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Characteristics of split mastic asphalt made with latex-bitumen binder.

Master Theses from JBPTUNIKOMPP / 2012-06-30 07:36:31
By : Firmansyah, S2 - Highway Systems Engineering
Created : 1999-00, with files

Keyword : Split Mastic Asphalt (SMA); Durability; Skid Resistance; Flexibility; Heavily trafficked Roads

Split mastic asphalt (SMA) is a wearing course mix specially formulated for improving durability, skid resistance, flexibility, strength, rutting resistance, and oxidation resistance, and for use on heavily trafficked roads, steep grades, intersections and other areas where the surface will be subjected to severe wheel loading. The high concentration of relatively single-size aggregate in SMA provides the voids space to hold a large quantity of bitumen. To minimize the problem of drainage of bitumen, it is usual to include an additive in the mix, typically a cellulose fiber material. Natural rubber is widely available in Indonesia and reserearch was shown that properties of bitumen are enhanced by the addition of latex. Natural latex emulsion containing about 30 dry rubber, termed the Dry Rubber Content (DRC), is tapped from the rubber trees. To meet the specification, natural latex is concentrated by a centrifuging process to about 60 dry rubber and is preserved with ammonia. The purpose of the investigation described in this thesis was to

evaluate in the laboratory the characteristics MA made with latex-bitumen binder, by means of the following tests: Marshall Immersion test, Indirect Resilient Modulus test, Wheel Tracking test, and Indirect Tensile Strength tset. The results indicate that the addition of latex to bitumen, in the amounts 2 %, 4 % and 6 % latex by weight of bitumen, reduced the penetration from 64.4 (0 % latex) to 56.4 (6 % latex), increased the softening point from 49.2 degree C (0 % latex) to 57.2 degree C (6 % latex) and improved the temperature susceptibility and durability of the binder. Marshall designs are almost identical for mixes made with and without latex. The mixes with latex have somewhat higher values of indirect tensile resilient modulus. At 25 degree C with 6 % latex had the highest value of resilient modulus (4406.00 Mpa) while 45 degree C the mix with 2 % latex had the highest value (673.10 Mpa). At 25 degree C and 45 degree C, the mix with o % latex had resilient modulus value of 4092.22 Mpa and 568.10 Mpa, respectively. The mixes containing latex also have somewhat higher indirect tensile strength; at 25 degree C, 35 degree C and 45 degree C, the highest tensile strength values were obtained for the mixes with 6 % latex, 122.57 psi, 61.43 psi, and 31.74 psi, respectively.

The corresponding values for the mix with 0 % latex were 115.28 psi (25 degree C), 58.50 psi (35 degree C), and 28.47 psi (45 degree C). The most significant influence of latex is evident in the wheel tracking test data; mixes containing latex-bitumen binder have superior resistance to deformation. Overall, the addition of latex improved the performance of the SMA mix and optimum performance is achieved at a latex content of 6 %. However as difficulties were experienced in mixing the aggregate and binder at this latex content, a latex content of 4 % by weight of bitumen is recommended. The use of the lower latex content willnot reduce performance significantly.

Description Alternative :

Split mastic asphalt (SMA) is a wearing course mix specially formulated for improving durability, skid resistance, flexibility, strength, rutting resistance, and oxidation resistance, and for use on heavily trafficked roads, steep grades, intersections and other areas where the surface will be subjected to severe wheel loading. The high concentration of relatively single-size aggregate in SMA provides the voids space to hold a large quantity of bitumen. To minimize the problem of drainage of bitumen, it is usual to include an additive in the mix, typically a cellulose fiber material. Natural rubber is widely available in Indonesia and reserearch was shown that properties of bitumen are enhanced by the addition of latex. Natural latex emulsion containing about 30 dry rubber, termed the Dry Rubber Content (DRC), is tapped from the rubber trees. To meet the specification, natural latex is concentrated by a centrifuging process to about 60 dry rubber and is preserved with ammonia. The purpose of the investigation described in this thesis was to

evaluate in the laboratory the characteristics MA made with latex-bitumen binder, by means of the following tests: Marshall Immersion test, Indirect Resilient Modulus test, Wheel Tracking test, and Indirect Tensile Strength tset. The results indicate that the addition of latex to bitumen, in the amounts 2 %, 4 % and 6 % latex by weight of bitumen, reduced the penetration from 64.4 (0 % latex) to 56.4 (6 % latex), increased the softening point from 49.2 degree C (0 % latex) to 57.2 degree C (6 % latex) and improved the temperature susceptibility and durability of the binder. Marshall designs are almost identical for mixes made with and without latex. The mixes with latex have somewhat higher values of indirect tensile resilient modulus. At 25 degree C with 6 % latex had the highest value of resilient modulus (4406.00 Mpa) while 45 degree C the mix with 2 % latex had the highest value (673.10 Mpa). At 25 degree C and 45 degree C, the mix with o % latex had resilient modulus value of 4092.22 Mpa and 568.10 Mpa, respectively. The mixes containing latex also have somewhat higher indirect tensile strength; at 25 degree C, 35 degree C and 45 degree C, the highest tensile strength values were obtained for the mixes with 6 % latex, 122.57 psi, 61.43 psi, and 31.74 psi, respectively.

The corresponding values for the mix with 0 % latex were 115.28 psi (25 degree C), 58.50 psi (35 degree C), and 28.47 psi (45 degree C). The most significant influence of latex is evident in the wheel tracking test data; mixes containing latex-bitumen binder have superior resistance to deformation. Overall, the addition of latex improved the performance of the SMA mix and optimum performance is achieved at a latex content of 6 %. However as difficulties were experienced in mixing the aggregate and binder at this latex content, a latex content of 4 % by weight of bitumen is recommended. The use of the lower latex content willnot reduce performance significantly.


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