Additional MMLS3 Laboratory Testing R80 and... · Additional MMLS3 Laboratory Testing and a Synthesis of Selected Tests for Evaluation of Rutting Performance of the HMA on a Trial

INSTITUUT VIR TRANSPORT INSTITUTE FOR TRANSPORT

TEGNOLOGIE TECHNOLOGY

Report

on

Additional MMLS3 Laboratory Testing

and a Synthesis of Selected Tests for Evaluation of Rutting

Performance of the HMA on a Trial Section of R80 under

HVS & MMLS3 APT Trafficking

for

Gauteng Government Department of Public Works and Transportation

Fred Hugo and Johan Gerber

Institute for Transport Technology

Stellenbosch

December 2008

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Abstract

During the past two years a range of laboratory and field APT studies were done on hot mix

asphalt (HMA) on the R80, near Pretoria. The HVS and the MML3 were used to conduct these

tests. Several reports have been written on the results of the tests. One focussed on the HVS

work by the CSIR while the other two were focussed on the MMLS3 tests. A third series of

MMLS3 tests were completed in the ITT laboratory in Stellenbosch during September through

December. The full dataset was subsequently critically analysed in order to compare the results

of the HVS with the results of the MMLS3. A synthesis of the findings was then completed and a

summary is presented in this report.

Three different asphalt mixes were tested namely, The Standard Reference (SR) Mix and Rut

Resistant Mixes (RR) 1 and 2. In this report the findings pertaining to mixes SR and RR1 are

compared since Mix RR2 has not yet been tested with the MMLS3. A single HVS RR2 test will

also be discussed.

The HVS test operation comprised different test protocols. To enable logical and plausible

comparisons to be made between the MMLS and HVS test findings, the latter were sorted into

categories related to the main objectives of the HMA APT study. This provided the basis for the

synthesis of the findings. Only channelized HVS tests were considered for this draft report.

Wandering tests will be reported in an update of the current draft.

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1 Contents

2 List of Tables....................................................................................................................................4

3 List of Figures...................................................................................................................................5

4 Tests Analysis Methodology.............................................................................................................6

4.1 Data Processing........................................................................................................................6

4.2 Temperature Data....................................................................................................................9

5 Overview of Findings.......................................................................................................................9

5.1 HVS Test Category 1: Temperature Impact ...............................................................................9

5.2 HVS Test Category 2: Thickness Impact .................................................................................. 12

5.3 HVS Test Category 3: Load Protocol Impact ............................................................................ 14

5.4 HVS Test Category 4: Standard Reference Mix Overview ........................................................ 16

5.5 HVS Test Category 5: Standard Reference and Rut Resistant Mix Comparison ........................ 17

5.6 HVS Test Categories Trend Line Evaluation............................................................................. 19

6 Conclusions ................................................................................................................................... 22

7 Recommendations......................................................................................................................... 22

8 References..................................................................................................................................... 23

9 Appendices.................................................................................................................................... 24

9.1 Appendix A – Summary of the R80 HVS Test Protocols ........................................................... 24

9.2 Appendix B – Summary of the MMLS3 Field and Laboratory HMA Test on the R80 Trial Section

26

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2 List of Tables

Table 4.1 Summary of the HVS Test Gradients and Temperatures............................................................7

Table 4.2 Summary of the MMLS3 Test Gradients and Temperatures ......................................................8

Table 4.3 Temperature Data of Test RR1 Lab JG5.....................................................................................9

Table 5.1 HVS Data used by Denneman to plot HVS Rate/Temperature (Denneman 2008a) .................. 20

Table 9.1A - Summary of the R80 HVS Test Protocols and related Data (Steyn, 2008) ............................ 24

Table 9.2A - Summary of the R80 HVS Temperature Data (Steyn, 2008) ................................................ 25

Table 9.3B - Summary of the MMLS3 Field and Laboratory HMA Test on the R80 Trial Section .............. 26

