Sustainable concrete pavements a manual of practice

Quantification of embodied energy and carbon footprint of pervious concrete pavements through a methodical lifecycle assessment framework. Abstract This study provided a systematic lifecycle assessment LCA methodology that was used to quantify the total embodied energy and greenhouse gas GHG emissions involved in construction of a … Expand. Procurement practice guidance document. It is becoming increasingly apparent that some human activities and development practices are negatively affecting the well-being of the planet and putting future generations at risk.

Public agencies … Expand. This synthesis will be of interest to pavement designers, construction engineers, and others interested in economical methods for recontstructing portland cement concrete PCC pavements. Information … Expand. This report describes better practices for constructing and texturing quieter concrete pavements; better practices that answer the question of how we can reduce tire-pavement noise; and better … Expand. View 1 excerpt, references background.

Life Cycle Assessment of Pavements. An ever-growing number of agencies, companies, organizations, institutes, and governing bodies are embracing principles of sustainability in managing their activities and conducting business.

This … Expand. Performance of concrete pavements containing recycled concrete aggregate. Interim report, October October This interim report documents the field performance of nine concrete pavement projects that incorporate recycled concrete aggregate RCA in the construction of the pavement.

Multiple sections were … Expand. Millions discover their favorite reads on issuu every month. Give your content the digital home it deserves. Get it to any device in seconds. Previous page Next page. Publish for free today. Typically the bottom lift is approximately 80 percent of the thickness and the top lift is approximately 20 percent. Constructing a concrete pavement in this manner allows for the use of different mixture designs for the bottom lift and top lift.

Harrington et al. RCC contains no reinforcing steel, reducing both the economic and environmental impacts from the use of steel reinforcement. In certain geographic areas that have an abundance of natural sands and a shortage of quality coarse aggregates, higher aggregate content makes RCC a sustainable solution for low-speed applications industrial lots, streets, and local roads. Roller-compacted concrete RCC is constructed using equipment similar to that used in the asphalt pavement construction industry Figure 5.

The mixture is placed with a heavy-duty paver and compacted with a vibratory steel wheel and pneumatic rollers. RCC mixtures utilize a greater amount of fine aggregate particles and reduced cementitious and water contents. Report EBP. Cable, J. Yet it is recognized that the use phase, particularly the traffic using the facility, often has the largest impact on the environment Wathne This chapter briefly considers both aspects.

Trafficrelated factors such as vehicle rolling resistance, which is influenced by pavement roughness and stiffness, are discussed, as is pavement-environment interaction including carbonation, lighting requirements, albedo, and leachate. The latter are discussed in greater detail in Chapter 9, as they are primarily a consideration in urban environments.

Vehicle Fuel Consumption Unlike buildings that have electricity and other energy-related metrics directly attributed to their use, the energy and associated environmental impact attributed to the use of pavements are more difficult to account.

Although some of the energy used in the operation of a pavement may be directly accounted for e. Many of these factors are the same regardless of pavement type. The rolling resistance, which is the vehicle energy loss associated with pavement-vehicle interaction, has to be minimized for agencies to improve the fuel efficiency of vehicles operating on their pavements Santero et al.

One of the biggest factors contributing to rolling resistance is road roughness, as it results in an excitation of the suspension systems in vehicles, consuming energy that is responsible for significant increases in fuel consumption AASHTO Further, increasing pavement texture as measured by the sand patch test results in significant increases in fuel consumption at lower vehicle speeds Zaabar Sandberg had previously observed this trend, finding that at higher speeds, rolling resistance is less dependent on pavement surface texture because vehicle fuel consumption is more heavily influenced by air resistance.

This enhances fuel efficiency and reduces environmental impact; it will also reduce the social cost of pavements by reducing crashes Tighe et al.

Figure 6. Higher pavement deflections may result in additional fuel consumption as a vehicle moves along the pavement surface Akbarian It is noted that data were not available for heavy trucks under winter conditions. As the surface stiffens, deflection decreases and rolling resistance is reduced. Preliminary results suggest that pavement stiffness does make a small but significant difference, with lower fuel consumption incurred for all vehicle types operating on stiffer pavements.

