Field performance comparison of asphalt crack-filling materials: hot pour versus cold pour

Yetkin Yildirim

Abstract: One of the most important components of pavement maintenance has been the sealing of cracks. The mostcommonly used materials for crack sealing are hot-pour sealants, such as hot rubber asphalt. However, this materialcan be hazardous at high operating temperatures and is more likely to be picked up by vehicle tires if the sealant isnot sufficiently adhered to the pavement. Thus, cold-pour sealants have been considered as an alternative for cracksealing purposes. This study aims to compare the performance of hot-pour rubber asphalt crack sealant and cold-pourasphalt emulsion crack sealant in five different Texas districts that experience different weather conditions. The com-parison includes seven different crack sealants: three cold pour and four hot pour. Five different roads in five districtswere selected for comparison of the sealants. The field study results indicate that hot-pour sealants performed betterthan cold-pour sealants.

Key words: sealants, emulsified crack sealants, crack sealing, asphalt pavements.

Résumé : L’un des aspects les plus importants de l’entretien des chaussées a toujours été le scellement des fissures.Les matériaux les plus fréquemment utilisés pour le scellement des fissures sont les bouche-fissures à chaud, parexemple l’asphalte caoutchouteux chaud. Cependant, ce matériau peut poser des risques à haute température et il a plusde chances de coller aux pneus des véhicules si le produit de scellement n’adhère pas suffisamment à la chaussée.Ainsi, les produits de scellement à froid ont été examinés comme solution de remplacement pour le scellement des fis-sures. La présente étude compare le rendement d’un bouche-fissures liquide à chaud, à base de caoutchouc, et d’unbouche-fissures à émulsion asphaltique à froid dans cinq districts du Texas à conditions climatiques différentes. Lacomparaison comprend sept différents bouche-fissures, trois à froid et quatre à chaud. Cinq routes différentes dans cinqdistricts ont été sélectionnées pour comparer les produits. Les résultats de l’étude sur le terrain indiquent que les pro-duits de scellement à chaud avaient un meilleur rendement que ceux à froid.

Mots-clés : produits de scellement, bouche-fissures émulsifiés, scellement de fissures, revêtement asphaltique.

[Traduit par la Rédaction] Yildirim 512

Introduction

One of the most common maintenance activities per-formed on bituminous pavements by transportation agenciesis the treatment of cracks. Crack sealing is the method usedto create a waterproof surface to prevent moisture fromreaching inner layers of the pavement.

Highway agencies have for the most part used hot-pourrubber asphalt crack sealants for many years. Although hot-pour sealants have shown to exhibit good performance, theconstruction procedure contains a number of safety hazardsthat are primarily caused by elevated operating temperatures.Hot rubber asphalt sealants must be heated to approximately350°F (177 °C) or higher before they are applied to thepavement surface (Yildirim et al. 2001). Also, the heatingprocess usually takes a long time to set up prior to installa-

tion. (Masson et al. 2002). Concerns arise from the risk ofburns and skin damage to personnel or to the public when ahose or a nozzle accidentally bursts (Yildirim et al. 2001).Another downfall of using this material is that when it is notproperly stiffened, it can adhere to vehicle tires and is subse-quently hard to remove (Yildirim et al. 2001). This problemcan also be associated with cold-pour sealants, but not as of-ten (Yildirim et al. 2001).

In contrast to hot-pour sealants, cold-pour asphalt emul-sion crack sealants are typically applied at ambient tempera-tures; therefore using cold-pour sealants eliminates thesafety risks associated with high operating temperatures.Generally, cold-pour sealants need less construction time be-cause less set-up time is required. Because of their very lowviscosity, cold-pour sealants can penetrate and fill cracksmore easily than hot-pour sealants.

However, cold-pour emulsions require a longer curingtime than hot pours, which means more interference withtraffic, and cold-pour emulsions are known for their highsusceptibility to ambient conditions (Yildirim et al. 2001).For example, high-humidity conditions slow the curing timefor cold-pour sealants, and immediate freezing weather afterapplication can have adverse impacts on their effectiveness(National Guide to Sustainable Municipal Infrastructure2003). A complete understanding of the long-term perfor-

Can. J. Civ. Eng. 34: 505–512 (2007) doi:10.1139/L06-143 © 2007 NRC Canada

505

Received 26 April 2005. Revision accepted 11 September2006. Published on the NRC Research Press Web site atcjce.nrc.ca on 2 May 2007.

