Manual Notice: 2008-1
From: Thomas R. Bohuslav, P.E., Director, Construction Division
Manual: Pavement Design Guide
Effective Date: November 01, 2008
Purpose
This manual notice is intended to transmit changes to the content of the Pavement Design Guide.
Changes
This manual has changed from fifteen chapters to twelve.
Chapter 1, Section 1, Guide Overview
- Under subsection, Purpose, added new subsection, Comprehensive Development Agreement.
- Subsection, Organization, in the first sentence, changed
the number of chapters from fifteen to twelve.
- In bullet reference to Chapter 9, deleted mix transport; added concrete mix design and delivery of concrete; added concrete to describe plant operation
- In bullet reference to Chapter 10, reordered rehabilitation options to parallel the section table of contents. Changed “full depth patches” and “partial depth patches” to “full depth repair” and “partial depth repair”; deleted “reducing rigid pavements”; added “diamond grinding.”
Chapter 2, Section 2, District Pavement Engineer’s Role
- Subsection, History, added content to provide more details of the DPE’s responsibilities in various roles.
- Subsection, Responsibilities
- Under the second set of bullets, deleted sentence “In addition, the DPE serves as the district expert in differentiating when preventative maintenance options are more pertinent than structural rehabilitation options.”
- The first paragraph under the second set of bullets, changed the wording in the sentence beginning “The DPE will often . . .” to “The DPE may be. . .”
- The last sentence under this subsection changed from “Because of the importance of understanding material properties and evaluation of materials used in pavements, the position of DPE has been consolidated under the district lab engineer in several districts.” to “Because of the importance of understanding material properties and evaluation of materials used in pavements, some districts have assigned DPE duties to the district lab engineer“
- Changed subsection name from District Pavement Engineer
(DPE) Certification to District Pavement Engineer (DPE) Skills.
Changed the corresponding content under this subsection; provides
DPE guidance for development and review of pavement designs instead
of DPE certification requirements.
- In table, Recommended and Required Training for the District Pavement Engineer, changed the wording under column heading, “Comment” from “Required for certification” to “Required for flexible pavement design” for the “Training” classes, MODULUS and FPS-19W; deleted “Required for certification” from “Training” class, PMIS Concepts for Administrators CON107; for the “Training” class TSLAB86, DARWin™ 3.1, changed “Comment” from “Required for certification” to “Required for rigid pavement design”
- Under the table, Recommended and Required Training for the District Pavement Engineer, the procedure to certify pavement designs was deleted. Added “PMIS and pavement design assistance from CST-M&P will be provided upon request.”
Chapter 2, Section 3, Pavement Types
- Second level subsection, Perpetual Pavement, end of second paragraph added “Detailed construction considerations are available through this link.”
- Second level subsection, Continuously Reinforced Concrete Pavement, modified and added characteristics of acceptable cracking.
Chapter 2, Section 5, Approved Pavement Design Methods
- Subsection, Flexible Pavement System - Windows version (FPS-19W), in the tenth paragraph, deleted “design check procedure” and replaced with “Modified Texas Triaxial Design Method”
- Subsection, AASHTO Design Procedure, first paragraph changed date range from “in 1959-1960” to “from 1958-1960”
- Second level subsection, Flexible Design, in second paragraph:
- Added “The AASHTO procedure for flexible design is automated in the DARWin™ 3.1 software.” to the beginning of the paragraph
- Added “and one design option using the DARWin software is to input layer resilient moduli instead of layer coefficients.” to the end of the last sentence.
Chapter 2, Section 7, Information Needed for Pavement Design
- Subsection, Traffic Loads:
- Second level subsection, Traffic
Distribution, after the first set of bullets, deleted paragraph “The
Transportation Planning and Programming Division (TPP) estimates
the directional distribution in the Traffic Analysis for Highway
Design report, but this distribution number is for the entire traffic
stream. If the designer anticipates that the truck distribution
number is different from that of the entire traffic stream, then
this should be indicated in the request submitted to TPP for project
level traffic data.” and replaced it with “The
Transportation Planning and Programming Division (TPP) posts the
directional distribution in the Traffic Analysis for Highway Design
report, but this distribution is related to peak ADT distributions
(the 30th highest hourly volume) that affect level of service for
geometric design versus loading for structural design.”
Added paragraph “The assumption made in the Traffic Analysis for Highway Design report is traffic loading is equivalent in both directions. If the designer anticipates the truck directional distribution to be different from 50/50 or loads to be significantly greater in one direction, then this concern should be indicated in the request submitted to TPP for project level traffic data.”
