U.S. Department of Transportation
Federal Highway Administration
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Federal Highway Administration Research and Technology
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Publication Number: FHWA-HRT-01-167
Date: April 2005
Structural Factors of Jointed Plain Concrete Pavements: SPS-2—Initial Evaluation and Analysis
Appendix A. Summary of SPS-2 Project Nomination and Construction Guidelines
To ensure proper selection of the SPS-2 sites and to maximize the uniformity of the design and construction details at all SPS-2 sites and sections, the following two documents were prepared for the SPS-2 experiment:
These guidelines were developed to control the quality and integrity of the SPS-2 experiment results and findings. A summary of the documents is provided in this appendix.
The following criteria are to be used to evaluate candidate projects for inclusion in the SPS-2 experiment:
These criteria and considerations will help identify projects in which the relative performance of the test sections is due to the design parameters used and not to external factors (e.g., changes in the subgrade or traffic patterns). They also serve to identify projects at different locations with relatively similar details so that differences in performance from one location to another are primarily due to differences in climatic conditions and subgrade types.
It is recognized that "perfect" projects containing all of the desirable characteristics are rare. Each proposed site will be evaluated individually and compared to other candidates in order to select the best set of projects to satisfy experimental considerations. Some deviation from the desired project characteristics may be necessary to obtain sufficient projects for the experiment. For example, projects will be considered where it is not possible to locate all of the test sections completely in cuts or on fills. In this case, it may be necessary to locate some test sections in cuts and others in fills.
Ideally, the test sections shall be located in shallow fills. However, if the test section cannot be placed in a fill, the entire length of the section shall be located completely in a cut section. Cut-fill transitions or side hill fills should not be located within a test section. In addition, rock cut sections should be avoided unless all test sections are located within the cut.
Subgrade soils shall be prepared according to the following requirements:
Note: The working platform is considered a pavement layer; therefore, sampling and testing, in addition to that required for the subgrade, must be planned and performed.
The discussion of construction guidelines for base materials is divided into two categories: undrained and drained base structures. The drained and undrained designations do not refer to external pavement drainage features such as cross-slope and ditches. Undrained base structures refer to relatively impermeable dense graded base layers consisting of DGAB or lean concrete LCB. The drained base structures refer to a system that consists of PATB drainage layer and edge drains.
Sections 1 through 8 and 13 through 20 of the primary experiment (25 through 28, 31 through 34, 37 through 40, and 45 through 48 of the supplemental experiments) are constructed with undrained base layers that incorporate DGAB or LCB. Drainage layers and longitudinal edge drains shall not be used on these sections.
DGAB is an untreated, crushed material. Requirements and construction guidelines for this material are presented in the following sections.
The quality and gradation criteria for selection of the aggregate required in the construction in the DGAB shall be as follows:
The base course shall be prepared to grade according to the participating agency's practice and the following requirements:
Lean Concrete Base
The LCB shall consist of a mixture of aggregate, hydraulic cement, water, and admixtures. The variability in specifications used by the different highway agencies makes it impractical to specify the same materials or mix design for all test locations. Therefore, the participating agency's procedures and specifications shall be used to produce and place an LCB with a target average compressive strength, slump, and air content as follows:
Cement and aggregate used in producing the LCB shall meet the following requirements:
It is important that the coarse aggregate meet the highest standard of durability specified by the agency. Coarse aggregate must be reasonably free from deleterious substances such as chert, gypsum, iron sulfide, amorphous silica, and hydrated iron oxide, and must be obtained from a source approved by the agency. Coarse aggregate for use in LCB that will be subject to wetting or extended exposure to moist ground shall not contain any materials that are deleteriously reactive with alkalies in the cement in an amount sufficient to cause excessive expansion of mortar or concrete. The potential reactivity should be determined in accordance with the procedure given in AASHTO M80.
Construction requirements for the LCB include the following:
Drained Base Structures
Sections 9 through 12 and 21 through 24 of the primary experiment (and sections 29, 30, 35, 36, 41 through 44, and 49 through 52 of the supplementary experiments) are constructed with drained base structures that incorporate a PATB and edge drains. The PATB is constructed in combination with the DGAB materials previously described.
