An Experimental Study on the Effectiveness of Anti-icing Operations for Snow and Ice 1
Control of Parking Lots and Sidewalks 2
3
4
S M Kamal Hossain 5
(Corresponding Author) 6
Ph.D. Student and Research Assistant 7
Department of Civil & Environmental Engineering, 8
University of Waterloo 9
Waterloo, ON, N2L 3G1 10
Email: [email protected] 11
12
Dr. Liping Fu, Professor 13
Department of Civil & Environmental Engineering, University of Waterloo 14
Waterloo, ON, N2L 3G1, Canada 15
School of Transportation and Logistics, Southwest Jiaotong University, Chengdu, P. R. China 16
Phone: (519) 888-4567 ext 33984, Email: [email protected] 17
18
Avalon J. Olesen 19
Field Research Assistant 20
Department of Civil & Environmental Engineering, University of Waterloo 21
Waterloo, ON, N2L 3G1 22
Email: [email protected] 23
24
25
26
27
Paper accepted for presentation at the 93rd Annual Meeting of the Transportation Research 28
Board 29 January 2014 30
Word count = 4300 (text) + 12*250 (figures and tables) ~ 7300 31
32
33
34
TRB 2014 Annual Meeting Paper revised from original submittal.
H o s s a i n , F u , O l e s e n 2
ABSTRACT 35
This paper describes an empirical study aimed at investigating the performance of the 36
anti-icing strategy for snow and ice control of parking lots and sidewalks. The research is 37
motivated by the need to address several key questions concerning various operational decisions 38
related to the anti-icing strategy, including its relative effectiveness under different weather and 39
site conditions, treatment options, and optimal application rates. Extensive field tests were 40
conducted under a wide variety of weather events using regular solid road salt, brine, and two 41
other liquid alternatives. Data collected from these tests was used to analyze the performance of 42
anti-icing operations such as friction level, bare pavement regain time, and the effects of various 43
external factors such as pavement temperature and application rate. The research has concluded 44
with findings that are directly applicable in real world winter maintenance practices. 45
TRB 2014 Annual Meeting Paper revised from original submittal.
H o s s a i n , F u , O l e s e n 3
1. INTRODUCTION 46
The cost of winter road maintenance is substantial in Canada. Over $1 billion is spent 47
annually for winter operations (TAC, 2003). This large cost includes the use of large amounts of 48
road salts for de-icing and anti-icing operations to remove snow and ice from transportation 49
facilities. However, salt is detrimental to the environment and has corrosive effects to the 50
infrastructure and vehicles damages (Mussato et al., 2004, NCHRP-577, 2007; Shi et al., 2009; 51
Jain et al., 2012). To reduce maintenance costs and the adverse effects of salts, a significant 52
amount of efforts have been made to improve the efficiency and effectiveness of winter 53
maintenance methods. One of the effective strategies is anti-icing, which involves applying salt 54
or other freezing point depressants prior to a snow event in order to prevent the formation of 55
snow or ice bond with the pavement surface (Ketcham et al., 1996; NCHRP-526, 2004). 56
Anti-icing has been recognized to have several significant benefits. First, it helps prevent 57
the snow from bonding with the pavement, thus achieving a higher level of friction over a snow 58
event. Second, for the same reason, anti-icing can substantially minimize the plowing efforts, 59
resulting in clearer pavement or minimal leftover snow. Third, in the case of a light snow event, 60
the pre-applied salt can melt all the snow, providing the level of service expected over a shorter 61
period. Lastly, anti-icing treatments can be made over a wider time window, enabling contractors 62
to be able to better manage their resources. 63
However, these benefits have mostly been shown or discussed in the context of roadway 64
maintenance with very few studies focusing on the effectiveness of this strategy and determine 65
its best practice when it is applied for snow and ice control of parking lots and sidewalks. The 66
operating conditions of parking lots and sidewalks are significantly different from roadways, 67
which means materials and rates that are ideal for roadway anti-icing treatments may not be 68
suitable for parking lots and sidewalks. For example, only liquid salt is effective for roadway 69
maintenance as solid would be easily dispersed by vehicular traffic; however, the vehicular 70
traffic within parking lots is substantially lower than on roadways. 71
The objective of this research is to address several critical questions related to anti-icing 72
operations for transportation facilities mainly concerned with pedestrian traffic such as parking 73
lots, sidewalks, and platforms. In particular, the research is to answer the questions as follows: 74
a) how effective is anti-icing treatment in preventing the bonding of snow and ice to pavement? 75
TRB 2014 Annual Meeting Paper revised from original submittal.