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3 List of Figures

Figure 4.1 Example of a Typical Average Rut Plot.....................................................................................6

Figure 4.2 Example of a Typical Average Rut Plot in Log-log Format.........................................................6

Figure 5.1 Rutting Rate versus Temperature HVS Test Category 1 – Temperature Impact for Different

Test Protocols........................................................................................................................................ 10

Figure 5.2 Cumulative rutting plots of HVS test category 1..................................................................... 11

Figure 5.3 Rutting Rate versus Temperature HVS Test Category 2 – Thickness Impact for Different Test

Protocols............................................................................................................................................... 13


Figure 5.5 Rutting Rate versus Temperature HVS Test Category 3 – Load Protocol Impact ..................... 14


Figure 5.7 Rutting Rate versus Temperature HVS Test Category 4 – Standard Reference Mix Overview . 16

Figure 5.8 Rutting Rate versus Temperature HVS Test Category 5 – Standard Reference and Rut Resistant

Mix Comparisons................................................................................................................................... 18


Figure 5.10 HVS Trafficking Trend Lines – Category 1 to 3...................................................................... 19

Figure 5.11 Comparison between HVS Test Category 1 Trend Line and the Original Trend Line by

Denneman............................................................................................................................................. 21

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4 Tests Analysis Methodology

4.1 Data Processing

Raw rutting data were obtained from the field and/or laboratory. These data represent the downward

rut over the number of axle load repetitions.

In the past the “rut” was generally graphically reported as indicated in Figure 4.1.

Figure 4.1 Example of a Typical Average Rut Plot

Figure 4.2 Example of a Typical Average Rut Plot in Log-log Format

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Recently data has also been reported in a new form that serves to compare rutting rates during the

secondary phase. This plotting form presents the data on log-log axes, where the gradient of the trend

line serves as an indicator of the rutting performance of the mix. The secondary phase sets in early and

is generally considered to start from between 2 500 and 25 000 load applications.

After numerous trial and error attempts, it was concluded that a power trend line should be fitted to the

rutting data obtained from 10 000 load repetitions onwards up to 200 000 load repetitions except when

the test was terminated prior to this. This was done so that comparisons could be made between the

MMLS field and laboratory data and the HVS field data obtained from the R80. The original analyses

reported by Denneman (2008a) also used this methodology.

The R80 research program also required a data plot consisting of the rate of deformation (mm/pass)

versus temperature. The equations of the power trend lines were used to calculate gradients of each

trend line, for each test. These gradients were then plotted against the temperature at which the

respective tests were conducted. An exponent trend line was then selected to define each specific series

of tests. The results are shown in Tables 4.1 and 4.2.

The temperatures in Tables 4.1 – 4.3 were extracted from Appendices A and B. It is noteworthy that the

temperature variation during HVS testing was such that it could impact on the performance of the mix.

This was not investigated.

