TABLE OF CONTENTS. 1) INTRODUCTION General Overview Background on the Project Research Objectives Project Challenges 1

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1 TECHNICAL NOTE TECH NOTE NO: 19 TITLE: Progress Report on Laboratory Soil Test Results AUTHORS: Erol Tutumluer and Marshall Thompson CONTACT: University of Illinois at Urbana-Champaign 125 Newmark Lab, MC-25 DATE/REV: 7/14/5 1

2 TABLE OF CONTENTS 1) INTRODUCTION General Overview Background on the Project Research Objectives Project Challenges 1 2) PROJECT TASKS Brief Overview of Tasks Drilling Program Tasks Performed at ATREL Grouping of Soils 5 3) LABORATORY TESTING AT ATREL Preparing the Soil Moisture - Density Test California Bearing Ratio (CBR) Test Unconfined Compressive Strength (UCS) Test Resilient Modulus Test 1 4) LABORATORY TEST RESULTS Moisture Density CBR Test Results Unconfined Compressive Strength (UCS) Test Results Resilient Modulus Test Results 22 5) SUMMARY OF RESULTS Moisture Density - CBR Tests Unconfined Compressive Strength Tests Resilient Modulus Tests 25 6) CONCLUSION 25

3 1. INTRODUCTION 1.1 General Overview The purpose of this research project is to provide testing and analysis to establish subgrade support and stabilization requirements for O Hare airport pavements, which will be constructed as part of the O Hare Modernization Program (OMP). The new 75-ft North Runway (9L-27R) paving is programmed as the first runway to be constructed starting in the spring of 26. The 9L-27R runway subgrade soils are primarily fill although there are some cut areas as indicated by the runway plans. A considerable quantity of excavated soil from the nearby Deep Pond, which was previously stockpiled will be used as fill material. Such issues as the adequate subgrade support requirements and the Stabilized Subgrade Zone have been recently dealt with to make design decisions and provide inputs to OMP for their evaluation and adoption. 1.2 Background on the Project This research project is an integral part of the development of the O Hare International Airport in Chicago, Illinois funded by the OMP through the Center of Excellence for Airport Technology (CEAT) established at the University of Illinois at Urbana- Champaign (UIUC). The objective of the OMP is to create a modern and efficient air traffic system based on parallel East-West runways. The $6.6 billion program includes construction of 35 miles of runways and taxiways, placement of 2.2 million cubic yards of Portland cement concrete (PCC), 29 million cubic yards of earthwork, 22 miles of storm sewers and underdrains, and 65 miles of duct banks and cabling. The CEAT at UIUC is the research partner with OMP. In the first year program, the CEAT has identified three technical areas, i.e., subgrade support and stabilization, raw materials and PCC mix designs for research. The research program has been intended to establish a partnership with the OMP engineers and provide them with improved and more costeffective alternatives. 1.3 Research Objectives The main objective of this research is to consider pavement design inputs for subgrade support like modulus of subgrade reaction, k, along with considering subgrade support and stabilization requirements with respect to need for lime modification of wet soils, subgrade stabilization, stabilization admixture(s) and stabilization depth. Another objective is to estimate subgrade support for various combinations of subgrade stabilization treatments and prepared subgrade conditions. 1.4 Project Challenges The main challenge in this project has been to ensure proper sampling of the North Runway (9L-27R) stockpiled soils and selecting and identifying representative soil samples for conducting tests like moisture-density-cbr (California Bearing Ratio), unconfined compressive strength, resilient modulus and permanent deformation. 1