The continued development of this type of model is justified, as the volume of traffic over the life of many pavements is so great that even a difference in fuel. Further, the inherent stiffness of concrete appears to result in reduced fuel consumption, especially for heavy vehicles operating at slow speeds during the warmer months of the year.

Other Environmental Impacts During Use In addition to environmental impact incurred due to vehicular use, other environmental factors warrant consideration, including solar reflectance, lighting, carbonation, run-off, and traffic delays.

Santero et al. Solar Reflectance Solar reflectance or albedo is a surface property of a material. Solar reflectance values range from zero to 1.

Light-colored materials have higher solar reflectance values than dark-colored materials. Solar reflectance has the greatest importance in urban areas as it is known to contribute to the formation of urban heat islands. Heat islands usually occur in urban areas as illustrated in Figure 6.

Urban heat islands are formed due to the warming of exposed urban surfaces such as roofs and pavements EPA Urban heat islands contribute to lower air and water quality and greater energy demands, especially in the summer. Due to its naturally light color, concrete is an excellent choice for paving material in an urban environment. This is illustrated in Figure 6.

Highly reflective pavement surfaces can be created using white titanium dioxide photocatalytic. Titanium dioxide photocatalyic coatings have the added benefit of breaking down the harmful compounds of nitrogen oxides NOx Chen and Poon And, because of evaporative cooling, the use of a light-colored pervious concrete pavement can be extremely effective in addressing the urban heat island while also addressing surface run-off.

Research continues into the impact of radiative forcing on mitigating global warming, but findings to date indicate that this could be an enormously important factor in reducing global temperatures in the future. Improved illumination leads to increased visibility, which is an important safety consideration. This is also discussed in more detail in Chapter 9. Carbonation Carbonation is a normal phenomenon that occurs between hydrated cement phases in concrete and atmospheric carbon dioxide CO2 , where the phases react with the CO2, absorbing some of it into the exposed surfaces.

Gajda gathered data on the amount of CO2 that could be absorbed by concrete based on more than 1, samples. Carbonation rates varied depending on the strength of the concrete and cement content, but the average rate of carbonation for uncoated concrete was found to be 4.

Run-Off and Leachate After a rainstorm, run-off from the pavement surface can carry pollutants with it, most of which originated from vehicles that used the pavement and not from the pavement material itself Santero et al. The use of a pervious concrete surface currently applicable for low traffic volume pavements, parking areas, and shoulders can help mitigate some of this effect by preventing most surface run-off from directly entering streams and lakes Borst et al. Instead, natural processes degrade the pollutants as the water slowly passes through aggregate and soil.

It is known that when concrete is recycled and stockpiled, run-off from the stockpiles initially has a pH of 9 or 10, but the pH diminishes within weeks as exposed cement grains and soluble cement paste phases react ACPA Additional discussion on the use of recycled concrete is presented in Chapter 8. Traffic delays incurred during pavement maintenance and rehabilitation see Figure 6.

The inclusion of this. Pavement designers, contractors, and owners may not have influence on the types of vehicles that use pavements. However, with proper consideration during design and construction and the adoption of an aggressive concrete preservation strategy, concrete pavements can be constructed and maintained in a smooth condition, reducing fuel consumption and related emissions. Over the life cycle, small improvements in fuel efficiency incurred due to the inherent stiffness of concrete pavements may significantly reduce the environmental impact of pavements.

Other factors that should be considered include carbonation, run-off and leachate generation, and traffic delays incurred during future maintenance and rehabilitation activities. Work is under way to. Indications are that the use phase has the greatest impact of all life-cycle phases and thus must be considered in sustainable design.

Recycling Concrete Pavements. Akbari, H. Lawrence Berkeley National Laboratory. Arthur Rosenfeld California Energy Commission. Pavement Interactive. When the Rubber Meets the Road. Life Cycle Analysis Research Brief. Ardekani, S. National Ready Mixed Concrete Association. Bennett, C. Version 3. ISBN: Borst, M.

