Basessubbases for concrete pavements transportation research. Base construction for interlocking concrete pavements continued from p. The subbase, while not mandatory, can provide added benefits to the construction and performance of the slab. Index properties and probable volume changes for highly plastic soils after earth manual 1985.
The primary objective of this report is to quantify the aggregate base properties required for concrete pavement foundations in accordance with currently established layer thickness requirements. Compacting the base icpi recommends that the base is installed. Using recycled concrete aggregate in pavement base products. When using base aggregate open graded, refer to fdm 14515. Typical road structure cross section sub grade, base. The material quality requirements for a subbase are not as strict as those for a base since, under concrete, the pressures imposed on this layer due to vehicle loadings are much lower than those under asphalt. Bo4 geotechnical properties of recycled concrete aggregate in pavement subbase applications abstract. The surface conditions of pavements with subbase andor base layers made with rca were comparable to those made with na in terms of the international roughness index iri and pavement condition index pci ceylan et al. It may be omitted when there will be only foot traffic on the pavement, but it is necessary for surfaces used by vehicles. The pavement is modeled as a multilayer structure subjected to static and dynamic loading. Installation steps typically include job planning, layout, excavating and compacting the soil subgrade, applying geotextiles optional, spreading and compacting the subbase andor base aggregates. A pozzolan material, such as fly ash, may be added to the. Pdf the influence of base course types on rigid pavement.
Concrete block surfaces are suitable for these applications. The base course or granular base or stabilized base is the second layer from the top and is constructed using crushed aggregates. Grading first the site is graded to cut high points and fill low. It provides stable platform to construct rigid pavement. Understand european practices for basesubbase design and construction. Joe nasvik concrete slabs perform best when they are even thickness.
Development of the numerical model a typical reinforced pavement system consists of hotmix asphalt layer, base course layer, subbase layer and subgrade layer as well as reinforcement layers. A concrete pavement is only as good as the grade on which the pavement is. If the gradation of the base course deviates from the specifications, the base course may not prevent pumping of the subgrade material through the base course. Costeffective base type and thickness for longlife. The subgrade material should be clean and free from organic matter and should be able to be compacted by roller, to form stable subbase. Optimizing pavement base, subbase, and subgrade layers for cost and. The sub base consists of a layer of clean course aggregate, such. Soil is the main constituent in subgrade and embankment aggregates are used in the sub base and base layer aggregates and binding material in the top layer sub grade and embankment provides support for the pavement different types of failures such as rutting and shoving in the flexible pavements, cracking in the rigid concrete pavements are. The subbase is an optional layer located on top of the subgrade and beneath the slab bottom see figure 1. Subgrade and subbase the subgrade is the ground on which the floor is built. Reclaimed concrete material user guideline granular. Bases and subbases for concrete pavements aashto classification a6 or a7 soil groups or the unified soil classification system ch, mh, and oh soils. It is also useful to provide sub surface drainage system. Typically, recycled concrete aggregate rca is used as granular.
The construction and design of concrete slabs on grade. This permits the use of thinner bases for rigid pavements than for flexible pavements. Subbases may be constructed of granular materials, cementtreated materials, lean concrete, or opengraded, highlypermeable materials. Surface course or wearing course all these components belong to a typical flexible pavement, whereas rigid pavement usually consists of subgrade, subbase and a concrete slab. 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 concretesurfaced flexible pavement. A typical fle xible pavement in malaysia consists of asphaltic concrete.
This course helps the surface course to take additional loads. The construction of the base or subbase for the pavement construction is dependent on the type of base chosen and the equipment available. Reusing concrete pavement minimizes the amount of raw materials required for a new pavement structure. The material quality requirements for a subbase are not as strict as. Well graded uniformity coefficient d60d10 should not.
