Engineered Water Repellency in Frost Heave MitigationMicheal Uduebor1, Emmanuel Adeyanju1, Mohammad Wasif Naqvi2, Md Fyaz Sadiq2

1 University of North Carolina at Charlotte, Charlotte, NC, USA, 2 Michigan State University, Michigan, MI, USA

Advisors: Dr. John Daniels, D.Eng., P.E., F.ASCE, Bora Cetin, Ph.D., M.ASCE

Introduction/Background

• Cold weather and frost action have a major effect on the design,construction, performance, and maintenance of roadways.

• The presence of Frost Susceptible Soils (FSS) coupled with freezingtemperatures and the availability of a water source provide suitableconditions for frost action (Heaving and thawing).

• Frost action causes changes in moisture content, stress, and strain leadingto substantial damage to road pavements (Figure 1a-c).

• National recurrent annual maintenance costs are estimated at over 2 billiondollars annually (FHWA, 1999). This excludes other economic impactsbecause of related vehicle damage, road closures, and weight restrictions.

• Remedial techniques utilized so far (Stripping and replacement, thermo-siphoning, soil stabilization or increasing pavement thickness) are generallycost prohibitive or unfeasible.

• Engineered Water Repellency (EWR) is an innovative approach thatimproves the properties of FSS by making it hydrophobic. This involves thetreatment of soil with organo-silanes(OS) to form a water repellent coating.

• This treatment is cost-effective and can be used in various applications tolimit the transport of water through these soils, therefore, the process offrost heaving can be mitigated.

Figure 1a-c: Road Damage due to Frost action (Heaving and Thawing)

Objectives

• As part of a larger research effort (Figure 2), thisstudy will focus on these objectives• To carry out treatment of Frost Susceptible

Soils (FSS) and determine the optimal dosageconcentrations of selected organo-silanepolymers.

• To determine the degree of hydrophobicityimparted to treated samples using the sessiledrop method (Contact Angle Tests, WaterDrop Penetration Time Test)

• To assess the performance of the treatedsamples using breakthrough and frost heavetests.

Figure 2: Research Project Task Flow

Study Areas/Materials• The soils were collected from Asheville (NC-AS) and

Boone (NC-BO) in North Carolina, PottawattamieCounty (IA-PC) in Iowa, Anchorage (AK-AC) in Alaska,and Hanover (NH-HS) in New Hampshire (Figure 3a).

• These areas have different climatic conditions and aresubjected to different magnitude of freezing index.

• All the index properties of soils were determined byfollowing proper ASTM methods (ASTM D854-14,ASTM D6913-17, ASTM D7928-21e1, ASTM D4318-17,ASTM D698-12, ASTM D5918-13e1) (Figure 3b).

• All soils met the criteria for frost susceptibility basedon the classification by the U.S. Army Corps ofEngineers (1965) with large amounts of silt and clay.

Figure 3a-c: US Map Showing the Soil Recovery Locations; Grain SizeDistribution Curve of Selected Samples; Soil Samples Recovered

Methodology

Organosilane Selection & Material Treatment

• While a number of products abound to impart hydrophobicproperties to materials, three Organosilane chemicals wereselected for this study (SIL-ACT ATS-100 (Advanced ChemicalTechnologies), DOWSIL IE6683 (Dow Chemicals), Terrasil(Zydex Industries)

• Soils were treated at varying ratios (OS to soil, batched byweight) and mixed with water at a ratio of 1:1 for watersoluble OS in a HDPE bottle on a laboratory tumbler for 24hours.

• The resulting mixture was placed in cans and separatesamples were either air dried or oven dried at 60oC.

• Treated samples should possess contact angles >90o

(hydrophobic). Contact angles >150o are considered super-hydrophobic.

Contact Angle Test Water Drop Penetration Time Test

• Three drops of deionized water (Figure 5a) were placedon the surface of 20g treated and untreated samples incans with a burette and the time taken for completepenetration of the droplets recorded (Figure 5b).

• The various time measurements where correlated intovarying degree of hydrophobicity by using repellencycategories.

Breakthrough Pressure Test Frost Heave Test

• A monolayer of treated soil sampleswas placed on a double sidedadhesive tape attached to a glass slideplaced on a goniometer (Figure 4a).

