2319.01 DESCRIPTION.
Slurry Leveling, Slurry Wedge, and Strip Slurry Treatment shall consist of a mixture of emulsified asphalt, mineral aggregate, and water. It shall be properly proportioned, mixed, and spread evenly on a prepared surface as specified in the contract documents. The cured slurry shall have a homogeneous appearance and a uniform texture, shall fill all cracks in the application area, and shall adhere to the surface.

Slurry leveling work involves filling shallow depressions in the pavement at and adjacent to cracks with fine slurry mixtures.  Application may be by hand lutes.

Slurry wedge work involves placing a fine or coarse slurry mixture in a narrow wedge-shaped strip to correct the differential elevation between the pavement edge and the shoulder as designated in the contract documents.

Strip slurry treatment work consists of longitudinal applications of fine or coarse slurry mixtures as designated in the contract documents.  A spreader box shall be required to place the slurry mixture to pavement centerline, widening unit , pavement edge, wheel paths, and lanes, or at other locations and widths as designated by the contract documents or as directed by the Engineer.

When crack cleaning and filling is a part of this work, that work will be covered by a separate specification.

2319.02 MATERIALS.

A. Asphalt Emulsion.
The emulsified asphalt used for this work shall be Grade CSS-1H or SS-1H. The emulsified asphalt shall meet the requirements of Section 4140.

B. Aggregate.
The mineral aggregate shall be crushed stone or a combination of crushed stone and mineral filler meeting the following requirements:

The use of other crushed aggregates will be allowed when approved by the Engineer. This may require the addition of an approved anti-strip additive to the slurry mixture.

1. Crushed Stone.
Crushed aggregates shall meet the requirements of Section 4124.

2. Mineral Filler.
Mineral filler may be required to obtain the desired mixture consistency and the addition rate will be established by the Engineer, based on laboratory or field trials. Mineral filler shall meet the requirements for Type I Portland Cement.

3. Gradation.
The composite aggregate, excluding mineral filler, shall comply with the following gradation limits for the specified slurry mixture required:

a. Fine Slurry Mixture.
The aggregate shall meet the requirements for Gradation No. 22 of the Aggregate Gradation Table in Section 4109.

b. Coarse Slurry Mixture.
The aggregate shall meet the requirements for Gradation No. 23 of the Aggregate Gradation Table in Section 4109.

C. Water.
All water used in the slurry mixture shall be fresh water which is free of sediment and salt contaminants. If the water is not compatible with the slurry mixture, the Contractor may be required to use water from another source.

D. Composition and Quality of Mixture.
Aggregate proposed for use on the project will be sampled by representatives of the Contracting Authority to determine a job-mix formula. After consulting with the Contractor, a job-mix formula for the mixture will be established by the Engineer on the basis of gradation, asphalt content, durability, stability and asphalt compatibility. This formula shall remain in effect until modified in writing by the Engineer. When noncomplying results or other unsatisfactory conditions make it necessary, the Engineer will establish a new job-mix formula, after consulting with the Contractor. Should a change in sources of materials be made, a job-mix formula shall be set before the new material is used.

The Contractor shall provide the Engineer with a copy of the certified gradations of aggregate proposed for use.

E. Stockpiling of Aggregate.
Precautions shall be taken to prevent stockpile contamination with oversized rock, clay, silt, or moisture in excess of that which would interfere with the amount of asphalt emulsion required in producing the desired homogeneous slurry mixture. The stockpile shall be placed in a well drained area. Segregation of the aggregate will not be permitted. In addition, the moisture in the aggregate shall be controlled within ± 1.5% of the moisture content of the aggregate at the time of calibration.

F. Storage.
The Contractor shall provide suitable storage facilities for the asphalt emulsion. The container shall be equipped to prevent water from entering the emulsion. Suitable and adequate heat shall be provided to prevent freezing and to facilitate handling of the asphalt emulsion.

G. Sampling.
Samples of materials shall be furnished by the Contractor as directed by the Engineer during the process of the work.

H. Asphalt Binder Content.
The estimated asphalt residue content shall be 7% to 14% of the dry weight (mass) of the aggregate. Mixture design film thickness shall be 7.5 microns (190 μm) (target value) with a ± 0.75 microns (29 μm) permissible range.

2319.03 EQUIPMENT.
All equipment, tools, and machines shall be subject to approval of the Engineer and shall be maintained in satisfactory working order at all times.