H o s s a i n , F u , O l e s e n 4
b) what is the relative effectiveness of anti-icing operation as compared to de-icing? c) what is 76
the optimal anti-icing application rate for specific weather and site conditions? and, d) what is 77
the comparative performance of different anti-icing materials? 78
This paper provides a detailed discussion of the results of a series of field tests conducted 79
to determine the conditions under which the anti-icing method can be more effective for a wide 80
range of pavement and environmental conditions in parking lots. The results of this study 81
provide a solid foundation for determining the optimum anti-icing methods, materials and 82
application rates for snow and ice control of parking lots and sidewalks under various winter 83
conditions. 84
85
2. LITERATURE REVIEW 86
Numerous past studies have attempted to determine the effectiveness of anti-icing on 87
road systems. Related guidelines and manuals have also been developed for highway anti-icing 88
treatments (Ketcham et al., 1996; NCHRP-526, 2004; Minnesota DOT-TRS-0902, 2009). 89
Blackburn et al. (1994) conducted a two year study to investigate the effectiveness of anti-icing. 90
They found that anti-icing can be effective at a temperature above -9°C with solid salt 91
application rate of 100lb/lane-mile (1.57 lbs/1000sqft), using saturate brine for pre-wet at a rate 92
of 0.021 to 0.025 Liter/kg (5 to 6gallons/ton). They also found that anti-icing is not effective 93
during prolonged snow fall or freezing rain. The study found that, compared to brine, magnesium 94
chloride was more successful for preventing bonding at a temperature of -5°C. Also, based on a 95
few case studies, they found that an anti-icing operation saves costs for both maintenance 96
organizations and road-users. For maintenance organizations, the cost saving is lower application 97
rates, and for road-user, the cost saving is fewer accidents due to the improvement in the 98
pavement condition. Several other studies also reported the end benefits of anti-icing as 99
compared to the conventional method of de-icing (Amsler D., 2006; O’Keefe and Shi, 2005). 100
Based on a series of workshops with the maintenance personnel, Amsler D. (2006) 101
reported that anti-icing operations can be effective with solid salts if they are properly applied 102
and can stay on the pavement after application. However, for the road sectors, solid salt with 103
water or another liquid chemical is recommended in order to minimize the bounce and scatter 104
tendencies of salts from the wind-blow caused by vehicular traffic. The NCHRP-526 report 105
TRB 2014 Annual Meeting Paper revised from original submittal.
H o s s a i n , F u , O l e s e n 5
(2004) also states that dry solid salt can be effective under pre-application (anti-icing) when 106
applied at traffic speed under 45km/h, and traffic volume under 100 vehicles per hour. The report 107
also indicates that parking areas present a unique potential for anti-icing operations with solid 108
salt for the reason of less expected dispersion effects. 109
Regarding anti-icing materials, past studies have evaluated the relative performance of 110
regular dry salt, pre-wet salt and regular brine. Fonnesbech J. (2007) conducted a study to 111
evaluate anti-icing performance of pre-wetted salt and brine. They compared pre-wetted salt (salt 112
and brine ratio of 70:30 by weight) at application rate 10gm/m2 (2.05lbs/1000sqft) to 20 % brine 113
applied at 20ml/m2(6.10L/1000sqft or 80gallons/lane-mile). The study showed anti-icing with 114
brine is more effective than pre-wetted salt due to the more evenly distribution and longer 115
retention of brine. Fu et al. (2012) conducted another study for the effectiveness of anti-icing 116
using different liquids and pre-wetted solid salt. The study evaluated the performance of regular 117
brine compared to a mixture of beet juice and brine (30:70 mixture). The effectiveness was 118
measured comparing the friction data from the test sections treated by the above mentioned anti-119
icing materials. They employed both materials as pre-wetting liquids, and direct applications. 120
Their study revealed that both brine and the mixture performed similarly by achieving the same 121
range of coefficients of friction when they were used as a pre-wetting chemicals, while the 122
mixture outperformed brine when they were applied alone as direct application on the roadways. 123
In summary, a number of studies have been conducted in the past to evaluate the 124
effectiveness of anti-icing, and to develop guidelines for anti-icing materials and application 125
rates; however, these studies have exclusively focused on highways. The results from these 126
studies cannot be transferred to the low volume transportation facilities, such as parking lots, 127
sidewalks, and transit platforms, due to the significant differences in service requirements and 128
operating conditions. The objective of this study is to develop a quantitative understanding of the 129
effectiveness of anti-icing for specific weather conditions, thus providing guidelines for selecting 130
the right anti-icing methods, materials, and application rates for snow and ice control in parking 131
lots and sidewalks. 132
133
134
TRB 2014 Annual Meeting Paper revised from original submittal.
