A mixture of asphalt emulsion, crushed aggregate, mineral filler, water and other additives properly proportioned, mixed and spread as a surface treatment. When applied the slurry seal shall have a homogeneous appearance, fill minor cracks, adhere firmly to the surface and provide a weatherproof friction course.

 Very cost effective surface treatment that extends the life of a pavement 5-7 years +  Restores surface texture  Will ultimately be placed at no more than 1.5 times the thickness of the largest stone  Treatment that preserves the underlying pavement from further oxidation related to climatic conditions.  Fast application. A typical residential street will take 15 minutes to place and 2-4 hours to cure to a point that will again support traffic.

 Proven Technology

 Early loss of surface fines  Protect the pavement from further oxidation by providing a new wearing layer  Only minor cracking present. Anything grater than 1/8” gets filled prior to slurry application  Alligator cracking and Pot Holes are repaired. Be careful of placing slurry over fresh patches.

 Project Candidates  Expectation  Specification  Mix Design  Materials  Equipment  Placement  Inspection

 PCI 80 and above  Cracks greater that 1/8” filled  Alligator cracking has been repaired  No rutting  Only minor surface fines loss

 Keep the public in the loop.  Try not to package a slurry project with an overlay project  Winter slurry color will vary more than summer. Give it time.  Most power steering scuffs will heal over time. (Most slurries will take a change of all seasons to complete its cure)  Initial shed or light raveling will occur (large stones that do not lay down may kick out)

 Caltrans Standard Specifications Section 37 tandards.html  Greenbook Section rd-specifications-public-works-construction  International Slurry Surfacing Association

 Verification of material compatibility  Provides starting point for start up of the project.  Targets optimum mixture but allows for minor adjustment in the field.

 Too Much oil will provide a long lasting surface but result in flushing and shoving  Too little oil will result in color variation and excessive rock loss up to and including 100% raveling.  Most materials will provide a good product outside of the recommendation as long as you evaluate the data. Particularly on the slightly high side of the oil content.

 Aggregate (manufactured) Type 1 Type 2 Type 3  Latex  Mineral Fillers / Additives  Emulsion  Other Microsurfacing Tire Rubber Modified RAP

Residential Streets Parking LotsAirports

 Finest gradation of aggregate 1/8” top size  Fractured faces  Generally parking lots and bike lanes  Placed 8-12 lbs per square yd  Low speed traffic or high foot traffic type areas  Airports

Residential Streets County RoadsShoulders

 Mid size aggregate top size ¼”  Fractured faces  Typically used on rural county roads, arterial roads, Collectors and primarily residential.  Application rate lbs/SY

4 Lane Highways Interstates 2 Lane Highways

 Most course gradation Max stone 3/8”  Fractured faces  Application Rate lbs/SY  Typically used on highways, rural county roads, arterial and collector roadways.

Benefits  Increases the softening point of the residual asphalt  Improves early strength of seal (Reduces Power steering burns)  Adds elastomeric properties to the residual binder (Better stone retention)  Typical addition rate of 2.5% of the emulsion

 Cement Can act as a retarder or accelerator of break depending on emulsion and aggregate properties. Generally will make the mix tougher at least initially Is not compatible with all aggregate sources  Aluminum Sulfate Generally acts as a retarder of break time in the field. Can act as a viscosity builder in the slurry preventing separation of the oil and rock during application.

 Generally a CQS-1H Cationic Quick Set (To a limited degree it uses the mineral to assist in the break) Compatible with most aggregates (negative charge offers resistance to stripping)  Other options could be a QS, SS or CSS

 Tire Rubber Slurry Color Multiple products  Some old Some New  Micro Surfacing Next Generation Night time Multiple Stone depth Chemical Break  Multi Layer 2 over 3 Cape Seal (Slurry on top of Chip)  RAP Close to a type 2 gradation Lower Oil Content Recycled Green Value Color

 Truck Mount Better in residential and tight areas Most commonly used Multiple Manufactures Typically multiple trucks per project that require calibration and adjustment  Continuous Machines Same capabilities with the addition of the ability to resupply while placing slurry Highways, Freeways Same machine places the entire project Reduced transverse joints.

 Gate settings (Determine rock to oil relationship and product application rates)  Oil  Water  Fines Feeder (Cement)  Sulfate Feeder

 Sets the depth of the slurry  Provides the uniform surface texture of the slurry  May or May not be augured  Varied widths

 Hand held Squeegees  Oil Tankers  Rock Trucks  Loaders  Conveyors  Sweeper  Traffic Control

 Things to consider Time of the year (Weather Conditions) Have large cracks been filled Is the surface clean and dry Trash trucks Schools and school traffic Sufficient Traffic Control Application rate over surface conditions Equipment Calibration

 Things to Consider 50º F and rising Slight breeze may be beneficial. High winds may make it a challenge to keep the surface clean Sunlight needed to cure. Much shorter work windows in the cold months. Minimize hand work Overlaps should not be in the typical wheel paths Chance of Rain?

 You only get what you inspect  Understand the process and the materials  Use a check list  If you have any questions lean on industry: Most suppliers and contractors are more than wiling to spend some time and answer your questions.  Learn what 25 tons of aggregate looks like in a stock pile (verify application rate)  Traffic Control  Joints  Hand work  Starts / Stops

 International Slurry Surfacing Association  The “Greenbook” Standard Specifications for Public Works Construction  Caltrans Specifications section 37 and MTAG Chapter 8  FP2

Todd Vargason Ergon Asphalt and Emulsion