A. Slurry Mixing Equipment.
The slurry mixing machine shall be a continuous flow mixing unit, capable of accurately delivering a predetermined proportion of aggregate, water, and asphalt emulsion to the mixing chamber and discharging the thoroughly mixed product on a continuous basis. The aggregate shall be pre-wet immediately prior to mixing with the emulsion. The pugmill shall be capable of thoroughly blending all ingredients together.

The mixing machine shall be equipped with an approved fines feeder that provides an accurate metering device or method to introduce a predetermined proportion of mineral filler into the mixer at the same time and location that the aggregate is fed. A fines feeder shall be used to add mineral filler when required as part of the aggregate blend.

The aggregate feed to the mixer shall be equipped with a revolution counter or similar device so the amount of aggregate used may be determined at any time.

The emulsion pump shall be a positive displacement type and shall be equipped with a revolution counter or similar device so that the amount of emulsion used may be determined at any time.

The pump for adding water to the mixer shall be equipped with a valve to establish the required water flow.

All controls shall be mechanically tied to ensure accurate proportioning of all materials at all times, including starts and stops. On some machines, this can be a simultaneous start and stop of all materials. On other machines, depending on where the materials are introduced into the mixing chamber, the feeds must be properly synchronized.

This shall be a one-lever or one-button operation with no means for the operator to adjust the mix proportions, except for the water.

Revolution counters shall count 0.1 revolutions on mechanisms which turn less than 100 rpm.

The addition of any additive to the mixture or any component material shall require a metering device attached to the slurry machine. This device shall have positive, quick-acting controls, shall be easily calibrated, and shall maintain accurate and uniform flow.

The mixer shall have a means for calibration. The controls for proportioning each material to be added to the mix shall be calibrated and properly marked. The controls shall be accessible for ready calibration and shall be placed so that the Engineer may determine the amount of each material being used at any time. A minimum of three aggregate gate settings will be required for calibration and, if changes in emulsion delivery are necessary, a minimum of three pump changes will be required.

The mixing machine shall be equipped with a water pressure system and fog type spray bar adequate for complete fogging of the surface preceding spreading equipment. It shall be controllable to an application range of 0.05 gallon per square yard (0.25 L/m²) Sufficient machine storage capability shall be provided to properly mix and apply a minimum of 5 tons (4.5 Mg) of the slurry, except when the mixing machine is operated in a continuous manner and is supplied by separate nurse type equipment.

B. Slurry Spreading Equipment.

1. Slurry Wedge, Strip Slurry Treatment
A mechanical type squeegee distributor equipped with flexible material in contact with the surface to prevent loss of slurry from the distributor shall be attached to the mixer machine. It shall be maintained to prevent loss of slurry on varying grades and crown. There shall be a steering device and a flexible strike off. The spreader box shall be capable of placing the slurry mixture to the width specified in the contract documents.

The spreader box shall be equipped with vertical adjustment devices attached to horizontal support devices, such as runners, located a minimum of 6 inches (150 mm) inside both ends at the side of the box to insure uniform distribution on varying grades and crowns. They shall be of sufficient weight (mass) to keep the runners in contact with the roadway surface during operation. The flexible strike off material shall be of sufficient stiffness to produce the desired texture and rate of application.

The spreader box shall be kept clean. Build up of asphalt and aggregate on the box shall not be permitted.

2. Slurry Leveling
Metal lutes of varying widths shall be used for spreading the slurry mixture in the depressed areas. The face of each lute shall be indented (arched) slightly (1/8 inch to 3/16 inch (3 mm to 5 mm)) to aid in controlling the spread. The Contractor may contact the Office of Maintenance Operations concerning design of these lutes.

C. Cleaning Equipment.
Power brooms, power blowers, air compressors, water flushing equipment, and hand brooms shall be suitable for cleaning the surface and cracks.

D. Auxiliary Equipment.
Hand squeegees, shovels, and other equipment shall be provided as necessary to perform the work.

E. Screening Unit.
A screening unit shall be required for removal of objectionable oversize and foreign material that may be encountered. Screening shall be done before loading the slurry machine and/or weighing for payment.

2319.04 PREPARATION OF SURFACE.
Immediately prior to applying the slurry material, the surface and cracks shall be cleaned of all loose material, soil tracked on the roadway surface, vegetation, and other objectionable material. If the cracks have not been completely filled prior to applying the slurry treatment, cracks shall be cleaned to a depth of 1 inch (25 mm). Any standard cleaning method used to clean pavements, such as power brooms, compressed air, high-pressure water, and hand tools will be acceptable, except water flushing will not be permitted in areas where considerable cracks are present in the pavement surface. The surface preparation shall be subject to approval of the Engineer.