Rowe, E. Stander, and T. Chatti, K. Lenngren, C. Chen, J. Netherlands: NPC. Chesher, A. De Graaff. Report no. The Netherlands. Environmental Impact and Fuel Efficiency of Roads. Industry Report. Are You Ready? Extreme Heat. Gajda, J. Kaloush, Kamil. Arizona State University.

Sandberg, Ulf S. West Conshochocken, PA. Santero, N. Masanet, and A. Loijos, M. Akbarian, and J. Draft Report. Sumitsawan, P. Romanoschi, and S. Taylor, G. Tighe, S. Li, L. Cowe Falls, and R. TRR Wathne, L. Zaabar, I. Zaniewski, J. Butler, G. Cunningham, G. Elkins, M. Paggi, and R. Preservation and rehabilitation play an important role in ensuring pavement longevity while maintaining the highest level of serviceability.

As such, renewal directly contributes to the sustainability of the concrete pavement. The two primary strategies that are discussed are preventive maintenance and rehabilitation. Preventive maintenance is a planned strategy employing treatments that extend pavement life, generally without increasing structural capacity. Pavement rehabilitation adds some structural capacity, usually through the application of additional pavement thickness in the form of an overlay.

Pavement Renewal Concepts Although many treatments and strategies are available that contribute to concrete pavement renewal, they can generally be classified under preventive maintenance or rehabilitation.

Preventive maintenance is a planned strategy employing cost-effective treatments e. Thus, the application of timely and appropriate preventive maintenance treatments will keep a smooth pavement smooth for an extended period of time. This is not only cost effective for the agency responsible for maintaining the pavement but, as discussed in Chapter 6, it also reduces the vehicle operating costs as well as the environmental impact of vehicles operating on the pavement.

As can be seen, preventive maintenance is only applicable when the pavement is in relatively good condition and has significant remaining life. Thus, a common precept is that preventive maintenance is used to keep good pavements in good condition. In some cases maintenance may be required on high traffic lanes only, in which case detailing should avoid elevation differences between lanes.

As can also be seen in Figure 7. This is illustrated in Figure 7. In summary, the concept of concrete pavement renewal requires that preventive maintenance and rehabilitation techniques be employed, using the right treatment at the right time. To be cost effective while reducing life-cycle environmental impact, preventive maintenance treatments are applied to pavements in generally good condition, keeping them smooth while extending life.

Over time, the structural capacity of most pavements will need to be restored or increased, at which juncture the use of pavement rehabilitation techniques will be the best approach. Not understanding the pavement condition can result in the application of an inappropriate treatment and, consequently, either an early failure or wasteful.

A typical concrete pavement evaluation will consist of the following steps Smith, Hoerner, and Peshkin : 1. Initial site visit and assessment — This consists of an initial visit to assess general conditions and help scope the future evaluation and includes general distress observations, an assessment of roughness, particularly sags and swells, and observation of moisture problems.

Field testing activities — These may include detailed distress and drainage surveys, nondestructive deflection testing, roughness and friction testing, and field sampling and testing.

Laboratory materials characterization — This may include determining the strength and stiffness of concrete and bound layers, petrographic analysis of concrete, density, and gradation analysis. These are discussed below. Cross stitching may be conducted on newer pavements that have early-age cracks ACPA Traffic Concrete is removed using partial-depth saw cuts to define repair boundaries and light-weight jack hammers to carefully remove the concrete from repair area.

Repair area is prepared by final removal of loose material and cleaned using sand-blasting and air-blasting. The patch is cured for the specified time, often using a white pigmented membrane curing compound. Blankets may be required in cooler weather. See Figure 7. This technique has been used successfully in a number of states, creating cost-effective, long-lasting repairs. Several materials are available for partial-depth repairs, with the choice being driven by the desired time to opening.

The selection of the repair material is based on multiple factors that are assessed as part of operations and maintenance. These distresses compromise the structural integrity of the pavement system, and the use of full-depth repairs restores the lost capacity while improving ride quality.

If the distress is present through a large percentage of the project, full-depth repairs may not be cost effective. Instead, a structural rehabilitation using an overlay might be more effective and potentially result in a more sustainable solution Smith, Hoerner, and Peshkin Full-depth repairs of jointed concrete pavement are accomplished according to the following steps: 1.

