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Manual for Emulsion-Based Chip Seals for Pavement Preservation (2011) / Chapter Skim
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Pages 15-21

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From page 15...
... The quantity of binder required depends on the size, shape, and orientation of the aggregate particles; embedment of aggregate into the substrate; texture of the substrate; and absorption of binder into either the substrate or aggregate. This design method is based on the following assumptions for aggregate, traffic, and embedment: • Aggregate: one-sized aggregates with a flakiness index of 15% to 25% • Traffic: 10%, or less, heavy vehicles • Embedment: 50% to 65% chip embedment after two years 6.1 Emulsion Application Rate The emulsion application rate is the spray quantity of asphalt emulsion applied during construction; it is determined as follows: B B EF PF A A A Ad b s e as aa= [ ]
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From page 16...
... 6.1.3 Adjustment for Traffic, Vt The basic voids factor, Vf, was developed for an average mix of light and heavy vehicles in a free traffic flow situation. When this is not the case due to composition; non-trafficked areas; overtaking lanes with few heavy vehicles or for large proportions of heavy vehicles; channelization and slow-moving, heavy vehicles in climbing lanes; or stop/start conditions, an adjustment, Vt, needs to be made.
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From page 17...
... when using asphalt emulsions. This factor allows a greater volume of binder around the aggregate particles to compensate for reduced aggregate reorientation as a result of rapid increase in binder stiffness after the initial breaking of the emulsion.
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From page 18...
... The sand patch test is a volumetric method for determining the average depth of pavement surface macrotexture. A known volume of small particles (either sieved sand or small glass beads)
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From page 19...
... c) Absorption of Emulsion into Substrate, Aas The correction for potential loss of emulsion to the substrate by absorption is applied primarily to chip seals constructed over surfaces other than hot mix asphalt pavements or previous chip seals.
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From page 20...
... W2 = [ ]  27.08 750Aggregate spread rate, m m ALD, mm2 3 = 6.3 Time Until Sweeping and Traffic The time required before sweeping or before traffic can be allowed on the fresh chip seal is related to the moisture content in the chip seal (Shuler 2009)
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From page 21...
... Loose unit weight, W = 110 lbs/ft3; Traffic = 1,500 veh/day/lane, channelized, with equivalent heavy vehicles, EHV%=16; Polymer modified emulsion binder with 70% residue; Sand patch diameter for texture = 18 in.; Ball penetration = 0.5 mm; Substrate is old chip seal with no expected absorption potential; and Chip-seal aggregate has 1% water absorption Design binder application rate (from Section 6.1) is: Vf = 0.85 gal/yd2/in., from Figure 2b; Va = −0.028 gal/yd2/in., from Table 8; Vt = −0.112 gal/yd2/in., from Table 9; B Vf Va Vt ALD EF PF A A A Ad s e as aa= + +( )
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Key Terms

  • glass beads
  • chip seal
  • asphalt emulsion
  • moisture content
  • pavement texture

  • chip seals
  • patch test
  • sand patch
  • test method
  • voids factor

  • aggregate particles
  • basic voids
  • pavement surface
  • african roads
  • aggregate embedment

  • patch diameter
  • basic binder
  • single layer
  • heavy vehicles
  • polymer modified

  • asphalt institute
  • surface texture
  • moisture contents
  • average depth
  • seal design

  • asphalt pavement
  • emulsion factor
  • meter test
  • pavement microtexture


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