- Second level subsection, Traffic
Distribution, after the first set of bullets, deleted paragraph “The
Transportation Planning and Programming Division (TPP) estimates
the directional distribution in the Traffic Analysis for Highway
Design report, but this distribution number is for the entire traffic
stream. If the designer anticipates that the truck distribution
number is different from that of the entire traffic stream, then
this should be indicated in the request submitted to TPP for project
level traffic data.” and replaced it with “The
Transportation Planning and Programming Division (TPP) posts the
directional distribution in the Traffic Analysis for Highway Design
report, but this distribution is related to peak ADT distributions
(the 30th highest hourly volume) that affect level of service for
geometric design versus loading for structural design.”
Chapter 2, Section 8, Pavement Design Reports
- Subsection, Projects Requiring
Pavement Design and Pavement Design Reports:
- Deleted three bulleted items, 1) “rehabilitation (2R) projects, where upgrading as defined in Chapter 5 (reconstruction and rehabilitation design criteria) of the Roadway Design Manual is performed, 2) projects that involve removal of water trapped in the pavement structure (underdrains, edge drains, restoration of drainage systems), and 3) “hot mix asphalt (HMA) overlays greater than 2 in. thick”
- For bullet beginning “hydraulic cement” added “unbonded” before “overlays of existing pavements”
- Under the first set of bullets added two paragraphs: 1)“Tie-ins,
such as bridge approaches, do not require pavement designs when
following department or district proven standards.”
2) “A new design is not necessary. Previously approved design can be used if through an analysis, considering traffic, environmental and subgrade conditions, the pavement design analysis yields the same thickness. However, adjustments to designs thicknesses and specific conditions, even within a project, should be considered in the design process for economic purposes.”
- Near the beginning of the fourth paragraph, inserted word “approximately” in front of “2-in thick and less. . .”
- In the sixth paragraph beginning, “The following list provides. . .” added “for projects greater than 500 ft long” to the end of the sentence.
- In the second set of bullets, deleted three bulleted items: 1)addition of shoulders, 2) addition of a travel lane and 3) matching the existing or the adjacent section. Added one bulleted item, “pavement widening including shoulder.”
- Subsection, Pavement Design and
Other Documentation:
- In the second bullet starting “Narrative discussing. . .” inserted the term “for 3-R projects” after “PMIS data analysis/pavement condition surveys.” In the sentence beginning “The narrative should. . .” deleted “section’s construction and maintenance history, identifying” The sentence now reads “The narrative should include a discussion of the factors that significantly affect pavement performance, and a summary of laboratory tests conducted on any materials extracted from the existing structure.”
- In the fifth bullet beginning “Soil map of. ..” added sentence to the end of the item “Provide information pertaining to shrink/swell potential and plasticity.
- Added bullet item, “The study of the presence of sulfate bearing compounds and organic content.”
Chapter 3, Section 2, Geotechnical Investigation for Pavement Structures
- Moved content from Chapter 4, Section 6, Geotechnical Investigation for Pavement Structures
- Subsection, Introduction:
- In the second level subsection, Scope of Guidelines, at the beginning of the section, added “This guideline is intended solely for pavement applications.”
- Subsection, Preliminary Investigation:
- In the numbered list, item 3, added “to” between “geometrics” and “predict”
- Second level subsection, Project Intiation, “Project
Type” bullet, first sub-bullet, at the end of the item,
added “ A review of existing data can indicate what information
is readily available.”
Second sub-bullet, deleted, “Review of Existing Data can help in defining what information is readily available.” from the beginning of the item. Now reads “It is necessary in all cases to determine what influence the roadbed soils will have or have had on the performance of the pavement structure.”
- Second level subsection, Field Reconnaissance, first bullet, Surface Soil Exploration, changed the following eight first level bullets to second level bullets, beginning with “Size and percentage. . .” ending with “Presence of certain. . .”
- Second level subsection, Field Reconnaissance, second bullet, replaced text, “Presence of certain sulfur-bearing compounds such as gypsum or lignite can indicate further testing is required. There are common occasions where two material types are present and are” with “When two material types are present, it is common for the materials to be”
- Second level subsection, Field Reconnaissance, third bullet, Physical layout and alignment, at the beginning of the first sub-bullet, deleted “An idea about the terrain” and replaced content with “Terrain features”
- Second level subsection, Preliminary Evaluation, first sub-bullet under item, Structural Support, second sentence changed from “Soil Conservation Service (SCS) maps” to “The older Soil Conservation Service (SCS) maps or online USDA, Natural Resources Conservation Service Web Soil Survey”
- Subsection, Subsurface Exploration:
- Second level subsection, Material
Evaluation, fourth bullet, Feasability of chemical modification,
first sentence, inserted “potential for” to describe “detrimental
effects”;
Second sentence, changed “Stabilization Guidelines” to “Guidelines for Modification and Stabilization of Soils and Base for Use in Pavement Structures” and added a link;
Third sentence, changed from “The protocol evaluates the potential for the occurrence of detrimental reactions after a soil has been placed and compacted.” to “ The protocol evaluates the potential for the occurrence of detrimental reactions after the introduction of a calcium based stabilizer.