The concrete is sawed the full depth of the slab, ensuring a smooth face for restoration of load transfer devices. Multiple saw cuts may be used to facilitate removal of the concrete. The lift-out method, in which lift pins are attached through drilled holes, has been found to be most effective, although other methods have also been successful. The repair area is prepared by removal of loose material, replacing it with compacted materials of similar properties or with concrete.

Load transfer at the transverse edges of the repair is restored through the use of steel dowels, which are grouted into holes created using gang-mounted drills. Concrete is placed and finished in accordance with appropriate specifications. Typically conventional concrete can be used, although often a high-early or even a very high-early strength mixture can be selected.

Use of recycled materials may help to balance this negative impact. Curing is typically accomplished using a white pigmented curing compound. Full-depth repairs are used when deterioration extends beyond one-third the slab depth and safety and ride quality are compromised. Load Transfer Restoration The restoration of load transfer is a technology that has had a significant impact on improving the ride quality of concrete pavements throughout the United States.

It was not uncommon in the past to construct jointed plain concrete pavement JPCP without load transfer devices, with the assumption that aggregate interlock would be sufficient to maintain load transfer with shorter joint spacing. Unfortunately, it has been found that JPCPs constructed without load transfer devices are susceptible to joint faulting, resulting in poor ride quality even though the pavement is otherwise sound.

In either case, load transfer restoration has provided an avenue to restore the ability of load to be shared across a joint, minimizing deflection and reducing cracking, thus positively affecting remaining life. Assuming drainage is also addressed using edge drains, and that the slabs have been restored to desired elevations, the pavement can then be diamond ground to improve ride quality.

Load transfer restoration is illustrated in Figure 7. The current practice for restoring load transfer is as follows Smith, Hoerner, and Peshkin :. A dowel bar is placed in each slot. The dowel bar is typically on a chair, coated with a bond breaker and capped with an expansion cap on one or both ends. A compressible insert is located at the bar center to establish the joint in the repair. The repair is then finished and cured to minimize shrinkage. The repair material is critical to the success of this treatment.

Slots for dowel bars are created using gangmounted saw blades mounted on specially designed slot-cutting machines. Production rates exceeding 2, slots per day are possible using this method. The existing. With the advent of slot-cutting machines, which ensure good productivity and quality, load transfer restoration has become a popular operation to address poor load transfer that is common in undoweled JPCPs and in older pavements in which load transfer has been lost.

In combination with diamond grinding, load transfer restoration can be used to effectively maintain a concrete pavement in a smooth condition over its design life. Using gang-mounted, closely-spaced diamond saw blades, diamond grinding uniformly removes a thin layer of concrete, restoring pavement ride quality while improving skid resistance. This treatment removes faulting, wheel path wear, surface irregularities, and polished surface texture, replacing them with a uniform surface that can be as smooth, quiet, and safe as the originally constructed surface.

Diamond grinding has been in use for decades, having been pioneered in California where it was first used in In general, pavements with faulting in excess of 0. In such cases, rehabilitation through the use of an overlay may be more appropriate Correa and Wong In some instances, it may be cost prohibitive to effectively grind a concrete made with extremely hard aggregates. Also, there have recently been efforts to remove asphalt overlays from some concrete pavements that were overlaid primarily to address ride quality issues IGGA ND.

This has the advantage of minimal future maintenance costs as well as increased reflectivity, thus lowering life-cycle environmental impact. Treatments such as partial- and full-depth repair replace deteriorated concrete while restoring ride quality and structural integrity of the pavement.

Load transfer restoration slows the progression of future faulting and, combined with diamond grinding which eliminates existing faulting, results in the long-term restoration of ride quality. Rehabilitation As defined by Harrington et al. Bonded concrete overlays may also be considered minor rehabilitation in that they generally add some structural capacity to pavements. Unbonded concrete overlays, which are generally 4-in. Concrete overlays can be placed on existing concrete, asphalt, and composite pavements.

