Environmental Effects of Deicing and Anti-icing Chemicals › sites › ltap › files › workshops...

Environmental Effects of Deicing and

Anti-icing Chemicals

Xianming Shi, Ph.D., P.E.

2011 Michigan Winter Operations Conference

Midland, MI

Outline

1. WM Best Practices

• Operational Strategies

• Chemical Usage

• Other

2. Environmental impacts of deicers

• Corrosion to vehicles

• Impact on infrastructure

• Impact on natural environment

3. Concluding Remarks

Winter Road Maintenance

in the U.S.

• Over 70 percent of

roadways in snowy regions

• 70% population affected

• Fatalities & injuries

• $2.3 billion/yr. on highway

snow/ice control

• 20 million tons of salts per

year for all roads in U.S.

• $5 billion/yr. cost to

infrastructure (FHWA)

Emerging Challenges of Winter Maintenance

• Reactive: Sanding, Deicing, Snowplowing

1. LOS concerns

2. Materials & labor hrs required

Improved Practices

Pre-wetting: addition of liquid chemical to an

abrasive or solid chemical at stockpile or

spreader – performance/ longevity on pavement

Anti-icing: application of liquid or solid

chemicals prior to a winter weather event

(proactive) – prevent/weaken the bond; BI

WM Best Practices: Operational Strategies


• Anti-icing & Pre-wetting

– material usage

– labor hours

• Cost savings by applying less material and clearing the road faster w/o the need for overtime

– maintenance costs while vulnerability of the highway system to winter weather

– reoccurrence of environmental contamination

– LOS (safety/mobility $)


• Toolbox approach

Local needs/Rd wx scenarios/Rules of practice

Funding/staffing/equipment/policy constraints

– Snow fencing

– Anti-icing

– Deicing (incl. pre-wet salt, DLA, etc.)

– Sanding (pre-wet sand)

– Mechanical (e.g., snowplowing)

– Thermal

– Pavement treatments

WM Best Practices: Chemical Usage

2007 Survey: 15 states + 2 other countries

• Chemical Usage:

NaCl(s)> abrasives > MgCl2 > agro-based > CaCl2 > others

• Less than 25% of them used alternative deicers

KAc, NaAc, CMA, KFm, etc.

• Perceived Performance:

agro-based ++; abrasives --

• Perceived Negative Impacts:

chlorides --; acetates/formates ++


Modified SHRP Ice Melting Test, 30°F

0.0

1.0

2.0

3.0

4.0

5.0

6.0

0 20 40 60 80

time (min)

ice

me

lt (

ml)

23% NaCl

32% CaCl2

30% MgCl2

NaCl (r,s)

CaCl2.2H2O(r,s)

MgCl2.6H2O(r,s)



0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 20 40 60 80

time (min)

ice

me

lt (

ml)

23% NaCl

32% CaCl2

30% MgCl2

NaCl (r,s)

CaCl2.2H2O(r,s)

MgCl2.6H2O(r,s)



0.0

0.5

1.0

1.5

2.0

2.5

0 20 40 60 80

time (min)

ice

me

lt (

ml)

23% NaCl

32% CaCl2

30% MgCl2

NaCl (r,s)

CaCl2.2H2O(r,s)

MgCl2.6H2O(r,s)


1. Ice melting by deicers: a dynamic, time-

sensitive process; f (deicer type/form, t, T)

2. For solid salt, sufficient t (60 min) should be

allowed in order to achieve its full potential.


1. Up to 20% replacement of the 23% NaCl

deicer by the 32% CaCl2 deicer had no

significant effect on the Tc , but slightly

increased the icemelt at 15F, 20 min and at

30F, 60 min.

2. Up to 15% replacement of the 23% NaCl

deicer by AGBP slightly increased the Tc ,

and slightly decreased the icemelt at 15F,

20 min and at 30F, 60 min.