Proper subgrade prep concrete construction magazine. If the gradation or density does not meet specification requirements, the k value may be reduced below the design value resulting in inadequate pavement strength. The properties of rca were compared with state road authority requirements to assess its performance as a pavement subbase material. Following are the different components of road structure. It is preferable that all materials, regardless of traffic category, conform to the requirements of clause 8. Rdgn042 pavement design for carriageway construction page 7 of 42 pavement type for different sections andor different lanes on the same road. The bearing capacity and permeability of the sub grade influences total pavement thickness. Pavement performance can be largely attributed to the care given in designing and preparing its foundation, which is comprised of the subgrade and base layers. Crushed concrete 90 percent crushed concrete that is substantially free of steel reinforcement and includes 75 percent asphaltic pavement or surfacing. Installation interlocking concrete pavement institute. In highway engineering, subbase is the layer of aggregate material laid on the subgrade, on which the base course layer is located. Feasibility of reclaimed asphalt pavement rap use as. The preparation of the subgrade and base course is a very important step since these materials have a considerable impact on the ride quality of the concrete.
Geotechnical properties of recycled concrete aggregate in pavement subbase applications article pdf available in geotechnical testing journal 355. A material of a designed thickness placed on a subbase or a subgrade to support a surface course. Pdf evaluation of subbase materials for mechanistic pavement. Stabilized subbase friction study for concrete pavements. Standard specification d294092, graded aggregate material for bases and subbases for highways or airports, annual book of astm standards, volume 4. Concrete pavement specifiers guidelines 2 foreword portland cement concrete pcc pavement refers to the rigid concrete layer of the pavement structure that is in direct contact with the traffic. A wellconstructed subbase will aid drainage and prevent settlement.
Cement treated base unstabilised base asphalt treated base lean concrete base contents. A base course can be compacted aggregate, cement or asphalt stabilized aggregate, asphalt or concrete. Subbase is often the main loadbearing layer of the pavement. Subbase and subgrade performance investigation and design.
Other factors responsible for non uniform foundation include variability due to a number of reasons including, natural causes, excavation and. When it comes to compacting a subgrade for a residential application, consistency, quality, and good practice by the contractor are. A subbase works by distributing a point load over a larger area. Base and subgrade layers must provide adequate and moisture resistant strength that meets the design modulus, in. Only class 2 dgb and dgs material traffic categories c and d material may be. In this article, some of the top base and subbase layers used for pavement construction are explained. The sub grade is either natural, undisturbed earth or imported, compacted till. Minimize waste and hauling by using rca base across full pavement section including shoulders when excess material is produced e. Optimizing pavement base, subbase, and subgrade layers for cost.
This also reduces the risk of tearing or puncturing the fabric. The pavement structure of a concrete pavement typically consists of a concrete sur face 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. For example, minnesota allows up to 3% asphalt cement by weight of aggregate and california has no limit on the relative proportions of re. Facilities development manual wisconsin department of. Drylines serve as a guide to ensure that the subgrade has proper elevation. Typical ranges of ls for various types of base materials. This finding was true for the full range of materials tested. The worker shown here is using a 2x4 to strike flat subgrade. Recycling concrete pavement, american concrete pavement association, illinois, 1993. Based on the achieved material characteristics, the tensile strength in bending of previously used road construction materials was compared to innovative alternative of foam concrete and the suitability for the base layers of pavement roads was determined. The subbase layer is the main load bearing element in the system and is designed to spread the load of the cellular paving grids and any traffic thereon to the subgrade below. Homomorphic model pavement with sub base layer of foam. Pdf subbase is an important layer in flexible pavement which. As a general guide, factors elaborated in section 3.
Its role is to spread the load evenly over the subgrade. This paper presents a laboratory investigation of the geotechnical properties of recycled concrete aggregate rca. The effects of properties of different base layers on concrete pavement performance were evaluated, based on an the mechanical and hydraulic. Whilst designs are based on type 1 subbase category a material, alternatives have been. Typical concrete is composed of coarse aggregate crushed stone and gravel, fine. Compaction of the soil subgrade and aggregate base materials are essential to the longterm performance of interlocking concrete pavements.
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