Chapter 7: Slurry Seals
4.0 Project Selection
4.1 Distress & Application Considerations
Slurry surfacing may be used for a range of applications, but job selection is critical and often pretreatments such as pothole patching, crack sealing, and dig outs are required. Table 5 lists general job selection criteria for slurry surfacing treatments and typical application rates.
Table 5: Job Selection Criteria
| Applications |
Aggregate Type I |
Aggregate Type II |
Aggregate Type III |
| Void Filling |
S |
S |
|
| Wearing Course (AADT) <100 |
S |
S |
|
| Wearing Course (AADT) 100-1000 |
|
S |
S |
| Wearing Course (AADT) 1000-20,000 |
|
|
S |
| Minor Shape Correction 10-20mm
(0.4-0.8 inch) |
|
|
S |
| Application Rates (kg/m2) |
4.3-6.5
(8-12 lb/yd2) |
6.5-10.8
(12-20 lb/yd2) |
9.8-16.3
(18-30 lb/yd2) |
| Key: (S = Slurry Seal) |
The main use of slurry surfacing materials is for pavement preservation as a part of a program of periodic surfacing before distresses appear. The main criteria for project selection are:
- Sound and well drained bases, surfaces, and shoulders
- Free of distresses, including potholes and cracking
Distress modes that can be addressed using slurry surfacing include:
- Raveling: Loose surfaces or surfaces losing aggregate may be resurfaced using slurry seals.
- Oxidized pavement with hairline cracks: These surfaces may be resurfaced using slurry seals.
- Rutted pavements: Deformation resulting from consolidation of the surfacing only. Rutting due to base failure or significant plastic deformation of the HMA cannot be treated except as a temporary measure.
Distress modes that cannot be addressed using slurry surfacing include:
- Cracking (including reflection cracking)
- Base Failures of any kind
- HMA Layers that exhibit plastic shear deformation
Slurry surfacing will not alleviate the cause of these distresses. As a result, the distresses will continue to form despite the application of a slurry surfacing.
4.2 Life Expectancy of Slurry Surfacings
Slurry seals have been estimated to last around 5 to 7 years (6). Much longer service lives (up to 15 years) have been observed when the seals are placed as true preventive maintenance treatments on suitable roads (6). Traffic is not a limiting factor.
The main failure mechanism is wear. Over time, the surface oxidizes and abrades under traffic. Premature treatment failure occurs from placement on highly deflecting surfaces, cracked surfaces, pavements with base failures, and on dirty or poorly prepared surfaces (resulting in delamination).
|