Non-

inhibited

solid

NaCl

Inhibited

liquid

MgCl2

K- or Na-

acetate/

formate

Non-

inhibited

solid

NaCl

Inhibited

liquid

MgCl2

K- or Na-

acetate/

formate

46.6 57.1 46.5Overall deicer composite index

24.2 48.4 64.5

71.3 71.3 55.4

46.8 46.8 70.2

47.4 47.4 63.1

54.3 54.3 23.3

58.6 58.6 25.1

23.8 63.5 71.4

34.2 68.5 42.8

9 9 7

Composite Indices

63.0 56.0 21.0

42.5 56.7 28.3

6 6 8

3 6 8

7 7 3

6 6 9

4 8 5

7 7 3

9 8 3

Overall low impact on air quality, incl. PM 10, deicer

aerosols, etc.

Attribute Value

Deicer Attributes for Decision-Making

Average

Decision

Weight

(CDOT)

6 8 4

3 8 9

Impacts on the

Environment

8.38

7.80

7.89

8.06

7.92

Overall low impact on water quality, including total

P/N/Cl, TOC, BOD, COD and aquatic toxicity

Overall low impact on plants, incl. Browning/singe,

senescence/death, root issues and native species

secession

Overall low impact on soil, incl. Conductivity, heavy

metal leaching, microbes, and food web.

Overall low impact on wildlife, incl. Attraction,

ingestion toxicity, habitat and migratory paths.

Corrosion to

Metals7.93

Impacts on

Pavement

8.56

7.76

Low corrosion effect on mild steel, galvanized steel,

aluminum, rebar or dowel bar, and slow penetration

into concrete

Overall low impact on concrete pavement, including

resistance to freeze-thaw, ASR, ACR, scaling,

strength loss and expansion

Overall low impact on asphalt pavement, including

aggregates (ASR), binder, degradation &

disintegration of asphalt pavement, and strength loss

Cost 7.00

Performance 7.08

Low materials cost per lane mile, also including

training, equipment and material handling

Low effective temperature, ability to use in higher Ts

at lower application rates, high ice melting capacity,

and improved pavement friction

4 Scenarios: D-Weights for Collaborative

Decision Making

0.000.06

0.110.17

0.23

20

40

60

80

100

0.330.54

0.760.98

1.20

Inhibitor Dosage

(ml/g NaCl)

Co

mp

osit

e D

eic

er In

de

x

CaCl2.2H2O Dosage

(g/g NaCl)

Anti-icer Composite Index, User Sceneario 1: Cost-First

80-100

60-80

40-60

20-40

0.000.06

0.110.17

0.23

20406080

100

0.33

0.65

0.98

1.30

Inhibitor Dosage

(ml/g NaCl)

Co

mp

osit

e D

eic

er In

de

x

CaCl2.2H2O Dosage

(g/g NaCl)

Anti-icer Composite Index, User Sceneario 2: Effects-First

80-100

60-80

40-60

20-40

0.000.06

0.110.17

0.23

20

40

60

80

0.33

0.65

0.98

1.30

Inhibitor Dosage

(ml/g NaCl)

Co

mp

osi

te D

eic

er

Ind

ex

CaCl2.2H2O Dosage

(g/g NaCl)

Anti-icer Composite Index, User Sceneario 3: Performance-First

60-80

40-60

20-40

0.000.06

0.110.17

0.23

3040506070

0.33

0.65

0.98

1.30

Inhibitor Dosage

(ml/g NaCl)

Co

mp

osi

te D

eic

er

Ind

ex

CaCl2.2H2O Dosage

(g/g NaCl)

