This chapter contains three main parts. The first part discusses the lab results of 16 hot-poured crack sealants using TAM test. The second part presents the effect of aging on sealant
performance. Sealants are tested at the same temperature using different preparation procedures:
lab-unaged, lab-aged, and field-aged. The third part investigates the relationship between the field performance and the lab results. Field performance data are recorded for all installed sealants (Ozer et al. 2014). Field samples are collected from four test sites: Minnesota (MN), Ontario (ON), New York (NY), and New Hampshire (NH). A statistical grouping is applied for the data. Games-Howell is used for the field performance data while the Tukey test is applied to lab results.
Lab Results of Sealants
Sixteen sealants are aged using vacuum oven aging. Each sealant is tested for at least three temperatures. Results for each temperature are based on at least four replicates. The temperatures are selected based on the expected sealant grade. Figure 5-1 shows the lab-aged results for the 16 sealants.
Figure 5-1 shows that sealant adhesive results are sealant composition dependent and vary among the tested sealants. All sealants are tested at -28 °C to provide a proper comparison.
Sealant Bb breaks prematurely at this temperature for all four replicates. The figure also shows the variability in the tested specimens. The lowest CoV is 2.62% and the highest is 27.18%, which was for a highly crumb-modified sealant (Ib) at a relatively brittle condition. Comparing sealants at one temperature may not reflect the sealant adhesive behavior. Three distinctive sealant adhesive behaviors can be detected through the results shown in Figure 5-1. These are sketched in Figure 5-2 and summarized in Table 5-1.
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(a) Ad (b) Da
(c) Bb (d) Ca
(e) Ed (f) Fb
(g) Gd (h) Hb
Figure 5-1: Effect of Temperature on Lab-Aged Specimens for 16 Hot-Poured Crack Sealants
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(i) Ib (j) Kc
(k) Jd (l) Nb
(m) Mb (n) Sd
(o) Ob (p) Pd
(Figure 5-1: continued)
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Figure 5-2: A Schematic Diagram of Adhesion Peak Load Patterns for Sealants Tested Using TAM Test Considering CSBBR Grade
Table 5-1: Summary of Adhesion Pattern with Temperature Drop for All 16 Sealants Tested Using Lab-Aged Specimens
Table 5-1 shows that for stiff sealants, the adhesive peak load drops with a temperature
reduction. This explains the premature failures for these sealants at extremely low temperatures.
In this case, the peak load at -28 ºC is around zero. Crumb rubber modified sealants show an increase in the peak load as the temperature drops. This might be due to the effect of temperature on the crumb rubber itself. Finally, most of the sealants maintain their adhesive peak loads, with a slight increase as the temperature drops. In general, peak load is sealant dependent.
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Aging Effect on Sealant Lab Test Results
Aging is a key factor in viscoelastic materials’ properties. As sealants experience the field conditions, the sealant properties change (Ozer et al. 2015). All 16 sealants were tested at -28 ºC using various aging conditions. These conditions include lab-unaged specimens, lab-aged specimens, field-aged specimens, and lab kettle specimens. Lab-unaged specimens were
prepared according to ASTM-D5167-13 2013. Lab-aged specimens were prepared according to AASHTO-TP-86-10 2015. Field-aged specimens were collected from the field two and/or three years after installation. Each test site is considered as an aging environment. Finally, lab kettle specimens were collected from the sealants conditioned using the lab kettle.
Figure 5-3 shows of the adhesive peak load at one temperature using TAM test. All 16 sealants have more than one aging condition. However, sealants having the most variable conditions are shown Figure 5-3. Most of the sealants studied showed no change due to the field aging
compared to lab aging procedure. However, field specimens showed a higher adhesive load compared to lab-aged specimens. This could be attributed to the complex nature of the actual field aging compared to that at the lab as well as the possible impact of traffic.
TAM test shows that aging does not have the same influence the temperature has. Figure 5-3 shows that field aging could be conservatively considered when using the AASHTO aging procedure. Hence, adhesive potential behavior could be predicted before sealant installation in the field. This provides sealant agencies the flexibility to select the proper hot-poured sealant for installation.
Relationship between Laboratory Test Results and Field Performance
Field-aged sealant specimens were tested using TAM test and the results were correlated to the field performance of the same sealant. Sealants from the test sites, described in Chapter Three and utilized for CSAT, were used for this purpose: Minnesota, Ontario, New York, and New Hampshire. Specimens were collected through different years after winter seasons. Each collected field-aged sample was correlated with the PI for the year when the samples were collected. Unlike CSAT, only one temperature was used for testing all sealants in the section.
This is because of the conclusion that aging does not alter the adhesive load. The selected tested temperature was -28 °C. This allows testing all sealants at the same temperature, close to that in
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the field. A full match between the lab test and field results is unlikely. Other factors influence the sealant field performance, including sealant installation, sealant stiffness, and pavement maintenance activities during the sealant lifetime. The same procedure applied to CSAT results in Chapter Three was used for TAM results. The field PI was computed for each sealant in the section and statistically grouped using Games-Howell distribution. The Tukey test was applied to the lab test results.
