DOES SANS 307 GUARANTEE FIT-FOR-PURPOSE ROAD BITUMENS?

A CRITICAL EVALUATION OF COMPLIANCE AND PERFORMANCE OF PENETRATION GRADE BITUMENS TESTED AT CSIR-TRANSPORTEK SINCE 1995.

Lead Author: E J van Assen, CSIR-Transportek, Pretoria Co-author: M Vlok, CSIR-Transportek, Pretoria J O’ Connell, CSIR-Transportek, Pretoria 1. Summary Amendments to SANS 307 are reviewed in this paper from a critical evaluation of compliance and performance of penetration grade bitumens tested at CSIR-Transportek since 1995. Salient properties of bitumen produced from 1985 to 2003 are chronologically compared within the relevant specified framework. In order to comply with these amendments the bitumen appears to have changed somewhat over the last three decades. Since SABS 307 (1992) specified both viscosity and penetration, the most obvious change noted was a tendency toward decreasing viscosity, especially at 60°C. The lower viscosity appears to be related to a slight decrease in asphaltene content over the same period. In terms of performance these small changes could indicate a small trade-off to favour durability versus stability. In all bitumens tested in the CSIR-Transportek laboratory, the properties of ex-refinery bitumens complied with the specified requirements. Results were within a relatively narrow band. These bitumens appear to have been fairly consistent over the years with regard to penetration and softening point. However there appears to be a tendency towards the production of bitumen with lower viscosities (60°C). This trend was also noticed in the rutting parameter compliance where current 60/70 bitumens on average comply with the 58°C maximum whereas earlier bitumen tended to comply with the 64°C requirement. The sample analysed since 2000 is however too small to make any definite deductions in this regard at this stage. Therefore, within the framework of properties appropriate for engineering road materials, these products appeared to be of consistent and reliable quality. Contaminated bitumen samples taken from tankers and site storage tanks in Southern Africa, raised concern. Some of these results have been used as examples to test the effectiveness and ability of the current specification requirements to identify ‘cut back’ bitumen readily. The case studies of laboratory investigations of asphalt failures indicated that application of the relevant bitumen specifications could be used effectively as a safeguard in the asphalt industry to ensure quality and consistency. Implementation of specifications and managing the quality chain throughout (from refinery to application on the road) appear to be more urgently in need of redress than the yardstick. Since SANS 307 is already a dual specification, including both penetration and viscosity grading, there could be a case for a user specifications menu with guidelines for a dedicated regime for specific requirements and applications (Fit for Purpose specifications). These user specific requirements should, however, be based on sound principles and appropriate ranges before any negotiation with suppliers.

2. Background and overview Since bitumen was first used commercially for asphalt roads up to now, procuring bitumen of appropriate quality and consistency has been a major issue for the asphalt industry. It is stated in Trinidad Asphalt Roads2), published by Trinidad Lake Asphalt Limited (TLA), London 1939 that: "Throughout the Empire the task of providing road surfaces adequate for modern motor transport………..asphalt remains the pre-eminently superior binding agent… function is to hold particles in place… give strength and resilience to composite mass." According to TLA the best efforts to produce bitumen synthetically (by petroleum refiners) have not yielded material equal in quality to TLA which, through aeons of natural seasoning has attained a state of chemical stability and uniformity of composition (for which TLA is esteemed in road construction) which is unapproachable through any known brief process of heat treatment. The performance properties of road bitumen should cater for both construction requirements (i.e. viscosity for ease of application, etc) as well as road performance (i.e. optimisation of stability and fatigue properties). Early failures (i.e. premature cracking and ravelling on the one hand, and rutting, shoving and bleeding on the other) are often ascribed to bitumen shortcomings or alternatively to shortcomings of the specification if the bitumen allegedly used complied with the relevant specification. Often in these disputes a verifiable reference sample is not available, which makes it very difficult to vindicate or repudiate these suspicions. The same concerns have been mentioned in the HMA project document, i.e. that variation within specified ranges causes asphalt to behave differently during manufacture and construction. A national specification therefore has to address many and varied issues which will satisfy the needs of the asphalt industry (i.e. consistent quality bitumens) but, at the same time, bitumen which can be produced reasonably economically from available resources. Furthermore the specification would be required to select appropriate properties that are easily measurable, and ranges for these properties that will ensure fairly consistent bitumen products to the asphalt industry. In order to evaluate the efficacy of SABS/SANS307 to deliver products within this mandate the specification was extensively reviewed in 19961). The review included commentary from international bitumen experts and comparisons with international specifications. The recommendations, which were deemed at that time to be optimal ranges, are indicated in the historical overview of the specifications and some of these recommendations were subsequently incorporated in follow-up amendments. Where applicable, these have been included in this review in the tables giving the properties of 60/70 and 80/100 penetration grade bitumen (cf. Tables 1 and 2). Properties used in national specifications should be easily measurable but still ensure good compositional balance and acceptable potential long-term performance of bitumen. However, since a national specification needs to recognize the practical and economical implications relevant to the local producers of road bitumen, both properties and ranges, which will be acceptable to all stakeholders, tend to be rather inclusive than exclusive. Apart from absolute quality, consistency of bitumen delivered to the asphalt industry is of most importance in order to deliver acceptable quality economically. The objective of this paper is to investigate the ability of SABS 307 to deliver on its mandate. Only results obtained in the CSIR-Transportek laboratory are reflected. Although some