Anti-icer Composite Index, User Sceneario 4: Balanced Approach

60-70

50-60

40-50

30-40

A “Supermix” (85% salt brine, 10% De-ice, and 5% CaCl2):

anti-icing above 15F @ 40 gallons/lane-mile or

pre-wetting above 2F @ 10 gallons/ton

WM Best Practices: Other

• Computer-aided design of snow fences

• Improved/customized weather forecasts

• FAST

• Pavement technologies

• Advanced snowplow technologies

• MDSS

Outline



• Chemical Usage

• Other






Deicer Impacts: Completed Projects

Deicer Impacts: Ongoing Projects

1. Understanding and Mitigating Effects of Chloride

Deicer Exposure on Concrete – ODOT/RITA

2. Best Practices and Guidelines for Protecting

DOT Equipment from the Corrosive Effect of

Chemical Deicers – WSDOT/RITA

3. Reducing the Effects of Roadway Deicers on

Natural Environment – NCHRP

Deicer Benefits vs. Impacts

1. WM: essential for winter roads

fewer accidents & improved mobility

reduced travel costs

sustained economic productivity

continued emergency services, etc.

2. Impacts: site-specific, average > 3 times of direct $

Infrastructure corrosion: >$615/ton

vehicular corrosion: > $113/ton

aesthetic costs: $75/ton (sensitive areas)

human health costs: uncertain

Deicer Corrosion to Motor Vehicles

1. Steel, cast Fe, Al alloys, Mg alloys, Cu alloys, etc.

2. Vehicles on unsalted roads: 50% less cosmetic corr., >

90% reduction in corr. rate of steel [Sweden, 1985-90].

3. Road salt corrosion to vehicles: $2.8 - $5.6B/yr [1992]

4. Total corrosion of vehicles: $23.4B/yr [2002]

5. 0-12% tensile strength loss (Al, steel, etc. after 1st yr.)

[2006]

Deicer Corrosion to Motor Vehicles

Extremely difficult to relate lab test results of

corrosion resistance to the actual field performance

of metals.

Relative corrosivity of deicers = f (metal/deicer

system, test protocol)

99.1

56.5

68.1

75.0

98.5

0

20

40

60

80

100

Perc

en

t C

orr

osio

n R

ate

(%

)

NaCl MgCl2 CaCl2 NaCl+10%MgCl2 NaCl+20%MgCl2

Deicer (w ith Chloride concentration of 0.5M)

Deicer Corrosion to Mild Steel

PNS/NACE Corrosion Test (Mild Steel)

-20

-10

0

10

20

30

40

50

1

Deicers Tested

Co

rro

sio

n R

ate

(M

PY

)

Di water

CF7

NAAC

IceBan

Apex Meltdown

CDOT MgCl2

NaAc/F

Peak SF

NaCl (r,s)

IceSlicer

Inhibitor Longevity in Storage or On Pavement

No significant degradation of inhibitor or loss of

chlorides: >12 months of field storage.

Fate and transport of the inhibitors generally differed

from those of the chlorides: dilution by precipitation

and likely wicking of the deicer into pavement & snow

layer.

Relative corrosivity: on pavement (Black Ice

event d4) vs. in lab (40, 15 & 35 vs. 32, 21 & 16).

How to Manage Corrosion of Deicers to

Motor Vehicles

Prevention is the key

Materials selection

Design Improvements

Maintenance practices

Anti-corrosion coatings, salt removers, etc.

Use less corrosive deicers and optimal application rates.

Deicer Corrosion to Rebar/Dowel Bar

Inhibitors in chloride deicers slowed down the

ingress of chloride into concrete.

The three inhibited deicers would generally lead to

lower corrosion rates of the top bar in concrete, when

the bar is not actively corroding (icorr < 1.5 A/cm2).

NaCl > I-NaCl > I-CaCl2 > I-MgCl2

Benefits diminished once active corrosion occurred.

How to Manage Corrosion of Deicers to

Rebar/Dowel Bar

Prevention: high-quality concrete, adequate concrete

cover, & alternative reinforcement

Control the ingress and accumulation of deleterious

species: sealers, CP, etc.

