Feasibility of using Mastic for Performance Grading in Place of Extraction using SPS10 Mixtures

Abstract

Because of the increased use of reclaimed asphalt pavement, reclaimed asphalt shingles, rejuvenators, and other additives, performance of asphalt mixtures can no longer be guaranteed by controlling properties of the binder. To determine the effect of additives on asphalt performance, the current procedure is to extract the binder from the mixture using solvents and recover the binder by removing the solvent. This is a two-step procedure, which can be time consuming and costly and which requires chemicals considered hazardous unless used with special care. Another issue is the quality of the extracted binder, as the process of dissolving the binder and recovering it from chemicals may affect the properties of the extracted binder. In this study, we suggest the use of mastic separated from the mixture, in place of extraction. The fine portion of the mixture (particles less than 0.25 mm) is physically separated from the mixture without use of solvents. This material is called composite mastic since it includes effects from all additives on the binder. The process of preparing composite mastic is significantly faster and less costly than extracting the binder. The separated mastic is tested following the Unified Performance Tests by incremental Method (UPTiM) using a dynamic shear rheometer to determine the high-, low-, and intermediate-temperature performance grades, similar to those of asphalt binder. This study shows strong correlations between properties of composite mastic, extracted asphalt, and asphalt mixture. Therefore, testing mastic could be a reliable alternative to testing extracted binder and compacted mixture.

Because of the increased use of reclaimed asphalt pavement (RAP), reclaimed asphalt shingles (RAS), rejuvenators, and other additives, performance of asphalt mixtures can no longer be guaranteed by controlling the properties of virgin asphalt binder. To determine the effect of the additives on the binder, the current procedure is to extract the binder from the mixture using solvents and recover the binder by a roto-evaporation process ( 1 , 2 ). This is a two-step procedure, which can be time consuming and costly and at the same time requires chemicals considered hazardous unless used with special care. Another issue is the quality of the extracted binder, as the process of dissolving the binder and recovering it from chemical solvents can potentially affect molecular structure and therefore properties of the binder.

One important challenge is that significant amounts of extracted binder are required for determining the properties of the material using the current binder testing protocols. Furthermore, some properties, such as low-temperature and fatigue cracking, require long-term aging of the extracted binder in a pressure aging vessel (PAV) ( 3 ). The extraction process and long-term aging of large quantities of binder is labor intensive and time consuming, and exposes the technician to potentially hazardous solvents.

Recently, the use of mastic separated from the mixture has been suggested by Mohseni in US Patent 10,416,057 ( 4 ). In this method, a small amount of the fine portion of the mixture (with particles less than 0.25 mm) is physically separated from the mixture without use of solvents. The mastic prepared with this method is called composite mastic since it has all the effects of the additives contained in the binder and mixture. Preparing composite mastic is faster and less costly than solvent extraction of binders.

Testing Methods

The separated mastic is tested following procedures of the Unified Performance Tests by incremental Method (UPTiM), using a dynamic shear rheometer (DSR) to determine fatigue properties and the high- and low-temperature performance grades (PGs), similar to those of asphalt binder. The UPTiM tests require a small amount (mg scale) of mastic and take a fraction of the time that current binder tests need to determine binder properties. A brief description of the UPTiM tests performed on asphalt binder, mastic, and mixture in this study follows.

UPTiM Binder, Mastic, and Mixture Performance Tests

UPTiM, which stands for “Unified Performance Tests using incremental Method,” is based on a unified concept that applies to low-, high-, and intermediate-temperature tests on asphalt binder, mastic, and mixture. The UPTiM tests are conducted in several stress/temperature increments to capture material performance at the most critical combination of stress and temperature. The test parameter is m*, which is the minimum permanent strain rate of the critical test increment. The unified concept of these test methods allows the performance of liquid binder, composite mastic, and mixture to be related ( 5 ).

Incremental Repeated Load Permanent Deformation Mixture Tests

The incremental repeated load permanent deformation (iRLPD) mixture tests used in this study determine resistance to rutting and fatigue cracking. The iRLPD high-temperature rutting test is described in AASHTO TP 116 ( 6 ). The iRLPD fatigue test is included in the new version of AASHTO TP 116. The iRLPD mixture rutting and fatigue tests are conducted using the iRLPD Dynamic Testing System (iDTS) developed by Pavement Systems (Figure 1). The iDTS is a 20 KN dynamic loading machine with the temperature control between 4°C and 64°C. The frame is large enough to accommodate samples 150 mm in diameter by 120 mm in height, compacted by the Superpave Gyratory compactor for mixture design.

Figure 1.

Incremental Repeated Load Permanent Deformation (iRLPD) testing machine developed by Pavement Systems.