2319.05 TACK COAT.
After surface preparation, the surface shall be given a tack coat of diluted emulsion of the same type and grade used in the slurry mixture. The emulsion shall be diluted, 3 parts water to 1 part emulsion, and applied to the surface at a rate between 0.05 to 0.10 gallon per square yard (0.25 L/m² to 0.45 L/m²). The rate of application used will be subject to the approval of the Engineer. The tack coat shall be applied the same day as the slurry seal.

An application of tack coat may be required for strip slurry treatment and slurry wedge applications only.

2319.06 COMPOSITION AND RATE OF APPLICATION OF THE SLURRY MIX.
The amount of asphalt emulsion to be blended with the aggregate shall be that determined by the laboratory mix design and after final adjustment in the field. Water may be added as necessary to obtain a fluid and homogeneous mixture. The mixture design application methods and the rate of application will be subject to the approval of the Engineer.

2319.07 LIMITATIONS.
Slurry placement shall be scheduled to ensure that the traffic lanes are opened to traffic 30 minutes before sundown of the same working day. When traffic is maintained, the entire roadbed shall be free of construction equipment during non-working hours. Work will not be permitted on days described in Article 1108.03.

Slurry mixture shall not be placed when the temperature on a shaded portion of the road is less than 50°F (10°C). Slurry mixture shall not be placed after October 1 without written permission from the Engineer.

When this work is done in conjunction with crack cleaning and filling, slurry work shall be done only after the crack has been cleaned and filled. The application of slurry and the crack cleaning and filling activity may be done as one coordinated operation. When placing a strip slurry treatment, both edges of the slurry box must run on the pavement surface. All pavement markings shall be replaced the day they are obliterated. Payment for pavement markings shall be at contract unit price for this work.

When the installation of strip slurry treatment is required at a pavement centerline or lane line, the Engineer may require such placement in two separate applications.

When performing slurry wedge placement, one edge of the slurry box must run on the edge of the pavement surface. This work shall not obliterate the pavement edge line. All pavement markings obliterated by the Contractor shall be replaced the day they are obliterated by the Contractor at the Contractor's expense.

2319.08 MAINTENANCE OF TRAFFIC.
Traffic Control shall be in accordance with the contract documents. The Contractor shall repair any damage to uncured slurry due to traffic at the Contractor's expense.

2319.09 APPLICATION OF THE SLURRY MATERIAL.

A. General.
The Engineer may direct that the surface of the pavement be fogged with water, approximately 0.05 gallon per square yard (0.25 L/m²), immediately preceding the pass of the spreader. The slurry mixture shall be of a consistency such that it "rolls" in the spreader box in a continuous mass. Slurry that segregates in the spreader box, so that flowing of liquids (water and emulsion) is evident, is not acceptable and shall not be applied. The total time of mixing aggregate and emulsion shall not exceed 4 minutes. A sufficient amount of slurry shall be present in the spreader at all times to ensure that complete coverage is obtained. Lumping, balling, or unmixed aggregate will not be permitted. Segregation of emulsion and aggregate fines from the coarse aggregate will not be permitted. If the coarse aggregate settles to the bottom of the mix, the slurry shall be removed from the pavement. Breaking of the emulsion in the spreader box shall be kept to minimum to allow for a uniform distribution of the slurry mixture on the pavement. Streaks, such as those caused by over-sized aggregate, shall not be left in the finished surfaces.

All applications of Strip Slurry Treatment shall be applied parallel to the center line, edge line, or other reference, using a guide extending at least 3 feet (1 m) ahead of the application equipment.

A mechanical device such as an auger may be used to distribute the slurry in the spreader box. The use of a mechanical device such as auger in the slurry distribution box for strip slurry treatment and slurry wedge application will not generally be required. The contract documents will state if a mechanical device is required.

B. Mix Consistency.
To obtain a workable mix consistency and to eliminate overwatering, the mix consistency shall be tested according to Iowa Test Method 508, using Procedure B.2., Slurry Flow Test. A maximum flow for each slurry mix will be determined by the Engineer. Once the maximum flow has been established, all slurry mix that is found to exceed this maximum shall be immediately removed from the roadway by the Contractor and shall be replaced with an approved mixture at the Contractor's expense. Testing for consistency will be at the Engineer's discretion. The Engineer will inform the Contractor of the boundaries represented by the test sample when a change in the mixture is apparent.

