Presented By Khalil Hanifa, E.I. Values of... · LTRC Design Values of Resilient Modulus for...

LTRC

Design Values of Resilient Modulus for Stabilized and Non-Stabilized Base

Presented By Khalil Hanifa, E.I. Geotechnical Research Engineer

10-3GT

Overview

o Background o Implementation Statement o Objective o Scope o Methodology o Discussion of Results (Preliminary) o Conclusions/Recommendations (Preliminary) o Key Questions from the PRC o Updated Testing Scope o Questions and Comments

Background

Co-PI’s: Gavin Gautreau, P.E. Sr. Geotechnical Research Engineer

Murad Abu-Farsakh, Ph.D., P.E. Associate Professor-Research, GERL Manager

Manager: Zhongjie “Doc” Zhang, Ph.D., P.E.

Pavement & Geotechnical Administrator

Implementation Statement

• This research is expected to establish resilient modulus design values for stabilized and non-stabilized base course materials which can be used as Level 2 input in AASHTOWare® Pavement ME Design™ (formally DARWin-ME)

Objective

To determine resilient modulus design values for typical base course materials, as allowed by LADOTD specifications.

Scope

Three stabilized soil types (classified as A-2-4, A-4, and A-6, according to the AASHTO soil classification) were evaluated as bound base materials. Three aggregates types (Mexican Limestone and Recycled PCC (crushed)) were evaluated as unbound base materials.

A laboratory testing program consisting of physical properties tests, tube suction tests, and repeated loading triaxial (RLT) resilient modulus tests were performed on the bound and unbound base materials.

Methodology

Physical properties tests were performed in accordance with LADOTD standard testing procedures to provide characterization and classification information for the tested base materials.

Methodology

Methodology

Test LADOTD Testing Procedure

Atterberg Limits TR 428-67

Sieve/Hydrometer Analysis TR 407-99

Sieve Analysis (Aggregates) TR 113-11

Moisture-Density Relationship

(Standard Proctor)

TR 418-98 Method B (Soils)

Moisture-Density Relationship

(Modified Proctor)

TR-418-98 Method G

(Aggregates)

Classification of Soils TR 423-99

• Cement Content for Stabilized Base Materials LADOTD often utilizes a cement stabilized base course

design in accordance with standard testing procedure TR 432-02.

Methodology

• Tube Suction Tests The tube suction test is a procedure to approximate free

moisture content in soils through capillary action by measuring its dielectric constant. The measured dielectric constant of a given soil specimen gives an indication of it’s moisture susceptibility.

Methodology

• Tube Suction Test Procedure

Methodology

Samples Ready for

Tube Suction Test

Capacitance Probe Taking Readings

• Repeated Load Triaxial (RLT) Resilient Modulus Tests

Resilient modulus test were performed in accordance with AASHTO procedure T 307-99 standard method.

Methodology

• Repeated Load Triaxial (RLT) Resilient Modulus Tests (Sample Preparation)—Stabilized Base Materials

Methodology

Hammer and

Mold

Sample

Compaction

Compacted

Sample

Sample Being

Tested

• Repeated Load Triaxial (RLT) Resilient Modulus Tests (Sample Preparation)—Unbound Base Materials

Methodology

Vibratory

Compactor and

Mold

Sample

Compaction

Compacted

Sample

Sample Being

Tested

Methodology

Material % Cement (By

Weight) Target

7-day

curing

28-day

curing

A-2-4 % to achieve

300 psi

+2% 3 samples 3 samples

Opt. 3 samples 3 samples

-2% 3 samples 3 samples

A-4 % to achieve

300 psi




A-6 % to achieve

300 psi




Mexican

Limestone N/A

+2% 3 samples

Opt. 3 samples

-2% 3 samples

Recycled PCC

(Crushed) N/A

+2% 3 samples

Opt. 3 samples

-2% 3 samples

• Resilient Modulus Testing Sequences

Methodology

Sequence

Number Confining

Pressure (psi) Max. Axial

Stress (psi) Cyclic Stress

(psi) Constant

Stress (psi) No. of Load

Applications

(Conditioning) 15 15 13.5 1.5 1000

1 3 3 2.7 0.3 100

2 3 6 5.4 0.6 100

3 3 9 8.1 0.9 100

4 5 5 4.5 0.5 100

5 5 10 9.0 1.0 100

6 5 15 13.5 1.5 100

7 10 10 9.0 1.0 100

8 10 20 18.0 2.0 100

9 10 30 27.0 3.0 100

10 15 10 9.0 1.0 100

11 15 15 13.5 1.5 100

12 15 30 27.0 3.0 100

13 20 15 13.5 1.5 100

14 20 20 18.0 2.0 100

15 20 40 36.0 4.0 100

• Review of Resilient Modulus Models

Methodology

• Regression Analysis Statistical analysis was conducted using SAS Institute Inc.

software to evaluate the resilient modulus data and establish k1, k2, and k3 values for each model being evaluated.