Inject beneficial species into concrete

Use less corrosive deicers and optimal application rates

Deicer Effects on Portland Cement Concrete

Expansion, mass change, loss in the dynamic

modulus of elasticity & strength

•Deicer Scaling (Physical)

•Reactions: Deicers (Mg2+/Ca2+) + cement paste

•Deicer Aggravating Aggregate-Cement Reactions

– NaCl, acetates/formates affecting ASR

– CaCl2, MgCl2 affecting ACR

Freeze-thaw weight loss of PCC following the SHRP H205.8 test

DI-H 2O CMA

CDOT

MgCl 2

KF (r)NaAc/F

CF7

(KAc)

NaCl (r)

IceSlicer

(NaCl)

-10

0

10

20

30

40

50

60

70

Deicers Tested

Pe

rce

nt

We

igh

t L

os

s (

%)

Diluted Deicers F-T Damage of PCC

Diluted Deicer vs. Concrete Durability

Physical distresses + chemical reactions

MgCl2 deicer NaCl (r) NaCl deicer

KFm (r) NaAc/NaFm deicer KAc deicer

How to Manage Deicer Effects on Portland

Cement Concrete?

The proper use of air entrainment, high-quality

cementitious materials and aggregates, and

mineral admixtures is promising.

Deicers Affecting Pavement Structure

Thermal cracking, differential heaving, and loss

of bearing capacity during spring thaw + impact

on skid resistance

•F/T dmg’ aggregate - water vs. deicer (1%-2%)

•Damage to asphalt mix & aggregate: Urea & NaFm vs.

NaCl (limestone) and KAc (quartzite)

•Indirect tensile strength: intact >> deicers (KAc,

NaFm, NaCl) > water > urea

•Elastic modulus: intact > other deicers > urea

Modern PDPs have been reported to

affect airfield asphalt pavement

Concurrent to the use of acetate/formate-based deicers in the 1990s, asphalt pavement in Europe saw the increase in durability problems

Binder

emulsification

Disintegration Stripping

How to Manage Deicer Effects on Asphalt

Concrete?

Follow best possible practices in asphalt mix design

and paving (e.g., low void contents).

Use binders with high viscosity or polymer-modified

binders

Use alkaline aggregates or high-quality (sound)

aggregates (avoid limestone filler or heavily

contaminated RAP when using acetate/formate-

based deicers)

Test the compatibility of the materials in advance.

Environmental Impacts of Deicers

Vegetation, soil, water bodies, aquatic biota, air

quality, wildlife, human health

Depend on a wide range of factors unique to each

formulation and the location of application.

Further testing is necessary for many of the

deicers.

The use of deicers can reduce the need for

applying abrasives

Environmental Impacts of Deicers

Soil and vegetation: high deicer use

Water quality: soluble in water/removal difficult

EPA: [Cl-]

Greeley Water Quality Data

0

1

2

3

4

5

6

7

0

5

10

15

20

25

Chlo

ride

0

50

100

150

200

250

300

4/3/2007

7/8/2007

11/15/2007

3/11/2008

Turb

idity

(NTU

)

BOD (m

g/L)

TKN (m

g/L)

PO4

-3 (mg/

L) pH

CO

D (m

g/L)

TOC (m

g/L)

DO

(mg/

L)

Chl

orid

e (m

g/L)

Measured Water Quality Parameters

Turb

idity,

BO

D,

TK

N,

PO

4

-3

pH

, C

OD

, T

OC

, D

O

Water Quality: Three Sites in CO

All relevant water quality parameters were generally below

EPA and Colorado State standards (250 mg/l).

The field data showed no immediate impact from chloride

deicers following application adjacent to waterways.

The large variation in chloride and PO43- concentrations

among the three sites were likely due to the inherent

difference in site conditions.

Impacts of Abrasives

Easier to remove

Outweigh those of chemical deicers

Vegetation : accumulate and cause stress

Habitat for aquatic organisms: bull trout in MT

Water quality: retain/transport other pollutants

D < 6.35 mm: detrimental effects on streams

D < 2 mm: Block the movement of O2 into

streambed

D < 0.01 mm (10 m): PM-10 air quality

How to Manage Environmental Impacts of

Deicers

It is crucial to make informed decisions by utilizing

available resources including existing test

methods and the PNS-approved deicer list.

