Concrete Technology for Transportation Applications (2019) / Chapter Skim
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10 Introduction This chapter includes an overview of established, emerging, and new concrete technologies and materials used by state highway agencies in construction, rehabilitation, and repairs of pavements, bridges, and other structures. The technologies include the following: • High-strength concrete (HSC)
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Overview of Concrete Technologies 11 High-Strength Concrete Introduction HSC is defined by ACI 363R-10 (1) as concrete having a specified compressive strength of 8,000 psi (55 MPa)
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12 Concrete Technology for Transportation Applications of the FHWA initiative to implement the use of HSC in bridges. Since then, the use of HSC has been expanded in all states as well as in more diverse applications such as bridge and tunnel components that are cast-in-place, precast/prefabricated, and prestressed and in pavement construction and repairs.
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Overview of Concrete Technologies 13 Normal-Setting Admixtures (ASTM C494/C494M, Type A)
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14 Concrete Technology for Transportation Applications Maximum aggregate sizes of 1/2 in.
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Overview of Concrete Technologies 15 however, may exhibit poor pumpability or may be significantly more prone to segregation during placement and consolidation (1)
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16 Concrete Technology for Transportation Applications to a higher rate of heat of hydration, tighter spacing between the hydrated cement, and a lower water–cement ratio. Resistance to Freeze-Thaw The use of air entrainment to increase resistance to freeze-thaw actions can contribute to lowering the strength of HSC.
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Overview of Concrete Technologies 17 Challenges of HSC The initial cost of HSC is higher than that of normal-strength concrete. This is due to the use of higher quantities of cementitious materials and admixtures in the mixture as well as higher cost of QA/QC to achieve a higher and more consistent quality of concrete during production and in various stages of construction from placement to curing.
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18 Concrete Technology for Transportation Applications Benefits SCC mixtures have become more widely used in construction due to their favorable characteristics, which include increased construction productivity, improved work environment and safety, and higher strength and durability (2)
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Overview of Concrete Technologies 19 part of the cement with a less reactive powder may prove beneficial when project requirements limit the heat of hydration. Aggregate The intended type of application of the SCC mixture dictates the appropriate shape, nominal maximum size, and gradation of coarse and fine aggregates (2)
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20 Concrete Technology for Transportation Applications characteristics of SCC include filling ability, passing ability, and stability (segregation resistance)
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Overview of Concrete Technologies 21 Placement. SCC is placed in the forms by concrete truck, pump, hopper, bucket transporters, or other specialized devices such as tremies.
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22 Concrete Technology for Transportation Applications conventional concrete, especially when the casting rate is high. Therefore, the formwork designs must accommodate the expected liquid head pressures.
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Overview of Concrete Technologies 23 strikeoff and finish need to be executed simultaneously with concrete placement because the mixture tends to set much faster when stationary than conventional concrete (38)
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24 Concrete Technology for Transportation Applications J-Ring. This test (ASTM C1621)
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Overview of Concrete Technologies 25 and viscosity-retaining admixtures. As a result of a low water–cement ratio and efficient cement hydration process, much higher compressive and flexural strengths are achieved compared to conventional concretes.
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26 Concrete Technology for Transportation Applications The higher the water–cement ratio of the mixture, the lower the autogenous shrinkage, and the higher is the drying shrinkage. Proper engineering and proportioning of the SCC mixture and early curing would minimize shrinkage at the fresh and hardened stages.
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Overview of Concrete Technologies 27 concrete, and shrinkage that may lead to cracking (47)
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28 Concrete Technology for Transportation Applications (52, 53, 54)
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Overview of Concrete Technologies 29 with the degree of hydration, results in self-desiccation as pores within the microstructure lose water below the level of saturation (52)
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30 Concrete Technology for Transportation Applications condition. Use of lightweight aggregate that has not achieved the SSD condition in the concrete mixture may have adverse effects, including slump loss and placement issues during pumping and finishing (62)
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Overview of Concrete Technologies 31 Figure 11. Paper-towel drying method.
