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Laboratory evaluation of Verglimit and PlusRide.

Laboratory Evaluation of Verglimit and PlusRide

Introduction

One technique to help control the formation of ice on asphalt pavements, and possibly reduce the use of salt, is to include deicing additives in the wearing course mixture. Two such additives are Verglimit and PlusRide rubber. Using these additives, however, increases pavement material and construction costs. These increases may be justified if ice-related accidents are reduced and the properties of the asphalt mixture are not adversely affected.

Background

Description of additives

This article describes a recent study, conducted by the Federal Highway Administration (FHWA) at its Turner-Fairbank Highway Research Center that investigated the effects of Verglimit and PlusRide rubber on the performances of asphalt mixtures. Specifically, the study examined the additives in terms of their effects on moisture damage, rutting, and low temperature cracking. The tests conducted included indirect tensile strengths, incremental creep moduli and permanent strains, and repeated load moduli and permanent strains. Specimens were also moisture conditioned to determine retained tensile strength ratios (TSR), retained resilient modulus ratios (MrR), and visual stripping. This study supplements various field trials now underway; most field studies formally evaluate only the effects on skid resistance and not other mixture or pavement properties.

Verglimit consists of 0.1-to 5-mm (0.004- to 0.21-in) particles of calcium chloride with a small amount of sodium hydroxide. The particles are encapsulated with linseed oil or polyvinyl acetate to seal the material and keep it inactive until the particles break under the action of traffic. The calcium chloride additive then mixes with moisture from the air or on the pavement to form a dilute salt solution. Verglimit is designed to work throughout the life of the pavement. Because it generally triples the cost of the bituminous mixture, Verglimit is used only in selected problem areas. The additional cost is not offset by the reduction in sanding and salting operations, but may be offset if it can be found that its use reduces accidents.

PlusRide is a patented bituminous mixture which contains granulated tire rubber. Most rubber particles are 0.16 to 0.64 cm (1/16 to 1/4 in). They act as elastic aggregates that flex on the pavement surface under traffic. This flexing helps to break up ice. PlusRide doubles the cost of the mixture and, like Verglimit, has been used only in selected problem areas.

Field applications

As noted above, several field studies are now under way to determine if and how Verglimit and PlusRide reduce the number of ice-related accidents. These studies are summarized below. Many of these field studies have indicated that Verglimit and PlusRide can affect mixture properties.

Verglimit

* A Verglimit project in New York performed

well in light snowfalls, but was less effective in

heavy snowfalls. No problems with pavement

performance were observed in 8 years. (1)(1)

* Verglimit did melt ice in two Colorado projects,

but the deicing action was so slow the effects

were often masked by normal salting and sanding

operations. (2) In an earlier Colorado project,

the pavement raveled. This raveling was attributed

to poor quality control at the hot-mix plant

and during pavement construction. The pavement

was also slick because of the attraction of

a high amount of moisture to the surface. It was

found that the Verglimit particles crushed by the

roller quickly absorbed moisture from the air.

Slickness on the other projects in Colorado was

controlled by applying sand on the pavement after

construction.

* In Pennsylvania, slickness was controlled by

first sanding the surface and later flushing it

several times with water. (3) This practice is

now recommended by the supplier. The slick

surface was attributed to the moisture absorption

of the crushed Verglimit particles, although

the linseed oit that encapsulates the

calcium chloride was suggested as a contributing

factor.

* No deicing benefits were found in Minnesota,

and portions of a pavement shoved and were

replaced. (4)

* In California, although poor compaction led to

raveling problems, icing nevertheless decreased. (5)

* Some Verglimit sections in Oregon and New

Jersey were replaced because of raveling. (6)

PlusRide

* The Alaska Department of Transportation installed

experimental pavement sections using

PlusRide in Fairbanks and Anchorage. (7) On

measuring vehicle stopping distances, significant

reductions in distance were observed during

icy conditions as compared to control sections.

Condition surveys were also made;

these showed some raveling.

* The New Jersey Department of Transportation

constructed a test site using PlusRide on route

NJ41 in Cherry Hill. (8) Periodic skid tests

showed that PlusRide improved the skid resistance

of the pavement. Initial condition surveys

indicated that there was slightly more rutting in

the PlusRide section than in the control section.

The rate of rutting then slowed, and the section

subsequently performed acceptably.