Mixture Rutting Test

The iRLPD mixture rutting test is conducted using the iDTS (Figure 1) setup. The procedure is described in AASHTO TP 116 as follows:

Specimens are gradually loaded in several increments.

Stress and temperature resemble field conditions.

Stress level is equivalent to truck tire pressure.

Repeated pulse loading mimics passing of truck axles at highway speed.

Following AASHTO TP 116, a damage curve is created for each mixture. The damage curve, which represents resistance to rutting at any temperature and stress level, has the power function shown in

m^{*} = a {(T \times P)}^{b}

(1)

where

m* (minimum strain rate) = the unit rutting damage,

T = temperature (°C),

P = stress (kPa), and

a and b = coefficients of the power curve.

While minimum strain rate (m*) changes with temperature (T) and stress (P), the “b” coefficient of Equation 1 is a unique parameter of the mixture and independent from stress level and test temperature. For this reason, the “b” parameter has been successfully used to rank various mixtures designed for different traffic levels and environments ( 7 ). In addition, the relationship between parameter “b” of asphalt mixtures and the PG of asphalt binder has been examined previously ( 8 ).

Using the data from the two published TRB papers ( 7 , 8 ), an equation was developed to determine mixture effective PG from the “b” coefficient. The equation for the effective mixture PG is

PG = - 42.35 \times b + 174.14

(2)

The basis of the mixture PG model is the data derived from testing 12 dense-graded mixtures prepared with the NCHRP 9-29 aggregate ( 9 ) and 12 modified and unmodified binders from four suppliers ( 8 ). The model was verified using nine mixtures with known binder properties from nine state departments of transportation ( 10 ). In addition to the effective PG, grade with traffic is determined using the table of grade bumps developed by Mohseni et al. ( 11 ) and included in LTPPBind V3.1 ( 12 ). Effective mixture PG is part of the new additions to AASHTO TP 116, which provides a tool to quantify the relationship between virgin mixtures and those containing RAP/RAS to determine the effect on mixture performance ( 13 ).

Mixture Fatigue Test

The UPTiM fatigue test for mixtures is similar to the iRLPD high-temperature test (AASHTO TP 116) with the following exceptions: (1) the test is performed at the intermediate temperature of the mixture, established by the intermediate temperature of the binder, extracted binder, or mastic; (2) the test specimen is a 150-mm diameter by 50-mm disk cut from volumetric cylinders and loaded in indirect tensile (IDT) mode; and (3) specimens are subjected to increasing stress in seven to 12 increments until failure. The parameter of the test is permanent strain (m*) of the last increment before failure. More details on the UPTiM mixture fatigue test can be found in the literature ( 14 ). Figure 2 shows the iRLPD fatigue test setup and the failed sample on the iRLPD Dynamic Testing System.

Figure 2.

Fatigue test setup for TP 116 (incremental Repeated Load Permanent Deformation, or iRLPD).

UPTiM Binder and Mastic Tests

The UPTiM tests for asphalt binder and mastic, which include low-, intermediate-, and high-temperature measurements are performed using a DSR. The tests provide low- and high-performance grades, compatible with AASHTO R 29 ( 15 ), high-temperature PG with traffic level, compatible with LTPPBind V3.1 and AASHTO M 332 ( 16 ), intermediate temperature, compatible with AASHTO R29 for unmodified binders, % elastic recovery, compatible with AASHTO T 301 ( 17 ), and crack tip opening displacement (CTOD) parameter of double-edge-notched tension (DENT) test, compatible with AASHTO TP 113 ( 18 ). UPTiM parameters are sensitive to the presence of additives and modifiers and differentiate between types and amounts of polymer and various amounts of re-refined engine oil bottom (REOB). The binder tests are performed using an 8-mm diameter plate geometry with 0.5-mm gap. The mastic tests are performed using an 8-mm diameter plate geometry with 1-mm gap. A brief description of the tests follows.

Low-Temperature Binder and Mastic Test

The low-temperature test, referred to as incremental creep for cracking at low temperature (iCCL), is a constant creep of 60 s like the bending beam rheometer (BBR). The test can be performed at several increments of multiple subzero temperatures or at multiple stresses at a fixed subzero temperature (e.g., –5°C). The duration of the test is about 30 min. The slope of the creep curve is used to determine the continuous low-temperature PG, equivalent to AASHTO R 29. More details on the iCCL test can be found elsewhere ( 19 , 20 ).

High-Temperature Binder and Mastic Test

The high-temperature test determines the high-temperature PG equivalent to AASHTO M 320 for unmodified binders. For modified binders, the high-temperature test, in addition to the continuous PG, provides traffic bumping similar to LTPPBind V3.1 and AASHTO M 332. These tests are performed at several temperature increments each including 60 cycles of repeated 0.1 s load followed by 0.9 s rest period. The secondary slope of the permanent strain curve (m*) is used to determine the PG. The test duration is 30 min. Details of the high-temperature test are found in the literature ( 8 ).

