Details:

Creators:
White, David ; Li, Shengting ; Vennapusa, Pavana
White, David ; Li, Shengting ; Vennapusa, Pavana Less -
Corporate Creators:
Iowa State University. Center for Earthworks Engineering Research
Corporate Contributors:
Iowa. Highway Research Board
Subject/TRT Terms:
[+]
Compaction Embankment Quality Embankments Moisture-density Testing Moisture Content Saturated Soils Soil Compaction Soil Tests Unsaturated Soils
Publication/ Report Number:
InTrans Project 14-507
Resource Type:
Tech Report
Geographical Coverage:
Iowa
Corporate Publisher:
Iowa. Highway Research Board
Abstract:
A specification for contractor moisture quality control (QC) in roadway embankment construction has been in use for approximately 10

years in Iowa on about 190 projects. The use of this QC specification and the development of the soils certification program for the Iowa

Department of Transportation (DOT) originated from Iowa Highway Research Board (IHRB) embankment quality research projects.

Since this research, the Iowa DOT has applied compaction with moisture control on most embankment work under pavements.

This study set out to independently evaluate the actual quality of compaction using the current specifications. Results show that Proctor

tests conducted by Iowa State University (ISU) using representative material obtained from each test section where field testing was

conducted had optimum moisture contents and maximum dry densities that are different from what was selected by the Iowa DOT for

QC/quality assurance (QA) testing. Comparisons between the measured and selected values showed a standard error of 2.9 lb/ft3 for

maximum dry density and 2.1% for optimum moisture content. The difference in optimum moisture content was as high as 4% and the

difference in maximum dry density was as high as 6.5 lb/ft3. The difference at most test locations, however, were within the allowable

variation suggested in AASHTO T 99 for test results between different laboratories. The ISU testing results showed higher rates of data

outside of the target limits specified based on the available contractor QC data for cohesive materials. Also, during construction

observations, wet fill materials were often observed. Several test points indicated that materials were placed and accepted at wet of the

target moisture contents. The statistical analysis results indicate that the results obtained from this study showed improvements over

results from previous embankment quality research projects (TR-401 Phases I through III and TR-492) in terms of the percentage of

data that fell within the specification limits. Although there was evidence of improvement, QC/QA results are not consistently meeting

the target limits/values.

Recommendations are provided in this report for Iowa DOT consideration with three proposed options for improvements to the current

specifications. Option 1 provides enhancements to current specifications in terms of material-dependent control limits, training,

sampling, and process control. Option 2 addresses development of alternative specifications that incorporate dynamic cone penetrometer

or light weight deflectometer testing into QC/QA. Option 3 addresses incorporating calibrated intelligent compaction measurements into

QC/QA.


Format:
PDF
Funding:
IHRB Project TR-677
Collection(s):
US Transportation Collection
Main Document Checksum:
[+]
urn:sha256:05d4abce4a9e637a5b8670f16fcc1bb86646c5d5de5a6c4d6495d4387526e4fc
Download URL:
https://rosap.ntl.bts.gov/view/dot/30692/dot_30692_DS1.pdf
File Type:

Supporting Files

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