* A PlusRide project was evaluated over 5 years

by the State of Washington. (9) The control

used was the State's standard asphalt-rubber

open-graded asphalt concrete. The required

density could not be obtained in the PlusRide

section, and the air void level was close to 12

percent. Sections of the PlusRide material

had to be patched. It was concluded that the

PlusRide material did not give better frictional

properties, noise reduction, or service life.

* Rhode Island constructed a 1.61-km (1-mi) test

section composed of equal segments of

PlusRide, Verglimit, and a control pavement.

Since there were no differences in the performances

of the three sections, the increases in

cost due to the Verglimit and PlusRide were

not offset.

Testing Program

A 50-blow Marshall mixture design was performed on each mixture to determine its optimum asphalt content. Specimens were then fabricated at this optimum content and tested for resistance to moisture damage, rutting, and low temperature cracking. The complete testing program is shown in table 1. All asphalt, aggregate, and mixture tests were performed according to American Association of State Highway and Transportation Officials (AASHTO) and other recommended practices.

Table : Table 1. Testing program

Resistance to moisture damage at 25 [degrees] C (77 [degrees] F) (Diametral tests on Marshall size specimens) * Tensile strength ratio * Resilient modulus ratio * Visual percent stripping Resistance to rutting (10.16- by 20.32-cm {4- by 8-in} cylinders) * Incremental creep modulus and permanent strain at 18.3, 25, and

40 [degrees] C (65, 77, and 104 [degrees] F) * Dynamic modulus and permanent strain at 18.3, 25, and 40 [degrees] C

(65, 77, and 104 [degrees] F) Resistance to low temperature cracking (Diametral tests on Marshall size specimens) (Temperatures from -30 to 90 [degrees] F (-34.3 to 32.2 [degrees] C) * Resilient modulus versus temperature * Tensile strength versus temperature Specimens tested for their resistance to moisture damage were cured at 25 [degrees] C (77 [degrees] F) for 2, 7, 14, 28, or 90 days to determine if curing had an effect on adhesion and the deicers.

Low temperature effects were determined at a reference modulus of 20,700 MPa (3,000 ksi) and a reference tensile strength of 2.07 MPa (300 psi) in accordance with current practices.

The data described in this article are from four mixtures: PlusRide, PlusRide control, Verglimit, and Verglimit control. Additional mixtures were tested; the results from these tests support the data presented in this paper.

Resistance to Moisture Damage

Verglimit

Data from the moisture damage tests are given in table 2 and the TSR and MrR are presented in figure 1. Verglimit had a significant effect on the retained ratios, providing retained ratios lower than the control and also below suggested passfall criteria (70 percent for MrR and 80 percent for TSR). Verglimit thus increased the susceptibility to moisture damage. However, there was no visual stripping, and the low retained ratios were attributed to the high amount of swelling in the specimen that occurred during the 24-hour 60 [degrees] C (140 [degrees] F) water soak. [Tabular Data Omitted]

PlusRide

Data from the moisture damage tests are given in table 3 and TSR and MrR are presented in figure 2. PlusRide decreased both the TSR and MrR and thus increased the susceptibility to moisture damage. No visual stripping was observed for this PlusRide mixture, but the specimens swelled during the water soak. Other PlusRide mixtures tested did, however, show some slightly higher levels of visual stripping compared to their control mixtures. [Tabular Data Omitted]

Resistance to Rutting

Verglimit

Creep moduli and permanent strains are presented in table 4. Verglimit increased the creep modulus and decreased the permanent strain at the high temperature for each creep time. Verglimit generally decreased the creep modulus but had a variable effect on permanent strain at low temperature. Overall, this indicated a slight decrease in the susceptibility to rutting.

Table : [Tabular Data Omitted]

Verglimit

The dynamic moduli at the 200th cycle and test temperatures of 18.3, 25, and 40 [degrees] C (65, 77, and 104 [degrees] F) for the control mixture were 5900, 3100, and 740 MPa (850,000, 450,000, and 107,000 psi), respectively. For the Verglimit mixture they were 4200, 3100, and 700 MPa (610,000, 443,000, and 102,000 psi). Verglimit caused a reduction in stiffness at the low temperature but had no effect at the other two temperatures. This finding generally indicates there should be no effect on the resistance to rutting.