4 2. PROJECT TASKS 2.1 Brief Overview of Tasks 1) The first task was to establish the Best Demonstrated Available Technology (BDAT) for subgrade soil evaluation and stabilization. Technical reports and publications related to Illinois DOT s subgrade stability manual, current synthesis of subgrade strength/stiffness evaluation techniques, working platform requirements for pavement construction, moisture limitations for lime stabilization, and admixture stabilization and lime treatment of subgrades were provided to OMP. 2) The second task was to evaluate the available data for the subgrade test sections constructed in the Fall of 23 and checking the necessity and usefulness of constructing additional subgrade treatment test sections at O Hare. The plate load tests conducted in August 24 on these test sections indicated that 12-in. quicklime and lime kiln dust (LKD) stabilizations worked satisfactorily. It was decided not to construct any new field test sections for this purpose. 3) Another task was to advise OMP on current and future test section monitoring and field test evaluation programs. For characterizing the treated subgrade, Dynamic Cone Penetrometer and Light-Weight Deflectometer tests were performed by OMP designated firms. 4) The available subgrade data for the North Runway had to be evaluated with emphasis on the stockpiled Deep Pond soils. Everest Engineering conducted preliminary soil sampling and testing on North Runway in October 24. It was recommended to conduct further soil drilling/sampling & testing by an OMP designated testing firm. The tests would consist of grain size distribution (including hydrometer), Atterberg limits (LL and PL for PI), moisture-density-cbr, PH value & calcareous content. 5) This task consisted of identifying representative soils and recommending an admixture stabilization program based on the data and information gathered in Task 4. To complete this task, testing would be conducted at the UIUC Advanced Transportation Research and Engineering Laboratory (ATREL) on both untreated & treated soils. The testing would consist of moisture-density-cbr tests, resilient modulus, unconfined compressive strength, and permanent deformation tests. Table1. Status of Various Tasks Task Status 1 On - Going 2 Completed 3 Completed 4 Completed 5 On - Going 2

5 2.2 Drilling Program For the soil samples, the drilling was done on the Runway 9L-27R from December 24 to February 25. This effort was undertaken by Everest Engineering Company, which was designated by OMP. The key features of the drilling program are given as follows: Auger borings, 17 boreholes, MT-1 to MT-17; 1 to 45 foot depths through both fill and cut areas; All reaching down to elevation 64 feet in the natural subgrade; Locations: 3 North of runway, 3 North edge of runway, 4 under runway, 2 South edge of runway, 2 between runway and taxiway, and 3 under taxiway; SPT testing and soil sampling conducted every at every 2.5 feet depth, Moisture content, LL, PI, grain size distributions including percent clay content; Shelby tube samples collected at each location at a depth of 638 to 642 feet; At least 1 bucket sampled for each major soil in each borehole; Two 5-gallon buckets (6-7 lbs./bucket) collected for each representative soil (composite sample) to test at the University of Illinois. 2.3 Tasks Performed at the University of Illinois Advanced Transportation Research and Engineering Laboratory (ATREL) The first task was to evaluate the data of the 62 buckets of soils received from Everest Engineering Company. The complete soil data of the 62 buckets are given in Table 2. Table 2. Data from 62 Buckets of Soils received from Everest Engineering Company Boring No. Location Bucket No. Depth Soil Description % Clay LL PI % Silt ph Carbonate Reaction MT 5 Under N edge of Taxiway 48 6'-1' Gray SILTY SAND 11.9 NP NP Weak MT 13 North of Runway 1 1'-3' Brown Sandy Silt 16 NP NP weak to strong MT 2 Under Taxiway 57 15'-18' Gray SILTY SAND 17.4 NP NP Weak MT 14 N edge of Runway 2 5'-1' Gray SILTY CLAY with Sand Strong MT 3 Under Taxiway 53 22'-26' Gray SANDY SILT 18.3 NP NP Weak MT 16 North of Runway 17 1'-5' Brown and Gray SANDY LEAN CLAY Weak to Strong MT 8 Under Runway 13 3'-6' Gray SANDY SILT CLAY Weak to Strong MT 4 Under S edge of Runway 43 1'-4' Gray LEAN CLAY with sand Strong MT 5 Under N edge of Runway 49 24'-28' Gray LEAN CLAY with sand Strong MT 3 Under Taxiway 54 29'-33' Gray SANDY LEAN CLAY Strong MT 12 North of Runway 9 3'-6' Brown and Gray SANDY LEAN CLAY Weak to Strong MT 13 North of Runway 2 6'-1' Gray SANDY LEAN CLAY Weak MT 3 Under Taxiway 52 6'-1' Gray SANDY LEAN CLAY Strong MT 3 Under Taxiway 51 2'-6' Gray LEAN CLAY with sand Strong MT 11 b/w Runway & taxiway 41 16'-2' Gray SANDY LEAN CLAY Weak to Strong MT 4 Under S edge of Runway 44 8'-12' Gray SANDY LEAN CLAY Strong MT 7 Under N edge of Runway 5 1'-5' Brown and Gray LEAN CLAY with Sand Weak to Strong MT 5 Under N edge of Taxiway 5 33'-36' Gray SANDY LEAN CLAY Weak 3

