I TRANSPORT RESEARCH LABORATORY TITLE by / 0 Research on hot rolled sheet overlays in Indonesia T Toole and A Tatang Dachlan Overseas Centre Transport Research Laboratory Crowthorne Berkshire United Kingdom IA TOOLE, T, S MAHMUJD and A TATANG DACHLAN, 1990. Research on hot rolled sheet overlays in Indonesia. In: Fourth Annual Conference on Road Engineering, lakarta, 19-21 November 1990. Bandung: Institute of Road Engineering. INSTITUTE OF ROAD ENGINEERING AGENCY FOR RESEARCH AND DEVE LOPIMENT MINISTRY OF PUBLIC WORKS IRE RESEARCH REPORT 1 1.025.TJ.90 RESEARCH ON HOT ROLLED SHEET OVERLAYS IN INDONESIA by T. Toole (Transport and Road Research Laboratory, UK), Ir. Salim Mahmud and Ir. A. Tatang. Dachian Road Eiiginieeriig Division Inistitute of Road Enigi-ieerling Baiduxig INDONESIA Janiuary 1991 CONTENTS Page No. PRE FACE ABS TRACT 1. INTRODUCTION 2. OBJECTIVES OF THE RESEARCH 3. DESIGN OF THE RESEARCH 4. FACTORS AFFECTING PERFORM4ANCE 5. IMPLEMENTATION 6. THE NETWORK LEVEL CONDITION SURVEY 6.1 Measurements 6.2 Results 6.3 Discussion 7. THE MONITORTIN~jG~-SEdT'IONS 7.1 Paveme~t cmposition 7.2 Properties of the bituminous overlay material s - o~iverlaj:-y.limterials - 8. SUMMARY AND CONCLUSIONS 9. ACKNOWLEDGEMENTS-- 10. REFERENCES 10 12 12 14 14 RESEARCH ON HOT ROLLED SHEET OVERLAYS IN IND)ONESIA PREFACE A better understanding of the behaviour of bituminous materials, their mode of failure and the optimisation of both the mixes and the structural design are of prime importance to Indonesia's Directorate General of Highways (DGH). Over the past five years many thousands kilometres of road have been subjected to a road betterment programme which includes an asphaltic overlay composed of Asphalt Treated Base (ATB) and a thin wearing course of Hot Rolled Sheet (HRS). The overlay materials are designed to accomodate a greater amount of binder than the traditional, alternative asphaltic concrete (AC) mixes. The aim is to impart greater flexibility and durability to the pavement surface so that it can tolerate the high deflections common in Indonesia and to reduce the. rate at which embrittlement of the bituminous material takes place, thus reducing the development of cracking. The HRS mixes are more similar to the UK gap-graded-hot-rolled asphalts than the continuously-graded asphaltic concretes of America origin. The adoption of the HRS technology followed studies in the early eighties in Indonesia. In order to develop suitable performance prediction models for both HRS and AC mixes and improvements to: mi'x s'p'ecificat'ions and thickness design, in-depth road performance and laboratory studies have been implemented as part of' a j)O'in't programme of research involving the Institute of Road Engineering (IRE) and the UK's Transport and Road Research Laboratory (TRRL). The project has been underway since 1988. -Th~i~s--repor-t~smaie h esig-n and --ip-eme-ntation- -of --- the research and describes the analysis of---th&e results of the initial field condition surveys and laboratory investigations which provide a broad picture of the behaviour of the overlays which had been constructed prior to the start of the project. A comprehensive description of the design and implementation of the research and of the measurement, sampling and test methods used is contained in a separate report. Subsequent reports will be issued which contain the results of the detailed performance studies and analysis. Bandung, January 1991 HEAD OF ROAD ENGINEERING DIVISION, INSTITUTE OF ROAD ENGINEERING, Dr. Hermanto Dardak, MSc. NIP . 110025773 i RESEARCH ON HOT ROLLED SHEET OVERLAYS IN INDONESIA ABS TRACT A comprehensive research programme has been established to develop performance prediction models for the alternative structural road surfacings in Indonesia and to improve specifications and thickness design. For this purpose detailed observations have commenced on 25 monitoring sections selected from a 360 km sample of the road network which was subject to a general condition survey. The road links and sections cover a wide range of design parameters and performance. This report describes the design and implementation of the research on existing bituminous overlays and contains some early results and details of the pavement structures and overlay mixes. In general, the performance of the mixes made to a hot rolled sheet specification is very variable. Although mean values for the rate of rutting and crack development can be low 90 percentile values are high with critical conditions being reached within a few years. Correspondingly, the properties. of the mixes' manudfactured to a common specification are variable, .ranging from gap-graded to continuously--gr-aded-and coverin~g a wide range of bitu'men content .and other properties. Given the degree of variability. it is no't-, .possib-le to make conclusive recommendations at this 'stage. Further -observation of the monitoring sectio~ns and at a network level. is required. 1. INTRODUCTION In tropical areas- of the. worl~d bituminous'-road surfacings are required to tolerate harsh climatic cnditions and heavy axle loads. In addition, in many areas, deflections are high because of weak subgrades. These conditions-impose severe .'demands on the design of mixes which must possess good load spreading properties to protect 'the lower pavement layers and the subgrade, good flexibility to withstand the high strains imposed by heavy traffic, good fatigue-properties to carry traffic for as long as possible and good durability so that their properties do not deteriorate (degrade) rapidly. Prior to about 1983 the predominant type of premix used in Indonesia for structural strengthening and overlaying was a continuously graded asphaltic concrete (AC) .to American specifications. This material is relatively stiff and can perform well if it is made properly. Unfortunately its properties are extremely sensitive to its composition and very small changes produce mixes which are unsatisfactory. 