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32 Concrete Technology for Transportation Applications An important benefit of ICC is the reduced shrinkage and the associated internal strains, which, in turn, reduce the early age cracking potential (48, 52, 56, 58, 70)
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Overview of Concrete Technologies 33 potential for increased strength will depend on factors including strength and degree of saturation of the lightweight aggregates and improved strength of the paste surrounding the lightweight aggregates that has benefited from the internal curing moisture. Use of prewetted absorptive materials other than lightweight aggregates has been shown to decrease compressive strength (49)
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34 Concrete Technology for Transportation Applications of ICC bridge decks largely report success. The Indiana DOT constructed four bridges utilizing prewetted lightweight aggregates to internally cure high-performance concrete mixtures and found that early-age autogenous shrinkage was reduced by 80% compared to non-ICC mixtures (69)
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Overview of Concrete Technologies 35 Requirements for use of internal curing in the Virginia DOT's bridge concrete are provided in a Special Provision entitled, "Low Cracking Bridge Deck Concrete." ICC mixtures can be used in both bridge decks and substructures. The Virginia DOT special provisions' guidance and requirements are minimal and allow for input from the manufacturer of the lightweight aggregate.
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36 Concrete Technology for Transportation Applications connections between precast or prestressed bridge elements including girders, pile cap closure pours, and prefabricated deck components (Figures 17 and 18)
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Overview of Concrete Technologies 37 of steel fibers (1% to 2% of mix volume) is an essential ingredient to provide the necessary reinforcement for enhanced compressive and tensile strengths and reduced shrinkage (4, 89, 90, 91)
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38 Concrete Technology for Transportation Applications Fine aggregates including quartz, limestone, and basalt aggregates are proportioned and sized in the dry constituents to facilitate the flowability of UHPC mixtures and increase the compressive strength. As mentioned previously, coarse aggregates are sometimes included in UHPC mixes to provide cost savings.
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Overview of Concrete Technologies 39 quartz sand. In some mixtures, a small quantity of coarse aggregate, small and medium-size fibers, and HRWR admixture were also added.
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40 Concrete Technology for Transportation Applications Specifications Use of UHPC requires the development of material and construction specifications. The material specifications define the constituent properties, testing protocol(s)
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Overview of Concrete Technologies 41 • Production procedures for precast and cast-in-place construction, • Broader geographic distribution of demonstration projects, and • Wider distribution of technical information. Temperature Control of Mass Concrete Introduction Mass concrete is defined as any volume of concrete with dimensions large enough to require that measures be taken to manage the generation of heat from hydration of the cement and associated volume change to minimize cracking (97)
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42 Concrete Technology for Transportation Applications Elements of TCMC Plan The TCMC plans may achieve effective temperature control by incorporating four elements: (a) proper selection and proportioning of mixture materials, (b)
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Overview of Concrete Technologies 43 high calcium content and tend to react in a manner similar to that of cement, and thus contribute to early concrete strength gain, but they are not as effective as Class F ash in lowering concrete temperature (5)
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44 Concrete Technology for Transportation Applications needs to be considered not only for adjustments in amount of batch water, but also in the heat balance calculations for control of the placing temperature (98)
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Overview of Concrete Technologies 45 surface temperatures, embedded sensors can also be used to apply the maturity method to predict concrete strength (102)
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46 Concrete Technology for Transportation Applications Also, delaying the removal of forms until a balance of temperature is reached between the concrete and ambient temperatures that meets the specification requirements may save additional efforts and cost of additional monitoring and insulation. However, if construction scheduling requires early removal of forms, insulation needs to be promptly installed against the exposed concrete surface.
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Overview of Concrete Technologies 47 Issues and Challenges Experience and cost are two major challenges when implementing TCMC plans. Training of construction personnel and utilization of knowledgeable professionals to prepare the TCMC and supervise its execution will produce an optimized plan and minimize failures in meeting the specification requirements.
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48 Concrete Technology for Transportation Applications • Reduced delay before lane opening to traffic -- PCP can be installed during nighttime lane closures and be ready to be opened to traffic in early morning. • Elimination of premature cracking or joint raveling -- Early age distresses due to shrinkage and thermal stresses or raveling sawed joints are almost eliminated when PCP is used.
