The objectives of this research were to investigate the effect of stay-in-place metal forms (SIPMFs) on the performance of concrete bridge decks in Utah. The research program included six bridge decks with SIPMFs and six decks without SIPMFs, which were all located within the Interstate 215 corridor in the vicinity of Salt Lake City, Utah, and therefore subject to similar traffic loading, climatic conditions, and maintenance treatments, including applications of deicing salts during winter months. All of the tested decks were constructed between 1984 and 1989 using epoxy-coated rebar. Several tests were performed at each of six locations on each deck, including visual inspection, chain dragging, hammer sounding, Schmidt hammer testing, half-cell potential testing, and chloride concentration testing. Because differences in deck age and average cover for the two deck types were found to be statistically significant, the collected data were subjected to analysis of covariance (ANOCOVA) testing, with age and cover as covariates. All calculated p-values were compared to the standard value of 0.05. The distress survey results indicate that the average crack width and crack density for decks without SIPMFs were greater by 41 and 25 percent, respectively, than the corresponding values for decks with SIPMFs and that decks without SIPMFs had more potholes than decks with SIPMFs. However, the delamination density for bridge decks with SIPMFs was 71 percent higher than that of decks without SIPMFs. The average Schmidt rebound number for decks with SIPMFs was higher than that for decks without SIPMFs by an equivalent of 1,400 psi. The half-cell potential for decks with SIPMFs was 0.123 lower than that of decks without SIPMFs, indicating that a more active state of corrosion exists on decks with SIPMFs. On average, the chloride concentration in the bridge decks with SIPMFs was 205 percent greater than the concentration in the decks without SIPMFs. Among all of the distress measurements evaluated in the ANOCOVA, crack width was the only parameter that was determined to be significantly different between the two types of decks at the time of testing. In addition, Schmidt rebound number, half-cell potential, and chloride concentration at 2-in. depth all yielded p-values less than 0.05, indicating that significant differences in these properties exist between decks with and without SIPMFs. Specifically, the decks with SIPMFs have a higher compressive strength, a more active state of corrosion, and a higher chloride concentration, which may all be attributable to elevated moisture contents in decks with SIPMFs arising from the reduction in deck surface area from which moisture may evaporate. These data indicate that decks with SIPMFs are clearly more susceptible to reinforcement corrosion compared to decks without SIPMFs and may therefore exhibit greater magnitudes of damage with time. Given these research findings, engineers should carefully compare the short-term advantages against the potential long-term disadvantages associated with the use of SIPMFs for concrete bridge deck construction. If SIPMFs are approved for use, engineers may consider applying surface treatments to the affected decks early in the deck life to minimize the ingress of chlorides into the concrete over time and therefore retard the onset of reinforcement corrosion.

The purpose of this research was to develop a new index for concrete bridge deck management in Utah. Data were collected in the summer of 2005 from 15 concrete bridge decks in the vicinity of Salt Lake City. The decks ranged from 2 to 21 years in age and were all constructed using epoxy-coated rebar. Visual inspection, sounding, Schmidt hammer testing, half-cell potential testing, and chloride concentration testing were performed on six 6-ft by 6-ft test areas randomly distributed within the single lane closed to traffic on each deck, and testing protocols followed American Society for Testing and Materials standards to the extent possible. Collected data were analyzed using statistics, and age, cover, and half-cell potential were ultimately selected for inclusion in a new Utah Bridge Deck Index (UBDI); these variables effectively reflect chloride-induced corrosion mechanisms active on Utah bridge decks, are highly correlated to delamination distresses, and are relatively easy to measure compared to chloride concentration. At the request of Utah Department of Transportation (UDOT) personnel, the UBDI equation was structured around a deduct system using a 100-point scale similar to the sufficiency rating system, in which a perfect bridge deck receives a score of 100. Coefficients were selected based largely on the judgment of the researchers and the UDOT personnel involved in the research, and threshold values for maintenance, rehabilitation, and replacement (MR&R) options were specified to be the same as those associated with the standard sufficiency ratings. The UBDI and corresponding MR&R recommendation were then provided for each of the bridge decks tested in this research; nine of the decks are recommended for preventive treatment, and six are recommended for rehabilitation. In addition, the possibility of treatment applications was considered, leading to required adjustments in the UBDI calculation; the treatment options that were considered include an epoxy seal, an HPC overlay, and an asphalt membrane overlay. Four case scenarios were developed to demonstrate the response of the revised UBDI equation to these treatments. Finally, as aids for UDOT personnel implementing this research, charts were created to facilitate rapid determination of the required number of half-cell potential and concrete cover measurements for different levels of reliability and tolerance. The UBDI developed in this research is recommended for implementation by UDOT personnel as a tool for optimizing the timing of MR&R treatments on concrete bridge decks similar to those evaluated in this project. In measuring cover and half-cell potential values, UDOT personnel should utilize the sampling guidelines presented in this report to ensure adequate characterization of each deck. Furthermore, to facilitate the inclusion of treatment effects in the UBDI, UDOT personnel should establish a policy of recording the types and dates of all MR&R treatments applied to bridge decks. As performance data are collected for specific treatments over time, the treatment lives proposed in this research for epoxy seals, HPC overlays, and asphalt membrane overlays should be revised as needed, and information for other treatments may be added. In addition, to maximize the predictive capabilities of the UBDI, more accurate relationships between half-cell potential values and deck age should be developed for estimating future deck condition.