• Drops of deionized water was placedon the surface of the specimen andcontact angle measurements takenusing the attached digital microscopeand accompanying software (Figure4b-c).

• The frost heave testing of soil specimens was conducted as perASTM D5918. The soil specimens were compacted at MDD andthe setup placed into a chest freezer after saturation for 24 hours.

• A temperature gradient was created using top and bottom plates(Maximum at -12oC and 12oC respectively) and temperaturereadings obtained throughout the specimen (Figure 11b).

• Heave was monitored with a laser displacement transducer.• Two freeze thaw cycles were carried out for a duration of 120

hours continuously being fed from a Mariotte water supply.

• Treated and untreated samples compacted at maximum dry densitywere setup in a triaxial cell similar to the saturated hydraulicconductivity test (ASTM D5084) (Figure 6a)

• DI water was supplied at a rate of 2.286kPa/s using a FlowTrac II setupfrom Geocomp. The pressure response at the interface of the treatedsample and porous stone was logged using a pressure transducerattached to the inflow valve.

• The breakthrough pressure is indicated by a sudden rise in slope of thepressure-time series plot due to the resistance developed at theinterface

Figure 4a-c: Goniometer Setup; Water Droplet on Soil Surface; Droplet Imaging for Contact Angle

Measurements

Figure 6a-c: Breakthrough Pressure Test Setup; Close up on FlowTrac II and Test Cell; Real-time Graph Plot on Computer Screen.

Figure 5a-b: Close up of water droplets on treated soil surface; Arrangement of test setup

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• Frost Heave Tests• Breakthrough Pressure Test Results

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Figure 8: Contact Angle of Treated Samples (a) ATS-100; (b) IE668; (c) Terrasil

Figure 9: Penetration Test Times of Treated Samples (a) ATS-100; (b) IE668; (c) Terrasil

Figure 10a-b: Typical Breakthrough Pressure Plot; Comparison between Breakthrough Pressure of Treated

and Untreated Samples

Figure 11a-d (L-R): Frost Heave Measurements for Selected Soils; Temperature Profile & Water Intake Measurements During Frost Heave Testing;

Bottom: Comparison of Frost Heave Results of Untreated and Treated Samples

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Figure 7a-c: Schematic Diagram showing Frost Heave Test Setup; Frost Heave Setup in Chest Freezer

• Contact Angle Test Results

Discussion/Conclusions

REFERENCESFHWA. A Quarter Century of Geotechnical Research, Chapter 4: Soil and Rock Behavior. McLean VA, USA 1999ACKNOWLEDGEMENTSThis research was sponsored by the National Science Foundation (Award #1928813) with counterpart Funding from the Iowa Highway Research Board.North Carolina Soil Sampling:Lance Byrd, P.E., Assistant District Engineer, N. Wilkesboro District OfficeJeff Winkler, Project Engineer R-2915C (U.S. 221)Jim Holloway, Head InspectorRESEARCH PROJECT WEBSITEhttps://coefs.uncc.edu/jodaniel/engineered-water-repellency-for-frost-susceptibility/

• All organo-silane products imparted hydrophobicity (contact angle > 90o) to the soil samples atratio of 1:10 ( OS:Soil, batched by weight). The degree of hydrophobicity varied with decreasein concentration. Soils tested with Terrasil where hydrophobic even at small concentrations(1:1000) (Figure 8a-c).

• Results from WDPT correlated with those from the contact angle testing (Figure 9a-c). Treatedsamples with ATS-100 and Terrasil became extremely water repellent.

• Breakthrough Pressure required was higher in treated samples. It will take a higher pressurehead/suction to transport water through the engineered barrier (Figure 10b). This is

• The amount of frost heaving in treated samples was reduced, indicative of a mitigation of frostaction within the soils. Parametric studies still being carried out will identify the optimalconcentrations for each of the soil samples.

• Engineered Water Repellency will be a cost-effective method for mitigation of frost heave. Thisinnovative solution can also be usefulness in stabilizing expansive soils that experienceswelling and shrinkage as well as in other applications requiring containment.

• Further studies on the relative Influence of matric and osmotic suction In the transport ofmoisture aiding frost action as well as numerical modelling is being carried out.