# Presentation: 418882

## Resilient Modulus Testing and Startup Procedures

- A           Product Line

**Notes:**
[NOTE TO SPEAKER: This is a technical presentation.  
As the presenter, you should have a working knowledge of the P46 test protocol. 
Experience working with laboratory test equipment and familiarity with the terms load cell, LVDT (or other strain measuring devices), servo-hydraulic systems, etc. is highly desirable. 
This experience is not critical, but would be helpful in answering questions posed by the audience.

Consider showing the videos related to this product as part of this presentation.  
For example, show video tapes:
 Laboratory Resilient Modulus Testing: Is This the Right Time, and
 Laboratory Resilient Modulus Testing:Start-Up and Quality Control Procedure
instead of slides #8-43]

## PRESENTATION OBJECTIVES

- Why Mr  Testing and the Startup Procedures are Important
- Development of the Mr Startup Procedure
- How to Conduct the Mr Startup Procedure
- Who Should Use the Mr Testing and Startup Product Line and Why
- How to Get Information on the Mr Testing and Startup Product Line

***What is the Resilient Modulus (M******r******) ***
***Testing and Startup Product Line***

**Notes:**
Let’s begin with a quick review of the LTPP Product Line for Resilient Modulus.

## LTPP Mr Start-up Procedure Product Line

- FHWA LTPP Protocol P46,  *Resilient Modulus of Unbound Granular Base/Subbase Materials and Subgrade Soils*

-      FHWA-RD-96-176, *Resilient Modulus of  Unbound Materials Laboratory Startup and Quality Control Procedure*

- FHWA Video Tape Series
*Laboratory Resilient Modulus Testing:  Is This the Right Time?*
*Laboratory Resilient Modulus Testing: Startup and Quality Control Procedure*
*Laboratory Resilient Modulus Testing: Sample Preparation and Test Procedure*

**Notes:**
The startup procedure product is made up of three items.

The first is the test procedure, LTPP Protocol P46.  This protocol has been adopted by AASHTO (with modifications) as T292.
The protocol was developed over many years.  It was initially based on AASHTO T274 (which has since been abandoned by AASHTO). 
The protocol was modified from T274 to meet the demands and objectives of the LTPP program.  

The second component is the Startup procedure.  
This procedure (as explained later in this presentation) was developed under LTPP to ensure the accuracy of the resilient modulus testing program.  
The procedure has been published as FHWA-RD-96-176.
There are tentative plans to revise the procedure to reflect the lessons learned over the last few years and incorporate new procedures which greatly simplify the process.

The third component is the series of video tapes produced in conjunction with the Minnesota Department of Transportation.

Please note that this particular presentation is about the startup procedure and not the test protocol.  

## Resilient Modulus Lab Tests Videotape 1

- “Laboratory Resilient Modulus Testing:  Is This the Right Time?”
- 8 minutes
- Explains resilient modulus and what it is used for.
- Describes developments that have made the testing more consistent and easier to adopt.
- Target Audience: Administrators and engineers

**Notes:**
The first videotape is targeted at administrators and engineers.  It provides an overview of what resilient modulus is and what it is used for.

## Resilient Modulus Lab Tests Videotape 2

- “Laboratory Resilient Modulus Testing: Startup and Quality Control Procedure”
- 15 minutes
- Gives detailed definition of resilient modulus.
- Explains the procedure developed to ensure that a lab is set up properly to conduct the test procedure and to collect accurate test results.
- Target Audience: Laboratory managers and technicians

**Notes:**
The second videotape is for laboratory managers and technicians.  It explains the procedure developed to ensure that a lab is set up properly to conduct the test procedure and to collect accurate results. 

## Resilient Modulus Lab Tests Videotape 3

- “Laboratory Resilient Modulus Testing: Sample Preparation and Test Procedure”
- 13 minutes
- Describes each step in the resilient modulus test procedure, including how to prepare soil and aggregate samples.
- Target Audience: Lab managers and technicians

**Notes:**
The third videotape is also for lab managers and technicians.  It provides a step by step guide to the resilient modulus test procedure.

## PRESENTATION OBJECTIVES

- What is the Resilient Modulus (Mr) Testing and Startup Procedure Product Line
- Development of the Mr Startup Procedure
- How to Conduct the Mr Startup Procedure
- Who Should Use the Mr Testing and Startup Product Line and Why
- How to Get Information on the Mr Testing and Startup Product Line

***Why M******r  ******Testing and the ***
***Startup Procedures  Are Important***

**Notes:**
[NOTE TO SPEAKER: You may, if you wish, show video tape 1
“Laboratory Resilient Modulus Testing:  It This the Right Time”After the video, return to slide #20]
If you do not plan on using the video, continue with the presentation and notes]

LTPP developed this product line for many reasons.  Let’s begin with why resilient modulus itself is important.