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Overview of Concrete Technologies 49 the Super Slab® system and to encourage competition, the Tollway worked with local industry to develop their own generic precast system (112, 113)
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50 Concrete Technology for Transportation Applications for the dowel grout and the bedding grout. Additionally, for even distribution of the bedding grout, grout distribution channel and foam gaskets are provided underneath the slab as shown in Figure 23.
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Overview of Concrete Technologies 51 forms and tensioned. The forms also include posttensioning ducts.
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52 Concrete Technology for Transportation Applications The design included an asphalt interlayer to change the transverse profile of the pavement from a centerline crown to a 2% cross slope toward the outside edge and also to provide a smooth base to place the PPCP panels, as shown in Figure 27. Plastic sheet was used to cover the asphalt layer prior to placement of the PPCP panels to minimize friction during the posttensioning process.
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Overview of Concrete Technologies 53 The expansion joints were sealed, and dowel slots and posttensioning blocks were patched. The pavement was later diamond-ground to establish a smooth riding surface (Figure 29)
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54 Concrete Technology for Transportation Applications It must be emphasized that PCPs are not "super pavements" and are not be expected to perform significantly better than CIP concrete pavements. Once installed, precast concrete pavements can be expected to behave similarly to CIP pavements under traffic loading and environmental effects.
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Overview of Concrete Technologies 55 With well-graded aggregates, proper cement and water content, and dense compaction, RCC pavements can achieve strength properties equal to those of conventional concrete, and with low permeability. In fact, a key advantage to this type of concrete paving is that the pavement may be opened to traffic shortly after construction, as soon as the strength reaches 3,000 psi (21 MPa)
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56 Concrete Technology for Transportation Applications pavements (120, 121, 122)
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Overview of Concrete Technologies 57 because the dry consistency of the mixture does not allow bonding with steel and the roller compaction will result in dowel/tie bar misalignment (7)
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58 Concrete Technology for Transportation Applications RCC needs to be placed and compacted while it is still fresh and workable, usually within 60 minutes of delivery. If the RCC is too dry, the surface will appear dusty or grainy and may even shear (tear)
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Overview of Concrete Technologies 59 Freeze-Thaw Performance RCC is not typically air entrained from conventional air-entraining admixtures. However, field performance studies in freeze-thaw environments have indicated that RCC performed well for more than three decades, whether air entrained or not (112, 130)
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60 Concrete Technology for Transportation Applications pavement surface thickness to be reduced. A separation layer (generally asphalt)
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Overview of Concrete Technologies 61 improved the ride quality of RCC pavements (127)
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62 Concrete Technology for Transportation Applications Applications and Benefits PCP is often used as a surface layer in streets and parking areas to reduce or eliminate stormwater runoff (133)
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Overview of Concrete Technologies 63 load-carrying capacity of PC pavements. However, the flow rate of water through the pavement is reduced with increase in the amount of fine aggregate (8)
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64 Concrete Technology for Transportation Applications aggregate will decrease the void content and increase strength (135)
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Overview of Concrete Technologies 65 Experience of local PC producers and paving contractors with track records of successful PC projects will be helpful in designing appropriate PC mixtures for the application. Design and Construction Pavement Design For thickness determination of a pervious pavement, structural adequacy and drainage efficiency are two important design considerations.
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66 Concrete Technology for Transportation Applications surface voids (145)
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Overview of Concrete Technologies 67 permeability of the PC in order to increase its strength, the risk of surface clogging is further increased (141)
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68 Concrete Technology for Transportation Applications Fibers seem to improve resistance to freeze-thaw. A study in Maryland concluded that using cellulose fibers in PC mixtures resulted in a significant improvement in freeze-thaw durability, increase in abrasion resistance, and improvement in tensile strength (138)
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Overview of Concrete Technologies 69 use of RCA in new concrete mixtures. With proper design considerations and testing, concrete containing RCA has been shown to provide performance equivalent to concrete containing conventional aggregates (154, 155, 159, 160)
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70 Concrete Technology for Transportation Applications During the recycling process, provisions need to be made to reduce the amount of contaminant material included in the RCA (155, 162)
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Overview of Concrete Technologies 71 vary by size, with larger sizes of RCA containing more aggregates from the source concrete, and finer sizes of RCA containing a greater fraction of mortar. The crushing process will also influence the shape, texture, and gradation of RCA particles.
