .T4 1986 M34 / Master of Science / Civil Engineering

Call number: LD2668 .T4 1959 R54

Factors such as water to cement ratio, moisture, mixture, presence and depth of rebar, and dimension of specimens, all of which affect apparent resistivity of concrete, were analyzed by experimental and modeling methods. Cylinder and rectangular prism concrete specimens were used in the experiments exposed in a high moisture room, laboratory room temperature, high humidity and outdoor weather environments. Single rebar and four rebar specimens were used to study the rebar effect on the apparent resistivity. Modeling analysis was employed to verify and explain the experimental results. Based on the results, concrete with fly ash showed higher resistivity than concrete with just ordinary Portland cement. Rebar presence had a significant effect on the measured apparent resistivity at some of the locations. The results could be used as a guide for field apparent resistivity measurements and provide a quick, more precise and easy way to estimate the concrete quality. / by Yanbo Liu. / Thesis (M.S.C.S.)--Florida Atlantic University, 2008. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2008. Mode of access: World Wide Web.