1. So You Have a Slurry Seal Project
Just the basics: material calculation and field testing

2. Material Calculation Application Rate Spread Rate Extra Long Tons
Wet Ton
Extra Long Tons

3. Material Calculation Aggregate Application Rate Aggregate Type
MINIMUM (Thinner, Lighter)
MAXIMUM (Thicker, Heavier)
Type I
8 lbs/yd2
10 lbs/yd2
Type II
12 lbs/yd2
15 lbs/yd2
Type III
20 lbs/yd2
25 lbs/yd2

4. Application Rate Used in 2012 Greenbook
Easy round numbers for calculations
Easy to visualize that a lower number means a thinner/lighter application and a higher number is a thicker/heavier application rate
Streets are more often measured in Square Feet
Aggregate is most often measured in Tons
Converting between to two can lead to mistakes

5. Material Calculation Aggregate Spread Rate Aggregate Type Area Covered
MINIMUM (Thicker, Heavier)
MAXIMUM (Thinner, Lighter)
Type I
1800 ft2/ELT
2200 ft2/ELT
Type II
1200 ft2/ELT
1500 ft2/ELT
Type III
900 ft2/ELT
1125 ft2/ELT

6. Spread Rate
Used in Greenbook prior to 2012 and still very commonly used in the field
Uses units more commonly used for measuring streets, square feet, and aggregate, tons.
More difficult to visualize that a lower number means a heavier application rate

7. Material Calculation Extra Long Ton (ELT)
An extra long ton of slurry is measured by 2,000 pounds of dry aggregate. The weight of the asphalt emulsion, additives, and water is not included in the measurement.
What this means is that we are only concerned with the weight of the aggregate in the slurry. The terms Tons and ELT are often used interchangeably when referring to slurry.

8. Extra Long Ton
Once understood it simplifies measuring slurry seal material quantities.
It gives the agency a verifiable way to measure slurry seal material quantities with aggregate delivery tickets.
Still the most common unit to describe slurry seal material
Can be difficult to understand, and was made confusing by an error in a past Greenbook when converting to Tonnes
No longer mentioned 2012 Greenbook

9. Material Calculation Wet Ton
An wet ton of slurry is measured by 2,000 pounds of dry aggregate and asphalt emulsion, the weight of the additives and water are not included in the measurement.
What this means is you must add the weight of the aggregate AND the emulsion to calculate a ton of slurry.

10. Wet Ton
It ensure the monitoring of both the aggregate and the emulsion on a project.
While the Wet Ton is common on Caltrans projects, the Extra Long Ton is still the predominate method used to calculate slurry seal.
It can complicate determining quantities by the engineer because spread rates are calculated based upon aggregate only.
Emulsion percentages can vary, which will again affect slurry seal quantities.

11. Material Calculation Examples
2,000,000 square feet of streets to slurry with Type II, how many tons of slurry will you need?
Type II slurry has a spread rate of 1200SF/Ton to 1500SF/Ton, or an average of 1350 SF.
2,000,000SF / = 1481 tons of slurry.
A contractor used 650 Tons of Type II aggregate to cover 1,000,000SF of streets. Was this a thick or a thin application?
1,000,000SF / 650 Tons = 1538 SF/Ton
Spread rate is 1200SF/Ton to 1500SF/Ton
Higher spread rate is thinner, this is a thin slurry (actually out of spec).

12. Material Calculation Examples At 16% Emulsion solve for aggregate
3) A job is bid for 2000 Wet Tons of type II slurry seal, how much aggregate and emulsion should be used on the project?
At 16% Emulsion solve for aggregate
.16x+x=2000
1.16x=2000
x=2000/1.16
x=1724 (aggregate tons)
Emulsion = .16*1724 = 276
1724(aggregate) (emulsion) = 2000 Wet Tons of Slurry Seal

13. Material Calculation Engineer Tips: Bid by area or weight? Area
Pro - Bidding by area is the simplest way to measure slurry seal.
Con - You most likely will the minimum application rate.
Weight
Pro - You know you are getting the material you are paying for, and the street will most likely receive a heavier application of slurry seal.
Con - Calculating and keeping track of the quantities is more difficult.
Application rates are controlled both by the contractor and the surface the slurry is being applied to.
Coarse street and first application of slurry seal = heavier application rate.
Street with multiple slurry seal applications = lighter application rate.
Cape Seal/Chip Seal, slurry seal may have to be applied heavier than normal application rate to cover chip.

14. Material Calculation Inspector Tips:
You should collect material weight tickets daily.
Both aggregate and emulsion
You should calculate square feet covered daily.
Estimate the remaining material left in the stockpile.
With this information you can estimate the spread/application rates, if the job is going to be over or under quantity, calculate progress payments, etc.
Material quantities can also be estimated by slurry machine calibration numbers, but this is not a replacement for material delivery tickets or visually verifying material in the stockpile.

15. Slurry Seal Field Tests
Water Content
Extraction Test
Consistency Test
Wet Track Abrasion Test (WTAT)
Field sampling methods and conditions have a strong effect on field test results. These tests where designed to be performed in a lab on lab prepared samples. Because of this there should always be some reservation when presented with failing results from field samples. More testing may be necessary as well as visually verifying that the test results are representative of how the material is actually performing.

16. Slurry Seal Sampling
Because slurry can segregate easily, it is important to take a sample from a location where all the components of the slurry are in suspension. The most common way is to take a sample from chute on the slurry seal machine. The difficulty in this is that the slurry seal machine is moving and the material exits the chute with great force.
Test results should always be confirmed by comparing them to the actual quantities of materials being delivered and used.

17. Water Content
Purpose - To determine if amount of water in the slurry seal is below the maximum allowed.
Too much water can cause a slurry to segregate, the aggregate falls to the bottom and the emulsion rises to the top. This results in a slick slurry.
Too much water can prevent proper bonding of asphalt and aggregate.
An overly wet mix will often produce a thin application rate.
Sample of slurry seal should be retained in a way that moisture will not escape the sample.
Quart sample jars with screw top lids are often used.

18. Extraction Test
Purpose - To determine the asphalt percentage of the cured slurry seal as well as the
calculated emulsion content.
Too much asphalt/emulsion may result in a slick slurry that may push and shove.
Too little asphalt/emulsion may result in a slurry that wears prematurely.

19. Consistency Test
Purpose - To ensure the slurry mixture remains homogeneous, does not separate, and is not
too ‘wet’. Below is a good example of how the consistency should look.

20. Wet Track Abrasion Test (WTAT)
Purpose - To test accelerated wear on a slurry seal sample.
Results can be highly impacted by the preparation of the sample. The sample should be collected in a shallow container and/or stirred to prevent segregation of materials. The sample should be quickly spread with only one or two passes of the squeegee. A separate sample of material should be obtained for each wet track patty.

21. The components of a quality slurry seal project:
Quality Specifications
Quality Contractor
Quality Material
Quality Inspection

22. References Slurry Systems Inspector’s Manual Available from:
International Slurry Surfacing Association
3 Church Circle, PMB 250
Annapolis, MD 21401
Tel
Fax

23. References Slurry Seal Application Checklist
Available from the FHWA website:

24. So You Have a Slurry Seal Project
Lance Allan
Pacific Emulsions, Inc.