Base material shall be manufactured from hard, durable stone or recycled building materials free of clay lumps, organic matter and other deleterious substances. The aggregate base layers serve a variety of purposes, including reducing the stress applied to the subgrade layer and. A typical flexible pavement consists of a bituminous surface course over base course and sub base course. Basessubbases for concrete pavements transportation research. Determination of mechanical properties for cement treated. The base or sub base layers are orders of magnitude less rigid than the pcc surface but still make important contributions to pavement drainage. Rigid pavement typically requires less base aggregate. It is also useful to provide sub surface drainage system. The main purpose of providing sub base layer is to permit the building of relatively thick pavement at a low cost. The sub grade is either natural, undisturbed earth or imported, compacted till.
It provides additional load distribution, contributes to drainage, uniform support to the pavement and a stable platform for construction equipment. The rigid pavement has rigidity and high modulus of. Pdf the influence of base course types on rigid pavement. Pdf a comparative study on rigid and flexible pavement. For rigid pavements, the modulus of subgrade reaction k is used to measure the strength of the underlying pavement layers. Grouted concrete roads are in the category of semi rigid pavements.
Bitumen emulsions for construction and maintenance of pavements. Base and subgrade layers must provide adequate and moisture resistant strength that meets the design modulus, in addition to durability and stability. Sub base is also considered as structural component of both bituminous and rigid pavement. Understand european practices for basesubbase design and construction. This is all most equal general design of rigid pavement but after getting the thickness of rigid pavement we are. The rigid pavement has a slab action and is capable of transmitting the wheel load stresses through a wider area below. Many times the design of rigid pavements includes a base course to prevent pumping of the underlying subgrade, support paving equipment, andor to. Pdf effects of subgrade and subbase materials quality on. Different pavement types use different types of joints and reinforcement to control the forces acting on the concrete pavement. Cta consists primarily of base aggregate mixed with a specified percentage of hydraulic cement by weight and field compacted at moisture contents that are. Flexible pavements are composed of asphaltic layer, base course sub base materials which laid over a well compacted and strong sub grade foundation soil.
These pavements have negligible flexure strength and hence undergo deformation under the action of loads. Introduction aggregates are used in granular base and subbase layers below the driving surface layers in both asphalt concrete and portland cement concrete pavement structures. Guidelines on composite pavement design and evaluation of. No rigid pavement can achieve its design requirements without it being built on a sound subgrade or sub base with satisfactory drainage. The rigid characteristic of the pavement are associated with rigidity or flexural strength or slab action so the load is distributed over a wide area of subgrade soil. Basic engineering properties of sub grade materials are required for design and coarse grained. Introduction to rigid pavement design ced engineering.
The subgrade is the natural ground, graded and com pacted, on which the pavement is built. The material quality requirements for a subbase are not as strict as those for a base. Since the 1970s, several realscale road applications comprising ra have been made, including unbound or hydraulically bound base and sub base layers, subgrade and embankments. Modern flexible pavements contain sand and gravel or crushed stone compacted with a binder of bituminous material. It enables traffic stresses to be reduced to acceptable levels in sub grade in the road cross section so that excessive deformation is prevented. 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. Base course for rigid paving and the words rigid pavement base course selected throughout. Prevention of rigid pavement distress is a challenge to the engineers. Types of pavements flexible pavement rigid pavement. Sub base course the sub base course is the layer of material beneath the base course and the primary functions are to provide structural support, improve drainage, and reduce the intrusion of fines from the sub grade in the pavement structure if the base course is open graded, then the sub base course with more fines can serve as a fi ller. The rigid pavements are made of cement concrete either plan, reinforced or prestressed concrete. Standard specification for urban infrastructure works 47 edition 1, revision 02 oct 2010.