This chapter, however, focuses on overlays of existing concrete pavements. Various pavement conditions for which different types of concrete overlays are appropriate are illustrated in Figure 7. Bonded Concrete Overlays In certain circumstances, a bonded concrete overlay provides a good treatment option to eliminate surface defects e.

The keys As the name implies, a good bond between the overlay and the existing substrate pavement must be achieved during construction and must be maintained during the life of the pavement, as the loss of bond will result in premature failure of the overlay. The following is a summary of the bonded concrete overlay process Harrington et al.

In general, it must be structurally sound, relatively free of distress, and must not be suffering from an MRD. Joint design must match the existing concrete pavement. Pre-overlay repair — Pre-overlay repair is essential for the successful performance of bonded concrete overlays. Table provides recommendations regarding the type of distresses that require repair and suitable treatments. As the overlay is intimately bonded to the substrate, existing distress will have a tendency to reflect through unless addressed.

After repairs are conducted, the surface should be roughened and thoroughly cleaned to enhance bonding. Construction — Key elements of construction include concrete placement, curing, and joint sawing. Table 7. Reflective cracking is likely if no repairs are made; use crack cages or full-depth repairs for severe cracks. Unbonded Concrete Overlays Unbonded concrete overlays have been successfully used in the rehabilitation of concrete pavements for decades and are viable treatments to address concrete pavements with some structural deterioration.

The overlay has an effective service life similar to a newly constructed concrete pavement. Unbonded concrete overlays are typically 6- to in. The keys to effectively using an unbonded overlay are as follow Harrington et al. Material-related distress MRD is not a concern as long as continued expansion will not result in blow-ups. The following is a summary of the unbonded concrete overlay process Harrington et al. Pavement evaluation — The existing pavement should be evaluated to ensure that it can provide good uniform support for the unbonded concrete overlay and, if not, to determine what actions are needed to obtain uniformity.

Although a candidate pavement can be suffering MRD, the evaluation should confirm that future expansion will not result in blow-ups of the underlying pavement in time. Overlay design — Unbonded concrete overlays are typically 6- to in.

The separation layer has traditionally been a 1-in. Joint design includes the use of dowel bars for unbonded overlays 8-in. Typical joint spacing is shown in Table Drainage must be considered to avoid damage to the asphalt separation layer. In combination, these factors make unbonded overlays a very sustainable treatment option to rehabilitate pavements nearing the end of their useful life.

Summary The application of proper concrete pavement preventive maintenance and rehabilitation strategies is essential to extend the life of a concrete pavement while ensuring that it remains in a structurally sound, smooth, and safe condition over its life cycle. The techniques described in this chapter offer a variety of preventive maintenance tools to address deterioration that results from usage and time. As a concrete pavement nears the end of its useful life, it can be rehabilitated through the use of an unbonded overlay, essentially constructing a new concrete pavement on the surface of the old pavement.

Thus, an engineer skilled in the use of these and other strategies in the pavement preventive maintenance and rehabilitation toolkit can sustainably manage concrete pavements into perpetuity.

Stubstad, R. Darter, C. Rao, T. Pyle, and W. Final Report. Guide for Design of Pavement Structures. Correa, A. Report No. Frentress, D. P, and D. Harrington draft. Field Trials. Hoerner, and D. Building Sustainable Pavements With Concrete. Meijer, P. Ram, K. Smith, and J. Boston, MA. Zimmerman, K. The ultimate goal of recycling is to achieve a zero waste stream target utilizing all byproduct materials encountered in the rehabilitation or reconstruction of a concrete pavement.

Achieving this goal ensures that a balance is struck among the economic, environmental, and social factors that are considered in the construction of concrete pavements. As discussed in Chapter 2, the concept of recycling must be viewed as a cradle-to-cradle undertaking as opposed to past thinking of cradle to grave. In the past, economic cost was the driving force that encouraged recycling, yet this is beginning to change.

In addition, land-use sensitivities, traffic considerations, as well as overall cost are also of greater importance in urban areas. The benefits of recycling include the following:. Introduction to Recycled Concrete A subtle but important benefit of recycling concrete is the potential benefit of reducing atmospheric carbon dioxide CO2 through carbon sequestration.

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