6 MT 17 Under Runway 22 1'-5' Brown and Gray LEAN CLAY with Sand Weak to Strong MT 11 b/w Runway & taxiway 42 26'-3' Gray LEAN CLAY with sand Strong MT 12 North of Runway 11 16'-2' Gray LEAN CLAY with Sand Weak MT 16 North of Runway 18 18'-23' Gray LEAN CLAY with sand Strong MT 9 Under S edge of Runway 28 1'-5' Gray LEAN CLAY with Sand Strong MT 12 North of Runway 1 8'-12' Gray LEAN CLAY with Sand Strong MT 4 Under S edge of Runway 45 24'-28' Gray LEAN CLAY with sand Strong MT 9 Under S edge of Runway 29 13'-18' Gray LEAN CLAY with Sand Strong MT 15 Under Runway 33 8'-12' Gray LEAN CLAY with Sand Strong MT 11 b/w Runway & taxiway 39 2'-6' Gray SANDY LEAN CLAY Strong MT 6 Under Runway 26 '-3' Black,Brown and Gray SANDY LEAN CLAY Weak MT 11 b/w Runway & taxiway 4 8'-12' Gray LEAN CLAY with sand Strong MT 5 Under N edge of Taxiway 47 1'-5' Gray LEAN CLAY with sand Strong MT 15 Under Runway 32 1'-5' Gray LEAN CLAY with Sand Strong MT 1 b/w Runway & taxiway 36 1'-5' Gray LEAN CLAY with Sand Strong MT 8 Under Runway 14 1'-15' Gray LEAN CLAY with sand Strong MT 13 North of Runway 3 16'2' Gray LEAN CLAY with sand Strong MT 1 b/w Runway & taxiway 37 15'-2' Brown and Gray SANDY LEAN CLAY Strong MT 9 Under S edge of Runway 3 28'-32' Gray LEAN CLAY with Sand Strong MT 7 Under N edge of Runway 6 11'-15' Gray LEAN CLAY with sand Strong MT 17 Under Runway 23 1'-13' Brown and Gray LEAN CLAY with Sand Strong MT 16 North of Runway 19 28'-33' Brown and Gray LEAN CLAY with Sand Weak MT 15 Under Runway 34 24'-28' Gray LEAN CLAY with Sand Strong MT 1 b/w Runway & taxiway 38 25'-3' Gray LEAN CLAY with Sand Strong MT 13 North of Runway 4 22'-27' Gray LEAN CLAY with sand Weak MT 4 Under S edge of Runway 46 31'-35' Gray LEAN CLAY with sand Strong MT 9 Under S edge of Runway 31 33'-37' Gray LEAN CLAY with Sand Strong MT 15 Under Runway 35 34'-38' Gray LEAN CLAY with Sand Strong MT 1 Under Taxiway 61 24'-28' Gray LEAN CLAY with sand Strong MT 1 Under Taxiway 59 1'-5' Gray LEAN CLAY with sand Strong MT 1 Under Taxiway 6 12'-16' Gray LEAN CLAY with sand Strong MT 17 Under Runway 25 3'-35' Brown and Gray LEAN CLAY with Sand Weak to Strong MT 1 Under Taxiway 62 3'-34' Gray LEAN CLAY with sand Strong MT 8 Under Runway 15 26'-29' Brown and Gray LEAN CLAY with Sand Weak to Strong MT 2 Under Taxiway 58 28'-32' Gray LEAN CLAY with sand Strong MT 17 Under Runway 24 18'-21' Brown and Gray LEAN CLAY with Sand Strong MT 8 Under Runway 16 3'-34' Brown and Gray LEAN CLAY with Sand Weak MT 2 Under Taxiway 56 8'-12' Gray LEAN CLAY with sand Strong MT 2 Under Taxiway 55 2'-6' Gray LEAN CLAY with sand Strong MT 12 North of Runway 12 3'-35' Brown and Gray LEAN CLAY with Sand Weak to Strong MT 7 Under N edge of Runway 7 26'-31' Brown and Gray LEAN CLAY with Sand Weak to Strong MT 6 Under Runway 27 6'-1' Brown and Gray LEAN CLAY with Sand Weak MT 14 N edge of Runway 21 2'-25' Gray LEAN CLAY with sand Strong MT 7 Under N edge of Runway 8 32'-35' Brown and Gray LEAN CLAY with Sand Strong 4