Using selective grading in cut and fill areas to place. Rigid pavement design relies on the structural carrying capacity of the pcc and on the uniformity of support provided by the base layers. Pavement, in civil engineering, durable surfacing of a road, airstrip, or similar area. For concrete pavements, the requirements may vary considerably depending on. Cc pavement slab using pqc paving quality concrete. It may be omitted when there will be only foot traffic on the pavement, but it is necessary for surfaces used by vehicles. Oct 04, 20 base course of rigid pavement this is the layer directly below the pcc layer and generally consists of aggregate or stabilized sub grade.
Rigid pavements generally require a minimum subbase thickness of 4 inches. The sub base course is the layer of material beneath the base course and the primary functions are to provide structural support, improve drainage, and reduce the intrusion of fines from the sub grade in the pavement structure if the base course is open graded, then the sub base course with more fines can serve as a filler between sub grade and. Since there is only one layer of material between the concrete and the sub grade, this layer can be called as base or sub base course. Jun 04, 2016 conclusion rigid pavement distress is a serious issue all over the world, the distresses causes some serious problems at wide range. Comparison between flexible pavement and rigid pavement in. A highway pavement is a structure consisting of superimposed layers of processed materials above the natural soil sub grade, whose primary function is to distribute the applied vehicle loads to the sub grade. The base course or granular base or stabilized base is the second layer from the top and is constructed using crushed aggregates. Design of rigid pavement it is a layer of selected granular soil, stabilized soil or gravels, boulders, broken stones, bricks etc.
Paul guyer is a registered civil engineer, mechanical engineer, fire protection engineer, and architect with over 35 years experience in the design of buildings and related. The special stabilized subbase is a vertically drainable, but stable layer that is 6 in thick and is used with the special. Following are the different components of road structure. The k value is determined by the plate bearing test. Subbase is often the main loadbearing layer of the pavement. Types of pavement flexible pavements and rigid pavements. The surface course is the rigid layer and provides the majority of strength. Section 5 rigid pavement construction standard specification for urban infrastructure works 51 edition 1, revision 0 september 2002 contents 5 rigid pavement construction 53 5. This pressure deformation characteristics of rigid pavement lead westergaard to the define the term radius of relative stiffness in cm is given by the equation. The surface course may consist of one or more bituminous or hot mix asphalt hma layers. Portland cement concrete pcc was originally used as a base and was surfaced with wooden. 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.
Specifications and method of cement concrete pavement construction pqc importance of providing dlc as. Maintenance and rehabilitation is to be properly done to prevent the distresses in rigid pavement. Grading first the site is graded to cut high points and fill low. The sub base consists of a layer of clean course aggregate, such as gravel or crushed stone. This applies equally to cobblestone pavements, plum concrete and unreinforced concrete pavements. Acts as a drainage layer, by protecting the sub grade from wetting up. The design of rigid pavement is based on providing a structural cement concrete slab of sufficient strength to resists the loads from traffic. A rigid pavement is constructed from cement concrete or reinforced concrete slabs.
Use of cement in layers of pavement will not only economically beneficial but also help to increase the design life cycle of road. When this guide specification is used in combination for a subbase course under flexible pavements and a base course under rigid pavements, the section title will be. Base course and sub base course of rigid pavement civil. In highway engineering, subbase is the layer of aggregate material laid on the subgrade, on which the base course layer is located. The bearing capacity and permeability of the sub grade influences total pavement thickness.
Rigid pavement is laid in slabs with steel reinforcement. This course helps the surface course to take additional loads. It provides stable platform to construct rigid pavement. As such, the pavement design engineer should not attempt to use the base subbase layers simply to increase the overall structural capacity of a rigid pavement system or to reduce the thickness of the. The primary function of a pavement is to transmit loads to the sub base and underlying soil. Base and subbase aggregates choker course wellgraded, crushed aggregates no fines. The rigid pavement slab as tensile strength, tensile stresses are developed due to the bending of the slab under the wheel load temperature variations providing a good base at sub base course layer under the cement concrete slab. Compared to flexible pavement, rigid pavements are placed either directly on the prepared sub grade or on a single layer of granular or stabilized material. Typical road structure cross section sub grade, base course.
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