Using Polymer Modified Asphalt Emulsions in Surface Treatments A ...

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intermediate testing frequencies (via dynamic shear rheometer) as polymer content is increased and when compared to unmodified asphalts (20). Similarly, Gahavari also reports a significant decrease in loss tangent values (i.e., decreased viscous, flow-type behavior) over low to intermediate frequencies with the addition of polymer – an indicator of increased elasticity. However, at higher testing frequencies, it has been shown that the aging condition of modified asphalts may reduce the preferential elastic response effects obtained via the addition of polymer modifiers which were observed at lower frequencies (20). 2.2.5 Reclaimed Rubber Whereas the abundance of used tires and their associated disposal problems are wellknown, the incentive to utilize reclaimed rubber to improve pavement performance and/or as a means of facilitating disposal is undeniable. CRM consists of scrap tire rubber that has been mechanically ground and reduced in size to particles generally less than or equal to 6.35 mm (0.25 inches) in diameter. Although most commonly utilized in HMA applications, reclaimed CRM has been used successfully on a limited basis in asphalt emulsions, particularly in those areas of the world where their lower cost and simplified application in remote locales are viewed favorably as compared to hot mixes. Reclaimed tire rubbers are not pure polymers, but represent blends of SBR latex, polyisoprene (natural rubber), carbon black, and other additives (21). While CRM can be successfully emulsified if particle size is sufficiently fine or if predigested, the crosslinked structure of the compounds in tire rubber generally result in the formation of two distinct phases upon blending (i.e., asphalt and rubber). This makes stabilization of the final emulsion difficult to achieve. Phase separation in CRM modified asphalt emulsions is characterized by two distinct mechanisms – coalescence and creaming (22). Coalescence occurs when polymer particles aggregate together within the emulsion through the process of molecular diffusion. Creaming occurs when polymer particles rise to the surface of the emulsion due to density differences between the modifier and binder components. 19
Sabbagh and Lesser (1998) note that the phase stability of CRM modified asphalt emulsions is governed in large part by both particle size and morphology. In unstable modified asphalt emulsions, polymer particles tend to coalesce, gradually increasing in size over time until they become sufficiently large for creaming to occur (22). Sabbagh and Lesser have experimentally determined the critical particle transition radius (between coalescence and creaming) to be approximately 4 µm at 110º C for polyolefin. With respect to morphology, polymer particles in unstable asphalt emulsions are predominately teardrop-shaped, whereas those in stabilized asphalt emulsions are characterized by either spherical and/or long-cylindrical shapes. The irregular, nonspherical shaped polymer particles which characterize unstable modified asphalt emulsions are commonly observed under high shear mixing conditions. Additionally, the use of steric stabilizing copolymers has been shown to promote more thermodynamically stable spherical polymer particle shapes (22). Sabbagh and Lesser have noted that while polymer particle sizes in stabilized asphalt emulsions are generally larger than those in unstable asphalt emulsions, the former are not more susceptible to creaming. This is believed to be due to the increased density of the particles in stabilized asphalt emulsions created by the use of steric stabilizers (22). Thus, stabilized asphalt emulsions are those which are characteristically stable with respect to both creaming and coalescence. Paradoxically, Sabbagh and Lesser have shown comparable increases in fracture toughness and improved high-temperature viscoelastic behavior with increasing polymer content for both stable and unstable asphalt emulsions. This suggests that actual field performance is relatively insensitive to initial polymer particle morphology. CRM can be added as a dry ingredient to slurry mixes to avoid problems of phase separation, but in such cases it serves primarily as a filler material. When used as filler, CRM fails to form a pervasive matrix or network, and thus does not impart the cohesive and viscoelastic benefits associated with most other forms of polymer modification. One solution to the phase separation problems associated with CRM modifiers involves the use of solvents to partially predigest the rubber particles prior to their introduction 20