Methodology

• Physical Properties of Materials Tested

Discussion of Results

Material LL (%) PL (%) PI (%) γdmax

(pcf)

ωopt

(%)

A-2-4 20 12 8 123.0* 10.4*

A-4 23 14 9 121.2* 11.3*

A-6 32 20 12 107.2* 15.9*

Mexican

Limestone N/A N/A N/A 125.1** 10.1**

Recycled PCC

(Crushed) N/A N/A N/A 118.6** 12.0**



Standard Proctor Compaction

Curves for Raw Soils

Modified Proctor Compaction

Curves for Aggregates

• Cement Content for Stabilized Base Materials


Standard Proctor Compaction

Curves for Cement Stabilized

Soils

7-day Cement Curves for

Cement Stabilized Materials

• Tube Suction Test Results


A-2-4

A-4 A-6 Mexican Limestone

Recycled PCC (Crushed)

0

2

4

6

8

10

12

Max

imu

m D

V V

alu

e

Marginal

Good

• Resilient Modulus Tests


Material % Cement (By

Weight) Target

Moisture

Content (%) 7-day curing 28-day curing

A-2-4 4

+2% 12.4 3 samples 3 samples

Opt. 10.4 3 samples 3 samples

-2% 8.4 3 samples 3 samples

A-4 4




A-6 6




Mexican

Limestone N/A

+2% 12.1 3 samples

Opt. 10.1 3 samples

-2% 8.1 3 samples

Recycled PCC

(Crushed) N/A

+2% 14.0 3 samples

Opt. 12.0 3 samples

-2% 10.0 3 samples

• Resilient Modulus Tests Results

• Regression Analysis Results


Resilient Modulus Test Results

1 2 3

AVG STD CV (%)

2.8 30.1 32.4 28.7 30.4 1.87 6.15

5.8 33.4 34.1 30.3 32.6 2.02 6.20

8.3 38.4 36.1 42.0 38.8 2.97 7.66

4.6 62.4 64.7 52.3 59.8 6.60 11.03

9.2 62.9 68.2 55.0 62.0 6.64 10.71

13.8 69.5 70.1 60.1 66.6 5.61 8.43

σd (psi)σ3 (psi)

Sample Number

Mr (ksi)

A-2-4 (Opt.) 7-day Curing

3

5

1 2 3

AVG STD CV (%)

2.8 70.6 79.4 68.1 72.7 5.94 8.16

5.8 67.5 78.6 65.2 70.4 7.17 10.17

8.3 62.5 72.5 63.4 66.1 5.53 8.36

4.6 118.9 119.0 115.1 117.7 2.22 1.89

9.2 105.6 114.0 107.6 109.1 4.39 4.02

13.8 93.3 110.9 102.8 102.3 8.81 8.61

A-2-4 (Opt.) 28-day Curing

Sample Number

σ3 (psi) σd (psi)

5

Mr (ksi)

3


1 2 3

AVG STD CV (%)

2.8 32.9 32.5 26.3 30.6 3.70 12.11

5.8 30.0 29.2 26.1 28.4 2.06 7.24

8.3 28.7 28.0 25.4 27.4 1.74 6.35

4.6 64.2 56.5 53.4 58.0 5.56 9.58

9.2 61.1 57.4 56.1 58.2 2.59 4.46

13.8 60.2 61.5 62.4 61.4 1.11 1.80

3

5

A-2-4 (-2%) 7-day Curing

Sample Number

σ3 (psi) σd (psi)Mr (ksi)

1 2 3

AVG STD CV (%)

2.8 65.3 69.0 63.1 65.8 2.98 4.53

5.8 60.2 62.8 58.2 60.4 2.31 3.82

8.3 57.9 53.4 56.1 55.8 2.26 4.06

4.6 142.3 130.2 116.3 129.6 13.01 10.04

9.2 129.4 120.9 113.3 121.2 8.05 6.65

13.8 121.5 118.0 111.1 116.9 5.29 4.53

5

Sample Number


3

A-2-4 (-2%) 28-day Curing


1 2 3

AVG STD CV (%)

2.8 25.8 21.0 20.6 22.5 2.89 12.88

5.8 28.2 29.3 26.2 27.9 1.57 5.63

8.3 31.0 38.4 32.0 33.8 4.01 11.88

4.6 51.7 65.5 38.4 51.9 13.55 26.13

9.2 43.6 62.6 44.9 50.4 10.61 21.07

13.8 50.1 61.8 52.0 54.6 6.28 11.49

3

5

A-2-4 (+2%) 7-day Curing

Sample Number


1 2 3

AVG STD CV (%)

2.8 52.4 51.9 50.1 51.5 1.21 2.35

5.8 50.8 47.4 45.1 47.8 2.87 6.00

8.3 47.5 46.9 44.3 46.2 1.70 3.68

4.6 98.8 96.7 86.2 93.9 6.75 7.19

9.2 98.5 92.3 80.9 90.6 8.93 9.86

13.8 94.0 89.0 77.0 86.7 8.74 10.08

5

Sample Number


3

A-2-4 (+2%) 28-day Curing

Regression Analysis Results

• Resilient modulus is not a constant value but varies with stress conditions

• For stabilized materials at 7-day curing, moisture content has an impact on resilient modulus

