LTRC. Presented By. Khalil Hanifa, E.I. Geotechnical Research Engineer 10-3GT

Transcription

1 Presented By Khalil Hanifa, E.I. Geotechnical Research Engineer LTRC 10-3GT Design Values of Resilient Modulus for Stabilized and Non-Stabilized Base

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

3 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

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

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

6 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.

7 Methodology 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.

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

9 Methodology Test LADOTD Testing Procedure Atterberg Limits TR Sieve/Hydrometer Analysis TR Sieve Analysis (Aggregates) TR Moisture-Density Relationship (Standard Proctor) TR Method B (Soils) Moisture-Density Relationship (Modified Proctor) TR Method G (Aggregates) Classification of Soils TR

10 Methodology Cement Content for Stabilized Base Materials LADOTD often utilizes a cement stabilized base course design in accordance with standard testing procedure TR

11 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.

12 Methodology Tube Suction Test Procedure Samples Ready for Tube Suction Test Capacitance Probe Taking Readings

13 Methodology Repeated Load Triaxial (RLT) Resilient Modulus Tests Resilient modulus test were performed in accordance with AASHTO procedure T standard method.

14 Methodology Repeated Load Triaxial (RLT) Resilient Modulus Tests (Sample Preparation) Stabilized Base Materials Hammer and Mold Sample Compaction Compacted Sample Sample Being Tested

15 Methodology Repeated Load Triaxial (RLT) Resilient Modulus Tests (Sample Preparation) Unbound Base Materials Vibratory Compactor and Mold Sample Compaction Compacted Sample Sample Being Tested

16 Methodology Material % Cement (By Weight) Target 7-day curing 28-day curing A-2-4 A-4 A-6 Mexican Limestone Recycled PCC (Crushed) % to achieve 300 psi % to achieve 300 psi % to achieve 300 psi N/A N/A +2% 3 samples 3 samples Opt. 3 samples 3 samples -2% 3 samples 3 samples +2% 3 samples 3 samples Opt. 3 samples 3 samples -2% 3 samples 3 samples +2% 3 samples 3 samples Opt. 3 samples 3 samples -2% 3 samples 3 samples +2% 3 samples Opt. 3 samples -2% 3 samples +2% 3 samples Opt. 3 samples -2% 3 samples

17 Methodology Resilient Modulus Testing Sequences Sequence Number Confining Pressure (psi) Max. Axial Stress (psi) Cyclic Stress (psi) Constant Stress (psi) No. of Load Applications (Conditioning)

18 Methodology Review of Resilient Modulus Models

19 Methodology Regression Analysis Statistical analysis was conducted using SAS Institute Inc. software to evaluate the resilient modulus data and establish k 1, k 2, and k 3 values for each model being evaluated.

20 Discussion of Results Physical Properties of Materials Tested Material LL (%) PL (%) PI (%) γ dmax (pcf) ω opt (%) A * 10.4* A * 11.3* A * 15.9* Mexican Limestone Recycled PCC (Crushed) N/A N/A N/A 125.1** 10.1** N/A N/A N/A 118.6** 12.0**

21 Discussion of Results Physical Properties of Materials Tested

22 Discussion of Results Physical Properties of Materials Tested Standard Proctor Compaction Curves for Raw Soils Modified Proctor Compaction Curves for Aggregates

23 Discussion of Results Cement Content for Stabilized Base Materials Standard Proctor Compaction Curves for Cement Stabilized Soils 7-day Cement Curves for Cement Stabilized Materials

24 Maximum DV Value Discussion of Results Tube Suction Test Results A-2-4 Marginal Good A-4 A-6 Mexican Limestone Recycled PCC (Crushed) 2 0

25 Discussion of Results Resilient Modulus Tests Material % Cement (By Weight) A A-4 4 A-6 6 Mexican Limestone Recycled PCC (Crushed) N/A N/A Target Moisture Content (%) 7-day curing 28-day curing +2% samples 3 samples Opt samples 3 samples -2% samples 3 samples +2% samples 3 samples Opt samples 3 samples -2% samples 3 samples +2% samples 3 samples Opt samples 3 samples -2% samples 3 samples +2% samples Opt samples -2% samples +2% samples Opt samples -2% samples

26 Discussion of Results Resilient Modulus Tests Results Regression Analysis Results

27 Resilient Modulus Test Results σ 3 (psi) 3 5 σ d (psi) A-2-4 (Opt.) 7-day Curing Sample Number M r (ksi) AVG STD CV (%) σ 3 (psi) 3 5 σ d (psi) A-2-4 (Opt.) 28-day Curing Sample Number M r (ksi) AVG STD CV (%)

28 Resilient Modulus Test Results σ 3 (psi) 3 5 σ d (psi) A-2-4 (-2%) 7-day Curing Sample Number M r (ksi) AVG STD CV (%) σ 3 (psi) 3 5 σ d (psi) A-2-4 (-2%) 28-day Curing Sample Number M r (ksi) AVG STD CV (%)

29 Resilient Modulus Test Results σ 3 (psi) 3 5 σ d (psi) A-2-4 (+2%) 7-day Curing Sample Number M r (ksi) AVG STD CV (%) σ 3 (psi) 3 5 σ d (psi) A-2-4 (+2%) 28-day Curing Sample Number M r (ksi) AVG STD CV (%)

30 Regression Analysis Results

31 Conclusions 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

32 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

33 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

34 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

35 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. k 1, k 2, and k 3 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

36 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)

37 Review of District Lab Survey 4 Districts Replied, 5 Districts Did Not Reply Response District 02 (New Orleans) District 03 (Lafayette) District 61 (Baton Rouge) District 62 (Hammond) No Response District 04 (Bossier City/Shreveport) District 05 (Monroe) District 07 (Lake Charles) District 08 (Alexandria) District 58 (Chase)

38 Review of District Lab Survey 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

39 Review of District Lab Survey 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

40 Updated Testing Scope 1. Existing Materials Material Unconfined Compressive Strength Tests Resilient Modulus Tests +2% Opt. -2% +2% Opt. -2% A 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 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

41 Testing Plan 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)

42 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

43 Questions?