1 Experience in Indonesia and elsewhere has shown that the most -Likely prcblem is poor.drblt and. flexibil.Aity gliving rise to premature cracking. IP 1983 Comne described an alternative composite overlay systsam comprising an asphalt treated base (ATB) and a wearing course of hot-rolled sheet (HRS) . These materials were designed to' accommodate a relatively high bitumen content to provide better flexibility and improve durability. The HRS i's based on the gap-graded hot-rolled asphalt used in the UK (BSI, 1985). This material is more tolerant of minor changes in mix proportions and is therefore easier to make successfully. It is also easier to compact than AC and is therefore potentially more reliable. .Despite these advantages gap-graded mixes have not been used extensively in the tropics because of the fear that they will deform under the combined effects of high temperatures and heavy wheel loads. However, experiments carried out in the tropics (SMITH and JONES, 1982) and experience in Southern Africa indicated that gap-graded mixes could be designed to overcome this prob lem. Comne's paper (CORNE, 1983) showed that such mixes performed reasonably well in IndonesiaL and the method. was adopted' by the Directorate General of Highways for use in the road betterment-programme. Over the past five years several thousand kilometres of road have been upgraded with composite overlays of ATB and HRS. The investmnent ',i'n"' HRS technology has been large and ensuring its successful performance is therefore of high priority to DGH. Quantification 'of't performance-'in comparison with alternative materials, refinements in the design method'jand in the specifications and improvements in construction practice are .necessary">ifQ""~HRS""is"'~to adh~ievi'its'full -potential for road rehabi~lltaionj And to remacin a-n important option for road strengthen"ing". "- 'To undertake this study a cooperative research project was established in 1988 between the Institute of Road Engineering in Bandung-(IRE) and the 'Transpom-t-and Road Research '--Labo~rat-ory ,af te~U TR) This report describes the design and implementation of the res~earch,..and- thie an-alysis -of^ the results of-the --initial field condition surveys-'and.'laboratory 'investigations which provide a broad pictxir~e~ofh behaviour of the overlays-which had been constructed 'pir'io:~r" t-o ',the start of the project. 2. OBJECTIVES OF THE RESEARCH At the outset of the research the following objectives and output were described: objective To evaluate the performance of structural road surfacings and rehabilitation methods in Indonesia. 2 output An established research programme leading to sound performance predictions and improved specifications for hot-mix surfacings together with a calibrated analytical structural design method for thickness design. 3. DESIGN OF THE RESEARCH Ideally the objectives of the research could be achieved by constructing a series of experimental overlays in which the key variables affecting performance were varied in a controlled way so that their effect on performance could be quantified. Such an approach would be scientifically correct but would be very difficult to carry out because of the large number of important performance related variables which would need to be controlled and varied systematically. Fortunately the scale of the betterment programme meant that a wide variety of roads had been overlayed under a wide range of conditions. Recognising that the nature of road making materials. and mix production processes are such that quite wide variations in mix composition occur within any project, it was anticipated that the range of conditions encountered on the roads which had been rehabilitated by 1988 would cover the ranges of most of the key variables which were required for the study. Any factors which could not be assessed by studying the completed overlays could be taken into account by studying overlays which are under construction at the prese nt time. Thus the scope of the research included the following principal components: (a) A desk--study of the design and construction procedures and problems encountered. (b)-- Condition survey .of-a sample of the roads to identify general performance trends. an-,mechanisms of failure. (c) S ~1 cth -o-f a _sa- mp' fth od ~fo: deta-i-ied investigation, including sample extraction, laboratory testing and performance monitoring over time. (d) Analysis of behaviour to quantify the effects of key *variables such as traffic level, traffic speed and mix pro perties. (e) Identification of components missing from the' sample and selection of additional samples of road from ongoing rehabilitation projects to provide the extra data. (f) Evaluation of problems associated with the HRS techniques from the design stage through to construction. (g) Theoretical analysis. The present structural design approach suffers from a number 'of difficulties concerned primarily with the analytical/ mechanistic principles rather than the mix design method itself. If the theoretical approach is to be of value in extending the design method to a wider 3 range of conditions, these problems need to be resolved and a thcc-retical. model. de-veloped, veri-fied. and -calibrated to describe the observed performance and modes of failure.. (k) Defining the limitations of the method based on field experience and theoretical analysis.. (1) Refinement of the design method, improvement in specifications and construction procedures and publication of results. The research design is illustrated in the form of a flow chart in Figure 1. This report is concerned with the results of the condition survey, (c) above, the selection of sections of road for detailed testing and longer term performance monitoring and finally with the initial results of the laboratory test programme. A comprehensive description of the design and implementation of the research and of the performance measurements, sampling and test -methods' used is contained in a separate report (TOOLE et al 1991). 