Binder and Mastic Fatigue Test

The fatigue tests for binder and composite mastic are referred to as FIT-B and FIT-C (Fatigue test at Intermediate Temperature for Binder and Composite mastic). These tests are performed at several temperature increments, each including 60 cycles of repeated 0.1 s load followed by 0.9 s rest period. The slope of the permanent strain curve (m*) at failure is used to determine parameters equivalent to the percentage of elastic recovery (AASHTO T 301) and to the CTOD parameter of the DENT test (AASHTO T 113). The temperature at failure, which is the temperature at which the material is most vulnerable to fatigue cracking, is the intermediate temperature. This temperature is comparable to the SHRP intermediate temperature for neat binders; however, the intermediate temperature of binders with additives and modifiers could be lower or higher than that of the neat binders. The UPTiM fatigue test is sensitive to the type and level of modification and clearly shows the effects of styrene-butadiene-styrene (SBS), polyphosphoric acid (PPA), and REOB on fatigue performance. More details on the binder and mastic fatigue tests can be found elsewhere ( 14 ).

The UPTiM binder and mastic tests are conducted by UPTiM modular compact rheometer (MCR) using UPTiM software that performs the tests (Figure 3).

Figure 3.

UPTiM MCR rheometer and UPTiM software.

Objective and Scope

The main objective of this study is to investigate the feasibility of using composite mastic as a replacement for binder extraction by comparing performance of extracted binder and composite mastic. Another objective is to determine the relationship between composite mastic and mixture performance tests.

The scope of this study is to test ten Missouri Department of Transportation (Missouri DOT) SPS10 mixtures, which were collected from the long-term pavement performance (LTPP) site, for high-, low-, and intermediate- performance properties. Some results for mixtures from other studies are also presented to complement the Missouri DOT SPS10 results. The asphalt binder of the ten SPS10 mixtures was extracted using ASTM D8159-18, recovered using ASTM D5404/D5404M-12 (2017) and then aged in the PAV using AASHTO R 28 by Ingevity (Lab A). Conventional binder performance tests to determine low and high PG were conducted on the extracted binders, also by Lab A. Composite mastic was separated from the ten mixtures by Pavement Systems (Lab B) according to the procedure outlined in ( 4 ) and tested to determine low-, high-, and intermediate- temperature PGs and properties according to UPTiM procedures. The test results on binder, mastic, and mixture were then compared.

Testing Plan

Table 1 provides the testing plan of the study. As indicated in the table, testing was carried out on unaged and PAV-aged extracted binders, recovered mastic, and compacted mixtures of SPS10 and Maryland State Highway Administration (MDSHA) at high, low, and intermediate temperatures according to conventional and UPTiM tests in Lab A and Lab B, respectively.

Table 1.

List and Number of Tests Conducted on Each Sample

		Test conducted by Lab B			Tests conducted by Lab A
Material type	Test temperature	UPTiM test type	Number of SPS10 mixtures + MDSHA samples	No. of tests	Conventional Test type	Number of materials	No. of tests
Unaged extracted binder	High	UPTiM HT	10	3	AASHTO R 29	10	1
	Low	iCCL	10	3	na	na	na
	Intermediate	FIT-B	10	3	na	na	na
PAV-aged extracted binder	High	UPTiM HT	10	3	na	na	na
	Low	iCCL	10	3	AASHTO R 29 (BBR)	10	1
	Intermediate	FIT-B	10	3	AASHTO R 29	8	1
Asphalt composite mastic	High	UPTiM HT	10 + 3 (MDSHA)	3	na	na	na
	Low	iCCL	10	3	na	na	na
	Intermediate	FIT-C	10	3	na	na	na
Asphalt mixture	High	AASHTO TP 116	7 + 3 (MDSHA)	2 to 5 + (6)	NA	NA	NA
	Low	na	na	na	ASTM D7313 (DCT)	9	3
	Intermediate	AASHTO TP 116	6	3	AASHTO TP 124 (I-FIT)	10	3

Note: UPTiM = Unified Performance Tests by incremental Method; MDSHA = Maryland State Highway Administration; no. = number; UPTiM HT = UPTiM high temperature; iCCL = incremental creep for cracking at low temperature; FIT-B = fatigue test at intermediate temperature (binder); PAV = pressure aging vessel; BBR = bending beam rheometer; FIT-C = fatigue test at intermediate temperature (composite mastic); DCT = disk-shaped compact tension test; I-FIT= Illinois Flexibility Index Test; na = not applicable; NA = not available.