H o s s a i n , F u , O l e s e n 6
3. DESCRIPTION OF FIELD TEST 135
In order to investigate the effectiveness of ant-icing, a series of field tests were conducted 136
during the winter season of 2012-2013. The tests were conducted under a wide range of weather 137
conditions covering 50 events (Figure 1). The following section details the test site, testing 138
method and results. 139
140
141
Figure 1: Winter Events 2012-2013 142
143
3.1 Test Site 144
The test site location was Parking Lot C, which is at the south-east end of the University 145
of Waterloo’s South Campus (Figure 2). The parking lot is made of asphalt concrete and is in 146
good condition, with a slight sloping throughout. There are 900 parking stalls and 8 driveways. 147
The tests took place in multiple locations within the parking lot. These locations were recorded 148
on a map to avoid repetition and contamination of the data. 149
150
-15
-10
-5
0
5
10
15
20
25
Days
Total Snow Depth (cm) Avg Pave. Temp (°C) Avg Air Temp (°C)
TRB 2014 Annual Meeting Paper revised from original submittal.
H o s s a i n , F u , O l e s e n 7
151
Figure 2: Test Site: University of Waterloo, City of Waterloo, Ontario, Canada 152
153
3.2 Test Method 154
Anti-icing treatments were performed 2 to 12 hours in advance of snow events while de-155
icing operations were done at the end of the snow events. Solid road salt was tested over all the 156
anti-icing events under both plowed and unplowed conditions while liquid salts were only tested 157
for the relatively long storms and under plowed pavement conditions. 158
The test sections were cordoned off to prevent traffic contamination of the tests. Hence, 159
the results from these tests can be directly applicable for foot traffic ways (platforms, side-walks) 160
and parking lots with low volume vehicular traffic. The results can also be equally used for the 161
worst possible case scenarios for any parking lots. Note that separate tests have been conducted 162
on driveways to account for traffic effects and the results will be reported in a separate 163
publication. 164
The solid material used in this study was solid regular road salt. The liquid salts used 165
were regular Brine, Caliber M1000, and Snow Melter 2. Table 1 shows the chemical 166
compositions of each type of material used in the tests. 167
168
169
170
171
172
TRB 2014 Annual Meeting Paper revised from original submittal.
H o s s a i n , F u , O l e s e n 8
Table 1: Materials Used in the Tests 173
Salt Name Constituents Composition Percentage
Regular Road Salt NaCl 100%
Brine NaCl
Water
23.3%
76.7%
Caliber M1000 Magnesium Chloride
Carbohydrate
Water
27%
6%
67%
Snow Melter 2 Glycerine
Polyether Polymer
Sodium Lactate
Sorbitol
Sodium Formate
Sodium Acetate
1, 2- Butanediol
Water
15%-20%
10%-20%
4%-10%
2%-4%
1%-4%
1%-4%
1%-2%
Balance
174
There are many similarities of how the anti-icing and de-icing experiments were 175
conducted. The salt types and application process were identical. The solid salts were measured 176
out using an electronic scale and were applied manually, and the liquid salts were applied with 177
the liquid sprayer called SnowEx SL-80. 178
The solid salt application rates varied from 5 to 50lbs/1000sqft, where 5 to 179
25lbs/1000sqft were commonly used, and liquid salts tested at rates of 3 to 10L/1000sqft. First, 180
trials were set on recommendations from manufacturers and then adjusted considering snow 181
conditions, pavement temperatures, and other variables as tests proceeded over the period. For 182
each liquid tested, the ejecting rate from the spray nozzle was calibrated first. Then the spraying 183
times for tested sections (a typical parking stall 8ft x20ft) for various application rates for each 184
liquid were calculated (this is due to the difference in their viscosity). The spraying times for 185
Brine, Caliber M1000, and Snow Melter 2 have been tabulated in Table 2 as an example. Several 186
iterations and calibrations of the spraying times were conducted, ensuring a uniform spray of 187
each material on the test sections. 188
TRB 2014 Annual Meeting Paper revised from original submittal.