## Resilient Modulus 101

- AASHTO Definition:
- “*A measure of the elastic property of soil recognizing certain non-linear characteristics*.”
- Resilient Modulus = Mr
- Resilient Modulus = elastic modulus (mod. of elasticity)
- Resilient Modulus = stress/strain
- Resilient Modulus = stiffness
- Resilient modulus ****** **strength

**Notes:**
This slide shows the AASHTO definition of resilient modulus.  It also shows other terms used to describe resilient modulus.  The terminology related to resilient modulus and elastic modulus can be confusing.  
For example, resilient modulus can be called elastic modulus although the test itself is not a purely elastic test (the sample  experiences some permanent deformation).  
However, for the purposes of pavement engineering elastic modulus can be referred to as resilient modulus.
The term Mr  (pronounced “M sub r,”) is a common abbreviation for resilient modulus.

It should also be noted that many get confused and refer to resilient modulus as the “strength” of the material.
The Resilient Modulus test is NOT a strength test.  
It is a test of  material elasticity or stiffness within the linear portion of the stress/strain curve (theoretically).  
This is a critical distinction as a strength test has an entirely different meaning in pavement engineering.

## Typical Elastic Modulus Values (ksi)

- PCC			3,000 – 6,000
- Asphalt Concrete	500 – 2,000
- Crushed Stone		20 – 40
- Silty Soils			5 – 20
- Clayey Soils		5 – 10

**Notes:**
This slide shows the elastic modulus values for various materials.  
The term elastic modulus is chosen carefully here as the modulus of PCC is derived from an elastic modulus test, not a resilient modulus test.  
Again, resilient modulus has a slightly different meaning than elastic modulus although theoretically they are the same thing.  

Please note values are in ksi, not psi.

For reference, here are some other elastic modulus values:

Rubber	1
Wood 	1,000 – 2,000
Aluminum	10,000
Diamond	170,000

## Usefulness of Resilient Modulus

- Used to define fundamental material properties
- Used in constitutive models
- Used to predict stress, strain, and displacement
- Used to develop performance models
- Used in current AASHTO pavement design guide
- Used in mechanistic design approach

**Notes:**
This slide shows several reasons why one would want to know resilient modulus (of soil and aggregate). 
Resilient modulus is a key material property in pavement engineering.  
Estimating its value correctly is critical and should be taken very seriously.

## The Resilient Modulus Startup Procedure

- Verifies the ability of equipment and personnel to perform resilient modulus testing
- Developed by LTPP to ensure consistent, repeatable and accurate results
- Implemented in FHWA, state DOTs, academia, and industry

**Notes:**
We need to be able to verify the ability of equipment and personnel to perform the resilient modulus test. 
The Resilient Modulus Startup Procedure was developed by LTPP to ensure consistent, repeatable and accurate results. 
It is already being used by state agencies and others, which shows that it is indeed a useful tool that has been accepted by peers in the industry.  

## Benefits Of Mr Startup Procedure 

- Procedure useful to anyone conducting resilient modulus testing
- Prepared for resilient modulus of soils but can be applied to asphalt
- Generic procedure useful to anyone performing testing using servo-hydraulic test systems (i.e. complex modulus, creep, etc.)

**Notes:**
This startup procedure is obviously useful to anyone conducting resilient modulus testing. The procedure, however can be applied to many other test procedures, not just resilient modulus or soils and aggregate.  It is an extremely powerful tool for verifying servo-hydraulic machinery.  

## PRESENTATION OBJECTIVES

- What is the Resilient Modulus (Mr) Testing and Startup Procedure Product Line
- Why Mr  Testing and the Startup Procedures are Important
- How to Conduct the Mr Startup Procedure
- Who Should Use the Mr Testing and Startup Product Line and Why
- How to Get Information on the Mr Testing and Startup Product Line

*** ******Development of the M******r  ******Startup Procedure***

**Notes:**
Some background on the development of the startup procedure may be useful.

## Testing and Protocol History

- 1987 - Strategic Highway Research Program (SHRP) adopts resilient modulus testing
- 1990 - Initial protocols developed
- 1991 - Resilient Modulus testing began
- 1992 - FHWA assumes leadership of LTPP
- Early 1993 - SHRP Resilient Modulus Testing Ends

**Notes:**
It should be noted that all initial resilient modulus testing was conducted under the SHRP program.  
FHWA was only involved in reviewing the data after the data had been submitted by the laboratories.