Materials Selection

Table 2 shows the information for ten SPS10 asphalt mixtures that were used in this study. The mixtures were part of Missouri DOT LTPP-SPS10 project and included PG46-34, PG58-28, and PG64-22H binders and different amounts of RAP and RAS. All mixtures had 1% MORLIFE 5000 liquid antistrip, and Mixture 3 also included 0.5% of EVOTHERM M1 by the weight of binder. Mixtures 5 and 10 had 3.5% EVOFLEX CA, an asphalt recycling agent used to improve RAP/RAS binder blending with virgin binder. All mixtures were dense graded and had similar aggregate gradation and binder content.

Table 2.

List of Missouri DOT SPS10 Mixtures Evaluated in this Study

Mixture no.	SHRP ID	Binder grade	RAP (%)	RAS (%)	Morelife	Aztec	Evotherm	IPC-70	Evoflex
1	291001	64-22H	25	0	1%/AC	na	na	na	na
2	291003	64-22H	25	0	1%/AC	Foam	na	na	na
3	291002	64-22H	25	0	1%/AC	na	0.5%/AC	na	na
4	291004	64-22H	0	0	1%/AC	na	na	na	na
5	291008	64-22H	34	0	1%/AC	na	na	na	3.5%/AC
6	291005	58-28	0	19	1%/AC	na	na	na	na
7	291007	58-28	19	16	1%/AC	na	na	na	na
8	291009	58-28	35	0	1%/AC	na	na	na	na
9	291010	46-34	16	31	2%/AC	na	na	na	na
10	291006	58-28	0	36	1%/AC	na	na	2.5%/AC	3.5%/AC

Note: no. = number; RAP = reclaimed asphalt pavement; RAS = reclaimed asphalt shingles; AC = asphalt content; na= not applicable.

Testing Protocols and Test Results

Tests were performed on the extracted binder, composite mastic, and mixture at the two laboratories to determine the material properties. Lab A performed extraction and recovery of binders following ASTM D8159-18 and ASTM D5404/D5404M-12 (2017) ( 1 , 2 ) in two different batches. For the first batch, Lab A conducted standard SHRP binder tests ( 17 , 21 , 22 ) on the extracted binders to determine the high-, low-, and intermediate-temperature PG. The multiple-stress creep recovery (MSCR) parameters ( 23 ) and ΔTc ( 15 ) were also determined in Lab A. A second extraction and recovery was later conducted by Lab A and sent to Lab B for conducting the UPTiM tests.

In addition, two mixture tests were conducted at Lab A: the low-temperature fracture test using disk-shaped compact tension geometry (DCT) according to ASTM D7313 ( 24 ) and the Illinois Flexibility Index (I-FIT) test for cracking at room temperature according to AASHTO TP 124 ( 25 ). Table 3 includes the results of the tests conducted at Lab A.

Table 3.

Results of Tests on Extracted Binder and Mixture Conducted at Lab A

Mixture no.	SHRP ID	SHRP cont. HTPG	SHRP cont. LTPG	Int. G* Sinδ	Int. temp.	MSCR, Jnr3.2	MSCR, R3200 (%)	ΔTc	DCT FE, J/m2 @ 12°C	DCT FE, J/m2 @ 18°C	I-FIT Flex. index
1	291001	78.6	−25.8	2.9	20.3	0.38	40.9	−2.4	351.0	NA	2.9
2	291003	71.6	−27.6	3.5	20.2	1.11	24.4	−1.5	302.8	260.0	3.5
3	291002	73.1	−27.3	2.8	21.2	0.90	27.1	−0.8	361.8	259.0	2.8
4	291004	70.7	−30.7	4.8	18.6	1.01	33.4	0.0	400.3	333.0	4.8
5	291008	78.7	−24.2	NA	23.8	0.41	34.3	−1.7	284.8	215.0	0
6	291005	73.8	−28.7	4.3	21.5	1.12	8.1	−2.3	382.5	368.0	4.3
7	291007	79.6	−22.4	1.3	23.8	0.42	22.9	−5.7	356.8	300.3	1.3
8	291009	73.2	−24.7	3.8	22.6	1.20	7.6	−2.5	401.3	293.8	3.8
9	291010	72.5	−27.2	1.5	19.8	1.20	9.2	−3.6	358.0	361.0	1.5
10	291006	75.7	−27.2	NA	18.3	0.72	19.0	−3.5	358.0	343.5	0

Note: no. = number; cont. = continious; Int. = intermediate; MSCR = multiple-stress creep recovery; DCT = disk-shaped compact tension test; I-FIT = Illinois Flexibility Index Test; HTPG = high- temperature perfomance grade; LTPG = low-temperature performance grade; temp. = temperature, FE = flexural energy, Flex. = flexibility; NA = not available.

