Subgrade and subbases for concrete pavements pdf file

Eb204 subgrades and subbases for concrete pavements. It emphasizes the major objective of obtaining longlasting uniform support for a concrete pavement. Still, placing a quality concrete pavement requires planning before paving to address not only material and constructability factors, but also to address the sub grade or subbase placed below the concrete pavement. Reclaimed asphalt 75 percent asphaltic pavement or surfacing. As shown in figure 4, loads applied to a pccsurfaced rigid pavement are spread over a large area of subgrade, compared to loads applied to an asphalt concrete surfaced flexible pavement. For heavy duty highway pavements its specified that the minimum thickness is 230 mm for crcp and 250 mm for pcp. The first deliverable is the 454page final field data report. Performing organization name and address texas transportation. Interlocking concrete pavement icp requires periodic. Finished subgrade elevation the top prepared surface of the subgrade. Design guide for subgrades and subbases iowa state university.

In the early 1900s, with the use of asphalt and cement bound surface layers, base and subbase thicknesses were decreased. Subgrade drag theory does not adequately define relationships. Pavement types flexible pavements rigid pavements cement concrete cc pavements semirigid pavements composite pavements pavement composition bituminous vehicle black topping115 to 200. The procedures for classifying soils and for testing and evaluating soils and pavement. Any concrete pavement, built of any thickness, will have problems on a poorly designed and. Most native soils are not too uniform and thus require some improvement or additional layers to compensate. Consortium national concrete pavement technology center partnership for geotechnical.

Concrete pavements, therefore, do not require strong foundation support. Construction of subgrade, subbase and base layers dr. Subbase and subgrade performance investigation and design. Thick pavement structures andor deep excavation may not always be possible due to existing curbs and buried utilities in existing roads. Again, never designed but requirements must change based on subgradesubbase, climate, etc. Crushed concrete 90 percent crushed concrete that is substantially free of steel reinforcement and includes pavement or surfacing, base, or a combination of asphaltic pavement, surfacing, and base, incorporated during the removal operation. Concrete provides a strong and durable surface for vehicle maneuvering and storage areas, making it especially suited for site paving at industrial and trucking facilities. Icpi tech spec 2construction of interlocking concrete pavements astm d698 standard test methods for laboratory compaction characteristics of soil using standard effort edge restraint references icpi tech spec 3edge restraints for interlocking concrete pavements geosynthetics reference tech spec 22 geosynthetics for segmental concrete.

Concrete pavement engineer fhwa office of asset management, pavements, and construction. When do you need to use a subbase under concrete pavements. Subgrade and subbases design subgrade strength is not a critical element in the thickness design. As a result, deflec tions are small and pressures on the subgrade are very low. Bases and subbases for concrete pavement performance. Research showed that a majority of the soils had a weak layer in the subgrade at depths varying from 6 to18 inches below the pavement andor subbase layer. In addition to functioning as part of the pavement structure, bases and subbases serve the following functions. Several conditions can lead to non uniform support and damage to the pavement. In any case, the objective is to obtain a condition of uniform support for the pavement that will prevail throughout its service life. Anjaneyappa department of civil engineering rv college of engineering bengaluru 59 email. However, experience shows that concrete pavements placed directly. After all, if a pavement is built upon a poorly controlled support system, even the most well constructed pave. Cbr and subgrade weak zones impact modulus of subgrade reaction.

Optimizing pavement base, subbase, and subgrade layers. The joints are filled with permeable aggregates that allow water to freely enter the surface. Concrete pavements can be placed directly on a compacted subgrade without concern for pumping or erosion, but a 4 to 6in. Examination of each of the cbr profiles showed that the weak layer in the subgrade did have an impact on the k.

A highway pavement is said to be only as good as the base under it. A reasonably uniform subgrade or subbase, with no abrupt changes in support, is ideal for any concrete pavement. The influence of the spatial variability of subgradesubbase on pavement performance was then evaluated by modeling the elastic properties of the pavement and subgrade using the islab2000 finite element analysis program. Use 21 for stabilized subbases atb, ctb, lean concrete or existing concrete or asphalt pavement. Slow down the intrusion of fines through upward pumping from the subgrade soil into pavement surface structural layer. Compared with other types of paving materials, concrete is by far the most rigid, spreading applied wheel loads over large areas of the subgrade.

Subgrade, subbases, and bases january 2005 300 general. Subbases and subgrades american concrete pavement association. Bases and subbases for concrete pavement federal highway. This material is generally of lower quality than any course placed over it, but it still carries and distributes the wheel loads. For concrete pavements, the requirements may vary considerably depending on subgrade soil type, environmental conditions, and amount of heavy truck traffic. Concrete site paving for industrial and trucking facilities has many similarities to other types of concrete pavements, such as. Subgrades and subbases institute for transportation. Subbase and subgrade performance investigation for concrete. Subgrade and subbases performance proper design and construction are absolutely necessary if the pavement is to perform.