Y. Yildirim. Texas Pavement Preservation Center, TheUniversity of Texas at Austin, 3208 Red River CTR 318,Austin, TX 78705, USA (e-mail: yetkin@mail.utexas.edu).

Written discussion of this article is welcomed and will bereceived by the Editor until 31 August 2007.

mance of cold-pour crack sealants is not yet well estab-lished.

The goal of this study is to compare the long-term perfor-mance of hot- and cold-pour sealants, as there has been littleor no comprehensive research previously done on this topic.The tasks conducted to achieve the objective of this researchproject were the distribution of a survey to determine sealingtechniques that are used in Texas and other states, the appli-cation of sealing materials on selected roads in five districtsof Texas, and the regular monitoring of the field perfor-mance of these crack sealants. This paper presents the re-sults of this research study on the difference in performanceof hot-pour and cold-pour sealants.

Background

Transportation agencies worldwide are now focusing moreattention on pavement preservation. Chen et al. (2003) statedthat each dollar invested in preventive maintenance at the ap-propriate time in the life of a pavement may save US$3 toUS$4 in future rehabilitation costs. Therefore, it is crucial toselect the appropriate type of procedure to be applied at theappropriate time.

Crack sealing has come to be considered one of the mostimportant methods in pavement preservation. Chen et al.(2003) investigated a method of evaluating treatment proce-dures, described as a “windshield survey”, where individualsubjective assessment of the treated sections is performed.Observations of distresses such as rutting and cracking areutilized to determine the performance of the treatments. Intheir study, which they conducted on 14 test sites, they con-cluded that crack sealing provides the best alternative forlow-traffic routes with sound underlying pavement structure.

Crack sealing is a tedious and labor-intensive operation;therefore most of the cost is attributed to labor expenses.Haas et al. (1996) reported that a crack treatment procedurecosts approximately US$1125 per kilometre with 66% attrib-uted to labor, 22% to equipment, and 12% to materials.Standard procedures for crack sealing are established in theUSA by the Asphalt Pavement Repair Manuals of Practice(National Research Council 1993), and in Canada by theGuidelines for Sealing and Filling Cracks in Asphalt Con-crete Pavement (National Guide to Sustainable MunicipalInfrastructure 2003).

Smith and Romine (1993a) developed a checklist detail-ing the most desirable properties for cold-pour and hot-poursealant materials, which include ease of placement, adequateadhesion, resistance to weathering, and traffic abrasion. Thestudy attempted to identify the effective materials, equip-ment, and procedures used in pavement maintenance. A partof the study was in the form of a survey in which manufac-turers and maintenance agencies were asked to evaluate dif-ferent aspects of maintenance procedures. Asphalt rubberand emulsified asphalt were among the crack sealing materi-als used in this study. The results of the survey showed thatlife expectancy of rubber asphalt is 4.3 years in warm condi-tions and 2.2 years in cold conditions. On the other hand,emulsions have a life expectancy of 2.3 years in warm dryconditions and slightly more than 1 year in wet climates.

Smith and Romine (1993b) also conducted an evaluationof a combination of various treatment materials, placementconfigurations, and crack preparation procedures. The ef-fectiveness of the treatment procedures was determined byvisual investigation of the treated sites. The failure rate wascalculated as the ratio of the length of treated section thatwas subjected to distresses (i.e., full-depth pullout and full-depth cohesion or adhesion loss) to its original length. Itwas found that the propriety emulsion sealant had a 100%failure rate in one of the five evaluation sites. The fiberizedasphalt sealant exhibited 40% failure on average. Amongthe placement configurations, the “band-aid” configurationhad the highest failure rate.

Masson et al. (1999) noted that the performance of crack-sealing treatments depends on the initial condition of thepavement, product selection, and product installation. Inturn, sealant product installation is affected by ambient airtemperature and humidity, asphalt concrete surface tempera-ture and humidity, and sealant application. Based on failurerates, Masson et al. established the cost-effectiveness of dif-ferent sealant products. Hot-pour sealant was more expen-sive than cold-pour, but had a longer service life (4 yearsversus 1 year).

Chong (1990) monitored the treatment performance andpavement conditions where rout-and-seal crack-sealing treat-ment had been applied to cracks in flexible pavements, for atime period that included three winters, in Ontario, Canada.Among his conclusions, Chong established that particularrout configurations were more effective in different regionsin the province and that the rout-and-seal treatment effec-tively delayed or even halted progressive deterioration.