• For stabilized materials, increasing the curing period from 7-day to 28-day caused a significant increase in resilient modulus. Also the impact of moisture content on resilient modulus is not as critical at 28-day curing as compared to 7-day curing

• For aggregate materials, moisture content has an impact on resilient modulus

Conclusions

• The three models evaluated to establish materials coefficients all performed well in predicting resilient modulus

• The data developed from all three models can be utilized to generate Level 2 inputs for base course resilient modulus in AASHTOWare® Pavement ME Design™

Conclusions

Recommendations

• The following initiatives are recommended in order to facilitate the implementation of this study

1. Make Model 1 (NCHRP Model), Model 2 (UKTC Model), and Model 3 (Uzan Model) for estimating the resilient modulus of bound and unbound base materials readily available for use by the design personnel of LADOTD

2. Implement the results of this study into the current design procedure

Key Questions from the PRC

1. Resilient Modulus Values Appear To Be Low

Based on Literature Review, Resilient Modulus Values Appear To Be Too Low

2. Is There A Relationship Between Unconfined Compressive Strength and Modulus?

As Strength Increases Modulus Generally Increases

3. Are There Models That Correlate Unconfined Compressive Strength to Modulus?

Yes and the Models That Relate to the Testing Scope of 10-3GT Will Be Investigated

Questions/Comments from PRC

4. Is There A Minimum Percentage of Cement Required In The Field?

Yes, 6% (By Volume) Due to Variation in Spread Rate and to Assure Uniform Mixing

5. k1, k2, and k3 Parameters Can Not Be Used in Pavement ME Design™

These Models Can Not Be Used For Chemically Stabilized Materials in Pavement ME Design™

6. Recommend A Range of Typical Design Values of Resilient Modulus for Each Tested Material

A Range of Typical Values Will Be Provided

Key Questions from the PRC

7. Cement Treated Base (150 psi) and BCS Materials Were Not Included In This Study

These Materials and Other Materials Recommended by

the PRC Will Be Included in the Updated Testing Scope

8. What base courses are typically constructed for Louisiana roadways?

Discussed in the Summary of the Survey Provided to the District Lab Engineers (Upcoming Slides)

Review of District Lab Survey

• 4 Districts Replied, 5 Districts Did Not Reply

Response No Response

District 02 (New Orleans) District 04 (Bossier City/Shreveport)

District 03 (Lafayette) District 05 (Monroe)

District 61 (Baton Rouge) District 07 (Lake Charles)

District 62 (Hammond) District 08 (Alexandria)

District 58 (Chase)


1. Base Courses Constructed in Districts a. 302: Cement Stabilized Base Course (300 psi) b. 303: In-Place Cement Stabilized Base Course (300 psi) c. 308: In-Place Cement Treated Base Course (150 psi) d. Other: Stone, RPCC, BCS and Asphalt Base Course 2. Is There a Minimum Percentage of Cement Required in

the Field? 6% (By Volume) Due To: a. Variation in Spread Rate b. To Assure Uniform Mixing


3. How Much Does Variation in Moisture Content (the ±2% of Optimum Range Allowed During Construction) Affect Strength in the Field?

a. The Lab Engineers informed me that they have no way of knowing this

b. I suggested that we investigate it since it is related to the scope of project 10-3GT

1. Existing Materials

• Note: A-2-4, A-4 and A-6 will be treated with

6%, 6% and 8% cement (by weight) respectively, an

Increase of 2% from previous testing

Updated Testing Scope

Material

Unconfined Compressive Strength Tests

Resilient Modulus Tests

+2% Opt. -2% +2% Opt. -2%

A-2-4 3 samples 3 samples 3 samples 3 samples 3 samples 3 samples

A-4 3 samples 3 samples 3 samples 3 samples 3 samples 3 samples

A-6 3 samples 3 samples 3 samples 3 samples 3 samples 3 samples

2. New Materials

a. Cement Stabilized Base Course (300 psi design strength)

b. In-Place (Recycled) Cement Stabilized Base Course (300 psi design strength)

c. In-Place (Recycled) Cement Treated Base Course (150 psi design strength)

d. Recycled Soil Cement (300 psi design strength)

e. Composite Base Course (4” Stone/8” Soil Cement)

• Testing Scope: 1. Gradation/Hydrometer Analysis

2. Atterberg Limits

3. Moisture-Density Relationship

4. Unconfined Compressive Strength Tests (7-day)

5. Resilient Modulus Tests (7-day and 28-day)

Testing Plan

3. In-House Literature Review

a. Kentucky Limestone

b. Mexican Limestone

c. BCS d. Asphalt Base Course

An in-house literature review will be conducted on these materials to gather information as it relates to the testing scope of 10-3GT

Testing Plan

Questions?

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