Concrete bridge decks in Utah are experiencing observable deterioration due primarily to freeze-thaw cycles and the routine application of deicing salts during winter maintenance activities. Given the need for increasingly cost-effective strategies for bridge deck maintenance, rehabilitation, and replacement (MR&R), the Utah Department of Transportation (UDOT) initiated this research to ultimately develop a protocol offering guidance as to whether deteriorated bridge decks should be rehabilitated or replaced. While threshold values for various non-destructive condition assessment methods were proposed in earlier UDOT research, this work focused on implementing the recommended test criteria. Twelve bridges were identified by UDOT engineers for inclusion in the study, and data were collected from each deck to determine whether the bridge decks warranted rehabilitation or replacement based on the proposed threshold values. Several evaluation techniques were employed to assess concrete bridge deck condition, including visual inspection, hammer sounding and chaining, dielectric measurements, ground-penetrating radar imaging, resistivity testing, half-cell potential testing, and chloride concentration testing. The condition assessment testing confirmed that chloride-induced corrosion of reinforcing steel is the primary mechanism of deck deterioration and that inadequate cover over the upper steel mat facilitated accelerated corrosion damage in many instances. The bridge deck condition analyses produced from the results of non-destructive testing were compared to the visual inspection ratings assigned to each deck by UDOT. Concrete bridge deck condition data should be collected regularly through inspection and monitoring programs to facilitate prioritization of MR&R strategies for individual bridges and to evaluate the impact of such strategies on the overall condition of the network. Performance indices based on selected condition assessment parameters should be developed for use in bridge management activities, and mathematical deterioration models should be calibrated in order to forecast both network-level and project-level conditions and predict funding requirements for various possible MR&R strategies. Further research, including statistical analyses of the data presented in this report, should be completed to develop relevant mathematical deterioration models for predicting the service lives of concrete bridge decks in Utah.