- Second level subsection, Material
Evaluation, fourth bullet, Feasability of chemical modification,
first sentence, inserted “potential for” to describe “detrimental
effects”;
- Subsection, Stabilization Guidelines:
- In the second paragraph, the fourth sentence starting, “In order to achieve. . .” deleted “by treating with modifiers, such as asphalt, cement, fly ash, or lime.”
- Added third paragraph “Most materials are made suitable by incorporating chemical additives, such as asphalt, cement, fly ash, or lime. Each of these additives is effective when the material is designed and applied properly. Proper design and application of materials with additives will minimize premature failures of the material and pavement structure.”
- In fourth paragraph beginning “The Guidelines
for Modification. . .” deleted the last sentence “Please
contact the Geotechnical, Soils & Aggregates Branch of the Construction Division,
Materials & Pavements Section (CST-M&P).”
Added content to the end of the paragraph “When soils and base contain soluble sulfates, use the “Guidelines for Treatment of Sulfate-Rich Soils and Bases in Pavement Structures” to identify the feasibility for treatment and construction consideration for incorporating chemical additives.”
Chapter 3, Section 4, Performance Graded Binders (PG Binders)
- Subsection, Selecting a PG Binder, third paragraph, changed the test reference from ("Tex-539-C, Measurement of Elastic Recovery of Tensile Deformation Using a Ductilometer") to (ASTM 6084, Standard Test Method for Elastic Recovery of Bituminous Materials by Ductilometer)
Chapter 3, Section 5, Hot Mix Asphalt Concrete Pavement Mixtures
- Subsection, HMA Mix Design, split
the first paragraph at the end of the second sentence; added a new
second level subsection title, Performance Concerns; moved content
under the new subsection starting at sentence beginning “Mix
design seeks to address. . .”
- Second level subsection, Performance Concerns, under the
bullet list, the paragraph beginning “Design is facilitated
by . . .” and ending with the sentence beginning, “Mixture designs
using the SGC. . .” was reformatted to seven paragraphs.
In the sixth paragraph beginning, “Mixture designs using the SGC. . .” changed the content at the end of the sentence from “Depending upon the mix type, an N design (Ndes) related to design air voids initial N (Nini) related to mix workability, and maximum N (Nmax) related to maximum desirable densification may be established (see "Tex-241-F" and "Tex-204-F," Part IV).” to “Depending upon the mix type, an N design (Ndes) related to design air voids will be established (see "Tex-241-F" and "Tex-204-F," Part IV).”
-
Added sentence to the end of the sixth paragraph, “Ndes can be adjusted to ensure sufficient asphalt cement content and mix workability.”
- Added second level subsection title, Voids in the Mineral Aggregate, before paragraph beginning, “Another mix design parameter. . .”
- Added second level subsection title, Evaluating Mix Stability, before paragraph beginning, “Historically, mix stability. . .”
- Added second level subsection title, Tools to Improve
HMA Mixes; added new paragraph at the beginning of the section, “Research
project 0-5123 developed a methodology to design a balanced HMA
mixture, considering both rutting (Hamburg) and fatigue (Overlay
Tester) properties.“
In the second paragraph, at the end of the first sentence, added, “found in Tex-248-F.” and deleted second sentence, “A current research project (0-5123, scheduled for completion in August 2007) combines the testing of a mix design for rutting using the Hamburg tester and for cracking using the Overlay Tester.”
- In Table 3-6: Tex-204-F Mix Design Options, Part IV, column heading, Must Meet, changed criteria from, “Must ensure stone on stone contact. . .” to “By plan note, designate stone on stone contact. . .”
- Second level subsection, Performance Concerns, under the
bullet list, the paragraph beginning “Design is facilitated
by . . .” and ending with the sentence beginning, “Mixture designs
using the SGC. . .” was reformatted to seven paragraphs.
- Added subsection, Use of Perpetual Pavements
Chapter 4, Section 6, Geotechnical Investigation for Pavement Structures
- Moved content to Chapter 3, Section 2
Chapter 5, Section 1, Overview
- Under the first set of bullet items, added “These pavement design procedures were briefly described in Chapter 2 and will not be further addressed here.”
Chapter 5, Section 2, Flexible Pavements
- Subsection, Types of Hot Mix
Asphalt-Surfaced Pavements:
- In
the second level subsection, Perpetual (HMA) Pavements, deleted, “The
idea of a structurally designed deep HMA pavement that would give
high assurance of a long pavement life was studied by the Flexible
Pavement Design Task Force (FPDTF) in 2001 with the expressed intent
of addressing the increased structural demands on heavy truck traffic facilities.
