National Academies Press: OpenBook
« Previous: Part I - Research Overview
Page 5
Suggested Citation:"Chapter 1 - Background." National Academies of Sciences, Engineering, and Medicine. 2020. Procedures and Guidelines for Validating Contractor Test Data. Washington, DC: The National Academies Press. doi: 10.17226/25823.
Page 6
Suggested Citation:"Chapter 1 - Background." National Academies of Sciences, Engineering, and Medicine. 2020. Procedures and Guidelines for Validating Contractor Test Data. Washington, DC: The National Academies Press. doi: 10.17226/25823.

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

5 Use of contractor construction materials test results in acceptance decisions of state highway agencies’ (SHAs) projects dates back to the 1970s (1). This acceptance decision is typically coupled with a validation process. Validation is defined as, “The mathematical comparison of two indepen- dently obtained sets of data (e.g., SHA acceptance data and contractor data). For example, using statistical tests such as F- and t-tests to determine whether it can be assumed the data sets came from the same population. (Validation of test results includes the verification test results.)” (2). Title 23 Code of Federal Regulations (CFR) Part 637 Subpart B (23 CFR 637B) permits the use of contractor test data for construction materials acceptance, as long as SHAs validate the contractor data with independent test results (3, 4). A combination of hypothesis tests is commonly used to statistically determine if contractor and SHA test results are from the same population. Implementa- tion Manual for Quality Assurance (5) and Quality Assurance Guide Specification (6) were developed to assist SHAs with specification development and making efficient use of resources and improving product quality. The implementation manual includes two validation procedures, F- and t-tests, and a simple comparison test between a single SHA test and a range of contractor tests (5). Recent FHWA reviews and surveys show that only about one-third of SHAs’ comparison pro- cedures are performed according to the first procedure described in the AASHTO implementation manual, and well over half of SHAs use contractor test data in acceptance processes, most of which use nonstatistical methods (7–9). The common deviations from the AASHTO implementation manual statistical procedure are: eliminating the F-test, using split rather than independent mate- rial samples, having an inadequate number of SHA test results, using comparison inappropriate methods [such as the single SHA test method or the Difference Two-Sigma Limit (D2S Limit) method], and performing unwarranted retests. These deviations could lead to erroneous accep- tance and payment decisions (10). The literature suggests a general distrust of contractor test data reported by some SHA personnel, and investigations have found misconduct and fraud (11–14). 1.1 Problem Statement NCHRP Project 10-100 was initiated to identify or develop statistically sound and practi- cal procedures for validating these data and prepare a recommended practice for using these procedures. 1.2 Objective and Organization of the Report The objectives of this research were to recommend procedures for validating contractor test data for construction materials and to prepare guidelines for their application. This report documents the research effort in two parts. Part I summarizes the research performed in four Background C H A P T E R 1

6 Procedures and Guidelines for Validating Contractor Test Data chapters; further details are provided in five appendices. Chapter 1 provides background infor- mation. Chapter 2 presents the research approach. Chapter 3 discusses the findings and applica- tions of the research and presents examples to illustrate use of the recommended procedures for different scenarios. Chapter 4 presents the summary and recommendations for future research. Appendices A and B present the survey of SHAs and its results, respectively. Appendix C presents the numerical simulations used to evaluate procedures. Appendix D presents the SHA data analysis, and Appendix E contains the statistical tables used in the report. Appendices A–E can be downloaded from the project summary page at ProjectDisplay.asp?ProjectID=4192. Part II, contained in this report, is a proposed AASHTO practice for validating contractor test data.

Next: Chapter 2 - Research Approach »
Procedures and Guidelines for Validating Contractor Test Data Get This Book
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

In the development of a quality assurance program, a state highway agency (SHA) incorporates policies and procedures for assessing how well the materials and construction used by a contractor on a construction project satisfy the agency's specifications.

The TRB National Cooperative Highway Research Program's NCHRP Research Report 946: Procedures and Guidelines for Validating Contractor Test Data reviews and evaluates the procedures and practices used in the acceptance of construction materials. The report also proposes a related practice for incorporation into AASHTO Standard Specifications for Transportation Materials and Methods of Sampling and Testing.

Supplemental files to the report include Appendices A through E, available as a single PDF file, a State Highway Agency Survey (Appendix A), Survey Responses (Appendix B), Numerical Simulations (Appendix C), State Highway Agency Date Analysis (Appendix D), and Statistical Tables (Appendix E).

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook,'s online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  6. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  7. ×

    View our suggested citation for this chapter.

    « Back Next »
  8. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!