Amendt - Year 1972 2 - 1992 3 - 1994 4 - 1995 5 - 1997 Current Recom.#Pen 60-70 Report Report 60-70 60-70 60-70Soft. Pt. 46-56 Report Report 46-56 46-56 46-56Visc 60 n/a 140 - 240 105 - 165 105 - 250* 120-250 120-250 160 - 240Visc 135 n/a 0,35 min 0,22 min 0,22 min 0,22 - 0,45 0,22 - 0,45 0,30-1LOH, max 0,8 0,5 0,5 0,5 0,5 0,5R visc % n/a 250 max 300 max 300 max 300 max 300 maxSoft. Pt min n/a Report Report Report 48 48 48Inc Soft pt Report 9 max 9 max 5,5Ret pen 33 min 33 min 33 minRet pen % 55 min 55 min 55 min 55 min 55 min 55 minSpot test 35 max 30 max 30 max 30 max 30 max 30 max 15-30Asphal orig** 9 - 19 12 - 14 9 -14Asphal RTFO** 12 - 22 14 - 16 12 - 17Rutting (°C) 58 - 64 58 SuperpaveFatigue (°C) 16 - 22 16 - 22 Superpave

Grade 80/100 B10 B8 B8/80/100 80/100 80/100 80/100Amendt - Year 1972 2 - 1992192 3 - 1994 4 - 1995 5 - 1997 Current Recom.#

Pen 80-100 Report Report 80-100 80-100 80-100Soft. Pt. 42-51 Report Report 42-51 42-51 42-51Visc 60 n/a 60-130 55-150 105 - 250* 75-150 75-150 80 - 120Visc 135 n/a 0,30 min 0,15 min 0,15 min 0,15-0,40 0,15-0,40 0,25-1LOH, max 1 0,5 0,5 0,5 0,5 0,5R visc % n/a 250 max 300 max 300 max 300 max 300 maxSoft. Pt min n/a Report Report Report 44 44 44Inc Soft pt n/a 9 max 9 max 5,5Ret pen 40 min 40 min 40 minRet pen % 50 min 50 min 50 min 50 min 50 min 50 minSpot test 30 max 30 max 30 max 30 max 30 max 30 max 15 - 30Asphal orig ** 9 - 16 8 - 13Asphal RTFO ** 12 - 20 11 - 16

categories of property ranges reported were derived from a small and probably not representative number of samples, they serve as examples to measure the capability of SABS 307 to discriminate between acceptable and unacceptable bitumen. The intention of this paper is therefore to address the following questions:

• To what extent is property compliance a safeguard to ensure that at least one of the asphalt’s components can be used with confidence;

• Are the ranges appropriate to ensure consistency and uniformity; and • Where do things (those that can definitely be attributed to bitumen properties, partially

or wholly) go wrong and can the specifications detect adulterated products? 3. Thirty years of SABS/SANS307 Properties and ranges specified over the past 30 years for 60/70 and 80/100 penetration grade bitumen are summarized in Tables 1a and 1b respectively. The ductility is not given since it is not a currently specified property. On the other hand, asphaltene (in n-hexane) ranges determined over corresponding time periods have been included. The actual ranges, as determined in the CSIR-Transportek laboratory, for specified properties are compared in Tables 2a and 2b for these two penetration grades.

