The Deleterious Chemical Effects of Concentrated Deicing Solutions on Portland Cement Concrete

The Deleterious Chemical The Deleterious Chemical Effects of Concentrated Effects of Concentrated

Deicing Solutions on Deicing Solutions on Portland Cement ConcretePortland Cement Concrete

Larry SutterLarry Sutter

Professor and DirectorProfessor and DirectorMichigan Tech Transportation InstituteMichigan Tech Transportation Institute

DirectorDirectorUniversity Transportation Center for Materials in University Transportation Center for Materials in

Sustainable Transportation InfrastructureSustainable Transportation Infrastructure

Michigan Tech and the U.P.Michigan Tech and the U.P.►► Largest undergraduate Civil and Environmental Largest undergraduate Civil and Environmental

Engineering program in MichiganEngineering program in Michigan

650 undergraduate students and 100 graduate students650 undergraduate students and 100 graduate students

►► StateState--ofof--thethe--art concrete laboratory facilitiesart concrete laboratory facilities

15,000 ft15,000 ft22 for concrete production and testingfor concrete production and testing

WorldWorld--class materials characterization facilitiesclass materials characterization facilities

►► Located in the U.P. 200 miles from the nearest Located in the U.P. 200 miles from the nearest Interstate and 100 miles from the nearest Interstate and 100 miles from the nearest Menards, Lowes, or Home Depot!Menards, Lowes, or Home Depot!

The Keweenaw Peninsula Is Also The Keweenaw Peninsula Is Also Home To Some Good Performing Home To Some Good Performing

Concrete PavementsConcrete Pavements

►►Oldest concrete pavement in MichiganOldest concrete pavement in MichiganBlome Granitoid pavement constructed in Blome Granitoid pavement constructed in Calumet in 1906Calumet in 1906

►►Original sections of US 41Original sections of US 41Paved in the 1930Paved in the 1930’’ss

►►Good performing sections of US 41 still Good performing sections of US 41 still carrying heavy trafficcarrying heavy traffic

Paved in 1959Paved in 1959

““The WorldThe World’’s Oldest Twos Oldest Two--Lift Pavement?Lift Pavement?””►► Granitoid pavementGranitoid pavement

►► Placed in two layersPlaced in two layers

►► A relatively porous 5A relatively porous 5¼”¼” thick thick layer of concrete with abundant layer of concrete with abundant gaps and air voidsgaps and air voids

►► Topped by an extremely dense Topped by an extremely dense 11¾”¾” thick layer of mortarthick layer of mortar

►► Tailings from local copper mines, Tailings from local copper mines, primarily basalt, were used as primarily basalt, were used as aggregateaggregate

►► Alpha brand portland cement Alpha brand portland cement was usedwas used

►► After placement, a machine After placement, a machine which traversed on rails was which traversed on rails was used to stamp a brickused to stamp a brick--like like pattern into the surface of the pattern into the surface of the pavementpavement

The Keweenaw Peninsula Is Also The Keweenaw Peninsula Is Also Home To Some Good Performing Home To Some Good Performing

Concrete PavementsConcrete Pavements

►►Oldest concrete pavement in MichiganOldest concrete pavement in MichiganBlome Granitoid pavement constructed in Blome Granitoid pavement constructed in Calumet in 1906Calumet in 1906

►►Original sections of US 41Original sections of US 41Paved in the 1930Paved in the 1930’’ss

►►Good performing sections of US 41 still Good performing sections of US 41 still carrying heavy trafficcarrying heavy traffic

Paved in 1959Paved in 1959

BackgroundBackground

►► Concrete pavements are inherently durable, Concrete pavements are inherently durable, having a history of exceptional longhaving a history of exceptional long--term term performanceperformance

►► In some instances, pavement service life has been In some instances, pavement service life has been adversely affected by the concreteadversely affected by the concrete’’s inability to s inability to maintain its integrity in the environment in which maintain its integrity in the environment in which it was placedit was placed

►► These distress manifestations are categorized as These distress manifestations are categorized as materialsmaterials--related distress (MRD)related distress (MRD)

What is MaterialsWhat is Materials--Related Related Distress?Distress?