7 2.4 Grouping of Soils The next task was to identify representative soils from the data and group them to perform further tests. All of the soil samples were grouped according to their clay contents. The clay contents were then broken up into four general ranges. Aided by visual inspection, four buckets from each general clay content range were chosen to represent all of the samples falling in that particular range. Below is the list of the four representative groups, and the four buckets that were used to represent each group. Table 3. Grouping of Soils at ATREL Boring No. Bucket No. Depth Soil Description Clay (%) LL (%) PI (%) Silt (%) ph Weight (lb) GROUP 1 MT '-1' Gray SILTY CLAY with Sand Brown and Gray SANDY LEAN MT '-5' CLAY MT '-4' Gray LEAN CLAY with sand MT '-33' Gray SANDY LEAN CLAY GROUP 2 MT '-1' Gray SANDY LEAN CLAY MT '-6' Gray LEAN CLAY with sand MT '-12' Gray SANDY LEAN CLAY MT '-36' Gray SANDY LEAN CLAY GROUP 3 MT '-5' Gray LEAN CLAY with sand MT '-5' Gray LEAN CLAY with Sand MT '-5' Gray LEAN CLAY with Sand MT '-2' Gray LEAN CLAY with sand GROUP 4 MT '-21' MT '-34' MT '-35' MT '-1' Brown and Gray LEAN CLAY with Sand Brown and Gray LEAN CLAY with Sand Brown and Gray LEAN CLAY with Sand Brown and Gray LEAN CLAY with Sand

8 3. LABORATORY TESTING AT ATREL 3.1 Preparing the Soil Air Drying The first step in preparing a soil for testing was to air dry the soil. This was accomplished by spreading the soil over a large area. The soil was spread thin enough so that it could completely air dry in a few days. When the soils had very high clay contents, much more time was invested in spreading the sample out. This typically included breaking the sample into small sections, so that it could air dry in a reasonable time. The length of time each sample was left out to air dry depended on its moisture content. Some of the very moist samples took up to five days to dry. Figures 1 and 2 show air drying of a soil sample taken from a bucket. Figure 1. Air-Drying of Sample Figure 2. Air-Drying of Sample Pulverizing After drying the samples, they were pulverized and placed back in their representative buckets. This process involved placing the sample in a large mixer, and attaching a pulverizing wheel to the mixer. The sample was then left to run in the mixer for approximately 2 minutes (depended on how long it took to create a fine soil mixture). Figures 3 and 4 show the pulverizing process. Figure 3. Pulverizing of Soil Sample Figure 4. Pulverizing of Soil Sample 6

