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5 Background In recent years many advances have been made in concrete ingredients and mixtures, includ- ing admixtures, and supplementary cementitious materials (SCMs) that allowed the develop- ment of new concrete technologies and improvement of existing technologies for deployment in transportation infrastructure. New and more effective admixtures have enabled the reduc- tion of cement content and waterâcement ratio and increased efficiency of cement hydration to produce high early and later strengths of concrete for accelerated construction and repair of pavements and bridges. Other admixtures have aided in retaining mix workability to increase flowability and mitigate segregation of self-consolidating concrete (SCC); and have facilitated placement, compaction, and smoother surface finish of roller-compacted concrete (RCC) and pervious concrete pavements (PCPs). Combined with better and more versatile admixtures, the inclusion of SCMs such as regular and ultrafine fly ash, slag, silica fume, and metakaolin at regular and high cement replacement proportions, has allowed reduction of the cement content and increased reaction efficiency of the SCMs. This has contributed to high-strength concrete (HSC) and ultrahigh-strength concrete (UHSC), with improved durability for better corrosion protection and freeze- thaw resistance and more sustainable structures and pavements. Also, incorporating steel fibers in concrete mixtures has contributed to the development of ultrahigh-performance concrete (UHPC) technology and application for accelerated bridge construction (ABC) and overlay methods. The use of prewetted fine lightweight aggregate in concrete has shown good potential for providing internal curing that supplements surface curing for enhanced durability and shrinkage reduction in bridge decks. Also, recycled concrete aggregate (RCA) is becom- ing increasingly available for use as base material or in concrete mixtures for pavements and drainage structures. This has contributed to more sustainability due to reduction in disposal of demolished concrete in landfills. Placement of mass concrete in piers, pile caps, and other large members generates significant heat that substantially increases concrete temperatures and temperature differential with poten- tial for induced cracking. Many state highway agencies require the development of an effective mass concrete control plan to control the rise in concrete core temperature and differential temperatures between the core and surface to mitigate cracking. With all the success in concrete technologies, potential challenges have also emerged, includ- ing shortages in quality aggregates and the availability of fly ash in some states. Depletion of quality aggregates is driving states to import aggregates, conserve resources, and modify specifi- cations to allow lesser-quality aggregates to be used in nonstructural applications. Also, because C H A P T E R 1 Introduction
6 Concrete Technology for Transportation Applications many power generating plants are converting from coal to gas as fuel, the potential shortage of fly ash is prompting departments of transportation (DOTs) to modify their concrete specifica- tions to allow more use of alternative SCMs such as slag, silica fume, and metakaolin. This also presents a research opportunity to enable, after second processing, the use of imported fly ash with high loss on ignition (LOI) and imported bottom ash as well as ashes from wood burning and rice husks. Utilizing landfill materials in concrete to enhance its properties will contribute to longer availability of landfill storage space and provide greater sustainability and environmental pro- tection. Municipal waste, rubber tires, and bottom ash have been used as sources of fuel in some cement plants. Also, research has been conducted on the use of granulated glass, crumb rubber, and solid waste from treatment plants in concrete applications to reduce and reuse these reclaimed products. The experience and implementation of the proven concrete technologies varies from state to state and among different regions of the country. The main barrier to the adoption and implementation is insufficient knowledge of these technologies with respect to specification, construction guides, quality assurance/quality control (QA/QC) testing requirements, and performance. Loss of experience due to retirement and heavy workload of engineers, internal and industry resistance to change, and limited funding for research in many DOTs are some of the other barriers to adoption of successful technologies. Although information about new and established concrete technologies is available in pub- lished literature, there is no single document available on existing applications and practices for DOTs. Beneficial to the DOTs would be the awareness and sharing of information on the application of appropriate concrete materials and technologies to encourage their wider implementation. Objectives and Focus Synthesis Objective The synthesis objectives were to 1. Provide an overview of concrete technologies suitable for transportation applications, 2. Report on the state DOT applications of the technologies, and 3. Identify information gaps in the technologies. Definitions The synthesis focused on new and traditional concrete materials and technologies defined below: High-Strength Concrete: HSC is defined by the American Concrete Institute (ACI), as con- crete having a specified compressive strength of 8,000 psi (55 MPa) or greater, and it does not include polymer-impregnated concrete, epoxy concrete, or concrete made with artificial normal-weight and heavyweight aggregates (1). Self-Consolidating Concrete: SCC is highly flowable, nonsegregating concrete that can spread into place, fill the formwork, and encapsulate the reinforcement without mechanical consolidation (2). Internally Cured Concrete: ICC is a concrete mixture that uses prewetted, highly absorptive material that releases moisture inside the concrete to enhance and maximize the cement hydration without increasing the waterâcement ratio (3).