Table 1a: SABS 307 requirements for 60/70 penetration grade bitumen

Table 1b: SABS 307 requirements for 80/100 penetration grade bitumen

# Recommendations as per reference 1)

* Optional requirement ** n-Hexane asphaltene

Table 2a: Comparison of 60/70 pen grade bitumen between 1985 and 2003 Specification Range 1985-1992

Low Visc High ViscRange 1992-1995

Low Visc High Visc Range 1995-2000

Low Visc High Visc SANS 307 Amdt 2002

Range 2000-2003 Low Visc High Visc

Penetration @ 25 °C, mm-1 72 42 85 49 70 55 60 – 70 71 55 Soft. Pt., °C 46 52 46 50 48 52 46 – 56 48 55 Viscosity @ 60°C, Pas (Recommended)

- - 105 300 152 227 120 – 250 (160 – 240)

98 166

Viscosity @ 135 °C, Pas (Recommended)

- - 0,27 0,42 0,30 0,41 0,22 – 0,45 (0,3 – 1)

0,29 0,4

Spot test, % Xylene - - - - 25 30 30 max 25 30 Mass change RTFOT, % - - - - 0,5 max 0,1 -0,2 Increase in Soft pt., °C Recommended Soft. Pt. (Recommended)

50

56

50

60

3

53

5

55

9 max (5,5 max)

48 min (48 min)

3

53

6

55

Viscosity @ 60°C, Pas - - 181 404 352 492 750 max 185 460 Increase in viscosity @ 60 °C, %

- - - - 217 232 300 max 168 210

Retained penetration, mm-1 47 33 51 36 47 38 33 min 49 40 Retained pen, % 69 55 min 77 61 Table 2b: Comparison of 80/100 pen grade bitumen between 1985 and 2003

Specification Range 1985- 1992 Low Visc High Visc

Range 1992 – 1995 Low Visc High Visc

SANS 307 Amdt 2002

Range 2000-2003 Low Visc High Visc

Penetration @ 25 °C, mm-1 109 71 143 72 80 – 100 96 83 Soft. Pt., °C 44 49 41 46 42 – 51 43 49 Viscosity @ 60°C, Pas (Recommended)

- 80 1202* 75 – 150 (80 – 120)

93 124

Viscosity @ 135 °C, Pas (Recommended)

- 0,23 0,37 0,15 – 0,40 (0,25 – 1)

0,29 0,33

Spot test, % Xylene - 30 max 25 30 Mass change RTFOT, % - 0,5 max 0,1 0 Softening pt., °C (Recommended) Increase in Soft pt., °C (Recommended)

48 52 45 50 44 min (44 min) 9 max

(5,5 max)

48

3

55 7

Viscosity @ 60°C, Pas - 132 2410* 450 max 203 247 Increase in viscosity @ 60 °C, % - - - 300 max 185 245 Retained penetration, mm-1 69 49 103 49 40 min 65 62 Retained pen, % 50 min 76 68

4. Where do things go wrong? Practical examples (case studies) of non-compliant and compliant penetration grade bitumen

Properties of ‘contaminated’ bitumen from site/tankers are compared with the relevant specification in Tables 3a, 3b and 3c. Variations in bitumen complying with the currently specified requirements are illustrated in Table 4 with comments on possible implications of these variations on road performance. The results obtained on international bitumen evaluated by means of SANS 307 and CSIR methods are given in Table 5. Table 3a: Effectiveness of SABS 307 to detect contamination of 80/100 pen bitumen

80/100 pen bitumen ex tankers Test A B C D

SABS 307 1997

Test Method

Penetration (10-1mm) 170* 94 114* 120* 80 – 100 ASTM D5 Softening Point (oC) 35,0* 49,0 44,3 44,1 42 – 51 ASTM D36 Viscosity @ 60oC (Pa.s) 16,2* 79,3 68,4* 68,5* 75 – 150 ASTM

D4402 Viscosity @ 135oC (Pa.s) 0,13* 0,23 0,24 0,24 0,15 - 0,40 ASTM

D4402 Ductility @10oC (cm) 100+ 100+ 100 + 100 + 100 min DIN 52013 Spot Test (% Xylene) Pass Pass Pass Pass 30 max AASHTO

T102 RTFOT: Mass Change (%m/m) (loss)

- 4,70%*

-0,50

-1,9*

-2,0*

0,5 max

ASTM D2872

Viscosity @ 60oC (Pa.s) (% of original)

236,2 1 456*

189,5 239

287 419*

270 394*

450 max 300 max

ASTM D4402

Ductility @10oC (cm) 14 59 3* 3* 5 min. DIN 52013 Softening Point (oC) 53,5 52,5 53,5 53,3 44 min. ASTM D36 Increase in Softening Point (oC) 18,5* 3,5 9,2* 9,2* 9 max ASTM D36 Retained Penetration, (mm-1) (% of original)

49 29*

53 56

40 35*

42 35*

40 min 50 min.