Considering the pervasive presence of chlorides in concrete bridge decks, bridge engineers have a critical responsibility to perform proper and effective preventive maintenance and rehabilitation operations. Bridge engineers often perform scarification and overlay (SO) procedures on concrete bridge decks to minimize the corrosion of reinforcing steel due to chloride ingress. Given the need to develop guidelines for the initial timing of SO treatments, the specific objectives of this research were to collect information from several department of transportation (DOT) personnel about their SO procedures and, subsequently, to determine the recommended timing of initial SO procedures on concrete bridge decks for preventing the accumulation of corrosion-inducing levels of chlorides and extending deck service life. A questionnaire survey of state DOTs was conducted, and numerical modeling of SO treatments was performed. Simulations involving both decks with and without stay-in-place metal forms (SIPMFs) were performed. Numerical modeling was performed for each unique combination of variables through a service life of 50 years to determine the recommended initial timing of SO treatment in each case. The research results show that, overall, bridge decks without SIPMFs can endure longer delays in SO treatment timing than those with SIPMFs; in all cases, the absence of SIPMFs extended the amount of time before an SO treatment was needed. For decks with SIPMFs, the allowable delay in SO timing ranged from 2 to 6 years, while on decks without SIPMFs the allowable delay in SO timing ranged from 6 to 18 years. These delays are only 1 to 3 years longer than allowable delays associated with placement of surface treatments investigated in previous research. On average, the period of additional delay allowed before an SO treatment is required in decks with SIPMFs was 2 years with each additional 0.5 in. of OCD. In decks without SIPMFs, the presence of a greater OCD had a more pronounced effect on the latest recommended timing of treatment than in the decks with SIPMFs; an average additional delay period of 5 years was obtained with each additional 0.5 in. of OCD in decks without SIPMFs. Together with the findings of this research and the specific properties of the bridge deck under scrutiny, engineers can determine the appropriate timing of rehabilitation procedures to prevent or mitigate corrosion of the steel reinforcement of a bridge deck and ensure the usability of the deck for its intended service life. Although the conditions studied in this research were consistent with bridges located in the state of Utah, bridge decks that exist in similar environments and that are subjected to similar treatments of deicing salts as part of winter maintenance could exhibit similar properties to the decks simulated in this research. Engineers should carefully consider the results of this research and implement proper timing of SO treatments on their respective bridge decks to protect against and minimize the effects of corrosion due to chloride ingress.

Numerous methods have been developed to measure corrosion potential relating to chloride infiltration in concrete, including an emerging application of electrochemical impedance spectroscopy (EIS). EIS involves measurements of electrical impedance to evaluate the corrosion potential of steel reinforcement in concrete. With EIS, current is injected vertically into the concrete bridge deck between the surface and the embedded reinforcing steel, usually the top mat, to evaluate the degree to which the reinforcing steel is protected from chloride infiltration by the entire bridge deck system. The objectives of this research were to 1) investigate the sensitivity of EIS measurements obtained at various frequencies to specific deck properties, 2) recommend a particular frequency or range in frequency at which impedance measurements can differentiate among various levels of corrosion protection for reinforcing steel in concrete bridge decks, and 3) compare impedance values measured at the recommended frequency(ies) to more traditional test measurements relating to corrosion of reinforcing steel in concrete bridge decks. This research involved impedance testing of 25 concrete slabs, divided into five sets. The effects of sealant presence, curing time, temperature, moisture content, cover depth, water-to-cementitious materials ratio, air content, chloride concentration, and epoxy coating condition on individual impedance measurements were evaluated. For the controlled laboratory experiments, sealant presence, curing time, temperature, moisture content, cover depth, water-to-cementitious materials ratio, air content, and epoxy coating condition were shown to have a statistically significant effect on impedance measurements, with p-values less than 0.05. The statistical analyses indicated that impedance testing in the frequency range of approximately 100 Hz to 1 kHz would be expected to provide the best data about the degree to which the reinforcing steel is protected from chloride infiltration by a bridge deck system. In this frequency range, a high level of differentiation among levels of corrosion protection is expected, and a high speed of data collection is also possible. For the uncontrolled laboratory experiments, a single frequency of 200 Hz was selected for impedance testing. Statistical analyses were performed to compare impedance with more traditional test measurements relating to corrosion of reinforcing steel in concrete bridge decks. Longitudinal and transverse cover, dry and wet resistivity, dry and wet half-cell potential, dry linear polarization, and chloride concentration were determined to be correlated with impedance, with p-values less than 0.15.