►►MRD is commonly associated with the MRD is commonly associated with the ““durabilitydurability”” of the concreteof the concrete

►►Durability is not an intrinsic material Durability is not an intrinsic material propertyproperty

““DurabilityDurability”” cannot be measuredcannot be measured

Concrete that is durable in one application may Concrete that is durable in one application may rapidly deteriorate if placed in anotherrapidly deteriorate if placed in another

►►Deicing chemicals can be an important part Deicing chemicals can be an important part of the concreteof the concrete’’s environments environment

Other Considerations for MRDOther Considerations for MRD

►►Strength does not equal durabilityStrength does not equal durability

►►The concrete constituents, proportions, and The concrete constituents, proportions, and construction all influence MRDconstruction all influence MRD

►►Water is needed for deleterious expansion Water is needed for deleterious expansion to occurto occur

►►Severe environments (e.g. high sulfate soils, Severe environments (e.g. high sulfate soils, freezing and thawing, deicer exposure, etc.) freezing and thawing, deicer exposure, etc.) are major contributorsare major contributors

Deicer BasicsDeicer Basics►►Highway agencies objective Highway agencies objective -- keep roads safe keep roads safe

& passable year round& passable year round►►Always looking for easier, safe, cost effective Always looking for easier, safe, cost effective

means for highway deicing/antimeans for highway deicing/anti--icingicing►►Brines have become the main tool for winter Brines have become the main tool for winter

maintenancemaintenance

Sodium Chloride (NaCl)Sodium Chloride (NaCl)Magnesium Chloride (MgClMagnesium Chloride (MgCl22))Calcium Chloride (CaClCalcium Chloride (CaCl22))Calcium Magnesium Acetate (CMA)Calcium Magnesium Acetate (CMA)

How do salt brines work?How do salt brines work?

►►Freezing point depressionFreezing point depression

►►Some substances when combined freeze at a Some substances when combined freeze at a temperature temperature lowerlower than either ingredientthan either ingredient

Eutectic mixturesEutectic mixtures

Solder (combination of lead and tin)Solder (combination of lead and tin)

Auto anti freeze (ethylene glycol and water)Auto anti freeze (ethylene glycol and water)

►►Salts and water form a Salts and water form a ““binary eutecticbinary eutectic””

►►Graphically represented with a Graphically represented with a ““phase diagramphase diagram””



X axis is the amount of salt dissolved in water. O% is pure water and 100% is pure salt.


Y axis is the temperature the solution is exposed to.



Brine Solution (Liquid)


Eutectic Point


Eutectic PointConcentration that produces a brine with the lowest possible freezing point


Brine + Ice (Slush)


Ice + Solid Salt (Solid)


Brine + Solid Salt


Eutectic PointConcentration that produces a brine with the lowest possible freezing point






Types of Common Pavement MRDTypes of Common Pavement MRD►►Physical mechanismsPhysical mechanisms

FreezeFreeze--thaw deterioration of hardened cement pastethaw deterioration of hardened cement paste

Deicer scaling/deteriorationDeicer scaling/deterioration

FreezeFreeze--thaw deterioration of aggregatethaw deterioration of aggregate

►►Chemical mechanismsChemical mechanismsAlkaliAlkali––aggregate reactivityaggregate reactivity

Sulfate attackSulfate attack

Corrosion of embedded steelCorrosion of embedded steel

Chemical Deicer AttackChemical Deicer Attack

Types of Common Pavement MRDTypes of Common Pavement MRD►►Physical mechanismsPhysical mechanisms

FreezeFreeze--thaw deterioration of hardened cement pastethaw deterioration of hardened cement paste