4. FACTORS AFFECTING PERFORMANE The main 'fac'tors which influen'ces the performance of overlays are (1) Type' of overlay and -t mxproperties'' -including :the properties of the individual 'components. (2) The condition of the'. e;x-':'isthg road on; which~ the overlay is placed.. Both structural cninand, surfab-condition are ilmor..tant--an-d terefore~ th -typeoiodsritr ilas h important. (3) Overlay thickness and the: c~ombined structural properties of the pavement after overlay. (4) Climate. Average temperatures and temperature range are important as well as rainfall. (5) Time. The materi~als- detoer'i6r~ate with time. (6) Traffic characteristics~. '.,6th volume and axle loads are important. (7) Road geometry. This affedt'c~E~ the! speed-of vehicles, the degree of .channelisation or wheeltracking and the tractive forces at the road surface. - In order to derive the interrelationships between performance and the main variables, the selectioh of sections for detailed 4 monitoring should cover the widest possible range of all of the variables. However, at the time of the general condition survey when sections had to be selected, details of mix- properties were not available. Visual inspection indicated that the inherent variability of mix properties along a site appeared to be too high for research purposes and therefore suitable information was not obtained until the laboratory analysis of site samples was completed. To take the above problem into account, the selection of sections was made using apparent overlay performance as an additional variable. In this way sections of road which were similar in all respects as far as all the other variables were concerned but which displayed different degrees of deterioration were selected in the belief that the differential performance could be explained by the differences in the mix properties. 5. IMPLEMENTATION A sample of 360 km of overlays, from a total of 3250 km built between 1985 and 1989, were selected and subjected to a network level condition survey, known as Pavement Condition Survey Level 1 (PCS 1). Brief details of the roads surveyed are contained in Table 1. Measurements were recorded for each lane and each loom length of road between succe!'ssive Kilometre posts. Finally, twenty five representative sections, most of which were 500 m in length, were -established for detailed studies. Each of these, so called monitoring sections, is being surveyed at 10 m intervals on a regular basis to determine the rates of change in surface and structur~al condition and of the hardness of the -bitunwen--in-th-e ove-r-lays. -- Bl-ock-a-nd-co-re:s-amp-les--o-f -t-he- asphalt mix and samples o unbound layers-have 'been tested in the laboratory. 6. THE NETWORK LEVEL CONDITION SURVEY 6.1 Measurements Representative rut depths were calculated from three measurements taken at equally spaced intervals in both the outer an-d inner wheeltracks (IWT and.OWT ;ifor each loom length of road. The maximum rut depth was;. determined by visually selecting areas of deepast rutting. A note was made of the type of rutting; either as deformation (D), where t he movement of the pavement surface is vertically downwards, or as pushing (P), where evidence of heave in the surfacing (as a ridge) on either side of a wheeltrack is apparent. The extent of cracking was recorded as the length of roadway parallel to the road edge which was affected by cracking. 5 During the survey the road was subdivided into the following .,five areas:, the ~~c edge (E) , OWT, and IWT, 'the mid--a-e(L and thle centrdline (CL) . The 1ten~t of cracking was. recorded as the most severe cracking in each lO0m length of road in one of the following 6 classes: none (0), single crack (1) , more than one crack, not connected (2), more than one crack interconnected, not closed (3), interconnected cracks forming closed polygons (4) and interconnected cracking with loose blocks (5). The type of cracking was also recorded as longitudinal (L), transverse (T), block (B), crocodile .(C), irregular (I) or parabolic (P). The areas of patching, potholing and depressions were also recorded as well as conditions such as slippage, bleeding and ravelling. 6.2 Results The main results of the survey are presented below, and discussed later, in terms of wheelpath rutting and cracking. Summary statistics of the representative rut depth for each road surveyed are given in Table 2. A typical distribution of rut depth data related to the type of rutting is illustrated in Figure 2. Summary statistics of the linear extent of all. wheelpath cracking are given in Table 3. The mean distribution of cracking for all roads studied related to roadway position is given in Table 4. The percentage of lO0m subsections occupying different performance categories, in terms of the representative rut depth and the linear extent and intensity of cracking, are given in Tables 5, 6, and 7 respectively.._... Tentative performance categories, have been chosen from two sources; those recommended by TRRL for use in assessing overlay performance in the United Kingdom (KENNEDY and LISTER 1978) and those recommended by TR RL's Overseas Unit (1987) for use as maintenance intervention levels. The TRRL UK divide overlay performance int6 three categories of sound, critical and failed. The onset of critical conditions has been defined as rutting in the wheeltracks of 10mm or the beginning of wheelpath cracking and'is'the preferred timing for a strengthening overlay to be applied. Structural failure is said to occur when rutting has reached 20-25mm or the appearance of severe wheeltrack cracking. The recommended intervention levels defined by TRRL's overseas Unit are as follows an extent of cracking of 5-10 per cent usually triggers resurfacing using a spray and chip surface treatment whilst values of greater than 10 per cent indicate more serious deterioration and warrant detailed investigation. In the latter case this is because strict prescriptive measures 6 1Z are not usually generally applicable in the tropics since the principal failure mechanisms and associated causes are often different to those in temperate climates and design and construction conditions are much more variable. The above criteria provide a benchmark. for assessing the observed performance although they need not be directly applicable to Indonesian conditions given possible differences in the types and modes of failure which actually occur and the prevailing traffic, climatic and economic conditions. 