The objectives of this research were to 1) monitor in-situ moisture and diffusivity for both conventional concrete and concrete containing pre-wetted lightweight fine aggregate (LWFA), 2) compare deck performance in terms of early-age cracking, compressive strength, and chloride ingress, and 3) compare concrete properties in terms of compressive strength, chloride permeability, elastic modulus, and water content in the laboratory using cylinders cast in the field at the time of deck construction. The research involved field and laboratory evaluations of four newly constructed bridge decks located in northern Utah, two constructed using conventional concrete and two constructed using pre-wetted LWFA to promote internal curing. Data from sensors embedded in the concrete decks indicate that the moisture content of the internally cured concrete was consistently 1.5 to 4 percentage points higher than the moisture content of the conventional concrete for the first 6 months following deck construction. By 1 year, however, the internally cured concrete showed little difference in moisture content compared to the conventional concrete. While the internally cured concrete decks had a higher average moisture content, the electrical conductivity values were not consistently higher than those measured on the conventional concrete decks during the first approximately 8 to 10 months. However, after 8 to 10 months, both internally cured concrete decks exhibited higher electrical conductivity values than those measured on the conventional concrete decks. Laboratory compressive strength data indicate that, for the first 6 months following deck construction, the two concrete mixtures exhibited very similar strength gain characteristics. However, at 1 year, the conventional concrete was stronger by an average of 12.9 percent, or nearly 900 psi, than the internally cured concrete. In rapid chloride permeability testing, the internally cured concrete consistently passed between 13.1 and 17.5 percent less current than that passed by the conventional concrete. Laboratory free-free resonant testing at 1 year showed that the modulus of the internally cured concrete was 3.9 percent lower, on average, than that of the conventional concrete. For the tested specimens, the moisture content of the internally cured concrete was 0.5 percentage points higher, on average, than that of the conventional concrete. In the field, Schmidt rebound hammer testing showed that the internally cured concrete was neither consistently stronger nor weaker than the conventional concrete. On average, the internally cured concrete exhibited higher chloride concentrations than the conventional concrete. On average, the conventional concrete bridge decks had 4.6, 21.5, and 2.8 times more cracking than the internally cured concrete decks at 5 months, 8 months, and 1 year, respectively. At 1 year, very distinctive reflection cracks from the joints between the underlying pre-cast half-deck panels were observed on all of the decks.

The objective of this research was to investigate the effects of twisted steel micro rebar (TSMR) fibers on 1) the mechanical properties of concrete used in bridge deck construction and 2) the early cracking behavior of concrete bridge decks. This research involved the evaluation of four newly constructed bridge decks through a series of laboratory and field tests. At each location, one deck was constructed using a conventional concrete mixture without TSMR, and one was constructed using the same conventional concrete mixture with an addition of 40 lb of TSMR per cubic yard of concrete. Regarding laboratory testing, the conventional and TSMR beam specimens exhibited similar average changes in height after 4 months of shrinkage testing. The electrical impedance measurements did not indicate a notable difference between specimens comprising concrete with TSMR and those comprising conventional concrete. Although no notable difference in behavior between conventional and TSMR specimens was apparent before initial cracking, the toughness of the TSMR specimens was substantially greater than that of the conventional concrete specimens. Regarding field testing, sensors installed in the bridge decks indicated that the addition of TSMR does not affect internal concrete temperature, moisture content, or electrical conductivity. The average Schmidt rebound number varied little between the TSMR decks and conventional decks; therefore, the stiffness of the TSMR concrete was very similar to that of conventional concrete. Distress surveys showed that the conventional decks exhibited notably more cracking than the TSMR decks. The TSMR fibers exhibited the ability to limit both crack density and crack width. For all of the decks, chloride concentrations increased every year as a result of the use of deicing salts on the bridge decks during winter. However, the chloride concentrations for samples collected over cracked concrete increased more rapidly than those for samples collected over non-cracked concrete. Although TSMR fibers themselves do not directly affect the rate at which chloride ions penetrated cracked or non-cracked concrete, the fibers do prevent cracking, which, in turn, limits the penetration of chloride ions into the decks. Therefore, the use of TSMR would be expected to decrease the area of a bridge deck affected by cracking and subsequent chloride-induced corrosion damage and thereby increase the service life of the bridge deck.