Permeable Asphalt-Treated Base
The PATB serves as a drainage layer in the pavement structure. Material and construction requirements for the PATB are presented below.
Construction requirements for the PATB include the following:
Filter fabric (or geotextiles) shall be used to prevent the clogging of the permeable material in the edge drains and transverse interceptor drains due to the migration of fine aggregates from untreated layers, the shoulder, and the subgrade. The requirements for the filter fabrics used in the edge drains are given below.
Nonwoven or woven geotextile materials, which conform to recommendations for Class B drainage applications where installation stresses are low, will be used in edge drains. Fabric for the transverse interceptor drains shall meet Class A requirements. The following physical requirements on an average per roll basis sampled in accordance with ASTM D4354 shall be met.
Construction requirements include the following:
Edge drains shall be used in the shoulders of the pavement sections with PATB to collect the water from the permeable base. The following requirements must also be met:
For the SPS-2 experiment, participating agency practice shall be used to provide asphalt concrete or PCC shoulders. PCC shoulders shall not be tied to the mainline pavement. Also, if the concrete shoulder is placed monolithically with the traffic lanes, then the shoulder joint shall be sawed to full depth. Tied PCC shoulders may be constructed in additional supplemental test sections. The longitudinal joint between the mainline concrete pavement and the shoulder shall be sealed.
The quality of concrete as delivered, as placed, and the subsequent strength development in concrete are critical factors in concrete pavement performance. Although only the strength property (flexural strength) is normally considered in evaluating the structural behavior of concrete pavements, durability-related properties (entrained air content, aggregate type, degree of consolidation) are also important in evaluating long-term performance.
The test sections in the SPS-2 experiment will be constructed for two levels of flexural strength (3.8 and 6.2 MPa) as determined from third-point loading tests at 14 days. The concrete mixture should be designed according to the procedures and specifications followed by the participating agency. It is recommended that a slip-form method be used for placement of the concrete. In such a case, slump of the as-delivered concrete shall not exceed 64 mm.
Concrete with an average 14-day flexural strength of 3.8 MPa is considered standard and readily available. However, some agencies have reported difficulty in achieving this strength level while maintaining sufficient cement content for acceptable durability. In such cases, an average strength level of 4.1 MPa is considered acceptable for the lower strength level criterion. For the higher strength concrete, well-planned laboratory testing may be required to design a mixture capable of achieving an average flexural strength of 6.2 MPa at 14 days. The higher strength should be achievable by using a higher cement content (cement factor). Laboratory mix design will be in accordance with participating agency practice, except for the determination of the strength level.
The following is a summary of the requirements for the portland cement concrete PCC:
Material requirements for the concrete should be based on the normal practice of the participating highway agency. Many agencies have specific requirements for coarse and fine aggregates based on durability concerns and local availability of quality aggregates. However, it is necessary to maintain a high degree of uniformity and consistency in the construction of the test sections to achieve the objectives of a coordinated national experiment. Therefore, concrete materials must conform to certain minimum requirements to ensure consistency in the concrete quality at the different sites.
Only Type I or Type II portland cement shall be used and shall meet the requirements of AASHTO specification M85.
Fly ash may be used as substitute for a portion of the portland cement. The amount of substitution shall not exceed 15 percent by weight of cement. The fly ash replacement amount shall be determined through laboratory trial mix investigations using the specific materials proposed for the project. Use of Class F fly ash meeting the specific requirements of the agency is permitted. The use of Type C fly ash is not permitted. Participating agency practice concerning the use of fly ash in concrete in certain months of the year should be observed.
Fine aggregate (passing the No. 8 sieve) shall consist of natural sand, manufactured sand, stone screenings, slag screenings, or a combination thereof, and meet the quality requirement of AASHTO M29. The fineness modulus of the fine aggregate shall not be less than 2.3 and shall not be greater than 3.1.
