Minnesota Department of Transportation

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NRRA Geotechnical and Intelligent Construction Technologies Teams

MnROAD | NRRA | Structure & Teams | Geotechnical Team

Continuous Moisture Measurement during Pavement Foundation Construction

Status: Active
Project Start Date: February 26, 2021
Project End Date: February 17, 2023

Project overview

Accurate and timely moisture measurement of earthwork during compaction of foundation layers is crucial to proper construction and long-term durability of the pavement structures. Since the traditional methods for measuring moisture are point specific, expensive and/or time consuming, it is desirable to explore new devices that can provide the full coverage of the spatial variation of moisture.

This project will document the current state of knowledge concerning field moisture measurement during pavement foundation construction that also includes case studies that demonstrate cost savings resulting from more effective moisture measurement. This project will also provide critical information regarding the most effective moisture measurement devices suitable for improving compaction near structures such as retaining walls and bridge abutments. Finally, this proposal will demonstrate a prototype device capable of continuously measuring moisture during pavement foundation construction.

Tasks

Task 1: Initial Memorandum on Expected Research Benefits and Potential Implementation Steps

During the proposal phase and the development of the work plan, key benefits were selected to clearly define the benefits the state will receive from the results and conclusions of this research. This task will provide an initial assessment of research benefits, a proposed methodology, and potential implementation steps.

  • Deliverable: A memorandum providing initial estimates of expected research benefits, documentation of the methodology, and potential implementation steps. Task 1 Memo (PDF), updated 5/10/2021
  • Date due: March 31, 2021

Task 2: Document current state of knowledge

In this task the current state of knowledge related to field and laboratory methods that can measure or estimate moisture content, degree of saturation and matric suction will be documented. As part of this task, several case studies that demonstrate the technical benefits and the cost savings resulting from more effective moisture monitoring will also be provided. Finally, this task will be concluded with a comprehensive and extended work plan for the smooth and timely execution of this project. This task also consists of developing an experimental test plan to test up to ten different geomaterials. Based on the interaction with the panel, up to six geomaterials will be selected as a baseline for verification of the outcomes of this study. These materials will be preferably from the home state of the panel members for close interaction and feedback. The University will sample an adequate amount of materials for laboratory and small-scale studies as described below. The current thinking is to select two fine-grained soils (CL, CH, ML, or MH), two sandy materials (SW, SP, SM, or SC), and two coarse-grained materials (GW, GP, GM, or GC). These ranges provide a good basis for materials with different characteristics in terms of their interaction with moisture, levels of suction, levels of moduli, and their use as compacted geomaterials.

  • Deliverable: A memorandum containing the current state of knowledge, case studies, an extended work plan, and an experimental test plan. Task 2 memo (PDF), 7/8/2021
  • Date due: May 31, 2021

Task 3: Test laboratory prototype

The laboratory work will closely follow the work that Sotelo (2012) carried out as part of NCHRP Project 10-84 to evaluate the accuracy, precision, and applicability of the available moisture content. The laboratory testing on each material selected includes:

  1. Conduction of gradation and Atterberg limits tests on soil samples.
  2. Development of moisture-density, moisture-CR (using the lab prototype), moisture-modulus (using Free-freeresonant column tests), moisture-Light Weight Deflectometer (LWD) modulus (using American Association of State and Highway Transportation Officials [AASHTO] TP 123-01), degree of saturation-CR. All these tests will be carried out at five different nominal moisture contents of optimum moisture content (OMC, OMC±10% OMC, and
    OMC±20%OMC). All tests will be carried out in duplicate to assess the repeatability of the results on the same specimens since all tests mentioned are nondestructive.
  3. Preparation of small-scale (24 in. high by 18 in. diameter) specimens (at strictly controlled densities and moisture contents placed in 2 in. lifts.
  4. Test the specimen with the prototype at least at five horizontal locations at three levels to determine the repeatability.
  5. Compare the moisture contents measured by the prototype with those from oven drying to determine the accuracy.
  6. Conduct analysis using statistical and process control tools to develop a preliminary operational tolerance, get a sense of the overall precision and bias of the device.
  • Deliverable: A memorandum containing the results of the laboratory testing with the prototype, SWOT analysis of the outcome, and a firm plan for field implementation. Task 3 memo (PDF), 2/2022
  • Date due: June 30, 2022

