As of October 1, 2016, the SWUTC concluded its 28 years of operation and is no longer an active center of the Texas A&M Transportation Institute. The archived SWUTC website remains available here.


SWUTC Research Project Description

Rapid Field Detection of Moisture for Base and Subgrade

University: Texas A&M University

Principal Investigator:
Stephen Sebesta
Texas Transportation Institute
(979) 458-0194

Funding Source: SPR Program

Total Project Cost: $241,829

Project Number: 0-6676

Date Started: 9/1/12

Estimated Completion Date: 8/31/13

Project Summary

Project Abstract:
Water content in pavement materials plays a critical role both in construction and performance.  During the construction phase, the water content influences compaction; in performance, water content significantly influences strength, modulus, and permanent deformation characteristics.  While efforts exist to link design and construction by accepting compacted materials based on modulus, these efforts historically have been hindered due to the dependence of modulus on water content.  For modulus-based acceptance to be implementable, companion water content measurements are necessary at the time of acceptance testing.  Although the nuclear gauge can provide water content measurements in the field, restrictions and licensing requirements make the use of that gauge somewhat burdensome to agencies; test procedures are needed using rapid, accurate, non-nuclear moisture-measurement methods.

Project Objectives:
To make the possibility of modulus-based acceptance an implementable reality by including non-nuclear moisture measurement, this project will:

  • Evaluate and rank non-nuclear techniques for measuring water content in soils and bases used in pavement construction.
  • Develop test procedures in TxDOT format for measuring water content with non-nuclear methods.
  • Produce a training workshop and training materials.
  • Produce a training DVD.

Task Descriptions:

Task 1. Review Available Moisture Measurement Technologies.

Task 2. Conduct Preliminary Evaluation of Promising Technologies.

Task 3.  Research Report Including Draft Test Methods and Future Research Plan.

Task 4. Experimental Design to Evaluate Devices on Construction Projects.

Task 5. Perform Experimental Design on Field Projects.

Task 6. Evaluate Bias, Precision, and Sensitivity of Each Test Device.

Task 7. Recommend New Test Device(s) and Test Method(s).

Task 8. Procure New Test Devices.

Task 9. Conduct Training Workshop.

Task 10. Training Video.

Task 11. Project Reports.

Implementation of Research Outcomes:
Properly applying water during compaction of roadway base and subgrade materials is important for achieving adequate compaction. Construction specifications determine the required water content, and field measurement historically takes place with a nuclear density gauge. However, with the regulatory requirements of using nuclear sources, and continued interest in stiffness or modulus-based compaction acceptance, researchers need to identify techniques to rapidly measure moisture content on base and subgrades without using a nuclear source.

Researchers surveyed potential technologies for such rapid measurement. Researchers chose three non-nuclear tests, the nuclear gauge for comparison purposes, and the oven dry gravimetric water content for the reference value.

The last stage focused on the new devices including the Electrical Density Gauge (EDG), the DOT 600, and a moisture analyzer. After collecting data on construction projects, researchers evaluated each test for bias, precision, and sensitivity, and then scored the devices according to bias, precision, sensitivity, cost, turnaround time, suitability for uncompacted materials, and suitability for compacted materials.

With these scoring parameters, the data showed the moisture analyzer most suitable for implementation.

Impacts/Benefits of Implementation:
Researchers produced a draft test procedure for measuring moisture content with a moisture analyzer. Using this method, and with the materials tested in this project, test turnaround time with the moisture analyzer was typically between 15 and 30 minutes. This test could be considered for implementation for materials that pass the No. 4 sieve, while implementation for materials retaining significant amount on the No. 4 sieve would require changes to construction specifications to include the moisture content on the passing No. 4 material.

Web Links:
Final Technical Report