Lab B recovered composite mastic from the ten mixtures according to the method described in ( 4 ) and conducted tests on extracted binder and composite mastic to determine the low-, high-, and intermediate-temperature properties using the UPTiM procedure. Lab B also conducted tests on volumetric samples of the mixtures according to AASHTO TP 116 methodology. The parameter of AASHTO TP 116 for the high-temperature test is the effective mixture PG and for the intermediate-temperature test is the fatigue index (FI). Table 4 includes a summary of the results of binder, mastic, and mixture tests conducted at Lab B. Note that there was not enough of Mixtures 3, 9, and 10 to test them for iRLPD rutting and fatigue and there was not enough of Mixture 2 for iRLPD fatigue testing (only enough for the iRLPD rutting test). Figure 4 shows the high-temperature (HT) PG, low-temperature (LT) PG, and FI of composite mastic of the ten Missouri DOT SPS10 mixtures determined by UPTiM.

Table 4.

UPTiM Results of Extracted Binder, Mastic, and Mixture Conducted at Lab B

Mixture no.	SHRP ID	UPTiMunaged extracted binder			UPTiMPAV-aged extracted binder			UPTiMcomposite mastic			AASHTO TP 116 (iRLPD) mixture
Mixture no.	SHRP ID	HT	LT	IT	HT	LT	IT	HT	LT	FI	HT PG	FI
1	291001	76.6	−21.1	29.0	75.9	−22.3	31.8	75.7	−21.9	13.4	74	19.7
2	291003	75.1	−19.7	29.3	73.3	−22.7	31.2	71.7	−21.0	22.5	75	NA
3	291002	72.7	−23.0	27.1	73.4	−23.7	30.8	71.1	−21.7	23.4	NA	NA
4	291004	73.1	−24.3	26.0	73.6	−24.7	29.4	72.8	−22.8	22.9	75	23.0
5	291008	88.0	−13.3	38.1	89.9	−14.1	41.3	95.4	−12.7	8.1	90	8.2
6	291005	73.1	−24.1	23.7	71.8	−25.6	27.3	68.0	−25.7	20.4	73	29.5
7	291007	79.3	−18.5	30.1	78.1	−21.3	31.4	75.0	−21.5	10.1	74	13.6
8	291009	72.6	−21.0	26.4	70.9	−22.8	28.1	68.5	−24.0	17.4	73	16.2
9	291010	89.1	−14.7	36.5	92.2	−17.0	38.2	91.8	−16.4	8.4	NA	NA
10	291006	97.0	−12.2	41.4	102.5	−13.4	42.7	104.7	−14.2	8.0	NA	NA

Note: no. = number; UPTiM = unified performance tests by incremental method; PAV = pressure aging vessel; iRLPD = incremental repeated load permanent deformation; HT = High temperature; LT = low temperature; IT = Intermediate temperature; PG = performance grade; FI = fatigue index; NA= not available.

Figure 4.

PG and fatigue properties of ten Missouri DOT SPS10 mixtures using composite mastic.

Comparison of the Results

Comparison of UPTiM PG of Extracted Binder and Mastic

To compare performance of composite mastic with extracted binder, two test parameters were utilized. These were the continuous low- and high-temperature PG of the extracted binder (unaged and PAV-aged) and composite mastic, which were determined using UPTiM methodology. Figure 5a shows the mastic HT PG versus the HT PG of the extracted and the PAV-aged extracted binders and Figure 5b shows comparison of the mastic LT PG with the extracted binder LT PG (unaged and PAV-aged). As can be seen from the graphs, mastic provides similar PG to those of both unaged and PAV-aged extracted binders.

Figure 5.

HT PG mastic versus extracted (a, c) and LT PG mastic versus extracted (b, d).

Figure 5, c and d , provide similar results from other studies ( 26 ). The graphs show comparison of HT PG and LT PG of mastic and extracted binders of 41 mixtures, which include 14 mixtures from Ontario, eight mixtures from MnRoad, and nine mixtures from FHWA alccelerated loading facility (ALF) fatigue study. These results indicate that composite mastic provides very similar high- and low-temperature grades to the extracted binder (unaged and PAV-aged) and may be used instead of extraction.

Comparing the SHRP PG and UPTiM PG of Extracted Binders

Figure 6, a and b , show comparison of HT PG and LT PG of SHRP and UPTiM for the extracted binders of SPS10 mixtures. Mixtures 5, 9, and 10 were not shown in the comparison since the results were substantially different (Tables 3 and 4). Both figures show a relatively good correlation between SHRP LT PG and UPTiM LT PG for the seven extracted binders. However, Figure 6b shows that UPTiM PG was about 2 to 5 degrees higher than the SHRP PG.

Figure 6.