Task 4: Develop and test field prototype

Concurrent with laboratory testing, a field version of the tool will be developed. This device will not be ruggedized or professionally packaged for day-to-day use but will be modular for ease of modification. The last three months of this task will be dedicated to field testing of the field prototype at local sites to debug the system and ensure accuracy. The goals of this activity are the following:

  • to verify the applicability of the results from small-scale and laboratory tests carried out as part of Task 2, and
  • to establish the variability of the prototype under less controlled condition to delineate the equipment variability (established in Task 2) from site variability.

Aside from the tests enumerated in Task 2, we will carry the following activities at each test bed.

  • Sample geomaterial from five points at windrow before compaction
  • Monitor the increase in density and modulus of the layer with number of passes at two points
  • Carry continuous measurement with prototype along five lines three times
  • Graphically summarize field data by mapping the spatial variation of moisture measurements
  • Test ten points at least three times with the device shortly before and after compaction along with one NDG test at each point
  • Retrieve samples for moisture content from ten points to validate the device’s results
  • Analyze field data to ensure that the two goals listed above are met

The research team will coordinate with the developers of Veta to ensure that the field data can be uploaded to that software.

  • Deliverable: A memorandum containing detailed information about the field prototype, the results of the preliminary field testing with the prototype, SWOT analysis of the outcome, and a firm plan for field implementation and an experimental test plan. Task 4 memo (PDF), 8/2022
  • Date due: July 31, 2022

Task 5: Demonstrate prototype

Upon satisfactory testing of the prototype, the device will be demonstrated to the National Road Research Alliance (NRRA) partners at a site either MnROAD or any other location selected by the panel. To attract a wide audience, the demonstration can be arranged concurrently with one of the annual meetings of NRRA. This demonstration will be carried out along with an extensive presentation to obtain feedback for future modifications and improvements to the prototype.

Task 6: Final memorandum on research benefits and implementation steps

This task will provide a revised version of the assessment of research benefits, a proposed methodology, and potential implementation steps provided in Task 1. In this task, the methodology used to calculate benefits, including any assumptions and steps required will be clarified and documented. In addition to quantitative calculations, a qualitative discussion of the estimated benefits will be included as appropriate. Key steps that the agencies could take to implement the research will also be included.

Task 7: Draft final report

A draft project report summarizing the results, findings, conclusions, and recommendations of the research will be delivered. The report will comply with State’s Editorial guidelines. The report will include an implementation plan for improving and deploying the products of the research, and a draft specification in standard AASHTO format.

  • Deliverable: A draft final report for Technical Advisory Panel (TAP) review, and a revised report that is technically complete and approved by the Technical Liaison for publication.
  • Date due: November 30, 2022

Task 8: Editorial Review and Publication of Final Report

The Principal Investigator will work directly with State’s contract editors to address editorial comments and finalize all final deliverables on time.

  • Deliverable: Final Publishable Report that meets MnDOT’s Editorial Guidelines and standards.
  • Date due: December 31, 2022

Project team

Email the Project Team
Principal Investigator(s): Soheil Nazarian, Ph.D., P.E., D.GE, University of Texas - El Paso (UTEP), nazarian@utep.edu; Mark Baker, private consultant, bakergrd@cs.com
Technical Liaison: Terry Beaudry, MnDOT, terry.beaudry@state.mn.us
Project Technical Advisory Panel (TAP): Contact us to join this TAP

  • Terry Beaudry, MnDOT (TL)
  • Eddie Johnson, MnDOT
  • Todd Mansell, Caterpillar
  • Deepak Maskey, Caltrans
  • Raul Velasquez, MnDOT
  • Eyoab Zegeye Teshale, MnDOT

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