Deicer scaling/deteriorationDeicer scaling/deterioration

FreezeFreeze--thaw deterioration of aggregatethaw deterioration of aggregate

►►Chemical mechanismsChemical mechanismsAlkaliAlkali––aggregate reactivityaggregate reactivity

Sulfate attackSulfate attack

Corrosion of embedded steelCorrosion of embedded steel

Chemical Deicer AttackChemical Deicer Attack

Physical Protection AgainstPhysical Protection AgainstFreezeFreeze--Thaw DamageThaw Damage

►► The hydrated cement paste is physically protected The hydrated cement paste is physically protected against Fagainst F--T damage by being relatively T damage by being relatively impermeable and having an acceptable airimpermeable and having an acceptable air--void void systemsystem

The size and spacing of the air voids is critical to The size and spacing of the air voids is critical to preventing the buildpreventing the build--up of stress as ice forms, acting as up of stress as ice forms, acting as pressure relief valvespressure relief valves

Total air is irrelevant but is related to airTotal air is irrelevant but is related to air--void size and void size and spacingspacing

The airThe air--void system is created through the use of air void system is created through the use of air entraining admixturesentraining admixtures

Big Bubbles, Few of Them

Small Bubbles, More of Them

Small Bubbles, Lots of Them

Impact of Poor Finishing

0.5 to 1 inch

AirAir--Void System AnalysisVoid System Analysis

Deicer Scaling/DeteriorationDeicer Scaling/Deterioration

►►Deicer chemicals can amplify paste freezeDeicer chemicals can amplify paste freeze--thaw deterioration thaw deterioration

Finishing may play a roleFinishing may play a role

►►Chemical mechanisms have also been Chemical mechanisms have also been identifiedidentified

►►Manifest as scaling, spalling, or map Manifest as scaling, spalling, or map cracking with possible staining near jointscracking with possible staining near joints

►►Typically appears within 1 to 5 years after Typically appears within 1 to 5 years after constructionconstruction

Traditional Deicing PracticesTraditional Deicing Practices

►►Solid deicing salts mixed with sandSolid deicing salts mixed with sand

Normally NaClNormally NaCl

Slow dissolution leads to low concentration Slow dissolution leads to low concentration solutions solutions –– solid may be blown off roadsolid may be blown off road

►►Applied after precipitation event to melt Applied after precipitation event to melt snow and icesnow and ice

►►Relatively low concentration of deicer in Relatively low concentration of deicer in melt watermelt water

Why Do Deicers MakeWhy Do Deicers MakeFF--T Damage Worse?T Damage Worse?

►►Primarily physical effectsPrimarily physical effectsIncrease level of saturationIncrease level of saturationCan lead to Can lead to ““thermal shockthermal shock””Increase osmotic pressureIncrease osmotic pressureCan produce salt recrystallization pressuresCan produce salt recrystallization pressures

►►Potential chemical effectsPotential chemical effectsCorrosionCorrosionDissolution of calcium hydroxideDissolution of calcium hydroxideFormation of expansive/weak phases in Formation of expansive/weak phases in hardened cement pastehardened cement paste

More Recent PracticesMore Recent Practices

►►Use of liquid antiUse of liquid anti--icing and deicing agentsicing and deicing agentsMagnesium chloride, calcium chloride, and Magnesium chloride, calcium chloride, and calcium magnesium acetate, among otherscalcium magnesium acetate, among others

Blended with food processing wastesBlended with food processing wastes

►►Very effectiveVery effectiveSome are more environmentally friendlySome are more environmentally friendly

►►Applied in Applied in high high concentrations (>25%)concentrations (>25%)

►►Liquid presentation can amplify both Liquid presentation can amplify both positive and negative effectspositive and negative effects

Disadvantages of New PracticesDisadvantages of New Practices

►►Greater potential for physical damage due Greater potential for physical damage due to higher concentrationto higher concentration