Table 4.1 Summary of the HVS Test Gradients and Temperatures

Test Temp Equation R2 Constant Power X1 X2 Y1 Y2 Gradient

441A4 59.10 y =

0.0022x0.6338

0.934 0.0022 0.6338 10000 200000 0.75 5.04 2.25E-05

442A4 42.10 y =

0.0762x0.2316

0.897 0.0762 0.2316 10000 200000 0.64 1.29 3.39E-06

443A4 49.55 y =

0.0017x0.5504

0.973 0.0017 0.5504 10000 200000 0.27 1.41 5.98E-06

444A4 50.60 y =

0.0234x0.3623

0.967 0.0234 0.3623 10000 200000 0.66 1.95 6.79E-06

445A4 49.25 y =

0.0228x0.3312

0.906 0.0228 0.3312 10000 200000 0.48 1.30 4.3E-06

446A4 59.70 y =

0.0173x0.431

0.926 0.0173 0.431 10000 200000 0.92 3.33 1.27E-05

447A4 63.30 y =

0.0142x0.4935

0.911 0.0142 0.4935 10000 200000 1.34 5.87 2.38E-05

448A4 62.10 y =

0.0658x0.3257

0.979 0.0658 0.3257 10000 200000 1.32 3.51 1.15E-05

449A4 58.25 y = 0.001x0.6732

0.976 0.001 0.6732 10000 200000 0.49 3.70 1.69E-05

450A4 62.35 y =

0.0005x0.6922

0.945 0.0005 0.6922 10000 200000 0.29 2.34 1.07E-05

451A4 61.40 y =

0.0489x0.2777

0.954 0.0489 0.2777 10000 200000 0.63 1.45 4.31E-06

452A4 70.80 y =

0.0024x0.5317

0.989 0.0024 0.5317 10000 200000 0.32 1.58 6.63E-06

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453A4 57.50

y =

0.0002x0.8943

0.938 0.0002 0.8943 10000 200000 0.76

11.0

1 5.4E-05

454A4 58.15 y = 4E-05x

1.0316 0.963 4.00E-05 1.0316 10000 200000 0.54

11.7

7 5.91E-05

455A4 60.05 y =

0.0242x0.413

0.996 0.0242 0.413 10000 200000 1.09 3.74 1.4E-05

456A4 52.05 y =

0.0014x0.885

0.926 0.0014 0.885 10000 200000 4.85 68.7 0.000337

Table 4.2 Summary of the MMLS3 Test Gradients and Temperatures


RR1 Lab

JG2 60.00

y =

0.1555x0.2602

0.975 0.1555 0.2602 10000 200000 1.71 3.72 1.06E-05

RR1 Lab

JG3 62.00

y =

0.0232x0.4507

0.993 0.0232 0.4507 10000 200000 1.47 5.68 2.22E-05

RR1 Lab

JG4 53.70

y =

0.1657x0.2474

0.978 0.1657 0.2474 10000 200000 1.62 3.39 9.35E-06

RR1 Lab

JG5 60.15

y =

0.1854x0.2777

0.982 0.1854 0.2777 10000 200000 2.39 5.50 1.63E-05

RR1 Field

Q 59.90

y =

0.0623x0.3265

0.987 0.0623 0.3265 10000 200000 1.26 3.35 1.1E-05

RR1 Field

R 61.55

y =

0.0317x0.3857

0.988 0.0317 0.3857 10000 200000 1.11 3.51 1.27E-05

SR Field J 60.00 y =

0.0601x0.3334

0.995 0.0601 0.3334 10000 200000 1.30 3.52 1.17E-05

SR Lab

EDV T1 60.00

y =

0.1174x0.308

0.987 0.1174 0.308 10000 200000 2.00 5.04 1.6E-05

SR Lab

EDEV T3 50.00

y =

0.2621x0.1647

0.989 0.2621 0.1647 10000 200000 1.19 1.96 4.01E-06

SR Field A 60.00 y =

0.0082x0.4308 0.999 0.0082 0.4308 10000 200000 0.43 1.58 6.01E-06

SR Field C 50.00 y =

0.0052x0.4317 0.992 0.0052 0.4317 10000 200000 0.28 1.01 3.86E-06

SR Field D 40.00

y = 3E-

06x1.045

0.941 0.000003 1.045 10000 200000 0.05 1.04 5.23E-06

SR Field E 50.00 y =

0.0088x0.3399 0.511 0.088 0.339 10000 200000 2.00 5.51 1.85E-05

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4.2 Temperature Data

In the latest series of tests (RR1 Lab JG2–5) thermocouples were installed in the test sections and/or test

bed as required by the recently published MMLS protocol (DPG1 2008). Table 4.3 is an illustration of

how the temperatures for Test RR1 Lab JG5 were processed.