SHRP HT PG versus UPTiM HT PG for extracted binders of SPS10 (a), SHRP LT PG versus UPTiM LT PG of PAV extracted of SPS10 (b), and Ontario (c) Mixtures.

To investigate whether the same trend exists for LT PG of extracted binders of other mixtures, results of a similar study on Ontario mixtures ( 26 ) were looked into. Figure 6c shows SHRP and UPTiM LT PG of the extracted binders of 18 Ontario mixtures. As indicated from the graph, LT PG of SHRP and UPTiM are well correlated and the values are scattered both sides of the prediction line. This suggested that there should be a reason for the difference between the Lab A SHRP and Lab B UPTiM results of the SPS10 mixtures. The inquiry revealed that different mixtures were used for the first and second batch of extraction and recovery. The batch that Lab B tested were from the mixtures collected from the first run of the plant, when the rejuvenators were not fully incorporated in the mixtures. The binder PG determined by Lab A was using the mixtures collected later during production, which were not available for the second batch of extraction. This could be the reason for the difference between the UPTiM PG and the SHRP PG of the extracted binders. This problem was not observed for the mastic results since mastic was recovered from the same material used in the second extraction.

Comparing Mixture Test Results with Mastic

Comparing iRLPD High-Temperature Mixture Test with Mastic

Volumetric specimens were manufactured from seven loose mixtures (all except Mixtures 3, 9, and 10). The 150-mm diameter and 115-mm high volumetric samples were compacted to 4% air voids by reheating loose mixtures collected in the field. A high-temperature mixture test was performed on the volumetric samples at 60°C using AASHTO TP 116 revised methodology, which involves applying 500 cycles of 0.1 s loading and 0.9 s unloading at 600 kPa followed by performing calculations to determine the high-temperature PG of the mixture according to Equation 2. Table 5 includes the mixture PG for two to five replicates of the seven SPS10 mixtures (total of 29 compacted specimens). In addition to the SPS10 mixtures, Table 5 includes mixture PG of five replicates of three mixtures from the MDSHA QA/QC (quality assurance and control) program. The average PG for each mixture and the coefficient of variation (C.V.) are provided in the table. The C.V. of mixture PG was between 1.0 and 6.9% and averaged 2.7%. Also included in the table are the HT PG of composite mastic (using UPTiM) and the grade bump of the ten mixtures. A grade bump for the PG was calculated as the difference between the average mixture PG and the local climate PG, which was 64 for all mixtures. The last column in the table includes the PG with traffic level, determined using the mixture grade and the LTPPBind grade bump table. These values are comparable to the MSCR PG with traffic as determined by AASHTO M 332.

Table 5.

Mixture Individual and Average PG and Average Mastic PG for Ten Mixtures

Study	Mix no.	Replicates					Avg. mix PG	Mixture PG C.V.	Mastic HT PG	Grade bump °C	PG w/ traffic
Study	Mix no.	1	2	3	4	5	Avg. mix PG	Mixture PG C.V.	Mastic HT PG	Grade bump °C	PG w/ traffic
Missouri DOT SPS10	1	75	74	72	78	73	74	3.2	76.5	12.5	64V
	2	74	77	NA	NA	NA	75	2.6	71.9	7.9	64H
	4	77	75	75	73	74	75	1.8	71.0	7.0	64S
	5	87	92	94	87	NA	90	4.0	97.3	33.3	64E
	6	75	70	73	72	74	73	2.7	73.7	9.7	64H
	7	75	74	75	74	NA	74	1.0	75.2	11.2	64H
	8	68	79	75	69	NA	73	6.9	68.5	4.5	64S
MDSHA QC	48	83	82	83	80	81	82	1.5	79.8	15.8	64E
	22	85	83	84	85	87	85	1.6	81.8	17.8	64E
	19	65	66	65	65	68	66	2.0	62.4	4.4	58S

Note: no. = number; Avg. = average ; PG = performance grade; C.V. = coefficient of variation; HT = high temperature; NA = not available.

Figure 7 shows the average mixture PG using AASHTO TP 116 versus average mastic PG using UPTiM for the ten mixtures in Table 5. As can be seen, the mixture and mastic PG are highly correlated and the HT PG values are all within 2°C. Figure 7 implies that the difference between mixtures HT PG is mainly a result of the difference in the mastic property since the aggregate gradations were similar. The HT PG of composite mastic is affected by the type and amount of binder, RAP/RAS, rejuvenators, and filler; therefore, it may be used to optimize the high-temperature mixture performance for a specific aggregate gradation.

Figure 7.

UPTiM mastic HT PG versus TP 116 mixture HT PG for ten SPS10 and MDSHA mixtures.