Liquid presentation contributes to a higher Liquid presentation contributes to a higher degree of interactiondegree of interactionIf storm event doesnIf storm event doesn’’t materialize, longt materialize, long--term term exposure to concentrated antiexposure to concentrated anti--icing agent icing agent resultsresults

►►Greater potential for chemical deterioration Greater potential for chemical deterioration from MgClfrom MgCl22 and CaCland CaCl22

Formation of hydrated calcium oxychlorideFormation of hydrated calcium oxychlorideWith MgClWith MgCl22, Mg(OH), Mg(OH)22 and Mand M--SS--H formationH formation

Research ObjectivesResearch Objectives

Determine the Determine the long term effects on concretelong term effects on concretefrom exposure to concentrated solutions of from exposure to concentrated solutions of MgClMgCl22, NaCl, CaCl, NaCl, CaCl22, and CMA, and CMA

Identify protective or design strategies that Identify protective or design strategies that minimize material damage from chemical minimize material damage from chemical exposureexposure

ApproachApproach►► Characterization of Field SpecimensCharacterization of Field Specimens

Determine distress mechanisms present in the fieldDetermine distress mechanisms present in the field

►► Phase I Laboratory ExperimentsPhase I Laboratory Experiments

Performed on Performed on mortarmortar specimens (cement, sand, and water)specimens (cement, sand, and water)

Identify distress mechanismsIdentify distress mechanisms

Assess the role of mixture properties and deicer typesAssess the role of mixture properties and deicer types

►► Phase II Laboratory ExperimentsPhase II Laboratory Experiments

Performed on Performed on concreteconcrete (cement, sand, aggregate, and water)(cement, sand, aggregate, and water)

Confirm distress mechanisms active in concreteConfirm distress mechanisms active in concrete

Determine the role of deicer concentration, concrete mixture desDetermine the role of deicer concentration, concrete mixture design, ign, and the effectiveness of sealantsand the effectiveness of sealants

Phase I Phase I -- DetailsDetails►►Expose mortars to deicer solutions at fixed Expose mortars to deicer solutions at fixed

concentrations (less than typical application concentrations (less than typical application conc.)conc.)

►►Monitor Physical EffectsMonitor Physical EffectsStrength LossStrength LossExpansionExpansionFreezeFreeze--Thaw PerformanceThaw Performance

►►Monitor Chemical EffectsMonitor Chemical EffectsPetrographic analysis to identify alterations to the Petrographic analysis to identify alterations to the mortarmortar

Phase I Phase I -- DetailsDetails►►Five different deicer solutionsFive different deicer solutions

MgClMgCl2 2 -- Magnesium Chloride (15 wt%)Magnesium Chloride (15 wt%)CaClCaCl2 2 -- Calcium Chloride (17 wt%)Calcium Chloride (17 wt%)NaCl NaCl -- Sodium Chloride (23 wt%)Sodium Chloride (23 wt%)Proprietary Proprietary -- Magnesium Based Agricultural Magnesium Based Agricultural ProductsProductsCMA CMA -- Calcium Magnesium AcetateCalcium Magnesium AcetateSaturated limewater (control)Saturated limewater (control)

►►Exposed for various timesExposed for various times►►Exposed at different temperatures (40, 72, Exposed at different temperatures (40, 72,

135135ººF)F)

Phase II Phase II -- DetailsDetails►► Concrete mixtures were made usingConcrete mixtures were made using

high quality, partially crushed gravel coarse aggregatehigh quality, partially crushed gravel coarse aggregatenatural sandnatural sand564 lb/yd564 lb/yd33 Type I/II cementType I/II cementvinsol resin and synthetic AEAvinsol resin and synthetic AEAw/cw/c of 0.45 and 0.55of 0.45 and 0.55

►► Two additional mixtures were prepared, Two additional mixtures were prepared, 15 percent replacement of cement with Class F fly ash15 percent replacement of cement with Class F fly ash35 percent replacement of cement with ground blast 35 percent replacement of cement with ground blast furnace slag (GBFS) furnace slag (GBFS)

►► Exposed to same deicers as Phase IExposed to same deicers as Phase I

Phase I Laboratory ResultsPhase I Laboratory Results

Cylinders exposed to Cylinders exposed to MgClMgCl22 solution after 84 days of exposure @ solution after 84 days of exposure @ 40 40 ººF. From left to right:F. From left to right:

0.40, 0.50, and 0.60 w/c mortar cylinders.0.40, 0.50, and 0.60 w/c mortar cylinders.