To improve the selection of sealing materials, studies havetried to correlate laboratory findings with actual perfor-mance in the field. Masson et al. (2002) attempted to explainthe performance of sealing materials in low and mediumtemperatures, using their chemical composition and physicalproperties. Physico-chemical laboratory analysis was con-ducted on four sealing material samples in this study. It wasfound that lower viscosity and lower filler content of thesealant resulted in lower adhesion, which adversely affectsshort-term performance. Furthermore, viscosity and fillercontent correlated well with the 1 year field performance ofthe sealant in a wet-freeze climate.

Survey

Two surveys were conducted to understand existing tech-niques utilized for crack sealing. Each survey had 10 differ-ent questions for rating performance of the hot-pour andcold-pour sealants and used poor, fair, good, and excellent asthe rating scale. These questions were answered by transpor-tation agency personnel. The first survey was distributed to21 districts in the state of Texas. According to survey re-sults, hot-pour sealants perform better than cold-pour seal-ants in general. However, hot-pour sealants were rated poorto fair with respect to resistance to flushing and bleeding.The second survey was completed by personnel in nine stateDepartments of Transportation. The results of the secondsurvey were analogous to the first one; hot-pour sealants

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rated better than cold-pour sealants, with the exception of re-sistance to flushing and bleeding.

Experimental field work

To compare the performance of hot-pour and cold-poursealants, a total of seven sealing materials were selected:three cold pour and four hot pour. Test section locations infive districts in Texas were selected for comparison of thesealants: Atlanta, El Paso, Lufkin, Amarillo, and San Anto-nio. Sealants were installed in these locations from Januaryto April 2001. Table 1 shows the ambient temperatures dur-ing the construction of the test sections. Figure 1 shows thetemperate zones for the five different districts in Texas.

For the purpose of this study, three different types of cold-pour sealants, designated C1, C2, and C3, and four types ofhot-pour sealants, designated H1, H2, H3, and H4, wereused. Prior to sealant application, materials were tested inthe laboratory to determine if they met TxDOT specifica-tions (TxDOT 1993, 1998). Table 2 shows the results of thelaboratory tests for the crack sealing materials. Standardtests were used to determine material properties of the seal-ants (TxDOT 1993, 1998). All the sealants used in this studymet the requirements for TxDOT specifications for their re-spective categories. Quantities of material used in the testsection and length of the sealed cracks are presented in Ta-ble 3.

The cracks were cleaned before the application of thesealants: compressed air was blown into the cracks to ensurecleanness. No routing was performed on the cracks in thisstudy. During the sealing process, a metal squeegee wasused for the hot-pour sealants and a rubber squeegee wasused for the cold-pour sealants. After the application of hot-pour sealants, the sections were allowed to cool for approxi-mately 20 min before exposure to traffic. In the case of cold-pour sealants, traffic exposure was not permitted for 2 h toensure proper curing.

The test sections were visited approximately 2 to4 months after initial construction in all five Texas districts.The sections were subsequently visited approximately 1 yearafter construction. In the evaluation process, the AmericanAssociation of State Highway and Transportation Officials(AASHTO) PP20-95 procedure (AASHTO 2000) wasadopted to calculate percentage of effectiveness. The maintypes of failure considered were opening of sealed cracks,full-depth adhesion or cohesion loss, and spalls. For the pur-pose of evaluating the performance of the test sections, fivesuccessive surveys were conducted after the first one. Re-gardless of the district in which the treatment was applied,the overall performance of hot-pour sealants was better thanthat of cold-pour sealants.

Performance of the test sectionsThe AASHTO evaluation procedure can be used for sev-

eral types of crack sealants such as cold-applied sealants,hot-applied sealants, and chemically cured sealants. It alsocan be used for the selection of crack-sealant filler materials,placement configurations, and finishing operations. The pro-jected life of the treatment can be determined by extrapola-tion of the function of treatment effectiveness versus time.

As illustrated in Fig. 2, the main product of this evalua-tion procedure is a chart depicting treatment effectiveness(in percentage) over time. A minimum of one evaluationmeasurement each year is needed to provide an estimate ofthe performance of the crack treatment. For the most effec-tive evaluation, measurements should be conducted duringthe mid-winter period when the crack is at its maximumopening size. It is suggested that the first inspection be per-formed during the first winter, followed by another inspec-tion after the winter season to assess winter damage. Alongwith traffic-control devices, the basic apparatus needed is adistance-measurement device such as a measuring wheel.