Table 4.3 Temperature Data of Test RR1 Lab JG5

Temperature Data (˚C)

Interval Probe 0 Probe 1 Probe 2 Probe 3 Probe 4 Prob5 Probe 6 Probe 7

2500 63.74 60.91 61.43 62.90 60.98 60.49 58.76 58.32

5000 64.07 61.41 61.40 63.24 61.47 60.47 58.90 57.91

10000 62.21 61.16 61.13 61.78 61.42 60.37 58.78 57.84

25000 65.31 63.33 62.76 65.00 63.59 62.11 61.46 59.96

50000 62.05 60.78 60.30 61.71 61.19 59.87 58.93 57.66

100000 60.98 59.76 59.20 61.27 60.26 58.77 58.29 56.88

150000 62.15 60.68 59.60 61.81 60.51 58.70 58.66 56.75

AVG 62.93 61.15 60.83 62.53 61.35 60.11 59.11 57.90

Weighted

AVG 62.12 60.69 60.01 61.97 60.90 59.37 58.87 57.35

The average temperature of each probe was calculated at the indicated intervals. The average and

weighted averages were then calculated for each probe. The latter was calculated relative to the

number of load applications applied during the respective trafficking intervals of the test. The mean of

the weighted averages of probe 1, probe 4 and probe 6 namely 60.15 °C was taken to represent the

controlling temperature condition during Test RR1 Lab JG5. The weighting was done proportionately to

the number of load applications during each phase.

Probes 1, 2 and 4 were situated 17 mm underneath the surface of the test section.

5 Overview of Findings Five different HVS Test Categories (TC) were selected for analysis and reporting. Variables that were

included are temperature, load frequency, layer thickness, mix type, trafficking direction, load

composition. These TCs were compared with the appropriate MMLS tests. Only channelized HVS tests

were considered for this preliminary report. It should be noted that the tyre pressures on the HVS were

selected to yield comparable contact stresses under the MMLS3 in accordance with the findings

reported by De Beer and Sadzik (2007).

5.1 HVS Test Category 1: Temperature Impact

• Layer thickness: 40 mm

• Mix type: Standard Reference (SR)

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• Traffic direction: Uni-directional (uni)

• Load composition: Standard case 40kN, 620 kPa

Figure 5.1 Rutting Rate versus Temperature HVS Test Category 1 – Temperature Impact for Different Test Protocols

The HVS test Category 1; 441A4 (59.1°C), 442A4 (42.1°C) & 443A4 (49.55°C). These test were compared

with the following MMLS3 tests:

• 50 mm Standard Reference (SR) laboratory (SR 50 mm Lab EDV),

• 40 mm SR field and laboratory tests (SR 40 mm Field RoadLab A,C, D and SR 40 mm Lab

Roadlab)

• 50 mm Rut Resistant 1 (RR) laboratory tests (RR 1 50 mm JG 2,3,4,5),

• 40 mm SR field test Roadlab (J)

• 50 mm SR laboratory tests (ITT 50 mm)

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It should be noted that the thickness of the asphalt cores provided by the CSIR to ITT was 50 mm thick.

This differs from the general statement pertaining to the asphalt layer thicknesses reported in the field

data files.

Figure 5.2 Cumulative rutting plots of HVS test category 1

As stated in the Test Analysis Methodology, these equations of the respective trend lines were used to

plot Figure 5.1. The calculations can be viewed in Table 4.1 and 4.2. Generally the trend lines are

parallel, but the results vividly demonstrate the effect of the initial rutting during the primary phase of

rutting.

The initial MMLS3 tests were conducted at 7 200 appl/h and the results were reported earlier in 2008

[Hugo and de Vos (2008 a,b)]. Therefore these will not be discussed in any detail in this report. Suffice to

say that:

• the increase in speed resulted in a reduction in the rate of rutting as well as the extent

of the rutting (see Figures 5.1, 5.2).

• it was also found that the increase in the rate of rutting reduced with an increase in test

temperature as the speed was increased from 2 400 to 7 200 appl/h (see Figure 5.1)

With respect to the Temperature Impact the spread of rutting rates increased markedly as the HVS test

temperature increased from 50°C to 60°C. From a comparison of the HVS and MMLS trend lines and

rutting rates in Figure 5.1 it can be concluded that:

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• the performance of the SR mix under trafficking by the two APT machines yielded very

comparable results, albeit that the extent of the rutting under the HVS was slightly greater. This

applies to both lab and field testing with MMLS.