Cylinders exposed to Cylinders exposed to CaClCaCl22 solution after 84 days of exposure @ solution after 84 days of exposure @ 40 40 ººF. From left to right:F. From left to right:


Cylinders exposed to Cylinders exposed to NaClNaCl solution after 84 days of exposure @ solution after 84 days of exposure @ 40 40 ººF. From left to right:F. From left to right:


Cylinders exposed to Cylinders exposed to lime waterlime water solution after 84 days of solution after 84 days of exposure @ 40 exposure @ 40 ººF. From left to right:F. From left to right:


MechanismMechanism

►►Specimens were held at a constant 40 Specimens were held at a constant 40 ººF so F so no freezing occurred that could result in the no freezing occurred that could result in the damage observeddamage observed

►►Expansion was caused by the formation of Expansion was caused by the formation of calcium oxychloridecalcium oxychloride

►►Results from the reaction of calcium Results from the reaction of calcium hydroxide (hydroxide (present in the hardened cement present in the hardened cement pastepaste) with chloride ions () with chloride ions (provided by the provided by the deicerdeicer))

Scanning electron microscope images of thin sections prepared Scanning electron microscope images of thin sections prepared from cylinders immersed in, from left to right, MgClfrom cylinders immersed in, from left to right, MgCl22, CaCl, CaCl22, ,

NaCl, and saturated lime solutions.NaCl, and saturated lime solutions.

►► SEM AnalysisSEM Analysis►► Backscattered Backscattered

electron imageselectron imagesParallel cracksParallel cracksCa(OH)Ca(OH)22 and and oxychloride oxychloride deposition in the deposition in the voids of the voids of the MgClMgCl22 and CaCland CaCl22specimensspecimens

From top to bottom: plane From top to bottom: plane polarized light, cross polarized polarized light, cross polarized light, and epifluorescent mode.light, and epifluorescent mode.

►► Petrographic AnalysisPetrographic AnalysisCracks and air voids filled with remnant Cracks and air voids filled with remnant calcium oxychloride crystals in thin calcium oxychloride crystals in thin section prepared from MgClsection prepared from MgCl22 solution solution immersed sampleimmersed sample

► Petrographic AnalysisCracks and air voids filled with remnant calcium oxychloride crystals in thin section prepared from CaCl2 solution immersed sample

►► Petrographic AnalysisPetrographic AnalysisCracks and air voids filled with remnant Cracks and air voids filled with remnant calcium oxychloride crystals in thin calcium oxychloride crystals in thin section prepared from CaClsection prepared from CaCl22 solution solution immersed sampleimmersed sample

From top to bottom: plane From top to bottom: plane polarized light, cross polarized polarized light, cross polarized light, and epifluorescent mode.light, and epifluorescent mode.

Compressive strength evolution with time of mortar cubesCompressive strength evolution with time of mortar cubes

CaCl2 ~10% loss

NaCl & Control

MgCl2 & MBAP ~60% loss

Length change of mortar barsLength change of mortar bars

~0.4% expansion MgCl2

~0.3% expansion CaCl2

~0.8% expansion MBAP

Mass change of mortar barsMass change of mortar bars

~6% mass gain MBAP

~4% mass gain MgCl2

~2% mass gain CaCl2

Laboratory Results Laboratory Results -- Phase IIPhase II

17% CaCl2 – 500 days – 40 deg F

15% MgCl2 – 500 days – 40 deg F

15% MgCl2 MBAP – 500 days – 40 deg F

Typical Diffusion Profiles for 0.45 Typical Diffusion Profiles for 0.45 w/cw/c Concrete Exposed to 15% Concrete Exposed to 15% MgClMgCl22 -- PCC, 15% Fly Ash, 35% GGBFS MixturesPCC, 15% Fly Ash, 35% GGBFS Mixtures