For testing, a sample of the treated pavement section wasselected. The AASHTO procedure recommends a samplelength of not less than 150 m. Generally, pavement sectionsare grouped according to the type of treatment, sealant, orsealing procedure. When a pavement sample has been previ-ously evaluated, it is best to use the same section for reeval-uation in successive evaluation procedures.

In this study, the initial crack lengths were measured andrecorded to the nearest 300 mm. A qualitative evaluationwas performed by visually examining the cracks, and thelength of the failure was recorded. Failures were observed inthe form of full-depth adhesion or cohesion loss, completepullout, spalls and secondary cracks, potholes, etc.

Field evaluation results for the test sections

AtlantaFive different sealants were evaluated in the Atlanta dis-

trict: two hot-pour sealants (H1 and H2) and three cold-poursealants (C1, C2, and C3). The treatment was installed on31 January 2001 when the average high temperature was7.8 °C. The first investigation test for performance evaluationwas conducted on 24 May 2001 when the average high was15 °C. The other investigations were conducted on 13 Febru-ary (9.4 °C) and 7 August 2002 (28 °C), 23 January (6.7 °C)and 30 August 2003 (27 °C), and 12 February 2004 (9.4 °C).

The pavement structure of this section was an asphalt con-crete overlay on jointed concrete pavement (JCP), wheremost of the cracks were reflection cracks over the joints.These cracks were spaced transversely and equally at 4.5 m.The main cause of the cracks, some of which could be seenwith the naked eye, was probably heavy truck traffic thatcaused movements of joints. Figure 3 depicts performancetrends for the sections in the Atlanta district.

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Temperature (°F)

Sealant AtlantaElPaso Amarillo

SanAntonio Lufkin

C1 46 65 67 77C2 47 67 75 61C3 64 70 77 76H1 49 45 82 70H2 59 66 77H3 77 72 78H4 74 73 75

Table 1. Ambient air temperatures during the construction of thetest sections, °F = 1.8 °C + 32.

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Sealant

Brookfieldviscosity at25 °C (Pa�s)

Evaporationresidual(%)

Rubbercontent(%)

Flashpoint(°C)

Penetrationat 4 °C(%)

Penetrationat 25 °C(%)

Resilienceat 25 °C(%)

Flow at25 °C(mm)

Ductilityat 4 °C(cm)

Bondtest at–18 °C

Softenigpoint(°C)

C1 12.9 67.8 0 235 12 42 15 5+ (fail) 100+ Broke 94C2 13.6 65 0 282 12 45 23 5+ 100+ Broke 70C3 32.6 67 0 304 14 60 20 5+ 100+ Pass 71H1 N/A N/A 25.8 204 13 34 59 5+ 7.5 Broke 76H2 N/A N/A 14.6 282 21 47 69 5+ 16 Pass 84H3 N/A N/A 24.6 210 11 33 54 5+ 8 Broke 68H4 N/A N/A 0 213 48 82 72 Pass 49 Pass 88

Note: N/A, not applicable.

Table 2. Laboratory test results for crack sealing materials.

Fig. 1. Temperate zones for the five districts in Texas.

Quantity, crack length (m)

Sealant Atlanta El Paso Amarillo San Antonio Lufkin

C1 197 L, 1295 57 L, 767 25 L, 107 57 L, 824C2 121 L, 838 45 L, 928 72 L, 996 53 L, 686C3 178 L, 1280 25 L, 152 45 L, 528 83 L, 920H1 163 kg, 1280 91 kg, 305 163 kg, 776 80 kg, 450H2 340 kg, 1257 95 kg, 830 146 kg, 809H3 196 kg, 652 59 kg, 146 126 kg, 1179H4 24 kg, 152 195 kg, 776 171 kg, 738

Table 3. Quantities of sealing materials and lengths of sealed cracks.

Hot-pour sealants exhibited excellent performance com-pared with cold-pour sealants in these sections. Both the hot-pour and cold-pour sealants decreased in overall effective-ness between 2001 and 2004. By the final investigation dur-ing the winter of 2004, H1 and H2 scored a treatmenteffectiveness rating of 73.7% and 68.2%, respectively. Con-versely, the cold-pour sealants experienced more rapid fail-ures, and by the winter of 2004, C1 and C2 exhibited totalfailure whereas C3 had a treatment effectiveness rating ofonly 6%.