• the primary phases of the respective tests differed significantly. This influenced the extent of

rutting after 100 000 load applications. This phenomenon is apparent from the results depicted

in Figure 5.2 when the mixes reach 60°C. It is important to note that 60°C is well above the

softening point of the binder that was used for the asphalt mix (Denneman 2008a).

• The results correlate well with mixes of a similar nature that have been tested with the MMLS3

and reported in the extensive MMLS3 bibliography (Hugo, 2008).

• the findings lend support to the guidelines selected for use in the Protocol for rutting evaluation

using the MMLS3 that was recently completed and approved for use by the industry (DPG1

2008)

5.2 HVS Test Category 2: Thickness Impact

• Layer thickness: Varies (25 mm, 40 mm & 60 mm)



• Load composition: Standard case 40kN, 620 kPa

The differences in layer thickness are evaluated in HVS Test Category 2 and comparisons are made with

applicable MMLS3 tests. HVS test consists of; 441A4, 442A4, 443A4, 444A4 and 445A4.

These HVS test were compared with the following MMLS3 tests:


• 50 mm Rut Resistant 1 (RR) laboratory tests (RR 1 50 mm JG 2,3,4,5),


The Rut Resistant 1 laboratory tests were excluded in Figure 5.4 in order to make way for the HVS tests

of different layer thickness. The Rut Resistant 1 laboratory tests are included in Figure 5.3, thus

comparison of the two different mixes are possible.

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Figure 5.3 Rutting Rate versus Temperature HVS Test Category 2 – Thickness Impact for Different Test Protocols


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The results depicetd in Figure 5.3 indicate that the thickness of the mix tested with the HVS at 50°C

influenced the rut rate. This increased progressively from 60 mm through 40 mm to the highest at 25

mm. It should also be noted that the results of the 40 and 25 mm layers are located on the same

gradient trend line above the 60°C. The reason for the difference in performance is not readily apparent

but, it could be as a result of differing temperature gradients with depth.

5.3 HVS Test Category 3: Load Protocol Impact



• Traffic direction: Bi-directional (bi) and (uni)

• Load composition: Varies (n-shape 60kN 800kPa, m-shape 60kN 420kPa)

Three HVS tests complied with Load composition in Category 3. Test 446A4 (n-shape, bi, 59,7°C), Test

447A4 (n-shape, uni, 63,3°C) and Test 448A4 (m-shape, bi, 62,1°C).




Figure 5.5 Rutting Rate versus Temperature HVS Test Category 3 – Load Protocol Impact

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The HVS data indicates that Test 446A4 had a slightly higher rutting rate than Test 448A4 at a lower test

temperature. This is also evident in Figure 5.6. This is ascribed to the higher applied contact stresses in

Test 446A4 compared to Test 448A4 (other trafficking conditions being similar). Test 447A4 can be

compared with Test 446A4. The contact stresses are the same but the trafficking direction and test

temperatures differ. In the case of Tests 448A4 and 447A4 the temperatures are approximately similar

but the contact stresses differ. Hence conclusive deductions are not readily apparent except for the fact

that the m-shape yielded smaller rates of rutting despite being at a higher temperature.

If Test 446A4 is compared with Test 441A4 (as defined in Test Category 1) both being at approximately

similar temperatures, it can be concluded that the uni-directional trafficking results in a higher damage

in terms of rutting rate than the bi-directional trafficking. Furthermore, the contact stress of the uni-

directional test was less than contact stress of the bi-directional test. This lends further support to the

above conclusion about the impact of the trafficking direction.

The rutting plot of Test 448A4 is almost identical to that of the MMLS3 Test SR Field J. The gradients of

Tests 448A4 and SR Field J compare favourably with the laboratory Test SR Lab EDV T1. All three of these

tests were done at a temperature close to 60°C.