Comparing DCT Energy with Mastic Low-Temperature Grade

Mastic and mixture low-temperature test results were compared to determine the correlation. Figure 8 shows the DCT energy parameter versus mastic LT PG. As indicated, DCT and UPTiM LT PG are moderately correlated with the exception of Mixture 2, which contained foamed asphalt.

Figure 8.

Mastic LT PG versus DCT energy at −12°C.

Comparing iRLPD Mixture Fatigue Test with I-FIT

The iRLPD fatigue test was performed using AASHTO TP 116 proposed methodology on six SPS10 mixtures (Mixtures 1, 4–8). Mixture 2, which had foam, was not used in this study. As mentioned earlier, adequate quantities of Mixtures 3, 9, and 10 were not available for performing this test.

The volumetric samples were cut to prepare 50-mm high specimens for the fatigue test. The test is an IDT configuration and applies several increments, each consisting of 100 cycles of repeated load (0.1 s load/0.9 s unload). The load starts with 3.0 KN and is increased by 1 KN for each increment until failure. Figure 9 shows the strain rate for each cycle for the six mixtures. For Mixtures 1, 4, and 5 only one replicate was tested but for Mixtures 6, 7, and 8 two tests were conducted using specimens cut from top (T) and bottom (B) of the volumetric samples. It is important to note that the method of incremental loading in the iRLPD test minimizes the differences in the volumetric properties of the top and bottom samples and they can be considered replicates. The iRLPD test parameter is the FI, or the minimum strain rate at the increment before reaching territory flow, which is failure as a result of cracking.

Figure 9.

iRLPD fatigue test results for six of the SPS10 mixtures (New addition to AASHTO TP 116).

Figure 10a shows UPTiM mastic FI versus UPTiM mixture FI. This figure indicates a fair relationship between mastic and mixture fatigue indices.

Figure 10.

Average iRLPD mixture fatigue index versus average mastic fatigue index (a) and average mixture flexibility index from I-FIT versus average mastic fatigue index (b).

The mastic FI values were also compared with the I-FIT flexibility index. Lab A conducted I-FIT tests according to AASHTO TP 124 for Mixtures 1–4 and 6–9. Eight samples for each mix were prepared and tested; however, the tests for Mixtures 5 and 10 were not successful and provided flexibility index of 0.0 (Table 3). Lab B recovered the mastic and conducted UPTiM fatigue tests on mastic from these mixtures as shown in Table 4.

Figure 10b provides UPTiM mastic FI versus I-FIT mixture flexibility index from AASHTO TP 124. This figure indicates that I-FIT flexibility index and UPTiM mastic fatigue index are moderately correlated.

Test Variability

Table 6 provides the coefficient of variations of the parameters examined in this study. As indicated from the table, the variability of the UPTiM parameters are significantly smaller than the variability of the DCT and I-FIT parameters. This indicates that UPTiM tests are reliable tools for characterizing asphalt materials.

Table 6.

Number of Test Specimens and Coefficient of Variations of the Parameters Examined in this Study

	HT		LT		IT
Material & test	N	C.V.	N	C.V.	N	C.V.
UPTiM extracted	58	1.0	58	2.5	53	13.6
UPTiM extracted + PAV	55	1.0	54	2.0	51	13.6
UPTiM mastic	71	2.5	69	4.9	64	15.3
Mixture TP 116	44	2.7	na	na	9	9.4
Mixture DCT	na	na	224	14.0	na	na
Mixture I-FIT	na	na	na	na	80	59.6

Note: HT = high temperature; LT = low temperature; IT = intermediate temperature; N = count; C.V. = coefficient of variation, UPTiM = unified performenac test by incremental method; PAV = pressure aging vessel; DCT = disk shaped compact tension test; I-FIT = Illinois flexibility index test; na = not applicable.

Summary and Conclusion

This paper presents the UPTiM testing system, which includes test procedures for determining continuous high-, low-, and intermediate-temperature PG of extracted binder and mastic as well as high-temperature grade and fatigue resistance of asphalt mixture. Ten Missouri DOT SPS10 mixtures and three MDSHA quality control mixtures were selected to be tested in this study. The Missouri DOT SPS10 extracted binder and mixtures were tested by Lab A according to AASHTO T 315, T 313, T 350, ASTM D7313, and AASHTO TP 124. The SPS10 extracted binders and mixtures were also tested by Lab B using the UPTiM methods. Additionally, Lab B recovered composite mastic for all mixtures and tested the mastic using UPTiM to determine their PG. The iRLPD mixture rutting and fatigue tests on volumetric samples, which are new additions to AASHTO TP 116, were performed on the mixtures in Lab B. The parameters of the high-temperature rutting test are the effective mixture high-temperature PG and the grade bump for traffic level. The parameter of the fatigue test is FI, which is the permanent minimum strain rate of a test increment before reaching tertiary flow. Table 7 includes a summary of all the data collected.

