Consortium national concrete pavement technology center partnership for geotechnical. Subbase and subgrade performance investigation and design guidelines for concrete pavement one of 87 reports in the series. Design guide for improved quality of roadway subgrades and subbases final report. 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. A reasonably uniform subgrade or subbase, with no abrupt changes in support, is ideal for any concrete pavement. Basics of concrete pavement thickness design pe civil exam for. Discuss the fundamentals of bases and subbases for concrete pavements understand the design, construction, and cost considerations of bases and subbases understand european practices for basesubbase design and construction understand the performance of various bases at experimental sections constructed at mnroad. For highly trafficked highways, aggregate or stabilized subbases are commonly used to provide improved. Download subgrades and subbases for concrete pavements. After construction, the floor is likely to settle and crack because. Division 03 section concrete slip forming for pavement construction. Design guide for improved quality of roadway subgrades and subbases 7. Engineers are cautioned that much of pavement design is governed by codes, specifications and practices of. Design guide for improved quality of roadway subgrades and.
Road surface or pavement is the durable surface material laid down on an area intended to. 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. Evaluation of subgrade strength and flexible pavement. Eb204 subgrades and subbases for concrete pavements. Common subgrade theories used for concrete pavements. Place a concrete floor on an unstable subgrade or subbase and youll probably pay for it two ways. The field study at each site included portable seismic properties analyzer pspa. A subbase is a thin layer of material placed on top of the prepared subgrade. 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. Several types of chemically stabilized materials are used under pavements as base courses, subbase courses, or treated subgrade. These include lean concrete, cement stabilized or treated aggregate, soil cement, limecement flyash, and limestabilized materials. The analytical relationship between a soils resilient modulus and it modulus, of subgrade reaction is a follows. Most native soils are not too uniform and thus require some improvement or additional layers to compensate.
Introduction to rigid pavement design ced engineering. When do you need to use a subbase under concrete pavements. Vertical deflections are small, and the pressure on the subgrade is very low. Subgrades and subbases for concrete slabs having good support for your concrete slab on ground is critical to success by bill palmer, concrete network columnist a wellcompacted subgrade keeps construction out of the mud and provides uniform slab support. Concrete pavement construction basics placing dowel baskets dowel bars transfer heavy loads across joints in the pavement, preventing faulting at the joint that can lead to pavement damage.
Subbase thickness10 subbase modulus30,000 psi subgrade m r10,000 psi to get k. Subbase and subgrade performance investigation for concrete. Eb204 subgrades and subbases for concrete pavements acpa. Alternatives to asphalt concrete pavement subbases for concrete pavement. This is an introduction to rigid pavement design for engineers.
Subgrades and subbases for concrete pavements trid. Subgrades and subbases for slabs concrete construction. New continuously reinforced concrete pavement designs. Dont miss the upcoming webinar, subbases and subgrade considerations for concrete pavements, scheduled for april 7, from noon to 1. Reference documents published by cement, lime, and fly ash industry organizations often include. Subbase design manual for portland cement concrete. In the early days of rigid pavement construction, concrete slabs were placed directly on top of the subgrade without any basesubbase layers. And one of the major functions of a highway pavement is to reduce the.
Design guide for subgrades and subbases iowa state university. For larger installations mechanical placement of pavers may be more economical. It emphasizes the major objective of obtaining longlasting uniform support for a concrete pavement. Basessubbases for concrete pavements transportation research. Guide specification for materials and construction of. But be prepared to deal with excessive air entrainment. Subgrade the roadbed materials beneath the pavement structure. Subbases and subgrades for concrete foundations networx. Estimation of key pcc, base, subbase, and pavement. It is not intended as definitive treatise, and it does not encompass the design of flexible pavements. Base and subgrade layers must provide adequate and moisture.