6.3 Discussion As indicated in Table 2, the average rate of rut development varied from virtually zero to 4mm per year. This is under conditions of both light and heavy traffic, in a variety of geometric situations and for three different specified mixes. The distribution of rut depth is also considerable as indicated in Table 2. For the representative rut depth statistic, the .90 percentile value is approximately twice the median value indicating that for a number of the roads the rate of rutting is more than 8mm per year over 10 per cent of their length. A similar picture emerges from Table 5 where the percentage of 100 m sub-sections in each performance category related to rutting is given. On average 10-15 per cent of all sub-sections on the most heavily trafficked roads were in a critical condition after two years.. on a linear projection approximately 50% of, the sub-sections -roads could be expected to be in a critical condition at the end of their 10-year design life. The rutt ing: .behaviour of roads carrying more lightly loaded vehicles dis- generally satisfactory. The roads included in this ~catg~oy iz~ltdeY~~iais-Ckijing,- -CijkijngCirebo n, -_ Ciawi- Cianjur, Kopo-Rancaba'li and Sadang-Subang. Exceptions to this are expected to be in areas of severe geometry. This has yet to be confirmed- by further analysis.~ Although the actual cause(s) of the rutting could not be determined with certainty during the surveys it was possible to assess likely causes by noting whether any pushing (or heave) was apparent at t he edge of the ruts. Whereas the former is a surfacing problem only the latter is usually indicative of structural weakness or secondary compaction.' However, the measures for controlling them may need to be quite different and would depend:.on the primary type of distress. The .percentage of rut depths where heave or pushing was apparent has been determined for each road link. However, as illustrated by the example in Figure 2, the existence of pushing is only apparent if substantial rutting has taken place (10 percent ile - 6mm) . In cases where the type of rutting was recorded as vertical deformation the distribution of the representative rut depths is less (90 percentile = 6 mm). This therefore suggests that only where serious rutting takes place can heave be 7 identi-."fi~ed and in such circumstancesth rutting is likely to Ibe a result *o: f-ajilure in temix rather, th:~an sru'za deteritJlration . Th netogt''hs the &~mto~ihi individual layers is being determined by digging trenches across the wiath of the road and measuring the profile or successive' layers. As indicated in Table 3 the average extent of cracking is relatively low, with a few exceptions. However, it is clear from the range of values that the variability is high with maximum values between 20 and 100 per cent, and an overall mean maximum value of approximately 60 per cent. The 90 percentile values range from less than 1 (5 cases) to 15 per cent. The sites which are badly cracked include three out of the five lightly trafficked routes, namely: Ciamis-Cikijing, Cikijing- Cirebon and part of Ciawi-Cianjur. The mixes used on these roads are to different target specifications; namely HRS A, HRS B and AC respectively (BINA MARGA 1986). However, in the case of Ciawi-Cianjur a deliberate change to the specification for .surfacing material was made for a substantial length of roadway. This has enabled the effect of nominal mix type to be identified under reasonably similar design conditions. The data in Table 6 indicates that greater than 20 per cent of the length of Ciawi-Cianjur surfaced by AC was cracked to a degree that would warrant r'eseal'ing after 2 years whilst 10 per cent was more severely 'affec~tedd.' only 2 per cent of the HRS B surfacing was f ound to be li.n 'a similar condition' The above discussion on 'crca'ckiing'~has been related to 'the linear extent of all Cracking i rtiEspecttive of intensity or type. The definition o0f~ pavement' con~dit'ion from TRRL UK is in terms of intensity of cracking. For this study the percentage of lO0m sub-sections in each ecategbry~,of crack intensity is shown in Table 7. This shows that of,~thb.e three most'.;badly cracked roads 'two6 of them, "-namely -C-ik-i j i --~ci:rebn~~.CaiCajrar-m sev-e-r-ei-y- cracked witli Il~and'. 18% respectively in a critical/fai~led condition.'' T-he ~corresponding value for Ciamis- Cikijing is 5%, and in this 'case most of the cracking is in classes 1 and 2 which is--indicat-ive of line (or longitudinal) cracking possibly asaresult of:. road widening. By illustra-ting performance~by ~in~tensity of cracking,. as opposed to linear extent,~ the pr~ese~nce o.f localised failures can, be detected. For the more heaV1'.iuy 'trafficked routes of Tangerang- Merak and-.Dawuan~Cirebon-Kalijaga 'the percentage of lO0m- sub- sections in acritical~/,faile~d condition is between 7 and 17. The HRS B on part of "Ciaw:di-Cianjur, Cirebon-Losari, Kopo- Rancabali and Sadang-Subang have less than one per cent in a critical/failed condition. The data in Table 4 which quantifies the distribution of cracking with respect to roadway position indicates that in most cases a greater amount of Cracking occurred in the OWT and road edge areas. These are normally recognised as the weakest positions in a road structure. The causes of cracking in these 8 areas can, however, vary and may be a result of fatigue in the bound layers due to inadequate structural design, a lack of side support, poor road widening practice or moisture ingress into the unbound layers. Swelling and shrinkage of the lower layers as a result of seasonal moisture changes may also occur. In summary, the data obtained during PCS1 allowed. a general assessment to be made of the performance of the overlays. More importantly for the purposes of this research, the results of PCS1 enabled sections of road with widely different performance characteristics to be identified. In the future, repeat surveys at intervals of two to three years are planned to further quantify performance at the network level. 