9 Mixing Once all four buckets in a group were pulverized, 5 kg of each bucket was placed in the mixer. While weighing out the 5kg, careful attention was paid to remove any rocks, extraneous material, or large solid hunks of the soil. The soils were then left in the mixer for approximately 15 minutes to make sure they were thoroughly mixed. Figures 5 and 6 show the mixing process of one group of soil. Figure 5. Mixing of Soil Samples Figure 6. Mixing of Soil Samples Oven Drying In order to make sure the samples were properly dried; the 2kg sample (5kg from each bucket) was placed in an oven at 6 C (14 C) for one day. 3.2 Moisture - Density Test (ASTM D698) Preliminary Steps The soil used to perform the moisture density tests was first prepared in the fashion mentioned in the previous section. After the soil was oven dried, it was removed from the oven and allowed to cool down to room temperature. The next step was to make sure the soil contained no large particles. This was achieved by pulverizing the soil by hand. A ceramic mallet and bowl were used to perform this process. Next, a certain weight of soil was measured out and mixed with the proper proportion of water in a small, automated mixing bowl until thoroughly mixed. For the samples with lime kiln dust (high calcium LKD used from Buffington, Indiana), the lime was also weighed out and added into the mixing bowl at this stage). Preparation and Testing of Specimens For moisture density testing, the 4 in. by 4.6 in. Proctor Standard compaction mold was used. The soil, natural or mixed with lime kiln dust (LKD), was placed into the mold in 3 even layers. Each layer was compacted with 25 blows using a 5.5-pound standard Proctor hammer, dropped from a height of 12 inches. To ensure proper bonding between each layer, the top portion of each layer was scarified before the next layer was added. Once the specimen was compacted, the mass of the soil and mold were measured. The mass of the mold was then subtracted to give the wet weight of the specimen. To obtain the wet density, the wet weight of the specimen was divided by the volume of the mold. The dry density was then computed by dividing the wet density by one plus the moisture content (the moisture content of the specimen was determined by averaging results from two moisture samples from the 7

10 mold). To determine the optimum moisture content (OMC), the dry density was plotted against the moisture content. Four points were used to create each moisture density curve. The peak point of the curve corresponded to the optimum moisture content. The maximum dry density could also be determined from this maximum point. A moisture density curve was created for each group of soil, and with in each group, an OMC was found for specimens with % and 5% lime kiln dust. 3.3 California Bearing Ratio (CBR) Test Preparation and Testing of Specimens The CBR test was performed on the same specimens used to obtain the density without soaking. The mold was inverted before being placed in the testing machine. The rate of deformation was.5 in. per minute, as specified in the AASHTO standards. Two digital displays of the displacement and load were used to record measurements as the test was being performed. A plot of the load versus deformation was obtained, and CBR at.1 in. deformation was reported (CBR at.2 in. deformation was also reported in case it was greater than the CBR at.1 in.). Moisture Content of Specimens To determine the moisture content for each specimen, a small portion of the soil used to make the specimen was placed overnight in a 1 C oven. Two moisture samples were used for each specimen to ensure accurate moisture contents were obtained. The samples were taken after the specimen was tested, one from the top of the specimen, and one from the bottom. The average of the two samples was reported as the moisture content for CBR and for the moisture density. Figure 7. CBR Test Machine 8