Chloride-induced deterioration of concrete bridge decks can be described in terms of three phases: 1) initiation of rebar corrosion, 2) rust formation and development of deck damage, and 3) accelerated deck damage towards structural failure. The first objective of this research was to investigate relationships among chloride concentration at the top mat of reinforcing steel, deck age, cover depth, and occurrence of delamination for concrete bridge decks with selected surface treatments and rebar types. Relating these factors can help establish greater understanding about the duration of each phase of the deterioration process. A second objective of this research was to investigate the relationship between chloride concentrations that develop between the bars and those that develop directly above the bars in the top mat of reinforcing steel to better understand the effects of the presence of reinforcing steel on diffusion of chloride ions through the concrete matrix.Data collected from 48 concrete bridge decks in Utah were used to address both of the objectives stated for this research. Surface treatment types included bare concrete, thin-bonded polymer overlays, and asphalt overlays, and rebar types included uncoated and epoxy-coated rebar. Regarding the first objective, baseline relationships between chloride concentration, deck age, and cover depth were developed for all three deck types. The results show that, as deck age increases, chloride concentration also increases and that chloride concentrations are much higher for shallower concrete depths than for deeper concrete depths. Based on these relationships, the duration of the first phase of the deterioration process was estimated using the critical chloride threshold of 2.0 lb Cl-/yd3 of concrete. For decks with asphalt or polymer overlays, development of clear relationships between chloride concentration, deck age, and cover depth required consideration of treatment time. The data show that chloride concentrations for decks that had an overlay applied 10 or more years after construction are higher than those for decks that had an asphalt overlay applied immediately after construction. Relevant to determining the duration of the second phase of the deterioration process, the relationship between delamination occurrence and chloride concentration for bare concrete bridge decks was developed. In general, the results show that the occurrence of delamination increases with increasing chloride concentration. Estimated durations of the second phase of the deterioration process were then determined using a chloride concentration threshold of 4.0 lb Cl-/yd3 of concrete for each of the same combinations of surface treatment and cover depth used for determining durations of the first phase of the deterioration process. Regarding the performance of epoxy-coated bar, the data clearly demonstrate the benefit of epoxy coatings on reinforcing steel for the purpose of significantly delaying the onset of chloride-induced delamination in concrete bridge decks. The relationship between the ratio of chloride concentrations directly above and between steel reinforcing bars and deck age was then developed. The results show that, as deck age increases, the average ratio of chloride concentrations directly above and between the bars asymptotically decreases from above 1.5 toward 1.0, which is reached at a deck age of approximately 30 years. Given that increasing deck age generally corresponds to increasing chloride concentration, which would in turn eventually lead to similar chloride concentrations directly above and between bars as the concrete pore water within the cover depth approached chloride saturation, this observed relationship is consistent with theory.

An attempt was made to predict the service life of the Black River Bridge using non-linear finite element analysis (NLFEA). Numerical modeling was performed using NLFEA software developed by Prof. Evan Bentz. A large number of analytical studies were conducted to assess the strength and behaviour of the bridge under normal truck loading and at failure loads. It was determined that the bridge is shear critical. Location of trucks that would cause maximum deflection and highest crack widths were identified. It is believed that these findings will have a significant impact on physical measurements that can be incorporated into future bridges, helping researchers determine the locations in the bridge that are ideal for instrumentation. Axial compression present in the bridge can significantly affect deflection and crack widths. Incorporating thermal and shrinkage effects into the NLFEA are recommended as topics for further research. Appropriate estimate of thermal and shrinkage strain will aid in better prediction of axial stresses.

An attempt was made to predict the service life of the Black River Bridge using non-linear finite element analysis (NLFEA). Numerical modeling was performed using NLFEA software developed by Prof. Evan Bentz. A large number of analytical studies were conducted to assess the strength and behaviour of the bridge under normal truck loading and at failure loads. It was determined that the bridge is shear critical. Location of trucks that would cause maximum deflection and highest crack widths were identified. It is believed that these findings will have a significant impact on physical measurements that can be incorporated into future bridges, helping researchers determine the locations in the bridge that are ideal for instrumentation. Axial compression present in the bridge can significantly affect deflection and crack widths. Incorporating thermal and shrinkage effects into the NLFEA are recommended as topics for further research. Appropriate estimate of thermal and shrinkage strain will aid in better prediction of axial stresses.