This thesis is the consequence of a research effort undertaken by the School of Civil and Construction Engineering at Oregon State University and funded by the Oregon Department of Transportation (ODOT) and the Federal Highway Administration (FHWA). The principal objective of the effort was to reduce the life cycle cost of bridges by developing one or more materials systems for precast and pre-stressed bridge deck components that improve the studded tire wear (abrasion) resistance and durability of bridge decks. Degradation of the concrete bridge decks due to abrasion caused by the studded tires and accelerated corrosion of the reinforcing steel in the concrete often triggers costly, premature rehabilitation or replacement of these bridges. High performance concrete (HPC) can provide improved abrasion resistance, but is more costly than ordinary concrete and can exhibit early age cracking when used for cast-in-place concrete members, which can accelerate corrosion of embedded reinforcing steel. However, several studies have suggested that HPC developed for precast members offers a viable alternative to cast-in-place concrete deck slabs due in part to improved control of the curing process. The scope of this research was to develop one or more mixture designs for HPC that improve the durability and abrasion resistance of the bridge decks through careful selection and proper proportioning of the constituent materials and improved control of the curing process. The materials investigated in this research included silica fume, slag, and fly ash as partial replacement of Type I and Type III portland cement mixed with crushed aggregate and river gravel. Phase I of the study included development of 15 mixture designs incorporating various combinations of the materials. Mixtures were cast under controlled laboratory conditions and cured using a variety of methods. The results of tests conducted on the cured samples indicated that the mixture with silica fume and slag had greater strength than the mixture with silica fume and fly ash mixture, and that mixtures with crushed rock provided better abrasion resistance than those with river gravel. Results from the chloride ion penetration test for permeability indicated that mixtures cured in saturated lime water for 28 days exhibited reduced permeability in comparison to mixtures which were steam cured followed by ambient curing. Following phase I, a pilot study was undertaken to identify the best curing method to apply during production at precast yards to assist high early strength gain so that the concrete member can be removed from the casting bed in a matter of several hours as well as to facilitate high ultimate strength, improved abrasion resistance, and low permeability. The pilot study indicated the best curing method to be steam curing followed by application of a curing compound. Phase II of the research study included seven mix designs and focused on various levels of supplementary cementitious materials. It adopted the curing method suggested by the pilot study. Results from phase II indicated that slag was better in enhancing durability of the concrete than fly ash. Increasing the proportion of silica fume did not improve the properties of high performance concrete significantly. Some other interesting results indicated that compressive strength was inversely proportional to wear rate and chloride ion penetration. Wear rate was directly proportional to chloride ion penetration. There was no relationship between durability factor (freeze-thaw test) and compressive strength or chloride ion penetration. Two mixtures were identified as having significantly improved abrasion and permeability characteristics over the control mixture (ODOT bridge deck mixture). Both included slag and silica fume as supplementary cementitious materials as a partial replacement of portland cement and one did not contain an air entraining admixture.

Bridge deck crack surveys were performed on twelve bridges on US-59 south of Lawrence, Kansas, to determine the effects of mixture proportions, concrete properties, deck type, and girder type on the crack density of reinforced concrete bridge decks. Of the twelve decks surveyed, eight are supported by prestressed concrete girders and four are supported by steel girders. Four of the decks supported by prestressed girders are cast on partial-depth precast deck panels, two are monolithic with synthetic fibers, and two have overlays. Of the four decks supported by steel girders, two have silica fume overlays (SFO) and two are monolithic. One of two decks with a silica fume overlay contains synthetic fibers in the overlay. Following the surveys, crack maps were plotted and analyzed and cracking trends were observed. The results for the US-59 bridge decks are compared with crack densities obtained in a study of low-cracking high-performance concrete (LC-HPC) bridge decks. The monolithic concrete bridge decks supported by prestressed concrete girders within this study exhibit less cracking than decks supported by steel girders. At an age of approximately three and a half years, the US-59 monolithic decks supported by prestressed girders with deck panels are not displaying significant cracking; most of the cracks are short transverse cracks aligned with the joints between the deck panels. The US-59 decks supported by prestressed girders with overlays exhibit significantly more cracking than the decks on prestressed girders without overlays. Bridge decks supported by steel girders without overlays have slightly higher crack densities than the decks with overlays. No benefits of using fibers in either the overlay or deck have been observed in this study, the sample size, however, is small. An increase in crack density was observed with an increase in average concrete slump for decks supported by both prestressed and steel girders. Decks with deck panels supported by prestressed girders exhibited an increased crack density with an increase in paste content.

Possibly the most pressing need in highway construction today is the repair or replacement of existing bridges. Due to increased needs and growing traffic, in addition to aging and extensive use, more than 2000 bridges in Kansas alone need to be replaced during the next decade. The majority of these bridges has spans of 100 ft or less, and has relatively shallow profiles. It is becoming increasingly important to implement a standard method for replacement in which the process is expedited and accomplished in cost-effective manner. Requirements for design and construction of concrete bridges have drastically changed during recent years. A main change in design is live-load requirements. Nebraska inverted-T bridge system has gained increasing popularity for its lower weight compared to I-girder bridges. However, there are some limiting issues when using IT system in replacing existing CIP bridges. Implementation of a post-tensioned IT system, which is the focus of this research, is believed to be one excellent solution for the IT deficiencies. Post-tensioning is added by placing a draped, post-tensioning duct in the stems of the IT members. Post-tensioning will lead to a higher span-to-depth ratio than IT system, and will reduce the potential transverse cracks in the (CIP) deck. Finally, the undesired cambers of pretensioned beams will be reduced, because fewer initial prestressing will be needed. This study was intended to explore the behavior of the PT-IT system, identify major parameters that control and limit the design of this system, and investigate different construction scenarios. This was achieved by conducting an extensive parametric study. For that purpose, PT-IT analysis program was developed and written using C++ programming language. The program was used to analyze various post-tensioning procedures for the post-tensioned inverted-T system. A Visual Basic friendly interface was provided to simplify the data input process. The findings of this research included recommendation of construction scenario for PT-IT system, as well as examining different methods for estimating time-dependent restraining moments. Effect of different concrete strengths on the behavior of PT-IT system was also determined. Most importantly, the effect of timing on different construction stages was also evaluated and determined.

In some countries durability problems with post-tensioning tendons have in the past led to fairly restrictive regulations. Improvements to execution procedures have been developed since, and new or improved prestressing systems have been proposed, too. This development was, of course, subject of discussions in fib Commission 9 Reinforcing and Prestressing Materials and Sytems and in IABSE Working Commission 3 Concrete Structures. It was decided to organise a workshop with the aim to review the different aspects of the problems encountered and to discuss solutions available today. Keynote speakers from various countries were invited to contribute. Their papers are published in this bulletin, grouped together under the following themes: Inventory and condition (6 papers) Investigation and repair (5 papers) Technical progress (4 papers) Strategies for improvement (6 papers) Supported by the international federation for structural concrete fib, and the international association for bridge and structural engineering IABSE, the workshop took place on 15-16 November 2001 at Ghent University, celebrating the 75th anniversary of the Magnel Laboratory for Concrete Research, whose director also chaired the Scientific Committee and edited the bulletin. It needs to be emphasised that in the bulletin invited experts present their individual views. Although not yet discussed in any of the association's working bodies, the highly topical contents of the bulletin is believed to be of general interest to fib's members and to document a starting point for future work in this field. Therefore, the Council of fib agreed to exceptionally publish these papers within fib's series of Bulletins.