Subgrade is the top surface of an embankment or cut section that is shaped to conform to the typical section upon which the pavement structure and shoulders will be constructed. Evaluation of subgrade strength and flexible pavement designs for reliability nayan saha follow this and additional works at. Concrete site paving for industrial and trucking facilities has many similarities to other types of concrete pavements, such as. Incorporating chemical stabilization of the subgrade in. Subbase and subgrade performance investigation and design. Refer to tech spec 11 mechanical installation of interlocking concrete pavements for additional information. Finally, it is likely that as this document is printed and distributed, some new and emerging technologies are advancing within the grading and paving industries. Also, five of the pavements were rigid concrete and the remaining fifteen were flexible asphalt. P that even the stone soling, sand cushioning at subgrade level could not check subgrade intrusion into overlying layers natarajan and shanmukha rao, 1979. Hence the performance of the pavement is affected by the characteristics of the subgrade.
Bases and subbases for concrete pavements aashto classification a6 or a7 soil groups or the unified soil classification system ch, mh, and oh soils. In this publication, a subbase is defined as the layer of material that lies immediately below the concrete pavement. For concrete pavements, the requirements may vary considerably depending on subgrade soil type, environ. As a result, concrete pavements do not require a buildup of foundation support. Portland cement concrete pavement or asphaltic concrete pavement. Report date august 2009 aggregate subgrade thickness determination 6. Pavement design guidelines rev a city of warrnambool. Design considerations for interlocking concrete pavements.
Bases and subbases for concrete pavements this tech brief presents an overview of best practices for the design and construction of bases and subbases for concrete pavements and its effects on performance. This section covers the requirements for the construction of unreinforced concrete pavements, with or without subbases, and may also include attached or integral curbs. The webinar will include essential information about the design and construction of subbases and subgrades, which are important to the quality of the finished pavement. Technical report texas transportation institute available on this site. Use a small triangular file to remove all nicks or projections in the stringline. When expansive soils are compacted in too dry a con. The design of the pavements will be carried out by qualified engineering consultants in accordance with this guide and the principles, practices and procedures detailed. Weak subgrade and subbase layers can settle differently across the surface and cause cracks in the concrete. They must be well drained, dry at the time of concrete placement, and provide uniform support for the weight of the slab and anything placed on the slab.
Use of subbases essentially discouraged except in special cases. This guide captures the fundamental parameters, recommendations, and considerations for subgrades and subbases for concrete pavement. Download here highstrength concrete an international perspective. Compared with other types of paving materials, concrete is by far the most rigid, spreading applied wheel loads over large areas of the subgrade.
Installation specifications for interlocking concrete. Subbases and subgrades for concrete foundations a concrete surface is only as stable and level as its subgrade and subbase. This thesis is brought to you for free and open access by the engineering etds at unm digital repository. Practices vary from state to state, but dowel bars are typically required in eightinch or thicker pavements. Subbase and subgrade performance investigation and design guidelines for concrete pavement. Cut across the e sb cut across m r to the tl vertically meet other line read kvalue k600pci topic 10 aashto rigid pavement design figure 12. Stabilized subbase friction study for concrete pavements. Installation specifications for interlocking concrete pavements unilock specifications page 2 foreword these outline specifications have been prepared for the general guidance of specifiers, engineers, contractor and superintendents associated with the construction of interlocking concrete pavements inany type of traffic applications.
Other factors responsible for non uniform foundation include variability due to a number of reasons including, natural causes, excavation and. Further, the contamination of upper layers of pavements by subgrade soil reduces the. Each site was visited by a research team, who made measurements at about ten points along the pavement. Background the need and use of bases and subbases for pavements has been well known for thousands of years. This paper describes how the analysis of the federal highway administrations fhwas longterm pavement performance ltpp data reveals that a pavements foundation base or subbase and subgrade is one of the most critical design factors in achieving excellent performance for any type of pavement. The scope of the pavement design guidelines covers the design and construction of pavements for residential and industrial subdivisions within the warrnambool city council.
Performance of concrete pavements on granular subbase. Subgrade construction subgrade is that portion of the earth roadbed which after having been constructed to reasonably close conformance with the lines, grades, and crosssections indicated on the plans, receives the base or surface material. Several conditions can lead to non uniform support and damage to the pavement. Design considerations for interlocking concrete pavements unilock specifications page 4 1.
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