Table 7.

Summary of Test Results

Mixture no. S= SPS10M= MDSHA	Extracted binder SHRP cont. PGAASHTO R 29			Extracted binder(PAV-aged) UPTiM			Composite masticUPTiM			Mixture conventionaltests		Mixture iRLPD AASHTO TP 116
Mixture no. S= SPS10M= MDSHA	Cont. HT PG	Cont. LT PG	G* Sinδ	HTPG	LTPG	IT	HTPG	LTPG	FI	DCTFE 12°C J/m2	I-FIT Flex. index	HT PG	FI
S1	78.6	−25.8	2.9	75.9	−22.3	31.8	75.7	−21.9	13.4	351.0	2.9	74	19.7
S2	71.6	−27.6	3.5	73.3	−22.7	31.2	71.7	−21.0	22.5	302.8	3.5	75	NA
S3	73.1	−27.3	2.8	73.4	−23.7	30.8	71.1	−21.7	23.4	361.8	2.8	NA	NA
S4	70.7	−30.7	4.8	73.6	−24.7	29.4	72.8	−22.8	22.9	400.3	4.8	75	23.0
S5	78.7	−24.2	NA	89.9	−14.1	41.3	95.4	−12.7	8.1	284.8	0	90	8.2
S6	73.8	−28.7	4.3	71.8	−25.6	27.3	68.0	−25.7	20.4	382.5	4.3	73	29.5
S7	79.6	−22.4	1.3	78.1	−21.3	31.4	75.0	−21.5	10.1	356.8	1.3	74	13.6
S8	73.2	−24.7	3.8	70.9	−22.8	28.1	68.5	−24.0	17.4	401.3	3.8	73	16.2
S9	72.5	−27.2	1.5	92.2	−17.0	38.2	91.8	−16.4	8.4	358.0	1.5	NA	NA
S10	75.7	−27.2	NA	102.5	−13.4	42.7	104.7	−14.2	8.0	358.0	0	NA	NA
M48	NA	NA	NA	NA	NA	NA	79.8	NA	NA	NA	NA	82	NA
M22	NA	NA	NA	NA	NA	NA	81.8	NA	NA	NA	NA	85	NA
M19	NA	NA	NA	NA	NA	NA	62.4	NA	NA	NA	NA	66	NA

Note: no.= number; cont. = continuous; HT = high temperature; LT = low temperature; IT = intermediate temperature; PG = performance grade; FI = fatigue index; DCT = disk shaped compact tension test; FE = flexural energy; I-FIT = Illinois flexibility index; Flex. = flexibility; iRLPD = incremental repeated load permanent deformation; PAV = pressure aging vessel; UPTiM = unified performance tests by incremetal method; NA = not available.

A summary from comparison of the results is as follows.

The UPTiM high- and low-temperature continuous PGs of extracted binders (unaged or PAV-aged) and those of mastics are highly correlated.

The SHRP high- and low-temperature PGs of extracted binders measured by Lab A are relatively well correlated with the UPTiM PGs, measured by Lab B.

The iRLPD high-temperature PG of the mixtures is highly correlated with the mastic high-temperature PG.

The UPTiM continuous low-temperature grade of mastic is correlated with DCT fracture energy parameter moderately well.

The iRLPD mixture fatigue index is correlated with I-FIT flexibility index moderately well.

The variability of the test results in the form of C.V. indicates that the UPTiM binder results have the lowest variability among the tests performed.

UPTiM mixture tests have lower variability than DCT and I-FIT test results.

The variability of UPTiM tests on mastic is lower than the variability of the tests on mixtures and slightly greater than the variability of the UPTiM tests on extracted binders.

From the above, it can be concluded that composite mastic is potentially a reliable alternative to solvent extraction. Mastic is derived from mixture without use of chemicals and provides equivalent properties to those of extracted binders.

It can also be concluded that the iRLPD rutting test on volumetric samples, which determines the high-temperature PG of the mixture, is a quick and effective tool for performance-based mix design and QA/QC process.

Because of the unified concept, the UPTiM results of binder, mastic, and mixture are highly correlated. This leads to the conclusion that UPTiM can be a powerful tool for controlling the properties of mixture components to achieve the desired mixture performance.

Footnotes

Author Contributions

The authors confirm contribution to the paper as follows: study conception and design: Haleh Azari, Alaeddin Mohseni, and Richard Steger; data collection: Alaeddin Mohseni, Dennis Muncy, Haleh Azari; analysis and interpretation of results: Alaeddin Mohseni, Haleh Azari; Dennis Muncy; draft manuscript preparation: Haleh Azari, Alaeddin Mohseni, and Richard Steger. All authors reviewed the results and approved the final version of the manuscript.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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