Permanent strains versus the number of cycles at 18.3, 25, and 40 [degrees] C (65, 77, and 104 [degrees] F) are presented in table 5. Verglimit reduced the amount of permanent strain at 25 and 40 [degrees] C (77 and 104 [degrees] F), and slightly increased the permanent strain at 18.3 [degrees] C (65 [degrees] F) at the high number of cycles. Thus, unlike the dynamic moduli, the permanent strains indicated a reduced susceptibility to rutting and slight trend toward decreasing temperature susceptibility. Permanent strains are a much better indicator of performance than moduli, and thus the conclusions from the strain data should be used.

Table : [Tabular Data Omitted]

PlusRide

Creep moduli and permanent strains are presented in table 6. PlusRide decreased the creep modulus and increased the permanent strain at all temperatures and creep times. This indicated an increased susceptibility to rutting.

Table : [Tabular Data Omitted]

The dynamic moduli at the 200th cycle and test temperatures of 18.3, 25, and 40 [degrees] C (65, 77, and 104 [degrees] F) for the control mixtures were 7000, 3000, and 1100 MPa (1,010,000, 439,000, and 165,000 psi) respectively. For the PlusRide mixture they were 3200, 1500, and 500 MPa (467,000, 218,000, and 72,000 psi). PlusRide caused a reduction in modulus at all temperatures.

Permanent strains versus the number of cycles at 18.3, 25, and 40 [degrees] C (65, 77, and 104 [degrees] F) are presented in table 7. PlusRide increased the amount of permanent strain at all temperatures and cycles. Both the dynamic moduli and the permanent strains indicated an increased susceptibility to rutting.

Table : [Tabular Data Omitted]

Low Temperature Cracking

Verglimit

Tensile strengths and resilient moduli versus temperature are presented in figures 3 and 4, respectively. The resilient modulus test produced a shift of -0.6 [degrees] C (-3 [degrees] F) at the 20,700 MPa (3,000 ksi) reference modulus for the Verglimit mixture relative to the control. This shift was due to a slight decrease in temperature susceptibility. The tensile strength test at 2.07 MPa (300 psi) produced virtually equal data for both the Verglimit and control mixtures, and no shift was found. Overall, both mixtures would be expected to behave similarly in the field.

PlusRide

Tensile strengths and resilient moduli versus temperature are presented in figures 5 and 6, respectively. The resilient modulus test produced a shift of -9.4 [degrees] C (-17 [degrees] F) at the 20,700 MPa (3,000 ksi) reference modulus for the PlusRide mixture compared to the control. The tensile strength test produced a shift of -7.8 [degrees] C (-14 [degrees] F) at 2.07 MPa (300 psi). The PlusRide mixture produced lower moduli and tensile strengths at all temperatures; it thus was more resistant to low temperature cracking.

Conclusions

Both Verglimit and PlusRide rubber were found to affect various asphalt mixture properties, as summarized below.

Verglimit

* Verglimit provided Marshall stabilities and

flows similar to the control.

* Verglimit mixtures had low retained tensile

strength and resilient modulus ratios. Thus,

Verglimit increased the moisture susceptibilities

of the mixtures.

* Verglimit reduced the temperature susceptibilities

of the mixtures as measured by the creep

moduli, repeated load moduli, and permanent

deformations and strains. The effects were

slightly below 25 [degrees] C (77 [degrees] F).

* Verglimit had no effect on the resistances of

the mixtures to low temperature cracking.

* Specimens containing Verglimit stored at

room temperature swelled within 28 days.

How this relates to field performance is unknown,

although it seems to explain why there

have been reports of raveling in pavements.

Verglimit absorbs moisture from the air.

* Some changes to the testing procedures were

required. Verglimit is water soluble so the

volumetric flask method of AASHTO T209 and

American Society for Testing and Materials

D2041 or a volumeter must be used to determine

the maximum specific gravity of the mixture.

For determining bulk specific gravity,

only a 1-minute period of immersion in water

can be used. To mix the materials, the

unheated Verglimit particles were added after

the asphalt cement and aggregate were mixed;

an additional 15 to 30 seconds of mixing was

needed to ensure coating and a visually homogenous

distribution.

PlusRide

* PlusRide mixtures had low retained tensile

strength and resilient modulus ratios. The rubber

particles increased the moisture susceptibilities

of the mixtures.

* PlusRide increased the resistance to low temperature

cracking and decreased the resistance

to rutting. PlusRide also reduced the Marshall

stabilities and creep and repeated load moduli,

while it increased the flow and permanent deformations

and strains.