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72 Concrete Technology for Transportation Applications using RCA as fine aggregates (162)
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Overview of Concrete Technologies 73 Construction Practical and economic factors determine whether a project is a candidate for use of RCA. A key consideration is whether the potential amount of RCA produced and utilized on a project warrants the mobilization of a mobile crushing and grading plant to the site.
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74 Concrete Technology for Transportation Applications Use of RCA in concrete for structural applications such as bridges continues to be rare, with concerns often expressed about issues affecting structural performance, including durability and corrosion potential (171, 172)
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Overview of Concrete Technologies 75 States (174)
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76 Concrete Technology for Transportation Applications When using RCA in jointed concrete pavements, the designer needs to include dowel bars at transverse joints to provide adequate load transfer between adjoining slabs. In pavements with undoweled joints, the recycled coarse aggregate can deteriorate due to the friction between interlocking slabs at the transverse joint, leading to loss of load transfer and joint failure issues.
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Overview of Concrete Technologies 77 Type III cement instead of Types I/II (175)
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78 Concrete Technology for Transportation Applications admixtures (175)
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Overview of Concrete Technologies 79 Accelerating admixtures aid in early strength development and reduce initial setting times by increasing the reaction rate of C3A. Energizing this reaction generates additional heat to increase the cement hydration to form more hydrated gel and achieve high early strength.
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80 Concrete Technology for Transportation Applications Joint Sawing HESC sets fast and gains strength early and rapidly. Therefore, there is a short window for saw cutting joints in an accelerated pavement project.
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Overview of Concrete Technologies 81 A few highway agencies, including Florida and Georgia, have revised their required opening strengths to values lower than 2,000 psi (13.8 MPa)
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82 Concrete Technology for Transportation Applications conditions (clean, dry, appropriate bonding texture and/or bonding agent) to achieve adequate bonding of the repair material (189, 190, 191)
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Overview of Concrete Technologies 83 rapid strength gain during the first 24 hours of hydration, with or without other constituents, processing additions, and functional additions. The specification covers four types of rapid-hardening cement, shown in Tables 6 and 7.
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84 Concrete Technology for Transportation Applications Alternative Cementitious Materials There has been increasing interest in use of alternative cementitious materials (ACMs) for a variety of sustainability and performance-related reasons (194)
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Overview of Concrete Technologies 85 can be provided in "super sacks" of several thousand pounds of preblended material. Agencies typically require prequalification of prepackaged products in order to appear on an approved materials list, which can be developed independently and/or with the support of documentation from the National Transportation Product Evaluation Program (NTPEP)
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86 Concrete Technology for Transportation Applications (179, 197)
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Overview of Concrete Technologies 87 Performance-Engineered Concrete Mixtures Introduction State highway agencies are faced with the challenge of maintaining an aging infrastructure with increasingly limited resources. A key to ensuring the integrity of concrete highway infrastructure includes construction of new infrastructure and repairs with concrete mixtures that provide durable performance and extended service life.
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88 Concrete Technology for Transportation Applications a framework and guidance for state highway agencies to develop a specification for PEMs that focuses on measurement and acceptance of concrete based on characteristics that have been linked to satisfactory long-term durability performance of the concrete (212)
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Overview of Concrete Technologies 89 ratio, have good workability, and take advantage of admixtures to create an adequately dispersed air void system (214)
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90 Concrete Technology for Transportation Applications Construction AASHTO PP 84 provides mixture proportioning guidance to assist in developing PEMs. Commentary provided within the standard and appendix provide insight into strategies to meet performance goals, such as optimizing aggregate gradation to assist in reducing paste volume, and meeting strength requirements while simultaneously economizing the mixture.
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Overview of Concrete Technologies 91 Although some states are currently utilizing some performance-related or performancebased specification provisions, implementation of PEMs is an ongoing effort to improve specifications. Research is being performed at a number of universities and DOTs to enhance the knowledge of the basic science, emerging tests, and field performance data to support the specification.
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