El PasoFour types of sealants were used in this district, two hot-

pour sealants (H2 and H3) and two cold-pour sealants (C1and C2). The treatment procedures were performed on5 May 2001, with an average high temperature of 21 °C.The first investigation was on 19 June 2001 (28 °C). Thesecond and third investigations took place on 10 April 2002(17 °C), and 22 August 2002 (27 °C), respectively, and thefourth, fifth, and final investigations were carried out on27 March 2003 (16 °C), 26 August 2003 (27 °C), and27 February 2004 (12 °C), respectively. These test sectionswere located in a heavy truck traffic area by the USA–Mexico border, and it was observed that most of the failuresoccurred on the wheel path. Figure 4 depicts performancetrends for the sections in the El Paso district.

As with the Atlanta district, the performance of cold-poursealants was, in general, much lower than that of hot-poursealants. However, in contrast, the treatment effectiveness ofthe hot-pour sealants dropped to 23.9% and 28.4% by the fi-nal winter 2004 investigation. Overall, hot-pour sealants inthis district dropped from an average treatment effectivenessof 70.6% during the winter of 2003 to an average of 26.2%

in the winter of 2004. Cold-pour sealants experienced totalfailure by the 2004 winter investigation.

AmarilloIn the Amarillo district, three hot-pour (H1, H3, and H4)

and two cold-pour (C1 and C3) sealants were used. Thetreatment procedures were undertaken on 19 February 2001,which had an average high of 5.6 °C. The six investigativevisits were made on 21 June 2001 (24 °C), 31 March 2002(11 °C), 15 August 2002 (25 °C),28 March 2003 (11 °C),25 August 2003 (24 °C), and 26 February 2004 (6.1 °C).Figure 5 depicts performance trends for the sections in theAmarillo district.

With the exception of H3, hot-pour sealants showed excel-lent performance 15 months after installation in the spring of2002. H1 declined to 6% treatment effectiveness by the finalvisit during the winter of 2004. H3 declined to 13.5% treat-ment effectiveness by the winter of 2004. Sealant H4 per-formed best, with a final treatment effectiveness of 47%during the 2004 winter visit. As with the other districts,cold-pour sealant performance revealed very low values; bythe winter of 2003, C1 and C3 experienced total failure.

San AntonioAll seven types of sealing materials were used in treat-

ment procedures in the San Antonio district. Treatment con-struction started on 25 April 2001, with an average hightemperature of 22 °C. An investigation visit was conductedon 18 July 2001 (29 °C). The next five investigation visitstook place on 8 March 2002 (16 °C), 14 September 2002(27 °C), 30 January 2003 (11 °C), 11 September 2003(28 °C), and 20 February 2004 (13 °C). Figure 6 depicts theperformance trends of the sealants used in test sections inthe San Antonio district.

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Fig. 2. Example graph of treatment effectiveness versus time.

Fig. 3. Performance trends for the sections in Atlanta district. Fig. 4. Performance trends for the sections in El Paso district.

With the exception of the decreasing performance of H2,first apparent during the winter 2002 investigation, and sub-sequent failure by the final investigation in the winter of2004, hot-pour sealants attained a high treatment effective-ness level. H1, H3, and H4 had a treatment effectiveness thathad exceeded 66% by the final investigation in the winter of2004. The failure of the H2 sealant may have been becauseit was located in an area where a busy store was situated.Thus traffic might have been heavier on the H2 section.Sealant H3 maintained the highest treatment effectivenesslevel of 71.2%.

Sealant C1 had failed totally by the winter 2002 visit. Un-like the other two cold-pour sealants, the performance of C1did not improve after the winter 2002 evaluation. SealantsC2 and C3 both failed completely by the winter of 2004.

LufkinIn the Lufkin district, two cold-pour sealants (C2 and C3)

and two hot-pour sealants (H1 and H4) were installed on6 February 2001, with an average high temperature of 11 °C.Subsequent evaluation tests were conducted six times:7 May 2001 (22 °C), 22 February 2002 (13 °C), 20 August2002 (28 °C), 1 January 2003 (8.9 °C), 4 September 2003(27 °C), and 13 February 2004 (11 °C). Figure 7 depicts theperformance trends of the sealants used in test sections inthe Lufkin district.