H o s s a i n , F u , O l e s e n 9
Table 2: Liquids Spraying Rates and Times 189
Material
3L/1000sqft
(40 gallons/lane-
mile)
5L/1000sqft
(65 gallons/lane-mile)
7L/1000sqft
(90gallons/lane-mile)
10L/1000sqft
(130 gallons/lane-mile)
Brine 23s 39s 54s 78s
Caliber M1000 21s 35s 50s 70s
Snow Melter 2 37s 62s 86s 124s
190
When applying the liquid salt, the desired amount of solution was poured into the 191
sprayer. A timer was set while someone walked uniformly back and forth inside the parking stall. 192
Spraying was continuous until the desired rate was achieved. After each material was used, the 193
container was emptied and cleaned before the next chemical was applied. A flow chart showing 194
the two test procedures is given in Figure 3. 195
196
a) Anti-icing Test b) De-icing Test 197
Figure 3: Anti-icing and De-icing Process 198
TRB 2014 Annual Meeting Paper revised from original submittal.
H o s s a i n , F u , O l e s e n 10
3.3 Data Collection 199
At the start of the test, a master event and maintenance form was first filled out, including 200
the start and end of the event. Then, a data form was filled out at a uniform interval (usually on 201
an hourly basis), recording: 202
Weather data from Environment Canada website (Region of Waterloo station) 203
Time 204
Pavement surface and snow top temperature (by IR surface temperature reader) 205
Percent bare pavement 206
Friction levels (qualitative, quantitative by T2GO Friction Tester) 207
Snow-pavement bonding state 208
Residual salts level (qualitative, quantitative by SOBO20 Salinity Meter) 209
Contaminate type (snow, slush, wet pavement, ice) 210
Note that, for each test date, data collection continued until the desired level of service was 211
achieved. A bare pavement of 80%-100% was considered as level of service, LOS_A. 212
213
4. DATA ANALYSIS AND RESULTS 214
This section examines all the data collected and compares different anti-icing methods, 215
materials, and application rates. Note that, there were a total of approximately 100 anti-icing 216
tests conducted with solid road salt, on average 20 tests were performed with three liquid salts. 217
Two key performance measures are used, namely, bare pavement regain time (BPRT) and 218
friction level. Bare pavement regain time (BPRT) is defined as the elapsed time from the end of 219
a snow event to the time when the pavement reaches at least 80% bare. The friction level of a 220
pavement is represented by the coefficient of friction and a descriptive measure of slipperiness. 221
The former is collected using the T2GO friction tester described previously while the latter is 222
checked manually by the observer. This section summarizes the results according to the three 223
questions raised in introduction. 224
225
4.1 Effectiveness of Anti-icing for Preventing Snow and Ice Bonding 226
As discussed previously, anti-icing treatments are motivated by their potential in 227
preventing the bonding of snow and ice to a pavement surface by lowering the freezing point of 228
TRB 2014 Annual Meeting Paper revised from original submittal.
H o s s a i n , F u , O l e s e n 11
water through the use of salt. To evaluate the effectiveness of anti-icing operations in achieving 229
this potential, the states of bonding and friction levels at the treated sections (i.e., anti-icing was 230
done) are compared to those of the control sections (do-nothing sections). For both cases, the 231
accumulated snow was first removed by the plow truck or using a shovel before observations and 232
friction were taken. 233
Figure 4(a) shows the measurements of the coefficient of friction for sections treated with 234
anti-icing as compared to those without anti-icing operations. As expected, anti-icing operations 235
were highly effective in preventing the bonding of snow and ice. Except two cases, the 236
improvement in friction level was over 50%. For the two events that anti-icing was not effective, 237
the main reasons were the relatively low temperature and high amount of precipitation of the 238
events, and long event duration. For instance, the event which occurred on January 22, 2013 had 239
an average pavement temperature -11.5°C, which is below the effective temperature range of 240
regular salt. Three additional tests were also conducted using liquid as an anti-icing agent. 241
Figure 4(b) shows the friction of coefficients observed across the two scenarios: do-nothing and 242
anti-icing using brine. Again, the effect of preventing pavement bonding was clearly shown for 243
both solid and liquid. This quantitative evidence was further confirmed by the visual observation 244
of slipperiness levels between treated sections and untreated sections. 245
246
a) Anti-icing Using Solid Road Salt 247
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Coef
fici
ent
of
Fri
ctio
n
Date
With Anti-icing Without Anti-icing (Do-nothing Sections)
TRB 2014 Annual Meeting Paper revised from original submittal.
