Browsing by Subject "Bond"
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Item Anchorage of Epoxy-Coated Rebar Using Chemical Adhesives(2018-09) Mills, ConnorPost-installed reinforcement is used to connect a new concrete member to an existing concrete structure. Typically, uncoated rebar post-installed with a chemical adhesive is used in these applications, which may lead to corrosion. Departments of Transportation and local bridge owners have used and continue to use epoxy-coated rebar in post-installed applications due to its inherent corrosion resistance. Unfortunately, chemical adhesive manufacturers provide tensile strengths of their products for use with uncoated rebar and not epoxy-coated rebar. This work examined what effects the epoxy coating had on the tensile pullout strength and compared the results for epoxy-coated and uncoated rebar. Two slabs were constructed. One slab contained epoxy-coated rebar post-installed using four different chemical adhesive products and the other slab contained uncoated rebar post-installed using the same four different chemical adhesive products. Results indicated that the epoxy coating slightly reduced the tensile pullout strength of the post-installed rebar. The ratio of the tensile pullout strength of the epoxy-coated reinforcing bars to the tensile pullout strength of the uncoated reinforcing bars ranged from 0.94 to 1.05 and varied based on the chemical adhesive manufacturer. T-Test results indicated that differences in the tensile pullout strength for epoxy-coated rebar compared to uncoated rebar were statistically different when using three of the four chemical adhesives during installation.Item Component terminal dynamics in weakly and strongly interacting blends.(2009-12) Ozair, Sehban N.Miscible blend dynamics have been long been a subject of interest and are not as well understood as dynamics of homopolymer melts. Their anomalous behavior, such as time-temperature superposition failure, broadening of calorimetric glass transition, etc., makes these systems very intriguing and challenges our understanding of miscible blend dynamics. In this work we investigated temperature and composition dependence of two different, dynamically heterogeneous blend systems using rheology and forced Rayleigh scattering (FRS). The first blend investigated was a weakly interacting one comprising poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA). Monomeric friction factors of PEO and PMMA were reported for a wide range of temperature and composition. PEO terminal dynamics were found to have strong composition dependence unlike that of PEO segmental dynamics previously reported. Also, PEO maintained its rapid relaxation mechanisms even in stiffer surroundings. The PEO hydroxyl end groups were found to have no significant impact on component chain dynamics. The FRS and rheology results agreed remarkably well for this system. The Lodge-McLeish model failed to describe the experimental results. In order to understand the role of hydrogen bonding on chain dynamics, a strongly interacting system of PEO/poly(vinyl phenol) (PVPh) was investigated using rheology. The blends consisted of a high molecular polymer tracer dispersed in low molecular weight matrix to extract relevant dynamic information from tracer contribution to material properties. Monomeric friction factors were reported for a wide temperature and composition range. Time-temperature superposition failure was observed in PEO tracer blends at high PVPh concentration. The shape of tracer relaxation spectra for PVPh tracer blends had a strong composition dependence while those for PEO tracer blends were independent of composition. The tracer contribution to blend viscosity had a strong temperature dependence at high PVPh composition. Across the composition range, single and narrow glass transitions were observed for these blends. PVPh chain conformations were investigated using SANS and contradictory conclusions were reached. Therefore, no conclusive remarks can be made regarding PVPh chain conformations in dilute solution.Item Effect of FRCM Repair on the Bond Behavior of Corroded Reinforced Concrete Beams Subjected to Static and Cyclic Loading(2017-08) Anderson, MirandaThis paper presents the evaluation of the effectiveness of Fiber Reinforced Cementitious Matrix (FRCM) repair in improving the bond behavior of corroded reinforced concrete beams under both static and fatigue loading. The study consisted of 30 full-scale beams, both corroded and uncorroded. The variables used in this study were corrosion level based on mass loss, repair method used, type of loading (monotonic or repeated loading), and load range applied. Corrosion was found to reduce the fatigue strength of reinforced concrete beams by introducing internal stresses in the concrete that ultimately cause reduction in the bond between the reinforcement and the surrounding concrete. FRCM was found to increase the fatigue strength of corroded concrete beams by providing confinement, thus making it an effective method for repairing beams damaged from corrosion. The use of a cementitious substrate with FRCM allowed for easier monitoring of the cracks developed in the concrete while testing.