Page 1 and 2: Using Polymer Modified Asphalt Emul
Page 3 and 4: 2.10 SURFACE TREATMENTS, DISTRESS,
Page 5 and 6: EXECUTIVE SUMMARY Needs to be Compl
Page 7 and 8: DISCLAIMER This document is dissemi
Page 9 and 10: 1. Compile published research on th
Page 11 and 12: 2.0 LITERATURE REVIEW OF POLYMER MO
Page 13 and 14: the emulsion solution is termed the
Page 15 and 16: molecular weights ranging up to 100
Page 17 and 18: Elastomeric polymers exhibit a low
Page 19 and 20: The first commercial process that w
Page 21 and 22: 2.2.3 Synthetic Rubber and Latex Sy
Page 23 and 24: Latex Modified Unmodified 80 Chip R
Page 25: of residual asphalt (3). Additional
Page 29 and 30: 2.2.6 Plastics The plastic polymer
Page 31 and 32: high temperature performance, but w
Page 33 and 34: 2.2.7 Polymer Blends Select polymer
Page 35 and 36: Table 2: Polymer Modification Metho
Page 37 and 38: Forbes et al found that asphalt emu
Page 39 and 40: Lubbers and Watson (2005) present t
Page 41 and 42: Takamura and Heckmann (1999) sugges
Page 43 and 44: Neat Asphalt + 8% LDPE1 + 8% LDPE2
Page 45 and 46: Figure 16: Effect of SBS Concentrat
Page 47 and 48: destruction of the polymer modifier
Page 49 and 50: emulsified and non-emulsified aspha
Page 51 and 52: However, in developing the SPG, Epp
Page 53 and 54: • Forced Air-Drying Method - This
Page 55 and 56: • Wet Track Abrasion Loss - used
Page 57 and 58: ductility (61). King characterizes
Page 59 and 60: Polymer modified asphalt emulsions
Page 61 and 62: 3 40-120º F 5.02 12.81 6.04 14.92
Page 63 and 64: emulsions require a much longer set
Page 65 and 66: Figure 20: Chip Seal Aggregate Rete
Page 67 and 68: design specifications are meticulou
Page 69 and 70: Holleran (n.d.) recommends using SB
Page 71 and 72: 22 20 18 Vertical Displacement (%)
Page 73 and 74: seal stone retention, and to provid
Page 75 and 76: Microsurfacing applications by defi
Page 77 and 78:
Thus, the cohesive properties of SB
Page 79 and 80:
dimensional polymer network is pres
Page 81 and 82:
Moreover, although the moduli of th
Page 83 and 84:
Numerous decision tools and best pr
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3.0 LABORATORY TESTING AND SPECIFIC
Page 87 and 88:
and performance-related specificati
Page 89 and 90:
were consistently twice as high as
Page 91 and 92:
• Polymer/Asphalt Compatibility a
Page 93 and 94:
angle at the lowest pavement temper
Page 95 and 96:
damaged by temperature. The problem
Page 97 and 98:
Because the industry survey and oth
Page 99 and 100:
conforming to the following criteri
Page 101 and 102:
with faster curing and longer wear.
Page 103 and 104:
Table 17: Comparison of Microsurfac
Page 105 and 106:
Emulsion/Aggregate Performance Test
Page 107 and 108:
the FLH report-only format be used
Page 109 and 110:
leading the negatives. If post-blen
Page 111 and 112:
opportunity to evaluate performance
Page 113 and 114:
traffic areas, as are durable, poli
Page 115 and 116:
esearchers, with the leading candid
Page 117 and 118:
Table 13 illustrates a draft Strawm
Page 119 and 120:
Laboratory Design Procedures • Ch
Page 121 and 122:
• Develop/improve performance met
Page 123 and 124:
specification tests will cost appro
Page 125 and 126:
PROPERTY TEST METHOD SPEC. RESULT B
Page 127 and 128:
14. Takamura, Koichi, “SBR Latice
Page 129 and 130:
38. Turk, Johannes, and Schmidt, Ma
Page 131 and 132:
62. Desmazes, C., Lecomte, M., Lesu
Page 133 and 134:
86. European Standard EN 14895, “
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