11 3.4 Unconfined Compressive Strength (UCS) Test Preparation A total of six specimens (3 natural soils and 3 soil-lime kiln dust) were prepared at the optimum moisture content for each group. The natural soil was prepared in the manner previously mentioned in the soil preparation section. The natural soil and lime were thoroughly mixed in the dry state until the proper amount of water was added. The soil was then cooled to room temperature before being used. After the proper proportions of natural soil, lime, and water were allowed to thoroughly mix, they were sealed in a container and allowed to mellow for a period of one hour before compaction. The natural soil specimens were created in a similar fashion except that no lime was added to them, and no mellowing period was used. Compaction of Specimens Each specimen was compacted in a 2 in. in diameter by 4 in. high mold. The cylindrical mold was filled in three equal layers, with each layer receiving 2 blows of a this time 4-lb hammer falling from a height of 12 inches. For this specimen size, the compaction effort applied was equivalent to that of the standard Proctor compaction (ASTM D698). Once the compaction was complete, the specimen was extracted from the mold, trimmed and weighed. A moisture sample was taken before and after the compaction was complete. The specimen was also weighed at this point. Curing of Soil-Lime Specimens After the specimens were compacted, they were sealed in a bag and placed in a 12 F oven for 48 hours. Before testing the specimens, they were removed from the curing bags and allowed to cool to room temperature. Testing of Specimens Each specimen was tested until failure at a constant rate of.5 inches per minute (see Figure 8). During the testing of each specimen, a load versus deformation plot was created. The ultimate load was recorded, and the average of the specimens was reported to find the unconfined compressive strength. A moisture sample from each specimen was also taken after the test was complete. Figure 8. Unconfined Compressive Strength Testing of An OMP Soil Sample 9

12 3.5 Resilient Modulus Test Resilient Modulus Tests were performed as per the University of Illinois procedure. The UTM-5P pneumatic testing system (see Figure 9) was used to apply repeated and static loads to soil specimens. Resilient modulus tests were conducted to establish the variation of resilient modulus with the applied deviator stress. Sample Preparation - Two of the three unconfined compression soil samples prepared were designed for resilient modulus testing first. Accordingly, these natural soil samples from each group were compacted at the optimum moisture contents without lime. Curing was done in the same way as for unconfined compression and for the same duration. After modulus testing, these samples, referred to herein as conditioned specimens, were also tested for unconfined compressive strength. Testing Procedure - In the University of Illinois resilient modulus soil test procedure, a haversine load pulse is used with load duration of.1 seconds and rest period of.9 seconds. No confining pressure is applied on the specimen. The unconfined conditions are applied for the sake of the weakest soil and the worst case loading conditions simulated in the laboratory. Also realistically, there are usually not much of horizontal confining pressures acting on top of pavement subgrades. The soil specimen is first conditioned by applying 2 load pulses at a stress level of 6 psi. Following this conditioning, the specimen is subjected to stress levels of 2, 4, 6, 8, 1, 12, 14, and 16 psi, respectively. Each stress level is applied 1 times and the resilient modulus is calculated based on the last 5 cycles. Figure 9 shows the resilient modulus equipment setup for testing the 2 in. in diameter by 4 in. high soil specimens. Figure 9. Resilient Modulus Testing of An OMP Soil Sample 1

13 4 LABORATORY TEST RESULTS 4.1 Moisture Density CBR Test Results Tables 4 and 5 present the moisture-density-cbr test results for all soil groups with and without lime. For each group, the results of the Proctor compaction and CBR test results are also given in detail at sample each moisture state. In addition, all compaction and CBR curves are individually graphed in Figures 1 through 17. Group No w (%) Table 4. Moisture-Density Results of All Soil Groups Dry Density (pcf) % Lime 5 % Lime OMC Max. Dry w Dry Density (%) Density (%) (pcf) (pcf) OMC (%) Max. Dry Density (pcf) Table 5. CBR Results of All Soil Groups % Lime 5 % Lime Group No. w (%) CBR w (%) CBR

14 OMC=12.1% OMC=13.8% % Lime 5% Lime Density (pcf) Moisture % Figure 1. Moisture-Density Relationship for Group 1 Soils Density (pcf) OMC = 14.1 % OMC = 16 % % Lime 5% Lime Moisture % Figure 11. Moisture- Density Relationship for Group 2 Soils 12

15 OMC=14.4 % % Lime 5% Lime Density (pcf) OMC=18.8 % Moisture Content % Figure 12. Moisture-Density Relationship for Group 3 Soils OMC= 18.8 % % Lime 5% Lime Density (pcf) OMC = 22.8 % Moisture % Figure 13. Moisture-Density Relationship for Group 4 Soils 13