ASTM D5

*Non-compliance From Table 3a it can be seen that binder A did not comply with any of the viscosity properties as required by SABS 307 (1997) and SANS 307 (2002). Although the fundamental RTFOT properties complied, the ratios of change after RTFOT did not. This indicates that the base bitumen prior to contamination would most probably have complied with the requirements. It was strongly suspected that the non-compliance was a direct consequence of contamination of the bitumen with a solvent (lower boiling point compounds) indicated by the high mass loss after RTFOT. Confirmation of this suspicion is however only of academic interest since the low viscosity property would have the following negative impacts on road performance:

• Softening of the substrate (depending on the substrate, and type of contaminant) leading to greater consequential punching by the aggregate than initially anticipated by the design, resulting in bleeding and/or reduced seal lifetime.

• Reduced binder-aggregate adhesive strength.

The presence of solvents can be confirmed by distillation, gas chromatography and/or chemical analysis. Refinery contamination is highly unlikely (no incidences have ever been

established) so these contaminants (solvents) may have originated from back contamination during haulage or site storage. The exact origin can be established unequivocally by comparing retained samples from site with retained samples taken by the refinery at the delivery point. Table 3b: Effectiveness of SABS 307 to detect contamination of 60/70 pen bitumen Test A B SABS 307

1997 Test Method

Penetration (10-1mm) 149* 130* 60 – 70 ASTM D5

Softening Point (oC) 44,9* 46 – 56 ASTM D36

Viscosity @ 60oC (Pa.s) 67* 120 – 250 ASTM D4402

Viscosity @ 135oC (Pa.s) 0,23 0,22 - 0,45 ASTM D4402 Ductility @10oC (cm) 100+ 100 min DIN 52013

Spot Test (% Xylene) Pass 30 max AASHTO T102

RTFOT: Mass Change (%m/m) (loss)

-5,3*

- 1,7%*

0,5 max

ASTM D2872

Viscosity @ 60oC (Pa.s) (% of original)

238 355*

750 max 300 max

ASTM D4402

Ductility @10oC (cm) 100+ 10 min. DIN 52013

Softening Point (oC) 52,6 48 min. ASTM D36

Increase in Softening Point (oC) 7,7 9 max ASTM D36

Retained Penetration, (mm-1) (% of original)

24* 16*

52 40*

33 min 55 min.

ASTM D5

Gas Chromatographic Analyses Area counts

29 000

RMT – 001

*Non-compliance Table 3b shows that neither sample tested complied with the requirements of SABS 307 (1997) for a 60/70 penetration-grade bitumen. This was due to the high levels of contamination as indicated by high mass loss after RTFOT, and confirmed by the gas chromatographic analysis (GCA) results in the case of sample B. Possible consequences and risks of such a magnitude of contamination would be bleeding and deformation of the asphalt. It is difficult to predict absolute future performance where such bitumen has been used for hot mix application since the risk of future failure would depend on the specific interaction of various key parameters that will govern performance, including volumetric properties of the asphalt, environmental factors and traffic loading. A more extreme case of contamination identified from GCA results and chemical analysis is highlighted in the following table, and discussed below.

Table 3c: Extreme case of contamination in road binders

Property Results Lab reference Test Method Gas Chromatographic Analyses

Area counts Identification

16 600 Coal Tar Naphtha

CSIR RMT – 001

Chemical Analysis (HPLC) (% m/m)

Saturates Aromatics

Resins Asphaltenes

"1 –4” “5 – 10” “60 – 80”

17,1

4 - 6 39 - 44 39 - 44 10 – 12

CSIR - RMT – 002

In this case of extreme contamination, the binder had a tar-like smell and was not homogeneous. The GCA results indicated the presence of a significant quantity of coal tar distillate. The “bitumen” sample was so highly contaminated that an accurate chemical analysis was not possible. Although the results were estimates they indicate a binder of very poor compositional balance:

• The low aromatic fraction, exacerbated by dissipation and evaporation of the lighter solvents and oils, affects adhesive and cohesive properties negatively and is insufficient for asphaltene mobilisation.