7. THE MONITORING SECTIONS 7.1 Pavement composition The mean and range of overlay thickness, the type of supporting layers and the subgrade strength on each section are given in Table 8. As indicated in Table 8 Considerable variation in thickness of the overlay occurs within several sections. In a number of cases the, variation is sufficiently large, and consistent - with chainage,. to warrant, further sub-division of these sections. This iqjill' be considere'd in-later analysis following further sampling and the grouping of all core, block and test pit data. It will lead to an increase in the number of sections and the range. of overlay thicknesses covered. The overall range. of overlay thfic~kn-e-s-ses covered i~ owev~er, considerable, ranging from approximately 50 mm to more than 2 00mm. Penetration Macadam (PM) is the most common upper base layer, and is, present in 21 of the 25 sections. It would also have been teoiia pre-overlay surface. Unbound granular materials have, been used as bases in the upper layer of the remaining 4 sections. This is a result of grade-raising or localised reconstruction. The lower, base layers comprise unbound granular materials (6 sections), ,PM (1 section).-or.Telford stone layers (10 sections). In a number of cases .there are two lower base layers of PM/Telford (1 section) or' Telford/Unbound (5 sections). -In a further example a single base layer exists lying directly on a weak subgrade. As indicated in Table 8, subgrade strengths are predominantly weak and twenty of the sections possess subgrades with CBR values in the range 1-6 per cent. 9 -7.2 .Properties of the bitl-umi-nous- overlay mater~ials Sampi's~' C bitm~ir~.Kz3mixes tak'-eri. from. tte. moin,.'itorilng tos have been analysed and the results are summarised in Table 9. In most cases the overlays comprised three layers; namrel-y the hot-rolled sheet surfacing (HRS), the asphalt'treated base (ATE) and the asphalt treated base levelling layer (ATBL) (BINA MARGA, 1986). The mean gradation of typical bituminous surfacings are plotted in Figures 3 and 4 and are compared with appropriate grading envelopes conforming to a hot-rolled asphalt (HRA) (BSI, 1985) or asphaltic concrete (AC) (TRRL, 1977). It is clear from Table 9 and Figures 3 and 4 that a significant variation in mix properties exist. In order to distinguish between HRA and AC-type mixes, a method of classifying mixes into gap-graded or continuously graded types has been devised and involves identifying the per cent gap in the mix. The method is based on the ES 594 (BSI 1985) specification for hot rolled asphalts in which an upper l imit is placed on the allowable percentage retained between the 2.36mm (No. 8) and 0.6mm (No. 30) sieves, particularly for Type F wearing courses which include natural fine aggregate. The limit is set according to stone content (per cent material retained on 2.36 mm sieve) and ranges from 9 to 14 per cent for stone contents of 55 and 30 per cent respectively. For this study three classes of mix were defined as follows: Gap-graded (G) - where the per cent reitained is'less than the upper limit for Type F surfacings., Inter'medic~tb (I)- where the amount retained is up to 5 per cent above' te upper limit-and continuous (C) - where the amount retained i's'-mord than 5 per. cent above the limit. on the above basis 15 per* cent.`of the mixes have been classified as ga-rded- 7--40-pier cent -fa~l into--the-i-nte-r-inedi-a-te--ci-ass -- and- 45 per cent a~re continuousl-y --,rc-ded-a. n circumstances where the specified mix type was HRS, Z-ith'er' class A or B, 17 per cent are gap-graded, 43 per cent are intermediate and the remaining 40 per cent are econtinuously .gia~ded..- In. addition all sections located on ligtytffceVrashv continuously graded mixes (40.,per cenit of.'all sltds")'w'hilst on heavily trafficked roads the division between ~gap-graded; intermediate and continuously graLded is 15, 35acfid '10 per cent respectively. The specified-minimum effective bitumen content for most of the sampled mixes was.6.8 per qcent an-d 6.2,per cent for HRS A and HRS B respe6tivey h '~p~iq ith> tes limits, approximately' 75 per cefitbf~the'mixles have mean effective bitumen contents which .are. les sthat 'the ~ specified minimum value. The dirtribution of the m-a effective and total bitumen content of all mixes is illustrated in Figure 5. The reported values each represent the arithmetic mean of up to eight samples. 10 Typical within-section distributions of bitumen content are illustrated in Figure 6.for a number of sections located on Tangerang-Merak. These indicate a true difference in the bitumen contents between most sites rather than heterogeneous variability. Within each site the standard deviation of bitumen content is between 0.2 and 0.4 per cent, with the exception of Section 8. The distribution of bitumen content shown in Figure 5 represents a number of reasonably homogeneous mixes. The causes of such widespread variation between sites is, however, unclear. The range of filler to binder (f/b) ratios is high (see Table 9) and although they conform with the specified value of greater than 0.7, past experience by TRRL in the tropics (ROLT et al, 1986 and SMITH and JONES, 1982)' has shown that values of 1.6-1.7 and above lead to early cracking. In this study approximately 35 per cent of all mixes have f/b ratios greater than or equal to 1.6. It remains to be confirmed whether this is of similar importance with the types of surfacing mixes used in Indonesia. Although only a limited number of pavements have been sampled during this study and therefore may not be totally representative of as-laid mix properties, compliance with the specification for HRS A and HRS B has been checked. The results are given in Table 10 and, in particular, these indicate problems with obtaining the specified effective bitumen content and satisfactory filler contents. In cases where the filler content criteria was not satisfied, too high a value was obtained. Table 10 Percentage of samples passing specification requirements The p~i~operti~es..1f the recovered bitumens are being determined on thin slices of overlay and on complete layers. Early results indicate a wide range in the recovered penetration. Further comment 1will nheed to await the completion of the laboratory. programme. 