As was the case in all the other districts, hot-pour sealantsattained a treatment effectiveness greater than that of cold-pour sealants. The high performance of H4 stayed relativelythe same through the August 2002 evaluation and was ob-served to have decreased slightly to 91.1% when investi-

gated during the winter of 2003. The performance of H1 haddecreased to 86% by the winter 2003 investigation.

The performances of both C2 and C3 declined after thefirst evaluation. C2 declined to 23.2% by the winter 2003 in-vestigation. The performance of C3 could not be measuredat the summer 2002 investigation or afterwards; this test sec-tion had deteriorated significantly and had been milled andgiven a new overlay.

As can be seen from the figures, an increase in the perfor-mance of the sealants was observed during the third and fifthinvestigations as opposed to an expected decrease in perfor-mance with time. This can be attributed to the fact thatcracks close during summer months. Also, at high tempera-tures the viscosity of the sealing material decreases, whichmay cause refilling of the generated cracks.

Discussion of results

The findings of this study were obtained from field visitsto the test sections in five Texas districts throughout a periodof 3 years. The first evaluations were conducted within 3 to4 months after crack sealants were placed. Subsequent eval-uations took place over the course of 3 years. This discus-sion of the results aims to understand and explain theperformance trends of the sealing materials.

In the case of hot-pour sealants, the sealant originally fillsprimarily the top part of the crack and does not penetrate allthe way down to the crack root. Hence, it is more likely thatthe failed sections treated with hot-pour sealants will recoverin high temperatures because of the decrease in viscosity.Because excessive amounts of hot-pour sealant usually accu-mulate near the surface, enough material will be available toseal the failed sections when the viscosity drops.

On the other hand, cold-pour sealants have lower viscosityin general than hot-pour sealants during construction. There-fore, when they are applied to a crack, they tend to penetratethe cracks more thoroughly. This leaves less surplus materialand subsequently less recovery in the failed sections whenthe viscosity drops because of high temperatures.

In the summer 2001 investigation, it was found that theoverall performance of hot-pour sealants was slightly betterthan that of cold-pour sealants. Across the districts, all hot-pour sealants had the best results, scoring an average treat-ment effectiveness level of approximately 100%. With theexception of Amarillo, where C1 performed with 87.7%

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Fig. 6. Performance trends for the sections in San Antonio district.

Fig. 7. Performance trends for the sections in Lufkin district.Fig. 5. Performance trends for the sections in Amarillo district.

treatment effectiveness, cold-pour sealants exhibited anoverall average treatment effectiveness of greater than 90%.

After the first visits, the performance evaluation involvedinvestigative visits each summer and winter for the next3 years. During the second investigation in the winter of2002, it was found that the performance of hot-pour sealantscontinued to be better than that of cold-pour sealants in ev-ery district. Hot-pour sealant H4 performed the best, with atreatment effectiveness average of 96.4%. Cold-pour sealantC1 had the least resistance to traffic and environmental in-fluences, with a treatment effectiveness level of 30.3%1 year after installation. The results show a general decreasein treatment effectiveness for all the sealants. However, thedecrease was much more rapid for cold-pour sealants.

Similar trends were observed in the remaining visits to thetest sections throughout the project. The third investigationwas conducted approximately 18 months after construction,during the summer of 2002. The fourth, fifth, and sixth in-vestigations were conducted during the winter of 2003, thesummer of 2003, and the winter of 2004. By the fourth in-vestigation, the treatment effectiveness level of all cold-poursealants had decreased to a level below 60%, and hot-poursealants were performing better comparatively.

The results from the final investigation in the winter of2004 are shown in Table 4. In the final investigation in theAtlanta district, H1 and H2 scored a treatment effectivenessof 73.7% and 68.2%, respectively. Cold-pour sealants had anaverage of 2.06% treatment effectiveness, with C3 having atreatment effectiveness of only 6%, and C1 and C2 exhibit-ing total failure. In the El Paso district, H2 and H3 had atreatment effectiveness of 23.9% and 28.4%, respectively,during the final investigation. They had an average treatmenteffectiveness of 26.15%. In contrast, the performance ofcold-pour sealants was much lower. Sealant C2 had experi-enced total failure before the final investigation in the winterof 2004, and C1 exhibited total failure in the winter 2004visit.