The Rut Resistant 1, rutting plots are not included in Figure 5.6. The Figure was used to compare

Standard Reference SR Mix tests. The Rut Resistant 1 data is included in Figure 5.5 for (comparative)

purposes.


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5.4 HVS Test Category 4: Standard Reference Mix Overview

• Layer thickness: Varies (25 mm, 40 mm & 60 mm)


• Traffic direction: Uni-directional (uni) & Bi-directional (bi)

• Load composition: Varies (Std case, n-shape 60kN 800kPa, m-shape 60kN 420kPa)

For this criteria the HVS tests include; 441A4, 442A4, 443A4, 444A4, 445A4, 446A4, 447A4 & 448A4. All

tests done on the Standard Reference Mix were included.

These HVS tests were compared with the following MMLS3 tests:



The cumulative rutting plots of HVS test category 4 are not included being a duplication of Figure 5.2,

Figure 5.4 and Figure 5.6 in one figure that could lead to confusion. Therefore reference should be

made to Figures 5.2, 5.4 and 5.6 respectively when inquiries arise about the rutting performance of HVS

Load composition.

Figure 5.7 Rutting Rate versus Temperature HVS Test Category 4 – Standard Reference Mix Overview

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The rutting rates related to the different test temperatures of the individual HVS and MMLS tests yield,

in general similar gradients when trend lines are added. This is evident from Figure 5.7. Furthermore,

the rates pertaining to the HVS and MMLS tests at the respective temperatures and similar load

compositions in terms of contact stresses are located in tight clusters.

5.5 HVS Test Category 5: Standard Reference and Rut Resistant Mix

Comparison


• Mix type: Rut Resistant 1 and Rut Resistant 2 (RR 1 & RR2)


• Load case Type: Standard case 40kN, 620 kPa

Only two Rut Resistant 1 channelized tests were conducted with the HVS. These tests include 451A4 and

452A2. Rut Resistant 2 HVS Test, 455A4 was included for comparison with RR1 and SR HVS tests.


• 50 mm Standard Reference (SR) laboratory (SR 50 mm Lab EDV) (T1 and T3)

• 50 mm Rut Resistant 1 (RR) laboratory tests (RR 1 50 mm JG 2,3,4,5)


• 40 mm RR1 Field EDV (R & Q)

The HVS RR 1 tests (451A4 & 452A4) yielded lower gradients at similar temperatures than the gradients

of MMLS3 field and laboratory tests (Figure 5.8). This is a concern, since the HVS Standard Reference

Tests correlated well with the MMLS tests. It is difficult to understand how this change in performance

has come about since the temperatures far exceed the Softening Point. In addition, the gradient became

flatter in comparison to the gradients that prevailed in the cooler MMLS and HVS test regimes.

Figure 5.8 includes all SR and RR HVS Channelised tests.

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Figure 5.8 Rutting Rate versus Temperature HVS Test Category 5 – Standard Reference and Rut Resistant Mix Comparisons


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5.6 HVS Test Categories Trend Line Evaluation

Figure 5.10 HVS Trafficking Trend Lines – Category 1 to 3

Figure 5.10 is a summary of the HVS trafficking trend lines. The gradients of the different trend lines

should be interpreted with due consideration to the different tests criteria of each individual test. The

following deductions can be made from the respective trend lines:

• C1 pertains to all HVS tests discussed in Category 1 (441A4, 442A4 and 443A4) similar layer

thicknesses

• C2 pertains to an expansion of the tests included under C1 to include 444A4 and 445A4

(different layer thcknesses)

• C3 pertans to an expansion of C2 to include 446A4, 447A4 and 448A4 (different load

compositions)

Figure 5.10 indicates how the gradient of the rutting rate versus temperature trend line progressively

changes as different HVS tests are added to the respective categories.

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This stresses the importance of selecting appropriate elements when structuring a category for

evaluation of trafficking performance.