* PlusRide specimens stored in air at room temperature

developed hairline cracks by 90 days.

How this relates to field performance is unknown.

The rubber particles on the outer

edges of the specimens also began to stick out.

This swelling of the rubber particles was attributed

to the absorption of asphalt hydrocarbons.

Recommendations

* Verglimit and PlusRide mixtures should be

tested for moisture susceptibility and an

antistripping agent used if necessary. This

practice will not, however, control the inherent

swelling that these deicers can cause.

* Most pavement sections in which these deicers

have been incorporated are less than 2.54 cm

(1 in) thick so as to reduce costs and because

the additives only act at the surface of the

pavement. Consequently, and because both

additives had some detrimental effects on the

test data, they should only be used in surface

layers less than 2.54 cm (1 in) thick.

References

[1] J.H. Tanski. Performance of Two Ice Retardant Overlays, Publication No. FHWA/NY/RR-86/132, New York State Department of Transportation, Albany, NY, 1986. [2] Technology Transfer Unit. "Verglimit Study Concludes," Colorado DOT Research Newsletter, Colorado Department of Highways Denver, CO, October 27, 1988. [3] K.E. Highlands. Verglimit Deicing Chemical Asphalt Additive, FHWA-PA-88-007-83-39, Pennsylvania Department of Transportation, Harrisburg, PA, December 1988. [4] C.M. Turgeon. Evaluation of Verglimit (A Deicing Additive in Plant-Mixed Bituminous Surface), FHWA/MN/RD-89/02, Minnesota Department of Transportation, St. Paul, MN, July 1989. [5] California Department of Transportation. Resurfacing with 'Verglimit' (CA-84-09), Elizabeth Lake Road," CALTRANS Newstech No. 5, Sacramento, CA, December 1987. [6] Oregon Department of Transportation. Progress Report from Oregon Department of Transportation, Project No. ER-331(4), Salem, OR, 1988. [7] H.B. Takallov, J. Mcquillen, Jr., and R.G. Hicks. Effects of Mix Ingredients on Performance of Rubber Modified Asphalt Mixtures, FHWA/AK/RD-86-05, Alaska Department of Transportation and Public Facilities, Juneau, AK, April 1985. [8] K.T. Diringer, and J. Smith. "Asphalt Additives," Construction Report FHWA/NJ-85/007-7713, New Jersey Department of Transportation, Trenton, NJ, October 1982. [9] R.E. Allison. PlusRide Asphalt Concrete Pavement, WA-RD 130.2, Washington State Department of Transportation, Olympia, WA, January 1990.

Kevin D. Stuart is a research highway engineer in the Pavements Division of the TFHRC, Federal Highway Administration (FHWA). He is the director of the Bituminous Mixtures Laboratory which designs and analyzes bituminous mixtures and evaluates and develops test methods for them. Mr. Stuart has been with the FHWA since 1980 and currently is program manager for the Nationally Coordinated Program C2, "Evaluation of Flexible Pavements." Mr. Stuart deals with the performance of bituminous mixtures and pavements.

Walaa S. Mogawer is an assistant professor in the Civil Engineering Department at the Southeastern Massachusetts University in Dartmouth, Massachusetts, where he teaches pavement and highway courses. Dr. Mogawer also is involved in research on the effect of natural sand on asphalt mixture resistance to rutting. Dr. Mogawer was a graduate fellow at the Turner-Fairbank Highway Research Center (TFHRC) when he conducted the present study. He holds a doctorate from the University of Rhode Island.

PHOTO : Figure 1. - Verglimit: MrR and TSR versus aging time.

PHOTO : Figure 2. - PlusRide: MrR and TSR versus aging time.

PHOTO : Figure 3. - Verglimit: tensile strength versus temperature

PHOTO : for evaluating low temperature cracking.

PHOTO : Figure 4. - Verglimit: resilient modulus versus

PHOTO : temperature for evaluating low temperature

PHOTO : cracking.

PHOTO : Figure 5. - PlusRide: tensile strength versus temperature

PHOTO : for evaluating low temperature cracking.

PHOTO : Figure 6. - PlusRide: resilient modulus versus

PHOTO : temperature for evaluating low temperature cracking.
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Title Annotation:deicing additives
Author:Stuart, Kevin D.; Mogawer, Walaa S.
Publication:Public Roads
Date:Dec 1, 1991
Words:2863
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