H o s s a i n , F u , O l e s e n 12
248
249
b) Anti-icing Using Brine 250
Figure 4: Effectiveness of Anti-icing Using Solid Road Salt and Brine 251
4.2 Comparative Performance of Anti-icing and De-icing Treatments 252
While the main motive of the anti-icing strategy (e.g., applying salt in advance) is to 253
prevent snow and ice from bonding to the pavement surface so that they can be removed easily 254
by plowing operations, it could also be implemented as pre-application of salt for the purpose of 255
melting snow and ice, similar to the conventional de-icing strategy (applying salt after the start, 256
mostly at the end, of an event). Intuitively, if little dispersion and dilution occur after salt is 257
applied, pre-application and after-application of the same amount of salt should perform 258
similarly in terms of snow melting capacity (total amount of snow and ice that can be melted). 259
However, the former should be expected to achieve better performance in terms of bare 260
pavement regain time because it does not need to break the newly formed bonds. If this is true, it 261
would mean that it is always preferable to apply salt in advance of an event (i.e., anti-icing) than 262
after the event for the snow storms when less dilution is expected for some form of precipitation 263
(e.g., freezing rain, wet snow). Furthermore, applying salt in advance has the advantage of an 264
easier workload management as it has a wider time window for operations. To avoid any 265
0
0.1
0.2
0.3
0.4
0.5
0.6
Feb. 18, 2013 Feb. 27, 2013 Mar. 6, 2013
Do Nothing Brine
TRB 2014 Annual Meeting Paper revised from original submittal.
H o s s a i n , F u , O l e s e n 13
confusion in terminologies, the following discussion still uses anti-icing and de-icing for pre-266
application and after-application, respectively. 267
Tests were conducted for a comparative analysis of these two types of operations, which 268
included applying the same amount of salt before and after an event, at different sections, with 269
multiple application rates. Figure 5 shows how the coefficient of friction changed over time for 270
anti-icing and de-icing sections treated with regular salt with application rate 5lbs/1000sqft for 271
two similar events. Note that snow was not plowed in both cases. It can be observed that, in both 272
cases, anti-icing performed significantly better than de-icing operations in terms of the overall 273
friction level over the events and bare pavement regaining period. 274
275
Figure 5: Comparison of Performance between Anti-icing and De-icing Operations 276
(Legend shows test date, treatment type, application rate in lbs/1000sqft, pavement temperature, 277
snow amount and snow type) 278
279
The differences between anti-icing and de-icing operations are also compared using the 280
performance measure of bare pavement regain time (BPRT). Two scenarios are considered, 281
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Before Event After Event 3 Hrs After 6 Hrs After
Coef
fici
ent of
Fri
ctio
n
Jan 16-17 2013, Anti-
icing, Rate 5, -3.5°C,
1.5cm, Very Loose
Jan 16-17 2013,
Deicing, Rate 5, -
3.5°C, 1.5 cm, Very
Loose
Feb 22- 23 2013,
Deicing, Rate 5, -
4.7°C, 1.3cm, Loose
Feb 22-23 2013, Anti-
icing, Rate 5, -4.7°C,
1.5cm, Loose
TRB 2014 Annual Meeting Paper revised from original submittal.