## Data Problems: 1993/1994 - SHRP data 

- Serious flaws found in the data
- Large amount of data deemed unusable
- Probable cause
- faulty electronics
- mechanical problems
- operator error

**Notes:**
FHWA LTPP review of the data uncovered serious problems with some of the data. 
The exact cause of the problems were never pinpointed because the contract had ended and the laboratory under question had modified the machine after testing had ended. 
Faulty electronics, mechanical problems, and operator error were probable causes.

## Causes of Data Problems

- Sample loading non-symmetrical
- Sample loaded too long
- Deformation occurs prior to loading *
- Deformation impulse shorter than load impulse *
- Deformation fluctuation
- Deformation “flat-line” or clipping phenomenon

**Notes:**
This slide presents a list of the problems found with the data.
The two most serious problems involved deformation occurring before loading and the deformation impulse being shorter than the load impulse.  

It is physically impossible for a sample to deform before the load is applied.  
It is also impossible for the sample to deform for a time period shorter than when the load is applied (Physics 101 says so!).  
These problems are very serious.  
They most likely indicate a problem with the machine electronics.  
You do not need a course on servo-hydraulic electronic systems to appreciate this. The detection of deformations that did not make sense was most likely due to a problem with the filter settings (or lack thereof). Filter setting problems can  lead to an  “attenuation” of the signal being read by the data acquisition system.
Attenuation simply means that the signal is made smaller than it is.  
This happens with the speakers in your stereo system.
The tweeters in your system filter out the low frequency sounds (bass) basically attenuating the low frequency signals so that they do not appear and thus you do not hear them.  

It is possible that the filters used in the resilient modulus testing equipment attenuated the LVDT signals.
Thus, if the sample was deflecting 100 inches (for example) you would only read 60 inches because the 100 inch signal would be attenuated to 60 inches.  

The main reason the startup procedure was developed was to ensure that these problems do not occur in future LTPP testing.  

## High Testing Variability and Low Confidence

- Poor precision and bias
- SHRP precision and bias testing yielded 100% variation between labs, 50% within lab
- Many practitioners have no confidence in test results
- Equipment standardization lacking

**Notes:**
There were other reasons behind the decision to develop the startup procedure. 
Historically there has been poor precision and bias in the conduct of this test.
The development of the startup procedure is aimed at reducing variability of testing within and between laboratory.

Experiments with two FHWA LTPP contract laboratories yielded 6-10% variability within the laboratories and 8–15% variability between labs.
These numbers are not based on a full precision and bias study but represent tests on 10 “identical” samples by both laboratories.  
To fully determine the precision and bias of this test procedure, a more rigorous investigation must be completed. 
However the results obtained are promising and within the acceptable range.

## The Mr Testing Challenge

- Significant modulus testing remained to be completed
- Need for equipment and operator verification procedure established

- Result
-  P46 test procedure revised to reflect
-    lessons learned
-  P46 startup procedure developed to address
-    equipment/operator issues

**Notes:**
In addition to the reasons mentioned previously, the startup procedure was needed because there was a significant amount of testing still to be done.

As such, the test protocol was revised. 
Lessons learned during the SHRP era were integrated in the development process.  
And the startup procedure was developed to address the equipment and electronics issues that we have discussed.  

A dry run of the procedure was performed at the Turner-Fairbanks Highway Research Center.  
There were a few bugs that were ironed out. 
The procedure was officially implemented in the FHWA LTPP Contract laboratories.

## The Startup Procedure Development Objectives

- Develop a simple, efficient and inexpensive methodology to verify equipment performance and accuracy of a laboratory
- Verify laboratory ability (personnel/equipment) to conduct  P46 Resilient Modulus Tests

**Notes:**
The objectives in developing the the startup procedure were straightforward as this slide shows.

IMPORTANT: Note that the startup procedure IS NOT a calibration procedure.  
It was developed to verify the calibration of selected components and test the performance of the entire system.
The goal is to detect GROSS problems with the equipment and procedures.  
Calibration of the individual system components should be conducted by qualified technicians and/or the equipment manufacturer.