In the Amarillo district, sealant H4 showed the best per-formance in the final visit, with a final treatment effective-ness of 47%. The other hot-pour sealants, H1 and H3, had a

treatment effectiveness of 6% and 13.5%, respectively, dur-ing the final visit in the winter of 2004. Cold-pour sealantsC1 and C3 experienced total failure before the final investi-gation in the winter of 2003. Finally, in the San Antoniodistrict, hot-pour sealants attained a high treatment effective-ness level in the final investigation. With the exception ofH2, which was placed in a section that was located in anarea next to a busy store where traffic was most likelyhigher, the hot-pour sealants had an average treatment effec-tiveness level of 68%, with H1 maintaining the highest treat-ment effectiveness level of 71.2%. All the cold-poursealants, on the other hand, had failed by the final investiga-tion. Test sections in Lufkin were not evaluated after thesummer 2002 investigation because the sections had beengiven a new overlay.

Hot-pour sealants performed better than cold-pour seal-ants in every district. All cold-pour sealants in all districtsshowed very low performance, with only one in the Atlantadistrict showing 6% treatment effectiveness in the final visitwith the rest at 0%. The overall average treatment effective-ness for cold-pour materials was 0.52%. Hot-pour materials,on the other hand, had an average treatment effectiveness of42.95%.

In a comparison of individual sealants, H4 achieved thebest overall treatment effectiveness of 56.75%, whereas C2achieved the lowest overall treatment effectiveness at 0%.However, no cold-pour sealant achieved more than 2% treat-ment effectiveness. Hot-pour materials did not go below the34% treatment effectiveness level, with a range from 33.87%to 56.75%.

Sealants also performed differently in different districtswith varying environmental and traffic conditions. As previ-ously mentioned, El Paso is located on the Mexican borderwhere there is heavy truck traffic. The hot-pour sealantsplaced on the test sections in the El Paso district had higherfailure rates than hot-pour sealants placed in other districts,perhaps because of the effect of heavy truck traffic at theborder. In addition, in the Amarillo district, there was agreater fluctuation in treatment effectiveness levels betweenwinter and summer investigative visits than experienced in

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Treatment effectiveness (%)

Atlanta El Paso Amarillo San Antonio Lufkin Average

SealantC1 0.2 0 0 0.1 N/A 0.07C2 0 0 N/A 0 N/A 0.00C3 6 N/A 0 0 N/A 2.00H1 73.7 N/A 6 67 N/A 48.91H2 68.2 23.9 N/A 9.5 N/A 33.87H3 N/A 28.4 13.5 71.2 N/A 37.70H4 N/A N/A 47 66.5 N/A 56.75

Average for cold pour 2.06 0.00 0.00 0.03 N/A 0.52Average for hot pour 70.95 26.15 21.17 53.55 N/A 42.95Overall average 29.62 13.07 13.30 30.61 N/A 21.65Date of investigation, 2004 12 Feb 27 Feb 26 Feb 20 Feb 13 Feb

Note: N/A, not available.

Table 4. Treatment effectiveness evaluation results for the performance after the final (sixth) in-vestigation, winter 2004.

other districts. In Amarillo, most cracks sealed were low-temperature cracks, which move according to pavement tem-perature differences.

Conclusions

This study was conducted to assess the field performanceof hot- and cold-pour crack sealants. A survey assessingcrack sealant performance was conducted in 21 districts inTexas and nine state Departments of Transportation. Testsections in five Texas districts were constructed during thefirst year of the study. then the long-term performance ofseven different sealants was monitored for the next 3 years.Performance was evaluated starting from the fifth month af-ter the construction of the treatment.

Similar to the findings of this study, the survey suggestedthat hot-pour sealants show better performance than cold-pour sealants overall. The field evaluation of the test sec-tions indicated that hot-pour sealants perform better overtime than cold-pour sealants. The results from the final in-vestigation show that hot-pour sealants performed betterthan cold-pour sealants in every district. All cold-pour seal-ants in all districts showed very low performance, with onlyone in the Atlanta district showing 6% treatment effective-ness in the final visit, with the rest at 0%. The overall aver-age treatment effectiveness for cold-pour materials was0.52%. It took approximately 3 years for hot-pour materialsto reach an average treatment effectiveness of 42.95%.

References

AASHTO. 2000. Standard practice for evaluating the performanceof crack sealing treatment on asphalt surfaced pavements. Des-ignation: PP20-95. American Association of State Highway andTransportation Officials, Washington, D.C.

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