Coarse aggregate (retained on the No. 8 sieve) shall consist of crushed gravel or crushed stone particles meeting the requirements of AASHTO M80. It is recommended that the coarse aggregate conform to AASHTO 57 gradation as follows:
Coarse aggregate with a 25.4-mm maximum size aggregate may be used if such use represents the common practice of the participating agency.
The coarse aggregate shall conform to the following specific requirements:
It is important that the coarse aggregate meet the highest standard of durability specified by the participating agency. Coarse aggregate must be obtained from a source approved by the agency and must be reasonably free from deleterious substances such as chert, gypsum, iron sulfide, amorphous silica, and hydrated iron oxide.
Coarse aggregate for use in concrete that will be subject to wetting, extended exposure to humid conditions, or contact with moist ground shall not contain any materials that are deleteriously reactive with alkalies in the cement in an amount sufficient to cause excessive expansion of mortar or concrete. However, if such materials are present in injurious amounts, the coarse aggregate may be used with a cement containing less than 0.6 percent alkalies calculated as sodium oxide equivalent or with the addition of a material that has been shown to prevent harmful expansion due to the alkali-aggregate reaction. The potential reactivity should be determined in accordance with the procedure given in AASHTO M80.
Other items used in the production of concrete, such as water and admixtures, shall conform to the requirements normally specified by the agency for interstate concrete pavement construction. Use of microsilica (silica fume) as an additive is not permitted. Also, the use of additives to accelerate the strength gain of the concrete is not permitted for the SPS-2 experiment.
Concrete pavement requirements for SPS-2 are summarized in the following sections.
The primary experiment SPS-2 addresses doweled JPCPs. The concrete pavement design for this experiment stipulates the following details:
The concrete pavement for the SPS-2 test sections shall be constructed in accordance with the practices and specifications that have proven successful for the participating highway agencies. It is strongly recommended that slip-form-paving procedures be used for concrete placement, and that the test lane and adjacent lane be slip-formed in one operation. The key items related to construction are outlined below.
The test sections at each site incorporate several variables pertaining to the concrete slabs, including pavement thickness, concrete strength, and lane width. Therefore, it is recommended that special consideration be given to arranging the test sections at the site in a manner that will facilitate construction operations. Concrete placement for each test section should be done in a single continuous operation.
When dowel baskets are used at transverse joints, concrete placement using side-dump procedures will facilitate placement of dowel bars ahead of concrete placement. Therefore, this procedure shall be used for placement of concrete.
Use of slip-form equipment is recommended. The equipment shall spread, consolidate, screed, and float-finish the concrete so that a minimum of hand finishing will be necessary and a well-consolidated and homogeneous pavement is produced. The machine shall vibrate the concrete for the full width and depth of the concrete. Internal spud-type vibrators shall be used at a spacing of no more than 610 mm.
Transverse contraction joints with dowel bars shall be provided at a spacing of 4.57 m and 9.14 m, respectively. These joints shall be sawed perpendicular to the longitudinal direction of the pavement. At these joints, dowel bars shall be provided using basket assemblies or dowel bar inserters. Dowels should be properly aligned and the dowel baskets, if used, should be securely anchored to the base layer and placed at pavement middepth. Dowels should be lightly coated with grease or other suitable lubricant over their entire length to prevent bonding of the dowel to the concrete.
All joints shall be sawed. For transverse contraction joints, an initial sawcut of D/3 is required, preferably made using up to an 8-mm-wide blade. A second sawcut should be made later, if necessary, to provide the required shape factor for the sealant material. Longitudinal joints between lanes should be sawed initially, preferably using up to an 8-mm-wide blade, to a depth of D/3. A second sawcut should be made later to provide for an 8-mm-wide by 25.4-mm-deep sealant reservoir.
The use of plastic inserts to form longitudinal joints is not permitted. The longitudinal joint will be tied using epoxy-coated deformed steel bars, No. 5 grade 40 steel, spaced at 762 mm center to center and 762 mm long. The tie bars shall be placed perpendicular to the longitudinal joint at a target depth of D/2.