The FPDTF was composed of pavement and construction experts from
TxDOT and industry. Their study resulted in the establishment of
department guidelines for materials to be used, the general (“conceptual”)
structural design format, and the locations where these structures
should be considered (2001).” and replaced with:
“In 2001, the Flexible Pavement Design Task Force (FPDTF) studied structurally designed deep HMA pavement; a type of pavement typically associated with high assurance of long pavement life. The intent of the FPDTF study was to address the increased structural demands on heavy truck traffic facilities. The task force was composed of pavement and construction experts from TxDOT and industry.
As a result of the 2001 study, the following guidelines were established: department guidelines for materials to be used, the general (“conceptual”) structural design format and the locations where these structures should be considered (2001).”
- Second level subsection, Perpetual (HMA) Pavements, deleted
the last paragraph “Exceptions to the use of these improved
performance mixes for heavy truck traffic routes must be granted
by the executive director or designated representative. These mixes
are designated as performance-designed or stone matrix asphalt (SMA)
mixes under the 2004 Specifications (Items 344 and 346). A pavement
structure composed of an RBL with multiple lifts of performance
and/or SMA mixes is commonly referred to as a perpetual pavement
structure that is not subject to traditional bottom-up fatigue damage
but will eventually experience surface distresses and will require
surface renewal.” and replaced with:
“Special attention is required in designing a durable foundation by investigating the underlying soils to determine the appropriate type and level of stabilization needed. In lieu of subgrade stabilization, a high quality granular base, cement-treated base, or other engineered foundation should be used.”
- In
the second level subsection, Perpetual (HMA) Pavements, deleted, “The
idea of a structurally designed deep HMA pavement that would give
high assurance of a long pavement life was studied by the Flexible
Pavement Design Task Force (FPDTF) in 2001 with the expressed intent
of addressing the increased structural demands on heavy truck traffic facilities.
The FPDTF was composed of pavement and construction experts from
TxDOT and industry. Their study resulted in the establishment of
department guidelines for materials to be used, the general (“conceptual”)
structural design format, and the locations where these structures
should be considered (2001).” and replaced with:
Chapter 5, Section 3, FPS-19W Design Parameters
- Subsection, Traffic Inputs
- Second level subsection, Ending ADT (vehicles/day), last sentence replaced “uniformly” with “linearly.”
- Second level subsection, 20-Yr. 18-kip ESALs (One Direction), replaced “exist in both directions” with “exist in the design direction.”
Chapter 6, Section 2, Base and Subgrade Preparation
Moved content from Chapter 6, Section 8, Base and Subgrade Preparation
Chapter 6, Section 3, Pavement Surface Preparation
Moved content from Chapter 6, Section 2, Pavement Surface Preparation
- Changed the name of the first subsection from “Introduction” to “Surface Condition”
- Subsection, Existing Surface Preparation for Overlays
- Second level subsection, Application, changed the third bullet from “type of tack coat according to standard TxDOT specifications from item 300.” to “type of tack coat according to standard TxDOT specifications on Limestone Rock Asphalt Pavement, Item 330, and hot-mix items 334, 340, 341, 342, 344, and 346.”
Chapter 6, Section 4, Special Considerations for the Construction of Perpetual Pavement
This is a new section.
Chapter 7, Section 10, Alternate Pavement Rehabilitation Options
This is a new section.
Chapter 8, Section 1, Rigid Pavement Design
- Subsection, Selection of Rigid Pavement Type, removed the effective date from the first paragraph and added paragraph under the bullet list.
Chapter 12, Section 3, Emergency Load Zones on Roads
- Subsection, Setting Emergency
Load Zones on Roads, Table 12-2, Emergency Load Zones on Roads:
- Step 1, Required Action, bullet 4, changed number of days from 60 to 120.
- Step 2, Required Action, bullet 2, changed the number of days from 60 to 120.
Chapter 12, Section 6, Super Heavy Load Evaluation Process
First paragraph changed from “CST-M&P will perform analyses for GVW over 500,000 lb. or a trailer tire load exceeding 6,000 lb. with input data supplied by the affected districts and the Pavement Management Information System (PMIS).” to “CST-M&P will perform analyses for GVW over 800,000 lb. or GVW over 500,000 lb. and a trailer tire load exceeding 5,000 lb. with input data supplied by the affected districts and the Pavement Management Information System (PMIS).”
Chapter 13, Pavements and Materials Research
This chapter was deleted.
Chapter 14, Trade Organizations
This chapter was deleted.
Chapter 15, Other Related References and Links
This chapter was deleted.
Supercedes
The revised manual supersedes prior versions of the manual.
Contact
Contact the Construction Division, Materials & Pavements Section (CST/M&P) at (512) 465-3686 for further information regarding the methods in this manual.
Archives
Past manual notices are available in a pdf archive.