## PRESENTATION OBJECTIVES

- What is the Resilient Modulus (Mr) Startup Procedure Product Line
- Why Mr  Testing and the Startup Procedure is Important
- Development of the Mr Startup Procedure
- Who Should Use the Mr Startup Procedure and Why
- How to Get Information on the Mr Startup Procedure

***How to Conduct the M******r****** Startup Procedure***

**Notes:**
[NOTE TO SPEAKER:  If you wish, you may show video #2 “Laboratory Resilient Modulus Testing:  Start-Up and Quality Control Procedure” at this point.
Following the video, return to slide # 44]
If do not plan on using the video, continue with the presentation and notes.]

We shall now turn to how to conduct the Mr Startup Procedure.

## Equipment

- Oscilloscope

- Function Generator

- Strain Indicator

- LVDT Modulator/Oscillator (optional)

- NIST Traceable Proving Rings

- Micrometer Calibrator

- NIST Traceable Pressure Gauge

**Notes:**

This slide lists the equipment needed to perform the startup procedure. 

It should be noted that the procedure was designed to make use of as much “off-the-shelf” equipment as possible.
The only custom piece used is the LVDT modulator/oscillator which is used to perform the electronics portion of the procedure.
Other off-the-shelf equipment can be used in place of the modulator/oscillator, if necessary, but it makes the test more difficult to perform.

## The 3-Phase Startup Process

*Verification of Electronic System*
- Verification of Mechanical System
- Verification of Laboratory Ability to Conduct P46 Resilient Modulus Test

**Notes:**
There are three primary phases to the startup procedure.  They are performed in the order shown here. 
Each phase is made up of several subtasks which we shall review in turn, beginning with verification of the electronic system.

## Electronic System VerificationElectrical Method (Method 1)

- Focuses on the signal path from the transducers to the digitized output data
- Input: an _electrical_ signal with known frequency and amplitude
- Output: acquired digitized data
- Compares input and output signals for a range in frequency

**Notes:**
There are 2 methods of verifying the electronics of startup portion of the procedure. 
Method 1 is the electrical method and is documented in detail in the startup procedure.

The procedure simply entails injecting a signal of known amplitude and frequency and measuring the output of the signal after it has gone through all of the system electronics.  The objective of the test is to make sure that the amplitude and frequency of the input and output remain constant, within a given acceptance criteria.

The procedure is described in detail in section III of FHWA-96-RD-176.  

Only an experienced electronics technician should perform this procedure.  
It is not for the faint of heart!!

## Electronic System VerificationMechanical Method (Method 2)

- Focuses on the signal path from the transducers to the digitized output data
- Input: a “reference” LVDT and the machine LVDT are exercised mechanically with known frequency and amplitude
- Output: acquired digitized data and visual reference to oscilloscope
- Compares input and output signals for a range in frequency
- Note: new procedure, not documented in FHWA-RD-96-176, simpler than Method 1

**Notes:**
The second method of verifying the electronic system is the mechanical method.
The LVDT modulator/oscillator is shown here performing method 2 (or the alternative method) of the electronic portion of the startup procedure.
It should be noted that this procedure is not part of the current documentation as it was developed in mid-1999.  
However, it is much simpler than the electrical method and reduces the risk of damage to the test equipment.

## Electronic System VerificationComponents Checked 

- Analog signal conditioning
- Digitized signal processing
- Transducers (load cells, LVDTs)
- Signal filters
- Various layers of data acquisition and control software

** **Acceptance Criteria
-  Matched input to output delays < .5 msec
-  Amplitude constant from 2 to 50 hz

**Notes:**
This slide presents a rundown on what the procedure does and presents the acceptance criteria.  

The photo shows the back panel of the FHWA MTS machine at the Turner-Fairbanks Highway Research Center.

This is where the signals are injected and outputs measured.

## The 3-Phase Startup Process

- Verification of Electronic System
- Verification of Mechanical System
- Verification of Laboratory Ability to Conduct P46 Resilient Modulus Test

**Notes:**
The second phase of the start-up procedure is to verify the mechanical system

## Mechanical System Verification

- Focuses on the performance capability of the laboratory equipment
- Uses NIST traceable calibrated proving rings and other measurement devices

**Notes:**
The mechanical verification phase focuses on the actual machine.  
All the valves, pistons, load cells, LVDTs, etc. are checked to make sure they perform in a manner suitable for P46 testing.  

## Mechanical System Verification Components

- LVDT Calibration
- Load Cell Zero
- Load Cell Calibration Certificates
- Load Cell Cal. Verification
- Dynamic Response
- Phase Angles
- Triaxial Pressure Chamber

**Notes:**
The mechanical system verification is made up of the sub-tasks shown here.  
We shall turn to each in turn, briefly review the verification done, and highlight acceptance criteria.