Introduction 7 Ultrahigh-Performance Concrete: UHPC is a mixture that includes portland cement, SCMs, well-graded fine sand, a high dosage of fiber reinforcement (usually steel), as well as super- plasticizers and other admixtures, and has a very low waterâcement ratio. It is a highly flowable and self-consolidating concrete that develops very high compressive and tensile strengths and exhibits durable performance (4). Temperature Control of Mass Concrete: TCMC is a construction plan for massive concrete members. The purpose of the plan is to control the rise in internal temperature of concrete and maintain the temperature differential between the interior and outside surfaces below threshold levels that may cause cracking and loss of durability (5). Precast Concrete Pavement: PCP systems are composed of concrete panels that are fabricated off-site, transported to the project site, and installed rapidly on an existing pavement or prepared base (6). Roller-Compacted Concrete: RCC is a stiff concrete mixture with very low or no slump that is used for road and highway pavements. RCC pavements are designed similarly to traditional concrete pavements, but are constructed similarly to asphalt pavements, without the use of forms, dowel and tie bars, or other reinforcement (7). Pervious Concrete: PC is an open-graded concrete mixture with only a small amount of, or no, fine aggregates, has a near-zero slump, and can contain 20% to 35% voids to allow rapid passage of water through the body of the concrete in pavement surfaces, base layers, and drainage structures (8). Recycled Concrete Aggregate: RCA is produced by crushing and grading concrete debris from infrastructure demolition, or by crushing returned âleftoverâ concrete from ready-mix concrete supplied to infrastructure projects. RCA is used to produce concrete mixtures for pavement construction and as a road base material (9). High Early and Very High Early Strength Concrete: These concrete mixes are used in acceler- ated construction and overlay and repair of pavements and bridges. The high early strength concrete (HESC) is a concrete mixture that is designed to achieve a specified high early strength within 24 hours, and, in many cases, in less than 12 hours (10). The very high early strength concrete (VHESC) is a concrete mixture that can achieve a specified high strength in less than 4 hours. Performance-Engineered Mixture: PEM is a new concrete technology used by a growing number of state DOTs to engineer mixtures based on specified performance indicators assessed using performance-related test methods (11). Synthesis Focus The synthesis focused on information related to the nature of the above technologies, their applications, aspects of materials and construction, benefits, performance, state users, suc- cesses and limitations in implementation, as well as any gaps in information. The information is intended to assist DOTs in making informed decisions about the appropriateness and appli- cations of these technologies in their transportation projects and in identifying resources to facilitate implementation of the technologies. Scope of Work The synthesis included three tasks: ⢠Task 1: Literature review ⢠Task 2: Survey of DOT practices and prepare case examples ⢠Task 3: Synthesis report
8 Concrete Technology for Transportation Applications Task 1: Literature Review The literature review synthesized information on the above technologies. Literature covered in the review included DOT, FHWA, industry and military publications, ACI reports and stan- dards, as well as research papers on work performed in university laboratories, at test tracks or at new and in-service projects. Where relevant, international publications and practices were also reviewed to supplement the information on the state-of-the-practice in the United States. Information derived from the literature review is presented in Chapter 2. For each technol- ogy, the following information is provided: an overview of the technology, applications, aspects of materials, mixtures and constructions, benefits, performance, usersâ experience, and limita- tions in technology implementation, as well as any gaps in the technology. Task 2: Survey of DOT Practices A draft survey questionnaire was prepared and submitted to NCHRP for review, comments and approval by the Topic Panel. Upon approval, the final version of the questionnaire was formatted, using a web survey tool, and sent electronically to the DOT representative serving on the AASHTO Committee on Materials and Pavements (COMP). The survey questionnaire is presented in Appendix A. It included 22 questions, inquiring the state DOTs about their implementation and performance records of the concrete technologies covered in the literature review. Additional established technologies, not covered in the litera- ture review, were also included in the survey questionnaire. These technologies included UHSC greater than 10,000 psi (69 MPa), lightweight concrete, lightweight cellular concrete, latex modi- fied concrete and polymer concrete. The survey questionnaire also sought information on technologies not addressed in the synthesis, shortages in quality aggregates, availability status of fly ash, extent of use of RCA, use of other landfilled/reclaimed materials in concrete, and barriers to wider implementation of established and new concrete technologies. The goal was to ensure at least 80% (40 states) response rate from the DOT COMP representa- tives. With follow up by the authors, 40 state DOT responses were received. The questionnaire results were analyzed and are presented with commentary in Chapter 3. Details of the responses are shown in Appendix B. Conclusions and gaps in the information derived from the survey responses along with the synthesized information from the literature survey were presented in Chapter 5 as conclusions and information gaps. Case Examples From the responses of state agencies, eight DOT agency representatives were invited to participate in preparing case examples on notable technologies or barriers to technology imple- mentation in their respective states. Five case examples were received from Florida, Illinois, Missouri, New York and Tennessee. The case examples included temperature control of mass concrete (Florida DOT), shrinkage control on bridge decks (Illinois DOT), precast concrete pavement (Missouri DOT), performance engineered mixtures (New York State DOT), and bar- riers to technology implementation (Tennessee DOT). Details of the case examples are pre- sented in Chapter 4. Specifications provided by the respective states are included in Appendix C. Task 3: Synthesis Report This report is prepared based on information collected from the literature review, survey responses, and case examples. The report is organized as follows:
Introduction 9 ⢠Chapter 1: Introduction ⢠Chapter 2: Overview of Concrete Technologies ⢠Chapter 3: Survey of State Practices ⢠Chapter 4: Case Examples of State Practices ⢠Chapter 5: Conclusions and Technology Information Gaps ⢠References ⢠Appendix A: Survey Questionnaire ⢠Appendix B: Responses to Survey Questionnaire ⢠Appendix C: State DOT Specifications/Special Provisions Goal of the Synthesis Report The report is prepared for the benefit of DOT engineers, consultants, and construction and industry professionals, as well as university students and researchers. The report provides infor- mation on a number of established and new concrete technologies to encourage more states to use these technologies and assist in removing barriers to wider implementation of the technolo- gies. Useful references are listed. They include state DOT, FHWA, and ACI reports, and relevant research papers in the specific technologies. These documents provide more detailed information about specific aspects pertaining to the concrete technologies.