If a concrete shoulder is used along the test sections, then the longitudinal joint between the outside shoulder and the travel lanes shall not be tied. The joint will be formed by placing the shoulder separately or by sawcutting to full depth if the concrete is placed at the same time as the travel lanes.
Timing of initial sawing of both transverse and longitudinal joints is critical. Therefore, sawing should begin as soon as the concrete is strong enough to both support the sawing equipment and prevent excessive raveling of the concrete surface. Longitudinal sawing shall be initiated at the same time as the transverse sawing. All sawing shall be completed within 24 hours of placement.
Only liquid curing compound is permitted for curing the concrete pavement. Curing compound shall be applied to the concrete surface within 15 minutes after the surface texturing operation and no later than 45 minutes after concrete placement. Participating agency practice shall be followed for surface texturing and in specification of the type of curing compound and application rate.
Joint sealing shall be accomplished using only silicone sealants. The sealant shall be either self-leveling or a tooled, no-slump material proven by the agency to work satisfactorily. Neither new or experimental sealants nor field poured liquid sealants shall be used for test sections. All pavement joints shall be sealed before opening to traffic.
It is necessary that every effort be made to obtain slab thickness as close to the target values of 203 and 279 mm as possible. Neither a deficiency nor an excessive thickness is desired. Final pavement thickness should be within 6 mm of the target values, as determined from cores and rod and level survey elevation changes. Elevation measurements are to be taken at intervals of 15.25 m or less within the test sections, both before and after concrete placement.
The surface of the finished pavement shall be tested with a California-type profilograph. Profiles shall be made in both wheel paths parallel to each edge of the pavement. The pavement shall have a prorated profile index of less than 158 mm per 1,000 m, as evaluated using California test 526. The contractor shall remove high pavement areas with vertical deviations greater than 11 mm in 8 m using diamond grinding devices or multiple-saw devices as approved by the agency. Only localized grinding is permitted; wholesale grinding of the finished pavement surface is not permitted.
The test section pavements shall not be opened to traffic before 7 days after concrete placement, or before concrete flexural strength has reached 3.8 MPa. Joint sealing must be completed before opening to traffic. No construction traffic will be allowed on the test section until that time.
Pavement slab panels exhibiting cracking before the test sections are opened to traffic shall not be repaired. In cases where slab panels are damaged to the extent that structural repairs are necessary, the FHWA Pavement Performance Division shall be consulted prior to performing any repair activity.
Construction operations shall be performed in compliance with the guidelines and specifications established by the participating agency for road and bridge construction. The agency's high- quality construction practice should be enforced for the experiment. Adequate attention shall be given to details and control of the mix plant, hauling, placement, and consolidation operations to prevent construction practices that result in poor pavement performance. In addition, care should be taken to ensure that the test sections are constructed in a manner consistent with normal highway construction.
The 183 m overall length of each test section includes 152.5 m for monitoring and 15.25 m before and after the section for materials sampling. The distance between these 183-m sections must be sufficient to allow changes in materials and thicknesses during construction. This distance is required to accommodate changes in concrete mix and slab thickness in a manner that will reduce the effect on the properties of the finished pavement. A minimum transition length of 36.6 m is recommended between the test sections to provide sufficient production in order to develop consistency after changes in materials, thicknesses, or lane widths.
The test site shall be surveyed to the extent that the limits of each test section location will be known to an accuracy of 0.305 m. The first test section occurring in the direction of traffic at a site will have the project station 0+00 at the beginning of the monitoring section. Subsequent test sections will have a test section station 0+00 at the beginning of each monitoring section. Site and individual test section beginning stations will be located 3.05 m before the first joint of the monitoring section. The ending stations will be 3.05 m beyond the last joint in the monitoring section.
An agency that wants to participate in the SPS-2 experiment, but finds it necessary to deviate from some of the guidelines described in the report, should review these deviations with the LTPP Regional Office or LTPP Division. These authorities will assess the implications of these deviations on the study objectives. If the implications of the noncompliance appear minimal, the deviations will be accepted; otherwise, LTPP will suggest alternatives for consideration by the participating agency.