11 Specified Bitumen content Bitumen Stone Fitter Fitter/ Mix type absorption Content Content binder Total Effective ratio HRS A 50 0 0 50 75 100 HIRS B 92 36 100 60 16 100 7.3 Compaction characteristics of the overlay materials The per cent air voids in surfacing samples taken from the road were determined using Rice's method (RICE 1953). The distribution of typical results are presented in Figure 7 and represent the grouping of all tests on samples taken from positions between and within wheeltracks. The specified range at the time of construction was 3-6%. The results indicate a substantial range in values, particularly for samples taken from Ciawi-Cianjur (CWI-CIA). For the three road links, between 60 and 95 per cent of all results are below the specified minimum. Although this may have occurred through additional compaction by traffic, ie. since completion of construction, the values are very low and can be expected to contribute to the occurrence of deformation (or pushing) within the mix. Conversely, the instances of high air voids may contribute to the reduction in bitumen penetration and, therefore, the embrittlement of the mixes. This in turn can lead to premature surface cracking. Further analysis of the data is being carried out to determine a relationship between air voids and other mix and physical properties. 8. SUMNMARY AND CONCLUSIONS 1) A comprehensive research programme has been established to develop performance prediction models for the alternative structural road surfacings used in Indonesia and to improve mix specifications and thickness design. For this purpose,,detailed.6' monthly surveys have commenced on twenty five monitoring sections located on existing roads. These sections-were choserf -from ageneral survey of ~&~360i-6sapl e of the road network. 2) The road-links and monitoring sections cover a wide range of -variables including design traffic, ADT, age, pre- overlay deflection,' overlay thickness, performance, terrain, geometry and mix type. To date the variables of age and mix type are not covered as comprehensively or as uniformly as desired and further sections need :to be identified and included in the study. In addition, insufficient --detail is available on the condition of the existing surface prior to 'overlay and this has led to the research being extended to include roads, on which new overlays are being applied. 3) The results from the network level condition survey indicates that substantial variations in the performance of the roads exist in terms of the accumulation of permanent deformation (rutting) and cracking after only two years. The key conclusions from the survey are as follows: 12 7 .3 (a) Average rates of rutting can vary from zero to 4mm per Year under conditions of light or heavy traffic, in a variety of geometric situations and for each of the three mix types investigated. (b) The 90 percentile value of rut depth is approximately twice the median value, indicating that in 10 per cent of the road length rates of rutting of twice the mean can be expected. (c) Where severe rutting occurs this is accompanied by pushing in the mix, indicating low surfacing stiffness. This is being confirmed by digging trenches across the road. (d) On average, rates of cracking are low although high variability exists. The 90 percentile values range from less than one per cent to 15 per cent and are highest on the more lightly loaded pavements. More * severe localised failures do, however, occur on the heavily loaded roads. (e) Extensive cracking was found on all mix types although in the case of one road, where substantial lengths were surfaced with two different mixes, the section overlaid with asphaltic concrete was more severely cracked; to an extent which would warrant resealing within 2 years. A higher bitumen content mix laid on other sections is performing satisfactory. (f) On' aver~age a greater amount of cracking existed in the' ro'ad' edge and outer wheeltrack areas. Likely contributing factors include inadequate side support and, possibly, poor road widening practices. 4): "The range of overlay thickness covered in the monitoring sebction varies between 50 and 200mm. Penetration macadams comprise the dominant pre-overlay surface and u pper base layer (21 sections) whilst unb-oun'd granular materials are used as bases in the remaining sections.. Lower base layers comprise combinations of the latter' two materials and Telford bases. Subgrades are predomina~ntly weak, twenty of the sections have CBR values between 1 and 6 per cent. 5) A substantial variation of mix properties are covered in '-the monitoring-sections. The.results indicate that the m~.~ixes produced under current specifications can vary from gap-graded Hot Rolled Asphalt-type mixes to continuously graded Asphaltic Concrete-type Mixes. In relation to mix properties the main findings are: (a) 15 and 45 per cent of all sampled mixes have been classified as gap-graded or continuously graded mixes 13 respe ctively. The remaining 40 per cent are of an intermediate gradation. (b) Where the specified mix type was to the specification for Hot Rolled Sheet (HRS), 17 per cent were gap- graded, 43 per cent were intermediate and 40 per cent continuously graded. (c) The range of total and effective bitumen contents in the surfacing mixes are between 5.5 to 8.4 per cent and 4.2 to 7.0 per cent respectively. The within- section variation of binder content is however acceptable. The range of filler to binder ratios and the air voids of samples recovered from the road are large varying between 1:1 and 2:1 and from virtually zero to seven per cent respectively. (d) The results indicate that the specification requirements for effective bitumen and filler contents are met least often. 9. ACKNOWLEDGEMENTS The work described in this report,- 'forms part of the collaborative research pr~oject being, undertaken by the Indonesian Institute of Road Engineering and the Transport and Road Research Laboratory.. The report ,is. published with the permission of the Director of TRRL, Mr. D..F. Cornelius, and the Director of IRE, Ir. Soedarmanto Darmonegoro. Crown Copyright. The views expressed in this report are not necessarily those -of -the 'Departmnent -of- Transp~ort, Uie ]kingdom. Exstr-a-cts ~from the,.text may be-sreproduced, except for commercial purposes, provided the source is acknowledged. 10. REFERENCES BINA MARGA (1986). IBRD highway Betterment Programme.: Specifications for high durability asphalts. Central Design office, Jakarta, Indonesia. BSI (1985). Hot Rolled.asphalt for roads-and other paved areas. British Standard BS 594 Part 1:1985:. Specification for Constituent materials and asphalt mixtures. London: British Standard Institution. BULMAN, J.J. and H.R. SMITH (1977). Pavement performance and deflection studies on Malaysian roads. department of the Environment, Department of Transport. TRRL Laboratory Report 795.. Crowthorne: Transport and Road Research Laboratory. 14
