Semester

Summer

Date of Graduation

2009

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

Julio F Davalos

Committee Co-Chair

Indrajit Ray

Abstract

Most of the concrete bridge decks in the cold regions undergo severe reinforcement corrosion due to the transport of chloride ions within the concrete by application of deicing salts on bridge decks in the winter. As a result, protective concrete overlays of about 2-inch thickness are applied on bridge decks. Concrete overlays provide: (1) protection against heavy traffic and the further infiltration of the chloride ions; (2) skid resistance surface; and (3) uniform appearance to extend the service life of bridge decks. Despite these advantages, concrete overlays undergo premature delaminations, edge curling, and corner lifting due to expansion/shrinkage of concrete, temperature changes, and repetitive truck loading.;This research work is a part of Phase-II component of a large-scale project sponsored by WVDOH which is focused on the performance evaluation of Latex Modified Concrete (LMC) and Silica Fume Modified Concrete (SFMC) overlays on Type K substrate concrete deck prototypes. This work evaluated four prototype slabs in two stages with each slab of plan size 1829 mm. (6 ft.) by 2438 mm. (8 ft.). In Stage-I, two bi-layer deck slabs were constructed with the same LMC overlay but with two different bonding conditions. Considering the better bonding condition from Stage-I, Stage-II consisted of two bi-layer deck slabs that were constructed with LMC overlay on one slab and SFMC overlay on the other. Pull-Off testing was conducted at different ages for assessing the bond performance of the overlays. The differential length change and differential temperature developed at the interface were continuously monitored using concrete embedment gages and thermocouple loggers, respectively. Debonding due to corner lifting was monitored by installing displacement transducers (LVDT) connected to a data acquisition system. Ultrasonic Pulse Velocity (UPV) testing was conducted to compare the delamination profile at the interface between different types of slabs. Simultaneously with the UPV tester, an oscilloscope was connected to record the time-domain waveform, which was converted into a power spectrum for analysis.;The Stage-I study showed that at 5% level of significance, both the interface bond strength of the LMC slab with and without bonding slurry were similar. However, the other critical delamination parameters such as differential length changes at the interface and vertical displacement due to corner lifting were much less when bonding slurry was incorporated. Also, the time-domain waveform of LMC with bonding slurry showed less attenuation of wave through the interface compared to no-slurry LMC. Further, the frequency spectrum analysis displayed that LMC with bonding slurry had higher peak magnitude compared to LMC without bonding slurry. Based on the results, the use of bonding slurry was preferred for the Stage-II study. This study showed that in-situ pull-off/bond strength results and nature of failure varied widely due to presence of local voids, compaction, and consolidations.;In Stage-II study where the bonding slurries were used for each case, the results showed that the bond strength values of slab with LMC overlay were higher than those of the slab with SFMC overlay, at 5% level of significance as analyzed by three-way ANOVA. The vertical displacement due to corner lifting was found to be lower for the slab with LMC overlay. The time-domain signal indicated that the amplitudes of LMC overlay were higher compared to those of SFMC overlay. Further, the power spectrum analysis showed that LMC had higher magnitude of peaks both at center and edge compared to SFMC overlays indicating the strength of the signals were stronger for LMC compared to SFMC.;The overall conclusion of this study is that the bonding slurry has positive effect to reduce delamination and corner lifting; and when slurry is used, the LMC has advantages over SFMC, although both overlay types are viable options. A full-scale study is required in order to conclude the findings and finally develop a performance based specifications for the overlays for the state of West Virginia.

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