• The very high resin fraction is a reservoir for ‘asphaltene production’ as ageing/oxidation progresses, thereby augmenting the already relatively high asphaltene quantities found in this binder, resulting in excessive premature ageing.

A binder containing solvents and oils, and having this chemical composition, would therefore be expected to have reduced adhesive and cohesive properties, and show accelerated premature ageing manifesting as fatigue cracking, crack propagation and/or ravelling, as the volatile compounds and lighter oils begin to dissipate and evaporate. It is a considered opinion that this bitumen would not pass the SABS 307 specification for bituminous binders for road construction and should not be used for this purpose. Table 4 now reviews the variability in ductility found on compliant 80/100 penetration grade bitumen samples tested during 2001/2002 to give an indication of variation within specification ranges.

Table 4: Ductility variability within specification compliant bitumen (2001 - 2002)

Property 80/100 pen grade bitumen ex site/tankers

SABS 307

1997

Test Method

Penetration (cm-1) 89 83 91 93 81 80 – 100 ASTM D5

Softening Point (°C) 48,8 48,6 46,8 46,1 48,1 42 – 51 ASTM D36

Ductility @10oC (cm) 100+ 100+ 100+ 100+ 100+ 100 min DIN 52013

Viscosity @ 60 oC (Pa.s) 98,3 102,5 92,3 114,5 105,7 75 – 150 ASTM D4402

Viscosity @ 135oC (Pa.s) 0,25 0,25 0,25 0,32 0,27 0,15 –

0,40

ASTM D4402

Spot Test (% Xylene) Pass Pass Pass Pass Pass 30 max AASHTO

T102

Loss on Heating (m/m %) -0,4 -0,1 0,04 0,06 0,03 N/a IP 45

Retained Ductility @10oC

(cm)

1

1

100+

76

15

N/a

DIN 52013

The results obtained indicate that the samples differ markedly from one another, especially with respect to their ductility values after RTFOT. The very low values (1 cm) of ductility @ 10°C after RTFOT are of concern. Although this property is no longer a requirement of SANS 307 (2002), a minimum value of 5 cm was previously specified in SABS 307 (1997) – a value that was generally easily attained. These low values may be an indication of bitumen becoming brittle with ageing through loss of volatile compounds and/or progressive asphaltene formation, resulting in premature cracking and/or chip loss. Table 5 presents a comparison of two overseas 80/100 penetration grade bitumen binders tested in accordance with the South African standards to give a broader view of the appropriateness of local standards. Table 5: Bitumen properties of international bitumen tested to SABS 307 (1997) and CSIR-developed tests

Test Sample ER Sample BT Specification SABS 307

80 –100 pen

Test Method

Penetration (10-1mm) 100 83 80 - 100 ASTM D5 Softening Point (oC) 48.5 49.3 42 – 51 ASTM D36 Viscosity @ 60 oC (Pa.s) 142 115 75 - 150 ASTM D4402 Viscosity @ 135oC (Pa.s) 0.33 0.25 0.15 – 0.40 ASTM D4402 Spot Test (% Xylene) Pass Pass 30 max AASHTO T102 Ductility @10oC (cm)* 33 46 100 min DIN 52013 RTFOT: Mass Change %m/m) - 0.32 + 0.03 0,5 max ASTM D2872 Viscosity @ 60 oC (Pa.s) (% of original)

582* (410)

229 (199)

450 (300 max)

ASTM D4402

Ductility @10oC (cm)* 7 7 5 min. DIN 52013 Softening Point (oC) 56,6 54,0 44 min. ASTM D36 Increase in Softening Point (oC) 8.1 4.7 9 max ASTM D36 Retained Penetration (10-1mm)

(% Of 0riginal)

55

55

53

64

50 min.

ASTM D5

Gas Chromatographic Analyses Area counts

20 604

7 530

CSIR RMT – 001

The viscosity @ 60°C of sample ER (142kPa) is high, but just within specification. However, the increase in viscosity @ 60°C after rolling thin film oven (410%) exceeds that allowed by the specification (300% max). The actual viscosity value of 582 kPa can also be considered as high compared to typical viscosity values of 250 to 450 kPa for South African 80/100 penetration grade bitumen after RTFOT. The GCA confirmed the suspicion that the exaggerated stiffening of the ER sample after RTFOT may be an indication of the presence of volatile components.

5. Comments on the specification changes over the years

• Penetration and softening point ranges have essentially remained constant, except that in 1992 when viscosity grades were introduced they were specified as "report only" properties.