Table 5.1 HVS Data used by Denneman to plot HVS Rate/Temperature (Denneman 2008a)*

Temperatures ˚C Gradients

45.14 4.18127E-06

43.23 4.74422E-06

44.84 3.42824E-06

53.91 9.36203E-06

53.29 7.38978E-06

53.08 9.23347E-06

61.24 2.15993E-05

60.04 1.92E-04

61.26 8.04724E-05

45.28 2.69616E-06

42.81 5.29468E-06

42.28 4.40809E-06

52.61 1.11E-05

54.21 6.42892E-06

52.99 1.10357E-05

61.45 1.37843E-05

60.00 7.84337E-05

60.00 2.43636E-05

* The data highlighted yellow in Table 5.1 was excluded by Denneman for the trend line plot

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Figure 5.11 Comparison between HVS Test Category 1 Trend Line and the Original Trend Line by Denneman.

Denneman developed a trend line from Test 441A4, 442A4 and 443A4. He utilized temperatures from

the HVS database that had been measured along the length of the respective test sections at 3m

intervals (Denneman 2008b).

The data of this trend line is presented in Table 5.1. This is the trend line (blue squares Figure 5.11) that

was utilized in the previous reports.

A comparison between the trend line of the HVS Test category 1 and the original trend line of

Denneman is presented in Figure 5.11. The trend line of the HVS Test Category 1 compares favourably

with the original trend line of Denneman. The gradients do not differ to a great extent, indicating that

the choice to generate trend lines from 10 000 axle load repetitions was a reasonable decision.

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6 Conclusions

The MMLS3 laboratory and field test results compare favourably with the HVS test results. This is valid

both in terms of rutting rates and extent of rutting except for the HVS results for the RR1 test. These are

not comparable to the full range of tests with the MMLS3. The reason(s) for the discrepancy with the

HVS Rut Resistant Tests 451A4 and 452A4 is unclear. The reference base is very small (only two tests)

while the test temperature range is at the upperlimit of the full HVS test series. None of the RR1 MMLS

tests displayed similar rutting characteristics.

If however the HVS data for tests 451A4 and 452A4 are indeed correct, then the Rut Resistant Mix is

more resistant to rutting than the Standard Reference Mix. Furthermore, if these two tests are excluded

from the evaluation criteria, then there is no real difference in the rutting rates of the two mixes at the

specified test temperatures. Further validation is therefore necessary to confirm the findings pertaining

to the performance of the mix.

It is noteworthy that the findings of the study evaluated in terms of the recently published MMLS

Protocol DPG1 (2008) indicate that the mixes would not meet the criteria for a critical temperature of

60°C. However the criteria for a critical temperature of 50°C is met and good performance of the mix

could be expected under those conditions.

7 Recommendations In view of the very positive performance of the two channelised RR1 HVS tests in contrast to the

generally poor performance of the same mix under lateral wander testing (not discussed in this report

see Table 4.1) the following recommendations should be considered:

• More HVS Rut Resistant 1 tests should be conducted before a decision is made about the

performance of the mix.

• The study should include at least one test at 60°C. Preferably three tests should be done using

the std load case with 40kN, 620kPa uni-directional traffic on 40 mm or 50 mm asphalt layer.

The test temperatures should then include 50°C, 55°C and 60°C.

As far as test procedures are concerned it is appparent that test temperatures are of paramount

importance hence:

• Temperatures of all tests should be logged in a data format to include time and dates

• Weighted averages of the temperatures at the different intervals should be used to represent

the final temperature at which the test was conducted.

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8 References

De Beer and Sadzik (2007), Comparison of Contact Stresses of the Test Tyres used by the 1/3rd

Scale

Model Mobile Load Simulator (MMLS3) and the Full-Scale Test Tyres of the Heavy Vehicle Simulator

(HVS) – A Summary, Proceedings of the 26th Southern African Transport Conference (SATC 2007),

Pretoria, July.