By identifying sensitive areas and species and

setting limits for air and water quality, minimum

impact requirements can be established which

all deicers must meet, so that a toolbox approach

may be implemented.

Minimizing the Impacts of

Traction Materials

1. REDUCE: source control

strategies w/o jeopardizing LOS

2. RECOVER: street sweeping /

snow storage / sand reuse

3. CAPTURE: structural BMPs

Non-structural BMPs

Incorporating environmental staff into

maintenance

Proper training of maintenance professionals

Erosion control

Snow storage/ Street sweeping / Sand reuse

Winter maintenance best practices

Structural BMPs

Roadside or off-site systems to physically

trap runoff and to allow pollutants to settle

out, evaporate, infiltrate, or be absorbed.

Treat the quality of runoff (suspended vs.

dissolved pollutants) as well as flow rate

Site-specific & properly sited, designed,

installed, and maintained

www.stormwatercenter.net

Outline



• Chemical Usage

• Other






Concluding Remarks (a)

1. The use of road salts, while improving roadway

safety & mobility, presents corrosion and

environmental concerns to various stakeholders.

2. Deliver the right type/amount in the right location at

the right time.

3. Minimize the salt usage while maintaining the

desired LOS: in both technology & management

domains.

Concluding Remarks (b)

4. Minimize the negative effects of deicing & anti-icing

chemicals: technology & management.

5. Research & Innovation: enabling WM best practices,

promoting sustainable winter road service, adopting

a holistic approach to balance performance &

impacts in a proactive manner.

6. Provide WM practitioners with sufficient

training/learning opportunities.

Contact:

Xianming Shi, Ph.D., P.E.

Program Manager, Winter Maintenance & Effects

Director, Corrosion and Sustainable Infrastructure Lab

Western Transportation Institute (WTI)

PO Box 174250

Montana State University

Bozeman, MT 59717-4250

Phone: (406) 994-6486

Email: [email protected]

Web: www.coe.montana.edu/ME/faculty/Shi/

http://www.wti.montana.edu/Winter/Default.aspxmailto:[email protected]://www.coe.montana.edu/ME/faculty/Shi/

Additional Slides for Q&A

• Founded in 1994 by Caltrans, MDT and MSU

• Part of the College of Engineering, MSU

• Now a National University Transportation Center (UTC)

• Research, Education and Technology Transfer

• Develop effective solutions to the real transportation

challenges facing rural America

WTI WME Research Sponsors

USDOT RITA

NCHRP / ACRP

FHWA

PNSA

Clear Roads

Aurora

Clear Roads

State DOTs

Private Sector

Key Findings of FOTs (4)

• Black ice event: 0.75 of precipitation (snow/ice) during d4-7.

• % Cl recovered by d4: ~ 30%, 20%, & 50% for NaCl+GLT, CCB, and FreezGard

• % CCB inhibitor recovered by d4: 80%.

• PCR by d4: 40, 15 & 35 for NaCl+GLT, CCB, and FreezGard

• The relative corrosivity of deicer solutions on the field pavement differed lab (32, 21 & 16).

• D5-: Cl recovery for all 3 deicers dropped: rain on d-3 and snow on d-3 (trace), d-4 (>1/2”), & d-5 (1/2”).

Structural BMPs w/ High

Applicability of Use in Cold Regions

Relatively effective in the presence of snow

Relative low costs

Relative high removal efficiency of suspended

solids

Dry ponds / Vegetated swales/ Vegetated filter strips

Sand cans (as pretreatment)

Wet extended detention ponds/Wet ponds /

Constructed wetlands

Environmental Effects of Deicing and Anti-icing Chemicals › sites › ltap › files › workshops...

Documents

Transcript of Environmental Effects of Deicing and Anti-icing Chemicals › sites › ltap › files › workshops...