H o s s a i n , F u , O l e s e n 14
namely, unplowed and plowed. For the unplowed conditions, the tests included nine snow events 282
with snowfall ranging from 0.3cm to 7.8cm and temperatures from ~0°C to ~-4°C. Salts were applied 283
before the event for anti-icing sections. For de-icing operations, salts were applied after precipitation 284
stopped using the same rates as the anti-icing sections. 285
Figure 6 shows the relationship between average level of service (LOS) improvement, as 286
represented as the reduction of BPRT, between anti-icing and de-icing operations, and salt 287
application rate. Several observations can be made from the test results. Firstly, anti-icing 288
operations outperformed de-icing in almost all cases with average BPRT being from ~0.5 to 3.5 289
hours shorter. Secondly, the advantage of anti-icing operations appeared to be higher in light 290
events as compared to heavier events. Thirdly, an interesting and important observation is the 291
trend between the salt application rates and the bare pavement regain time. It shows that the 292
snow melting performance of salts is marginally sensitive to the application rate in general. It 293
can also be seen that anti-icing was less effective when event duration was relatively longer, or the snow 294
was wet. This result makes intuitive sense, as the salt applied in advance could be lost due to the high 295
dilution, which is also supported by literature (Blackburn et al. 1994; Ketcham et al.1996; Fu et al. 2013). 296
297
298
Figure 6: Benefit of Pre-application (Anti-icing) - LOS Improvements (BPRT Reduction) 299
as Compared to After-application (De-icing) 300 301
302
0
0.5
1
1.5
2
2.5
3
3.5
4
5 10 15 20 25
LO
S I
mpro
vem
ent
(hrs
)
Salting Rates (lbs/1000sqft)
Dec 29 2012, -1.45°C, 2cm, Packed Feb 22 2013, , -3.32°C, 1.3cm, Loose
Jan 16 2013, -3°C, 2.25cm, Very Loose Jan 19 2013, -0.7°C, 0.5cm, Packed
Feb 19 2013,-2.3, 3.5cm, Packed Mar 6 2013, -0.7°C, 7.8cm, Wet
TRB 2014 Annual Meeting Paper revised from original submittal.
H o s s a i n , F u , O l e s e n 15
4.3 Optimal Anti-icing Application Rates Using Solid Road Salt 303
When anti-icing is implemented for the sole purpose of preventing bonding of snow to 304
pavement, the amount of salt being used may not need to be large. To find out the minimum 305
application rates for achieving this anti-icing objective, a series of tests were conducted using 306
different anti-icing application rates. Figure 7 shows the coefficient of friction of a pavement 307
surface as a function of the anti-icing application rate for the plowed anti-icing sections. An 308
application rate of zero means that the section was not treated with anti-icing. As it can be 309
observed, an application rate as low as 5 lbs/1000sqft could achieve the main purpose of 310
preventing the bonding and improving the friction level. This is also true with respect to bare 311
pavement regain time, as shown in Figure 8. 312
It can be clearly seen that only a small amount of salt (5lbs/1000sqft or less) was needed to 313
achieve bare pavement immediately after plowing. 314
315
316
317 Figure 7: Friction Performance of Anti-icing Treatments 318
(Notes: Friction measurements were taken after plowing. Legend shows different test days with 319 pavement temperature, snow amount and snow type) 320
321 322 323 324
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 5 10 15 20 25 30
Coef
fici
ent
of
Fri
ctio
n
Salt Application Rate (lbs/1000sqft)
-1.7, 2cm, Packed
-2.3, 3.5cm, Packed
-3.32, 1.3cm, Loose
-5.6, 1.3cm, Very wet
TRB 2014 Annual Meeting Paper revised from original submittal.
H o s s a i n , F u , O l e s e n 16
325 326
Figure 8: BPRT Performance of Anti-icing Treatments 327 (Notes: Bare pavements regain time from plowing. Legend shows different test days with 328
pavement temperature, snow amount and snow type) 329
330
4.4 Comparison of Different Materials for Anti-Icing 331
Tests were also conducted to investigate the differences in anti-icing performance between 332
three liquid products, including regular brine, Caliber M1000, and Snow Melter 2. As shown in 333
Figure 9, all sections treated with liquid anti-icing had higher friction levels than those which 334
were not treated. The differences between the three liquids were relatively small, which were 335
also true in terms of bare pavement regain time (BPRT), as shown in Figure 10. It can be 336
observed that the three liquids had similar performances under all application rates, similar to the 337
results for rock salt. The anti-icing treatment sections generally reached 100% bare pavement at 338
similar times, regardless of application rates. This suggests a low application rate 339
(e.g. 3 L/1000sqft) is needed to reach the desired level of service immediately after plowing. 340
Note that, snow started again, after the plowing operation, during the tests conducted on 341
February 27, 2013, resulting in relatively longer bare pavement regain time. 342
In addition to the testing results shown in Figure 10, the three liquids were also tested for 343
a big event amounting in 21cm snow, which was plowed at the end of the event. Three pavement 344
0
1
2
3
4
5
6
7
8
9
0 5 10 15 20 25 30
BP
RT
(h
rs)
Salt Application Rates (lbs/1000sqft)
-1.7, 2cm, Packed
-2.3, 3.5cm, Packed
-3.32, 1.3cm, Loose
-5.6, 1.3cm, Very wet
TRB 2014 Annual Meeting Paper revised from original submittal.