1 J 2 CORNE, C.P. (1983) . Optimising pavement overlay design for Indonesia. Proc. Fourth Conference of Road Engineering Association of Asia and Australia, Jakarta, Indonesia. KENNEDY, C.K. and N.W. LISTER (1978). Prediction of pavement performance and the design of overlays. Department of Transport, TRRL Laboratory Report 833. Crowthorne: Transport and Road Research Laboratory. LISTER, N. W. (1972) . Deflection criteria for flexible pavements. Department of the Environment, Department of Transport, TRRL Laboratory Report 375. Crowthorne: Transport and Road Research Laboratory. RICE, J.M. (1953). New test method for direct measurement of maximum density of bituminous mixtures. The Crushed Stone Journal, September 1953, pp. 10-17. ROLT,- J.R. et al (1986). The design and performance of bituminous overlays in tropical environments. In: WARD, C and CK KENNEDY (Eds). Proc. 2nd International Conference on Bearing Capacity of Roads and Airfields, Plymouth, 15-18 September 1986. Bristol: WDM Limited, 419-413. SMITH, H.R. and C.R. JONES (1982). Early performance of some experimental bituminous overlays in Kenya. Department of Transport, TRRL Laboratory Report 1043. Crowthorne: Transport and Road Research Laboratory. TOOLE, T et al (1991). Research on hot rolled sheets in Indonesia: Desigrn and'implemen~tation of studies of existing overlays. IRE.' ~Resia~r~ch 'Aeipor'ts,, No. -11.024.TJ.90. Bandung: Institute of Road Engrineering. TRRL (1977)... A guide to the structural design of bitumen- surfaced -roads----in - tropical-~ -arid- -sub-tropical -countries. Department of Environme'nt, Department of Transport, Road Note 31 (3rd edition).' Londo'n: H.M. Stationery office. TRRL OVERSEAS UNIT (1987).--Ma-intenanice management for district engineers. TRRL Overseas Road Note 1 (2nd edition). Crowthorne: Transport and Road Research Laboratory. 15 r, 000000 15 C c *d-H-,-4 ~4 4 * ,.--40 r -- 4 C-4'~~~~~ 4 ~ 4 44 J 4 4 PLC C C -. --A 1 - ~~-4 00 PL p 4 P0 U 1 --4U)I0 C4 ---4 ,-I r.- -L. 4 - -4 .4 ,4 e C0 XLOr n 000 c n O -fLA 0_ l C enL0 U)W W R U U )U Q)( nU J )(n W-W U)4 0) 0 0U)-U U- cn 0nu(AN -4E-4 0 0 0 0 0 00 0 0000 0 14 1 r r i00 U) 4 0 0 0 0OD00on 7 r_ .0 ---4 -4 -4 1-4 ~ ~ ~ ~ ~~~4~ to~ ~~~U U-U U) - M-C 0 0C 4c W CC Cd CC, ~ - 0 0.0Z 0 0 0-0 0 0,0 0 0 0O ~~4-I .-4 0 F Uf N ) 0. 4- 0 0 0 b -4 -4 44JC40 U-) U ) 00 V Wl 4) c0 0 0) C 4) 0 0) r 4) 0) Table 2 Summary statistics of representative rut depth Table 3 Summary statistics of the linear extent of all wheeltrack cracking No0. of Representative rut depth (rrnm) Specified Road link 100 mn Median Range 90 per- mix sections centile type Ciamnis-Cikijing 994 2 0-40 4 HP.S A Cikijing-Kuningan-Cirebon 1008 2 0-23 4 HRS A/HaS B Cirebon-Losari-Pejagan 754 6 1-40 12 HRS B Ciawi-Cianjur I 6 72 4 0 -20 7 HRS B8 Ciawi-Cianjur II 294 3 1-25 4 AC Tang3ereang-Ciujung 9 72 5 0-33 12 HRS B Ciujung-Cilegon 728 5 1-43 11 HRS B Cilegon-Merak 252 6 1-22 12 HRS A 1Dawuan-Cirebon-Kalijaga 1 92 5 1-23 9 HRS B IKopo-Rancabali 816 2 0- 9 3 HRSA 1Sadang-Subang 838 3 0-10 4 HRS A Road link No. of 100 mn Ex~tent of all wheeltrack cracking (%) Specified Sections ~Median Range 90 percentile ni type Ciamnis-Cikijing 9 94 5 0-89 14 HRS A Cikijing-KuningAn;,-Cirebon, 1008 5 0 -9 4 15 HRS A/HRS B Cirebon-Losari.~Pejagan 754 1 0-75 <1 HRS B Ciawi-Cianjur I 672 <1 0-24 <1 HRS B Ciawi-Cianjur II 294 3 0-39 11 AC Tangerang-Ciujung 972 1 0-73 4 HRS B Ciujung-Cilegon 728 1 0-100 1 MRS B Cilegon-Merak 252 2 0 -83 5 MRS A Dawuan-Cirebon-Kalijaga 192 2 0-32 6 MRS B Kopo-Rancabali 816 <1 0-20 <1 HRS A Sadang-Subang 8 38 <1 0 -5 0 <1 HMRS A. Table 4 Mean distribution of cracking related to roadway position Roadway Linear extent of all cracks(% Position Median Range 90 percentile Edge 2 0 -1 00 4 OWT 2 0-100 5 Mid-lane 1 0-100 2 IWT 0.5 0-100 1.5 Centreline 0.6 0-100 1.7 Table 5 Percentage of 1 00 mris~ubsections in each performance cat egory: Representative rut. depth Representative rut depth (mma) Road link <10 10-20 >20 SOUND CRITICAL FAILED Ciamiis-Cikijing 98 2 0 Cikijing-Kuningan-Cirebon 99 <1 <1 Cirebon-Losari-Pejagan 86 11 .3 Ciawi-Cianjur I 96 4 0 Ciawi-Cianjur II 98 1 1 Tangerang-Ciujung 88 10 .2 Ciujung-Cilegon 85 12 3 Cilegon-Merak 83 15 ~ 2 Dawuan-Cirebon-Kalijaga 96 3 1 Kopo-Rancabali 100 0 0 ,Sadang-Subang 100 0 0 Table 6 Percentage of 1 Q0m subsections in each performance category;: All wheelpath cracking Table 7 -Percentag'e of 100 m sub-sections in~each performance category: - - ___ ___ Intensity-o-f W 6i-tai k ra kng- Road link] All wheelpath cracking (%J <5 5-10 10 -30- >30 Ciamis-Cikijing 77 9 12 2 Cikijing-Kuningan-Cirebon 83 6 7 4 Cirebon-Losari-Pejagan 97 1 1 1 Ciawi-Cionjur I 98 1 1 0 Ciawi-Cianjur II 80 10 8 2 Tangerang-Ciujung 92 3 4 1 Ciujung-Cilegon 94 3 2 1 Cilegon-Mera~k 8 8 6 4 2 Dawuan-Cirebon-Kalijaga 87 5 4 4 Kopo-Rancabali 99 1 0 0 Sadeng-Subang 97 2 <1 <1 Intensity of wheeltrack cracking Road' link 1None C/C C3 >=C4 SOUNMD INTERMEDIATE CRITICAL FAILED CiamiG-Cikijing, 49 46 4 1 Cikijihng-Kuningan-Cirebon 66 23 10 1 Cirebo'n-fLosar~i-Pejagan 93 5 2 0 Ciawi-Cianjur I 92 5 2 <1 Ciawi-Cianjur II 51 26 18 5 Tongeirang-Ciujung 79 14 5 2 Ciujung-Cilegon 84 9 5 2 Cilegn-Mr'ak 7 0 1 3 8 9 Dawda'n-tirebon-Kalijaga J 77 13 8 2 Kopo-Rancabali 96 3 1 0 1Sada ng -Suba ng 1 95 5 0 0 Table 8 Overlay thickness and pavement composition of the monitoring sections overlay SECTION LANE Thickness (run) Upper base Lower base Mean (**) (**) ~Subgrade Rane benCBR (%) CBN KI4G 1 KNG -95-~22 00 140(*) PM UB 3.5 CON KN4G 1 C BN 65-150 98(*) PM UB 3.5 CBON KN4G 2 KNG 85- 9 5 91 PM UB >100 CBIN KNG 2 CBN 110 110 PM USB CBN KEG 3 KNG 85-135 118 PM UB 5. 