PCC

Fly Ash Concrete

Slag Concrete

Silane Sealer ProfilesSilane Sealer Profiles

17% CaCl2

15% MgCl2

Surface concentration 0.3%

Sorptivity of 15% MgClSorptivity of 15% MgCl22 into 0.45 into 0.45 w/cw/c Concrete MixturesConcrete Mixtures

Sorptivity of 15% MgClSorptivity of 15% MgCl22 into 0.45 into 0.45 w/cw/c Concrete MixturesConcrete Mixtures

Freeze Thaw Testing Freeze Thaw Testing -- Length change of concrete prismsLength change of concrete prisms

ConclusionsConclusions

►►MgClMgCl22, CaCl, CaCl22, and proprietary deicers , and proprietary deicers containing MgClcontaining MgCl22 cause expansion, cracking, cause expansion, cracking, and loss of strength for concrete and and loss of strength for concrete and mortars exposed at 40 mortars exposed at 40 ººFF

►►NaCl caused no observed distress to NaCl caused no observed distress to concrete, however it is known to be concrete, however it is known to be detrimental to reinforcing steel in concretedetrimental to reinforcing steel in concrete


►►Cyclic freezeCyclic freeze--thaw exposure exacerbates thaw exposure exacerbates the damage caused by these deicersthe damage caused by these deicers

►►In all cases, the mechanism of failure is In all cases, the mechanism of failure is the formation of oxychloride phases by the the formation of oxychloride phases by the interaction of the deicer with calcium interaction of the deicer with calcium hydroxide in the hardened cement pastehydroxide in the hardened cement paste


►► Concrete mixtures prepared with ground blast Concrete mixtures prepared with ground blast furnace slag or fly ash as a portland cement furnace slag or fly ash as a portland cement replacement replacement performed significantly betterperformed significantly better in tests in tests as compared to concrete prepared with portland as compared to concrete prepared with portland cement onlycement only

►► Silane and siloxane sealantsSilane and siloxane sealants both both improvedimproved the the performanceperformance of concrete exposed to deicing of concrete exposed to deicing chemicalschemicals

►► Sealants are a good maintenance strategy but Sealants are a good maintenance strategy but need to be reapplied every 3need to be reapplied every 3--5 years in order to 5 years in order to remain effectiveremain effective

QuestionsQuestions

►►How quickly will distress occur in How quickly will distress occur in ““realreal--worldworld”” applications?applications?

Exact concentration of deicers, as applied, variesExact concentration of deicers, as applied, varies

►►Concentration variesConcentration varies

►►Application ratesApplication rates

Deicers are Deicers are diluted by weather eventsdiluted by weather events (positive)(positive)

When deicers are applied in an antiWhen deicers are applied in an anti--icing icing strategy, high concentration solutions are strategy, high concentration solutions are presented to the concrete and if the weather presented to the concrete and if the weather doesndoesn’’t occur t occur no dilutionno dilution results (negative)results (negative)

SummarySummary

►►The greatest threat is to lower quality The greatest threat is to lower quality concreteconcrete

Residential/commercial/municipalResidential/commercial/municipal

Paving concrete not meeting specsPaving concrete not meeting specs

►►Evidence suggests that liquid based Evidence suggests that liquid based MgClMgCl22 and CaCland CaCl22 pose the greatest risk pose the greatest risk of negatively affecting concreteof negatively affecting concrete

And if you are ever up in our way, stop in for a cold one, eh!

Documents

The Deleterious Chemical Effects of Concentrated Deicing Solutions on Portland Cement Concrete