16 CBR OMC=12.1% OMC=13.8% Moisture % % Lime 5% Lime Figure 14. Moisture-CBR Relationship for Group 1 Soils OMC = 16 % % Lime 5% Lime CBR OMC = 14.1% Moisture % Figure 15. Moisture-CBR Relationship for Group 2 Soils 14

17 6 5 % Lime 5% Lime 4 CBR 3 2 OMC=14.4 % OMC=18.8 % Moisture Content% Figure 16. Moisture-CBR Relationship for Group 3 Soils CBR OMC = 18.8 % Moisture % % Lime 5% Lime OMC= 22.8 % Figure 17. Moisture-CBR Relationship for Group 4 Soils 15

18 4.2 Unconfined Compressive Strength (UCS) Test Results Tables 6 and 7 present the unconfined compressive strength test results for with and without lime, respectively. For each group, the individual specimen results are also given in detail at each sample moisture state together with the final average unconfined compressive strength value for the group. Typically 5 % lime kiln dust was added for soil treatment to all 4 groups of soils. Only in the case of Group 4 soils with the highest clay contents, an additional 7 % lime treatment was also applied. However, not much improvement was reported over the 5 % treatment as indicated in Table 6. In general, a major increase in strength or soil condition improvement was achieved through lime treatment for all soil groups including the low clay content Group 1 soils. This improvement is clearly indicated in Table 8 with the lime reactivity values defined and presented as the difference between unconfined compressive strengths of the treated and natural soil specimens. Table 9 presents the unconfined compressive strength results for natural soil samples tested after the specimens were first subjected to resilient modulus testing. The results obtained after the additional conditioning with modulus testing indicate an increase in strength for low clay content Group 1 soils and somewhat of a decrease in strength for the rest of the soil groups. Nevertheless, these decreases from the strength values of the lime treated virgin, unconditioned specimens are not significant since they are still considerably higher than those of the natural soils. Figures 18 through 25 show typical unconfined compressive strength test results. The applied axial stresses are graphed with the measured axial strains to indicate a maximum at about 1 % strain level corresponding to the strength value of the specimen. Table 6. Unconfined Compressive Strength (UCS) Test Results with Lime Group No. Lime Content (%) OMC (%) Sample No. Moisture Content (%) Dry Density (pcf) UCS (psi) Avg. UCS (psi)

19 Table 7. Unconfined Compressive Strength (UCS) Test Results without Lime Group No. OMC (%) Water Content (%) Dry Density (pcf) UCS (psi) Group No. Table 8. Lime Reactivity Values UCS with Lime (Q u lime), psi UCS without Lime (Q u ), psi Lime Reactivity = (Q u lime - Q u ), psi Table 9. UCS Test Results on Natural Soils Obtained after Resilient Modulus Tests Group OMC No. (%) Sample Water Dry Density UCS (psi) No. Content (%) (pcf)

20 Axial Stress, psi Sample 1 Sample 2 Sample Axial Strain, % Figure 18. Unconfined Compressive Strength (UCS) of Group 1 Soils with 5% Lime 25 2 Sample 1 Sample 2 Sample 3 Axial Stress, psi Axial Strain, % Figure 19. Unconfined Compressive Strength (UCS) of Group 4 Soils with 5% Lime 18

21 Axial Stress, psi Sample1 Sample2 Sample Axial Strain, % Figure 2. Unconfined Compressive Strength (UCS) of Group 4 Soils with 7% Lime 12 1 Group 1 Group 2 Group 3 Group 4 Axial Stress, psi Axial Strain, % Figure 21. Unconfined Compressive Strengths (UCS) of all Soil Groups without Lime 19

22 Sample 1 Sample 2 Axial Stress, psi Axial Strain, % Figure 22. Unconfined Compressive Strength (UCS) of Group 1 Soils without Lime after Resilient Modulus Testing Sample 1 Sample 2 1 Axial Stress, psi Axial Strain, % Figure 23. Unconfined Compressive Strength (UCS) of Group 2 Soils without Lime after Resilient Modulus Testing 2