(a) Da (b) Fb
(c) Gd (d) Mb
Figure 5-3: TAM Test Results at -28° C: LA = Lab-Aged, LK = Lab-Kettle, MN = Minnesota Section, ON = Ontario Section, NH = New Hampshire, NY = New York, FA2 = Second-Year Specimen, FA3 = Third-Year Specimen
Minnesota (MN) Test Site
The Minnesota test site shows a fair correlation between the field PI and field-aged specimens tested in the lab. Field-aged specimens were collected after the second winter for the seven different sealants installed in this section. These samples were chosen since they showed higher scatterings in field PI. The coldest temperature for this test site was -22.2 °C. Table 5-2 shows the statistical subsets for this site. Sealants Mb and Fb are among the best performing in the field and in the lab.
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Table 5-2: Statistical Grouping of the Sealants Installed in Minnesota Test Site Based on their Field Performance and Lab Results at -28 °C after Second Winter
Sealant ID
Field Performance TAM (-28 ºC) PI
The Ontario test section shows an excellent correlation between the field performance and the results of the field-aged specimens tested in the lab. Field-aged specimens were collected after the third winter for the seven different sealants installed in this section. These various sealants showed good scatterings in field PI data. Table 5-3 shows the statistical subsets for this site. A perfect match between peak load subsets and field performance subsets exists; this could be due to the coldest temperature experienced by this section (-29.2 °C). Sealant Bb shows the lowest peak load and the poorest field performance. Pd experienced a poor field performance and showed low adhesive peak loads. Sd and Da showed the best performance in the field and their adhesive characteristics were the best in the lab. Finally, sealants Rb, Mb, and Gd showed fair field performance, and the lab results categorized them in the second rank of the statistical groups. In general, this section shows that TAM results could be used to predict field performance.
New York (NY) Test Site
The New York test section shows a very good correlation between the field performance and the results of the field-aged specimens tested in the lab. Field-aged specimens were collected after the second winter for the six different sealants installed in this section. These samples showed good scatterings in field performance. The coldest temperature for this test site was -20.3 °C.
Table 5-4 shows the statistical subsets for this site. A very good match between peak load subsets and field performance subsets exists. The exception is for Kc and Ob. Other sealants
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showed very good correlation. Sealants Ca and Ib exhibited an inferior field performance as well as lab adhesive characteristics. On the other hand, sealants Jd and Da were performing well in the field and their adhesive characteristics were also good. This section shows that TAM test is working.
Table 5-3: Statistical Grouping of the Sealants Installed in Ontario Test Site Based on their Field Performance and Lab Results at -28 °C after Third Winter
Sealant ID
Field Performance TAM (-28 ºC) PI
Table 5-4: Statistical Grouping of the Sealants Installed in New York Test Site Based on their Field Performance and Lab Results at -28 °C after Second Winter
Sealant ID
Field Performance TAM (-28 ºC)
PI
New Hampshire (NH) Test Site
The New Hampshire test section shows a good correlation between the field performance and lab test results of field-aged specimens. Field-aged specimens were collected after the third winter for the five different sealants installed in this section. The coldest temperature for this test site was -23.8 °C. Table 5-5 shows the statistical subsets for this site. A good match between peak load subsets and field performance subsets exists. Sealant Ob shows the worst field performance
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and the lowest adhesive peak load. Moreover, sealant Ed shows superior performance in the field and has the highest peak load. This section shows that TAM is working just as in the New York and Ontario test sections.
Table 5-5: Statistical Grouping of the Sealants Installed in New Hampshire Test Site Based on their Field Performance and Lab Results at -28 °C after Third Winter
Sealant ID
Field Performance TAM (-28 ºC)
PI
Correlation between Field Performance and Lab Results
TAM test was used to correlate lab adhesive characteristics and sealant field performance in four test sites. Results show a good correlation between TAM peak loads and the PI for the tested sealants. In general, a change in the adhesive peak load corresponded to similar field
performance change. This correlation was investigated through statistical analysis. Ontario, New York, and New Hampshire showed an acceptable correlation between the lab test results and field performance. Figure 5-4 shows a good correlation between the adhesion peak load and the PI for these sections. Minnesota shows a fair correlation and shows the best performances in the field and lab are the same.
Summary
Sixteen sealants were installed in four test sites and tested using TAM. Lab test results on lab-aged specimens reveals three main patterns for the effect of temperature drop. The first shows an increase of adhesive load for crumb rubber modified sealants. The second maintains the adhesive peak load at a certain level. The peak load is slightly increased as the temperature drops. This is the case for most sealants. The third shows the peak load is dropped in stiff sealants. The
AASHTO aging procedure was found to be appropriate for conservatively simulating field aging.
The correlation between TAM results and the field PI is satisfactory. TAM test is a good step
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towards developing a true understanding of the adhesion characterization of hot-poured crack sealants.
Figure 5-4: Correlation between Performance Index and Adhesion Peak Load Using Data from Ontario, New Hampshire, and New York
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