0 CON KNG 4 KNG 80-100 87 PM US 4.2 CBN LOS I LOS 90-150 .122 UB PM 3.0 CON4 LOS 2 LOS 8 0-1 00 9 5 US PM/T 6. 0 CBN LOS 3 LOS 12 0-1 60 135(*) PM - CON LOS 4 LOS 75-255 166(*) US US 22.0 CWI CIA 1 CMI 170-210 1 90 PM T 1.1 CWI CIA 2 CWI 1 6 0-2 10 1 85 PM T 2.0 C1MI CIA 2 CIA 1 40 140 PM - C1MI CIA 3 CMI 1 40 140 PM UO/T 2.0 CMI CIA 3 CIA 135 135 PM CWI CIA 4 CMI 205 205 PM T 4 .0 CM1I CIA 5 CMII 210 210 PM T 2.5 CWI CIA 5 CIA 11B5o-190 1 87 PM CWI CIA 6 CIA 115-190 154(*) PM T 4.0 CWI CIA 7 CIA 180-200 187 PM T 3.1 TNG MRK 1 MRK 9 0-1 65 127(*) US US 6 .2 TNQG MPK 2 MP.K 110-190 152(*) PM UBIT 3 .7 ITN4G MRK 3 MRK .65-70. 6 9 PM T 9. 0 't4G MRK--4 MR.K t*o'0~6 5 56 PM UBIT 1.9 TNG MRK74. 7 G 6-0~ 8 1 PM P/UB 2.0 TNG MRK 5 MRK 80-270 154 PM T 2.8 TN4G RK 6 MRK 100-170 I 1 34 PM T 12.0 TNG-MRK 7 TN4G 1-00-155 133 PM T/UB 5.0 TNG MRK 8 TNG 50-1,50 95(*) PM T/UB 12.0 KOP 'RAN 1 RAN 95-100 9 9 PM - 4.1 KOP PAN I KOP 110 I 100 PM-- KOP RAN 2_ RAN 90-115 102 PM T 6.2 KOP RAN 2_ KOP 100 1 00 PM - * Sections which may need to be sub-divided due to a consistent change in overlay thickness with chainage. ** PM -Penetration Macadam T -Telford stone UB -Unbound granular material Table 9 Bituminous mix properties of surfacings from monitoring sections BITUMEN CONTENT Stone Filler Percent retained Effective Specified~ Mix SECTION LANE TOTAL EFF content content between Filler/binder Mix clans % % ~~~~~~~2.36-0.6mm ratio CBN KI4G K1~~G- 1.6 6.2 46 7 14 1.1 HRS BI CBN 7 .4 6 .2 40 7 15 1.1 HMRS B I CBN4 KNG 2 KG 7.5 6 .3 37 9 20 1.4 MRHS B c CBN 7 .7 6 .3 35 9 17 1.4 HRS B I CBN KNG 3 KNG 7.2 ,5.7 38 9 13 1.6 MSB I CBN KNG 4 KN4G 7 .0 5.3 41 9 13 1.7 HRS BI CBN LOS 1 LOS 7.5 6.1 53 8 11 1 .3- H MRS B I- C B1 LOS 2 LOS I7.8 6.3 50 I 9 1 1 1.4 HPMRS B I CBN~ LOS 3 LOS 7.8 6 .2 51 8 1 0 1.3 MRP.S B G CBN LOS 4 LOS 7.5 6 .0 49 8 1 0 1.3 MRS B G CWI CIA 1 CWI 7.1 6.1 50 8 18 1.3 HRS B c CWI CIA 2 CWI 6 .7 5.7 53 9 1 7 1.6 HRS B c CIA 6 .9 5.7 50 8 1 6 1.4 HRS B c CWI CIA 3 CWI 7.1 6 .0 4 6 8 1 9 1.3 HRS B c CIA 6.8 5.5 50 8 17 1.4 HRS B c CWI CIA 4 CWI 5.8 4.7 56, 9 .16 . 1.9 HRS B c CWI CIA 5 CWI 6.0 4.8 53 9 16 1.9 AC C CIA 6.1 4.7 58 9 1 5 1.9 AC c CWICIA 6 CIA 6.1 4.9 54 8 181.6 AC c CWI CIA 7 CIA 5.5 4.2 56 8 51.9 AC c ,.TNG;>MRKV11l'4R 7.7 6 .4 4 49 -.- 9.. .8 1.4 MRS B G TNGMRK 2 }4RK`~7' 5.9 51 7 9 1.2 HRS B G TNG MRK3W MRK '7.4 6.1 53 7 10 1.1 HRS B I Tb1G MRK' 4 !4Rk c.6. 5.5 60 9 13 1.6 MRS B c TI4G~~ ,. .~.5 5.3 50 .11.. 14 2.1 MRS B c *TNG -MRK -51. '~14RX :7.2 5.8 48 10 10 1.7 MRS B G TNG 70 - 60 '10 12 - HRS B I TNG MRK 6~ MRK 7.2 5.1 52 11 11 2.HRS-B- I --TNG-MRK.7 - `ING -7-.4 - 52 9 - 12 - HRS B I TN4GMRK 8. TNG 8.4 7.0 49 9 11 1.3 MRS B I KOP RAN-- RAN, 61. 8 5.8 52 1.0 15 1.7 HRS A c KOP.RAiN i, '.KXP I, .1 I5.8 I 49 9 12 1.5 H RS A j I KOP RAN1.2 P-RAN 7.4 5.8 50 .9 15 1.5 HRS A c KOP RAN 2 KOP 7.4 5.6 52 8 16 1.4 HRS A c DESIGN ANO CONSTRUCTION PAVEMENTr CeNO I I ON ROUGHNESS REVIEW SRE, FS1 TDE Summary of designs, actual Road linLs survey ori roads To provide data oin Post construction for mixes arid covering [140 arid Ar mixes oierlay condition arid to structures. Identification to quarrtify performance calibrate measurement of range of mixes and and focus detailed studies dvcs structures, etc. ANAL SIS ND C MPAR SON ..~cANALYSIS P, SITE SELECTION Design with as-constructed. Idenitify distress types As-constructed with as- and causes arid provide Comparison of dat.i reported (ie. this study). summary statistics on acrcec overall performance. LABORATORY STUDY OF. MIX PROPERTIES < SITE INV/ESTIGATIONI AND SAMPLING. FCS 2 AND 3 To provide Independent data and detailed data To provide detailed stuctu- for all sections and ral, mix & Performance data to evaluate change In as evideirce~on the causes of properties with time, overlay performance and to assist in Focussing labora-, ry studies.' EVALUAT ION/ANALYSIS !EECItOFST-1 A- NEW CONTRACTS FRLiGi >~~~~ Estimate likely behaviour ) TERN PERFOR?.CE MIITOPIN from empirical/mechanistic principles.' Part 'of longer term,'pro,3grn'r,,, Compare HRS and' AC. td ~obtain-acc'ur'ate :bel'~av iour .Devise potential new models *model s and. to .con-tlirm~- ___________ _____________ ~ efjnene w spe~c-if-icat-ion ---- -.~ -- -- -mpr-ovement-s-t-o-spec -i-fic c- t-icnis limits. ... and ~~~~~structura t dl~~ CALIBRATE EXISTING COST/BENEFIT DETERIORATI1ON MODELS AAYI eg. The World Bank's HDM III. I1mPPROVEMENIT INl MIX IDENTIFICATION I DESIGN,.STRUCTURAL OF RESEARCH tiEEDS:''. DESIGN & CONSTRUCTION FOR FUTURE FRO.JECT51` Figure 1 Research design flow chart *.' t.A t t~~ SELECTION OF P.~.E/Iw FOP STU'OY A representativo u, o of road links need to be closely exariined. 1 1 0 2 0 Re present i ve rut depth ( mm) Figure, 2 Typiccit distribution of rut depth for sections where `'pushing in the mix-- is evident or cibsentk. 100 90 8 0 7 0 6 0 s0 4 0 ,00'I Cr 0~ E= 3 0 2 0 0 0 11 1 11 1_r -- --;-.. -i - - - -- -I -- - N K--N I I K I I 1 I. I I I I …-t --- - I 0-c-QG2Z 1 1111 1-l- 14 1 1 11 -1t--- -l- - - I- -~~~~~~j --4 -- - L -1 - --l- -- i I -C - -A- * c: c= :, C c. C cC> c-' c 0'1 CC c- U0 ~' -? C-- * buissod aboluae)ied tn C, 0, 01) .E r-c0) Q_) a, E0 U_ V) L-ic Ul U) 0 -0 0' C) a,2 CO- E c;5 cn ri:C> 0 0 cl,- 0-' CY' U- 1111111 --- -1-11 11 1 1 1 ---- I - -- -- 1 1 1111 - r- ---
- - 1 1 1 1 1 1 111 ....... --- I I i I I I I I I I I I I I I II I I 1 1 I I I I I I I I I -- I - I I - I _ I _ I- 111g1.1 1-r-1 11 '11111111 11 111911 --1 -~1 - 1 * I I I i11 1 1 1 -- -I- ~ -- i ~111111 91111 C) <= c)o C= C=> C> <=, C> 6uIssrod a6oiua:)jad ) we C D- C- cIn LCi 'n c--t E N C) wL C> C=) CS, I- C> 0 E E 0 r_ cj Cn I I 1 ~1 - I I I I I I I I C)~ C> C) 0'1 --1- ---I- --- 1110 111 191 4 .Figure 5 5 6 7 8 9 1 0 B itfumen content ( % by weight) Cumulative frequency distribut'io~n of mean to'tal and effective bit~umen contents forcall mo~nitoring sections 4 ... 5 6 7 B 9 10 .Bit1u men content ( 9/0by wei ght Cumulative frequency distribution of total bitumen contents of selected monitoring .sections on Tangercing- Merak 100 0 0 c CJ 1- EEU 60 40 10 0 -80- 0c 0It EnI-i 6 0 4 0 2 0 0 Figure 6 ::
, 1 -, -