23 12 1 Sample 1 Sample 2 Axial Stress, psi Axial Strain, % Figure 24. Unconfined Compressive Strength (UCS) of Group 3 Soils without Lime after Resilient Modulus Testing Sample 1 Sample 2 Axial Stress, psi Axial Strain, % Figure 25. Unconfined Compressive Strength (UCS) of Group 4 Soils without Lime after Resilient Modulus Testing 21

24 4.3 Resilient Modulus Test Results The resilient modulus tests were conducted on the natural soil samples only. Figures 26 through 31 present the individual modulus responses graphed with the applied deviator stresses according to the stress sequence given previously in Section 3.5. Only one specimen was tested each for Group 1 and Group 2 soils, whereas, two specimens were tested for Groups 3 and 4. All the moduli decreased with the increasing applied deviator stresses, which is in accordance with the stress-softening behavior of fine-grained soils. Resilient modulus, ksi Deviator Stress, psi Figure 26. Resilient Modulus Test Results of Group 1 Soils Resilient modulus, ksi Deviator Stress, psi Figure 27. Resilient Modulus Test Results of Group 2 Soils 22

25 Resilient modulus, ksi Deviator Stress, psi Sample 1 Figure 28. Resilient Modulus Test Results of Sample 1 of Group 3 Soils Resilient modulus, ksi Deviator Stress, psi Sample 2 Figure 29. Resilient Modulus Test Results of Sample 2 of Group 3 Soils 23

26 Resilient modulus, ksi Sample Deviator Stress, psi Figure 3. Resilient Modulus Test Results of Sample 1 of Group 4 Soils Sample 2 Resilient modulus, ksi Deviator Stress, psi Figure 31. Resilient Modulus Test Results of Sample 2 of Group 4 Soils 24

27 5. SUMMARY OF RESULTS 5.1 Moisture - Density - CBR Tests There are a few key points to highlight from the graphs of the moisture density and CBR: From Figures 1 to 13 covering all four groups, the optimum moisture content was always lower for the soils without lime when compared to the same soils with 5% lime kiln dust (LKD) added. The maximum dry density was always higher for the natural soils without lime. The CBR curves, Figures 14 to 17, indicate that the treated soils with 5% lime gave always much higher CBR values than the natural soils with no lime. This was true at all moisture contents for all four groups. The unsoaked CBR values obtained from testing the compacted specimens tend to drop sharply after the optimum moisture contents for the soils without lime. In general, the 5% lime treatment was effective for increasing sufficiently the strength of the North Runway 9L-37R subgrade soils tested. 5.2 Unconfined Compressive Strength Tests Table 6 and Figures 18 to 25 clearly indicated that there is a large increase in unconfined compressive strengths when 5% lime is added. This can also be seen from the lime reactivity values given in Table 8. Lime reactivity is greater than 5 psi for all the groups except for Group 1. Group 1 soils have the lowest clay contents and showed less reactivity with lime. In the case of Group 4 soils with the highest clay contents, an additional 7 % lime treatment did not improve unconfined compressive strengths over the 5 % treatment as indicated in Table Resilient Modulus Tests From Figures 26 to 31, all the four groups exhibited stress-softening behavior, which is typical of fine-grained soils. Corresponding to a deviator stress of 6 psi, all groups of soils tested at the optimum moisture contents gave high modulus values, in the range of 15-2 ksi, which are somewhat higher than expected for these subgrade soils. Group 3 and 4 soils indicated almost similar average moduli of 18 ksi whereas Group 1 and Group 2 soils indicated 17 ksi and 15 ksi, respectively. 6. CONCLUSION From the results of all tests performed, the 5 % lime kiln dust treatment seems to be working quite well in increasing the soil strengths and, therefore, is suggested as the stabilization choice for the subgrade soils at the new North Runway 9L-27R of O Hare International Airport. 25