• The minimum viscosity values at both 60 and 135 °C as specified in 1992, were higher

than those currently specified. In order to comply with the mandatory viscosity requirement the penetration values varied significantly. In 1995, Amendment no.4, reintroduced penetration as a mandatory requirement together with viscosity at 60 °C as an optional requirement, but assigning a wider range to enable producers to comply with both penetration and viscosity requirements. In the 1997 amendment 5, a maximum value for viscosity at 135 °C was introduced. Limiting both maximum and minimum values strives towards balancing durability and stability performance of the binder.

• The reduction in maximum mass change after RTFOT from 0,8 to 0,5% was very

positive toward enhancing durability and minimising volatile compounds.

• Ductility was first specified at 25 °C but since this temperature in practice was found to be rather non-discriminatory, the option of lower test temperatures as practised in Germany (DIN Specification) was investigated. In 1992 (Amendment no. 2) the modified low temperature ductility test (LTD) was included as a "report only" requirement, followed by the 1995 Amendment no.4, which specified minimum values for the before RTFOT bitumen. In 1997 (Amendment no. 5) minima were also specified for the RTFOT bitumen. Ductility as a specification requirement was dropped in Amendment no. 6 of 2002. This was probably motivated by practical considerations and questions around appropriateness of ranges relative to road performance.

• In our opinion and experience, SANS 307 ensures adequate classical road bitumen

ex-refinery but the problems that we are aware of generally occur further downstream where it really matters and with potential negative impact on the performance of the end product. The specifications therefore have to cater for situations that go beyond the good quality control that can be exercised at SA refineries, not too mention bitumens used elsewhere in Southern Africa and wherever SA consultants and contractors may require assistance regarding available products. Judged by the results shown in this paper, the current specifications appear to be able to control quality irrespective of bitumen source.

6. Recommendations for future amendments to current SANS 307

While the overall framework is viewed as satisfactory, there are however some aspects which require reviewing in order to weed out potential poor performers, and sometimes even hazardous materials on site. The latter issue of petroleum (or tar) distillates in bitumen that is to be used for hot mix production is controlled by both viscosity and mass change during the (Rolling) Thin Film Oven Test ((R)TFOT). Furthermore the degree of change after RTFOT is an important indication of potential ageing. The RTFOT viscosity is an indication of stability and durability

performance. Based on these concerns the following amendments are proposed for deliberation by the specifications committee:

• Mass (loss) change of 0,5 max is too high.

• Softening point increase after RTFOT of 9°C is too high (based on top of original range). It is proposed that the increase should not exceed 7°C. This recommendation is based on the results presented in this paper. It should be noted that in the study conducted in 1996, a maximum increase of 5,5°C in softening point was recommended. Whilst the 1996 recommendation is still considered more appropriate and ideal, a maximum increase of 7°C is probably more practical and achievable in the short term.

• Ductility after RTFOT, both with regard to test temperature and appropriate ranges

could be revisited. Considering the practical implications of this test’s use as a general specification item, it could be an appropriate property to specify in a Fit for Purpose menu (FFP).

• The rutting parameter, as specified in the Superpave P-G grades relates to viscosity at

60°C. The values obtained on a relatively small number of ex-refinery bitumens appear to be fairly consistent for penetration grade but some overlapping has been found between grades. The correlation of this parameter with laboratory rutting tests has not been established. This parameter could be suitable for FFP projects.

• The pressure ageing vessel (PAV) test can be used to measure potential durability but

would not be suitable as a national specification property due to the time and cost involved to execute the procedure. Good correlation has been found between PAV, chemical composition, and ductility at 25°C and road performance where binder fatigue was very obvious. The test could be appropriate in FPP evaluations.

Change is a process that needs to be recognized and accommodated. To this end the knowledge base regarding binder properties relative to performance needs to be extended and upgraded on an ongoing basis in order to provide for an ever-increasing variation in road binders on offer, especially in Southern Africa. In this context it is not only variation in the quality of available bitumen, but in addition change in quality during long haulage time required to procure road binders and asphalt, which can impact considerably on the quality of the residual binder ending up in the end product (hot mix and seals) on the road. 7. References

1. Van Assen, E J and M van de Ven. Review of South African bitumen specification to take cognisance of compositional balance relative to long-term behaviour. Contract report CR96/034. Pretoria 1996.

2. Trinidad Asphalt Roads,Trinidad Lake Asphalt Limited, London 1939.