Denneman (2008a), Technical memorandum Assessment of the permanent deformation characteristics

of a standard Hot-Mix Asphalt; Level one analysis of laboratory study results, Technical memorandum

CSIR/BE/IE/ER/2007/0014/B, prepared for Gauteng Provincial Government Department of Public

Transport, Roads and Works Directorate by CSIR Built Environment, Pretoria, March.

Denneman (2008b) Personal communication by Hugo

DPG1 – Method for evaluation of permanent deformation and susceptibility to moisture damage of

bituminous road paving mixtures using the Model Mobile Load Simulator (MMLS3) (2008), Best Practice

document developed under the auspices of the Road Pavement Forum (RPF) and approved for use and

distribution at the bi-annual meeting held in Pretoria, Nov.

Hugo, F, De Vos, ER (2008a), Evaluation of HMA Rutting Performance Under MMLS3 Trafficking in the

Laboratory and in the Field on a trial section on the R80, First Report prepared for Gauteng Government

Department of Public Works and Transportation, May.

Hugo, F, De Vos, ER (2008b), Evaluation of HMA Rutting Performance Under MMLS3 Trafficking in the

Laboratory and in the Field on a trial section on the R80, Second Report prepared for Gauteng

Government Department of Public Works and Transportation, September.

Hugo, F MMLS3 Workshop (2008) SATC Pretoria, July.

Steyn, Wynand, JvdM (2008) Data provided via email, Research Group Leader: Transport Infrastructure

Engineering, CSIR Built Environment, Pretoria, Dec.

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9 Appendices

9.1 Appendix A – Summary of the R80 HVS Test Protocols

Table 9.1A - Summary of the R80 HVS Test Protocols and related Data (Steyn, 2008)

25 | P a g e

Table 9.2A - Summary of the R80 HVS Temperature Data (Steyn, 2008) †

† The single test temperature assigned to each individual test was calculated by taking the average temperature of the

recorded temperatures at caravan side and traffic side of each test.

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9.2 Appendix B – Summary of the MMLS3 Field and Laboratory HMA Test on

the R80 Trial Section

Table 9.3B - Summary of the MMLS3 Field and Laboratory HMA Test on the R80 Trial Section‡

Test Mix Lab/Field Temperature Appl/hour

Layer

Thickness

(mm)

Conducted by

RR1 Lab JG2 Rut Resistant 1 Lab 60.00 2400 50 ITT - J Gerber




RR1 Field Q Rut Resistant 1 Field 59.90 2400 40 ITT - E de Vos

RR1 Field R Rut Resistant 1 Field 61.55 2400 40 ITT - E de Vos

SR Field J Standard Reference Field 60.00 2400 40 Roadlab - R Odendal

SR Lab EDV T1 Standard Reference Lab 60.00 2400 50 ITT - E de Vos

SR Lab EDEV

T3 Standard Reference Lab 50.00 2400 50

ITT - E de Vos

SR Field A Standard Reference Field 60.00 7200 40 Roadlab - R Odendal

SR Field C Standard Reference Field 50.00 7200 40 Roadlab - R Odendal

SR Field D Standard Reference Field 40.00 7200 40 Roadlab - R Odendal

SR Field E Standard Reference Field 50.00 7200 40 Roadlab - R Odendal

ITT 7200 60 ˚C Standard Reference Lab 60.00 7200 50 ITT - E de Vos

ITT 7200 50 ˚C Standard Reference Lab 50.00 7200 50 ITT - E de Vos

Lab 40C 10k

(7200) Standard Reference Lab 40.00 7200 40

Roadlab - R Odendal

Lab 50C 10k


Roadlab - R Odendal

Lab 60C 10k


Roadlab - R Odendal

‡ MMLS3 lateral wander and Rut Resistant 2 tests are not included in the current report

Documents

Additional MMLS3 Laboratory Testing R80 and... · Additional MMLS3 Laboratory Testing and a Synthesis of Selected Tests for Evaluation of Rutting Performance of the HMA on a Trial