H o s s a i n , F u , O l e s e n 17
conditions were clearly noticed. First, the snow was bonded to the pavement, degrading the 345
performance of the plowing operation. Second, the pavement condition remained the same across 346
the test sections, regardless of salt type and application rate. Third, the sections treated with 347
Snow Melter 2 had marginally higher coefficient of friction than other sections, but the 348
differences were relatively small. 349
350
351
Figure 9: Coefficient of Friction for Do-nothing Sections and Liquid Salts Applications 352
(Note: Snow Melter2 was not tested on Mar. 6, 2013) 353
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
2013-02-18 2013-02-27 2013-03-06
Co
effi
cien
t of
Fri
ctio
n
Do-nothing Sections Regular Brine CaliberM1000 Snow Melter2
TRB 2014 Annual Meeting Paper revised from original submittal.
H o s s a i n , F u , O l e s e n 18
354
Figure 10: Anti-icing Events Comparing Liquid Salts Performances 355
(Notes: Legend shows test days with different chemical, pavement temperature, snow amount 356
and snow type) 357
358
5. CONCLUSIONS 359
360
This paper has presented the results from a series of field tests aiming at determining the 361
performance of anti-icing treatments for snow and ice control of parking lots and sidewalks. The 362
research is mainly concerned with the issues of the effectiveness and relative performance of 363
anti-icing operations using different materials and application rates under different weather 364
events. The main findings from this study include: 365
366
Anti-icing was found highly effective in preventing the bonding of snow, improving 367
friction levels, and improving bare pavement regain times; 368
Anti-icing operations, when used as pre-application, were found to perform much 369
better than after-application (de-icing) for light snow events; 370
0
1
2
3
4
5
6
0 1 2 3 4 5 6 7 8 9 10 11
BP
RT
aft
er P
low
(h
rs)
Application Rate (L/1000sqft)
Feb 19, 2013, Brine, -
0.3°C, 3.5cm, Wet
Feb 19, 2013, Snow
Melter2, -0.3°C, 3.5cm,
WetFeb 19, 2013, Caliber
M1000, -0.3°C, 3.5cm,
WetFeb 27, 2013, Brine, -
3.32°C, 1.3 cm, Packed
Feb 27, 2013, Caliber
M1000, -3.32°C, 1.3 cm,
PackedFeb 27, 2013, Snow
Melter2, -3.32°C, 1.3 cm,
PackedMar 6, 2013, Caliber
M1000, -1.67°C, 7.8cm,
Very Loose
TRB 2014 Annual Meeting Paper revised from original submittal.
H o s s a i n , F u , O l e s e n 19
Compared to solid salt, brine was found to be more effective under the condition that 371
the same amount of salt (NaCl) was used; 372
The two other alternative liquid products were found to perform similar to regular 373
brine for anti-icing treatments; 374
The performance of anti-icing operations also depends on the nature of the snow 375
event. For long and intense events, anti-icing operations were found to be ineffective 376
in preventing the snow bonding with the pavement. 377
378
It should be noted that additional field tests will be conducted in the coming winter 379
season to address some of the limitations and remaining issues of this research. More tests will 380
be conducted using alternative liquid products for both anti-icing and de-icing purposes. In 381
particular, there is a significant interest in applying non-chloride de-icers for minimizing the 382
environmental and corrosive effects of chloride salts used for maintenance operations. Future 383
research will also attempt to quantify the effects of other various factors, such as dilution 384
potential, traffic, and pavement type on the performance of anti-icing operations. 385
386
387
ACKNOWLEDGEMENTS 388
389
The authors wish to acknowledge nine other research assistants who helped during field data 390
collection. A complete list of the research assistants is available in our project website: 391
www.sicops.ca. This research was supported through a Collaborative Research Development 392
(CRD) project funded by NSERC (National Science and Engineering Research Council) and 393
Landscape Ontario. A number of other organizations supported this research, as acknowledged 394
on our project website. 395
396
397
REFERENCES 398
399
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TRB 2014 Annual Meeting Paper revised from original submittal.
H o s s a i n , F u , O l e s e n 20
402
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TRB 2014 Annual Meeting Paper revised from original submittal.