Dec 02, 2017 clean concrete pavement additional fines come mainly from excavating underlying soils when loading the broken concrete gradation specifications should consider. Typical maintenance activities include weeding and manual removal of debris. The field data report describes test results and comparative analysis from 16 different portland cement concrete pcc pavement sites on local city and county roads. Conventional flexible pavement design and construction methods have been easily adapted to the concept of concrete interlocking pavements. When expansive soils are compacted in too dry a con dition or are allowed to dry out prior to paving, sub sequent nonuniform expansion may cause pavement roughness. As a result, concrete pavements do not require a buildup of foundation support. This report describes some of the work accomplished by summarizing data on subbase performance and testing relative to concrete pavement subbase and subgrade erosion but mainly addresses guidelines for concrete pavement subbase design. A base is part of an asphalt pavement structure, while a subbase is an optional element of a concrete pavement structure. It is much more important that the support be reasonably uniform with no abrupt changes in 8in. Several reconstructed pcc pavement projects in iowa were studied to document and evaluate the influence of subgradesubbase nonuniformity on pavement. For highly trafficked highways, aggregate or stabilized subbases are commonly used to provide improved. Design considerations for interlocking concrete pavements. Pdf evaluation of aggregate subgrade materials used as.

Technical report texas transportation institute available on this site. Eb204 subgrades and subbases for concrete pavements acpa. Central mix plants check all scales with standard weights for accuracy before the mixture is delivered to the site. Construction specifications several other acpa publications,subgrades and subbases for concrete pavements 1, design and construction of joints for concrete streets2, and. May be constructed from existing project materials or from imported borrow. The subbase, the layer of aggregate material immediately below the pavement, provides drainage and stability to the pavement. The purpose of the subbase is to provide uniform support to the base concrete layer and to provide sufficient resistance to erosion of the subbase material under traffic and environmental conditions. Guidance for improving foundation layers to increase. Subgrade the roadbed materials beneath the pavement structure. Pavement types flexible pavements rigid pavements cement concrete cc pavements semirigid pavements composite pavements pavement composition bituminous vehicle black topping115 to 200 base250 road crust sub base. Portland cement concrete pavement or asphaltic concrete pavement. Oct 21, 2008 subgrade has a cbr value less than 10, the subbase material will deflect under traffic loadings in the same manner as the subgrade and cause pavement deterioration. Subbase layer of material directly below the concrete pavement. Base, subbase and subgrade layer references astm d 2940 standard specification for graded aggregate material for bases or subbases for highways or airports icpi tech spec 2construction of interlocking concrete pavements.

Permeable interlocking concrete pavement, also referred to as picp, consists of solid concrete paving units with joints that. Guidance for improving foundation layers to increase pavement. This permits the use of thinner bases for rigid pavements than for flexible pavements. To provide insight into subgrade nonuniformity and its effects on pavement performance, this study investigated the influence of nonuniform subgrade support on pavement responses stress and deflection that affect pavement performance. Subbases for concrete pavements 1, design and construction of joints for concrete streets2, and. Eb204 subgrades and subbases for concrete pavements acpa wiki. Natural subgrade soils, fly ashstabilized subgrade, reclaimed hydrated fly ash subbase, and granular subbase were studied. The lean mix concrete subbase has a characteristic 28 day compressive strength of 5 mpa and is designed with a low shrinkage characteristic of less than 450 m. Performance of subbases for concrete pavements under. Proven dowel bar retrofit uses 50% of the steel of standards. It is intended for use in designing f lexible pavements subject to the geometric design cri teria set forth in em 11103. Subbase and subgrade performance investigation and design guidelines for concrete pavement one of 87 reports in the series. Figure 2 distribution of wheel loads under concrete pavements subbases do not make a significant structural contribution to concrete pavements.

Permeable interlocking concrete pavement, also referred to as picp, consists of solid concrete paving units with joints that create openings in the pavement surface when assembled into a pattern. Design methodology for subgrades and bases under concrete. Alternatives to asphalt concrete pavement subbases for concrete pavement. Use of recycled concrete materials in basesubbase applications. Jul 01, 2020 pavement foundations serve as a support for the surface layer and distribute the wheel loads to subgrade material. Fly ash soil stabilization for nonuniform subgrade soils. Flexible pavement structure, a typical flexible pavement structure is shown in figure 11, which illustrates the terms used in this manual to refer to the various layers. Uses in north america, the present predominant use of interlocking pavements is in the residential and architectural segments. The field data report describes test results and comparative analysis from 16 different portland cement concrete pcc pavement sites on local city and county roads in iowa.

Subgrades and subbases municipal pavement design subgrade natural ground, graded, and compacted on which the pavement is built. Subbase the layers of select or engineered material of planned thickness placed between the subgrade and a concrete pavement that serve. However, the role of different base and subbase layers and rationale for. Poor subgradesubbase preparation can not be overcome with thickness. Vertical deflections are small, and the pressure on the subgrade is very low. Aashto 1993 may be used, but it may calculate thicker subbases than would those derived from using the ucprc method. Concrete pavement joint design and construction louisiana transportation. Recycled concrete aggregate either from an existing concrete pavement or another source produces good results in freedraining subbases. The pavement structure of a concrete pavement typically consists of a concrete surface and subbases placed upon a prepared subgrade a base is part of an asphalt pavement struc ture, while a subbase is an optional element of a concrete pavement structure. This engineering bulletin provides the necessary background information for the proper selection and application of subbases and the appropriate consideration of subgrade variables for concrete pavements used for streets, roads and highways. This document is the second of two deliverables for the project optimizing pavement base, subbase, and subgrade layers for cost and performance on local roads tr640. General specifications for base and subbase courses this specification applies to all base and subbase courses except asphaltic concrete. A subbase is a thin layer of material placed on top of the prepared subgrade.