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into dense graded mixes by using dry process referred as GenericTAK RUMAC mixes while PlusRide RUMAC mixes was described for incorporating the crumb rubber with gap
graded mixes. The CRM used can range from 1 to 6 by weight of the total mix. However, 1 to 3 CRM was commonly being used Chehovits et al, 1993.
Initially, only coarse rubber was being used in dry process. However, some experience with the mix indicated that a better durability was obtained with an increase of fine rubber
content. Hence, after 1981, 20 of the originally used coarse rubber was replaced with fine rubber passing sieve no 200 Esch, 1984. Takkalou et al. 1985 reported that the required
asphalt content used in CRM mixes was 1.5 to 3 higher than the conventional mixes with similar size and type of aggregates. Koh and Talib 2006 also agreed that RUMAC mixes
required higher binder content as the percentage of crumb rubber increased. Elliot 1993 stated that effect of CRM on the optimum Asphalt content OAC and volumetric properties
was significant for RUMAC mixes with 3 CRM. This could be attributed to the absorption of asphalt by the CRM which increase the asphalt content requirements for the
mix to attain the required volumetric properties. Recent research on rubber-Asphalt interaction has demonstrated that during the mixing period, crumb rubber does swell and the
amount of Asphalt absorb by crumb rubber was significantly increased which causes the residual Asphalt become stiffer, elastic and consequently affect the performance of the
asphalt mixes Singleton et al, 2000 and Airey et al, 2004. Besides, the addition of crumb rubber seems to reduce the stiffness as indicated by a
reduction in the Marshall stability. Studies by Troy, et al 1996 discovered that gap graded CRM mixes had lower Marshall stability than dense-grade CRM mixes. However, Takkalou
et al. 1985 stressed out that performance evaluation on Marshall properties was significantly dependent on the crumb rubber gradation, air voids, aggregate gradation,
mixing temperatureand curing conditions.
2.7 Evaluation of CRM Mixes Performance
A major consideration for this evaluation was performance related to rutting and fatigue resistance. The primary purpose of using rubber modifiers in hot mix asphalt HMA
was to obtain a stiffer HMA at high service temperatures, a more elastic HMA to resist
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fatigue cracking at intermediate service temperatures, and a lower or unchanged stiffness at low service temperatures to resist thermal cracking.
Rutting was a flexible pavement distress caused by the accumulation of permanent deformation in the pavement layers due to the repeated application of traffic. Heitzman
1992 and Epps 1994 claimed that incorporation of CRM into asphalt mixes will make the mixes more elastic at higher service temperature thus enhancing their rutting resistance.
Stroup, M, and and Krutz, N 1992 discovered that the addition of CRM by using dry process enhance the rutting resistance of the mixes at higher temperature. Similarly, Rebala,
S, and Estakhri, C, K 1995 stated the used of CRM in the dry process allows it to serve as discrete particles which may enhance the rutting resistance. While Koh and Talib 2006
found that rutting of asphalt mixes at 2,000 load cycles was reduced by 22 with the addition of 3 crumb rubber. Chehovits et al 1993 indicated through Figure 2.5 that the
TAKGeneris mixes offer higher rutting resistance compared to the conventional asphalt mixes.
Figure 2.5: Comparison of rutting resistance for conventional
Hanson et al. 1994 evaluated the field cores taken from mix test section in Mississipi, along with the laboratory samples prepared, concluded that the field compacted
control mixes deformed more than the field compacted CRM mixes. However, the
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laboratory compacted samples of the control and CRM mixes did not show any significant different in their rutting resistance. The evaluation of field projects indicated that after 2
years, the amount of rutting in the control and modified section were insignificant. Most of the previous researches showed a general trend about Marshall mixes, that the
dry process of incorporating CRM into asphalt mixes reduced the rutting resistance while wet process of incorporating CRM into the mixes enhanced the rutting resistance. However,
another study did by Troy, et al. 1996 discovered CRM pavement sections done in Louisiana exhibit similar or lower rut depth than control sections after five to seven years in
service.
2. 8 Tests of Material
This stage includes the tests of all materials used in this study; that was, asphalt, coarse aggregate, fine aggregate, filler and crumb rubber.
a Tests of Asphalt
There were several testing for asphalt. It has done to check asphalt quality to ensure that it could fulfill the specifications. The testing are as follows:
1. Penetration
Not all uses of asphalt with a large penetration will produce good result, the use of asphalt must be appropriate to conditions, location, and type of pavement that will be used.
The Asphalt consists 3 three penetration type, namely 6070, 80100, and 100120. The greater of penetration, it means that the asphalt more liquid. This examination was intended to
determine the penetration of hard or soft Asphalt solid or semi-solid by inserting a needle size, weight, and time into the Asphalt at a certain temperature. Examination procedures refer
to the AASHTO T - 49-89 or ASTM D - 5 - 86 or SNI 06-2456-1991 see the pictures of penetration test in Appendix B.
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2. Softening Point
The softening point means the temperature at the steel ball with a certain weight, pressing down a layer of asphalt or tar which stuck in the ring of a certain size, so that the
asphalt was touching the base plate located below the ring at a certain height, as a result of a specific heating rate. This examination was intended to determine the softening point ranging
from 30 to 200 . Experiments conduct to determine at what temperature the asphalt began softening due to air temperature and traffic load. Examination procedures refer to the
AASHTO T - 53-89 or SNI 06-2434-1991. see the pictures of softening point test in Appendix B.
3. Ductility
The purpose of this inspection was to measure the longest distance that can be drawn between the two molds that contains the hard asphalt before the end at a certain temperature
and pull speed. The purpose of this inspection was to determine the ductility of asphalt materials experiments. Examination procedures refer to the AASHTO T - 51-89 or ASTM D -
113-79 or SNI 06-2432-1991. see the pictures of ductility test in Appendix B. .
4. Asphalt Solubility with Carbon Tetrachloride CCl
4
This examination was intended to determine the levels of soluble Asphalt in carbon tetra chloride CCl
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. The purpose of this inspection was to determine the purity level asphalt. Examination procedures refer to the AASHTO T - 44-70 or ASTM D - 165-42 or SNI M-04-
2004.
5. Specific Gravity
The specific gravity of Asphalt or tar was the ratio between the weight of heavy Asphalt or tar and distil water with the same content at a specific temperature. This examination was
intend to check the weight of the hard Asphalt or tar. The purpose of this inspection was to get the heavy types of hard Asphalt or tar. Examination procedures refer to the AASHTO T- 228-
90 or ASTM D - 70-76 or SNI 06-2441-1991. see the pictures of specific gravity test in Appendix B.
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6. Loss on Heating LoH
This examination aims to determine the weight reduction due to evaporation of volatile materials in the asphalt. Examination procedures follow AASHTO T - 79-88 or ASTM D-
1754-83 or SNI 06-2440-1991.
a. Sieve Analysis