C. Joints.
Excessive build-up or unsightly appearance will not be permitted on longitudinal or transverse joints. The use of burlap drags or other types of drags will be subject to the approval of the Engineer.

A stringline will be required to obtain a neat appearing, straight line, longitudinal alignment. Reference points will be established by the Engineer. The stringline shall be set, followed, maintained, and removed by the Contractor. The stringline may be referenced to the mixing machine or the spreader box.

D. Hand Work.
Approved squeegees shall be used to spread slurry in areas non-accessible to the slurry mixer. Care shall be exercised to not leave an unsightly appearance from hand work.

E. Curing and Opening to Traffic.
The treated area shall be allowed to cure until it may be opened to traffic without pick-up or raveling of the slurry mixture. Any damage caused to the slurry surface by premature opening to traffic shall be repaired or replaced by the Contractor at the Contractor's expense.

F. Application of Slurry Leveling.
The surface to which the slurry leveling is to be applied shall be moist and clean of dust and foreign material. Scraping and brooming may be necessary.

The slurry leveling mixture shall be spread in depressions at and adjacent to cracks in the pavement. Spreading shall be for the full width of the depression. The slurry shall be leveled with a metal lute of the proper width to provide a smooth riding surface. The slurry leveling shall be neat in appearance, and spillage around and between leveled areas will not be allowed. Excess material at the pavement edge shall be kept to a minimum. Excess material shall be scattered across the adjacent shoulder.

The slurry leveling shall be allowed to cure until such time as the area may be open to traffic without pick-up or raveling of the leveling mixture.

2319.10 METHOD OF MEASUREMENT.
The slurry wedge, strip slurry treatment, and slurry leveling will be measured by the Engineer as follows:

A. Slurry Leveling.
The number of centerline miles (kilometers), measured to the nearest 0.1 mile (0.1 km), of slurry leveling will be computed by the Engineer based on the two-lane pavement width which exists in the limits of the work area. Application of slurry leveling work to auxiliary lanes within the limits of the project will not be measured for payment.

B. Slurry Wedge.

1. Aggregate for Slurry Wedge.
The quantity of Slurry Wedge Aggregate, of the type specified, in tons (megagrams), measured to the nearest 0.1 ton (0.1 Mg), will be the quantity by weight (mass) of individual loads of aggregate used in accepted portions of the work. Deduction will not be made for moisture naturally occurring in the aggregate. The quantity of mineral filler will be included with the aggregate quantity.

2. Surface Preparation for Slurry Wedge.
Surface Preparation for Slurry Wedge placed on the shoulder will be measured in shoulder miles (kilometers) measured to the nearest 0.1 mile (0.1 km).

C. Strip Slurry Treatment.

1. Aggregate for Strip Slurry Treatment.
The quantity of Strip Slurry Treatment Aggregate, of the type specified, in tons (megagrams), measured to the nearest 0.1 ton (0.1 Mg), will be the quantity by weight (mass) of individual loads of aggregate used in accepted portions of the work. Deduction will not be made for moisture naturally occurring in the aggregate. The quantity of mineral filler will be included with the aggregate quantity.

2. Surface Preparation for Strip Slurry Treatment.
Surface preparation for Strip Slurry Treatment will be measured in miles (kilometers) of Strip Slurry Treatment placed.

D. Asphalt Emulsion for Slurry Leveling, Slurry Wedge, Strip Slurry Treatment.
Asphalt emulsion used for slurry leveling, slurry wedge, or strip slurry treatment work will be measured in gallons (liters). This volume will be computed using a calibrated tank stick or by the weight (mass) of asphalt emulsion used. No deduction will be made for water in approved emulsion. The gallons (liters) will be corrected for temperature to 60°F (16°C).

E. Tack Coat for Slurry Wedge and Strip Slurry Treatment.
The undiluted asphalt emulsion used for tack coat shall be considered incidental to asphalt emulsion, and will not be measured separately for payment.

Materials used for calibration purposes will be included in quantities measured for payment. These amounts shall not exceed 5 tons (5 Mg) of aggregate and 100 gallons (400 L) of asphalt emulsion.

2319.11 BASIS OF PAYMENT.

A. Slurry Leveling.
For the number of miles (kilometers) of slurry leveling completed, the Contractor will be paid the contract unit price per mile (kilometer). This payment shall be full compensation for furnishing all the materials for the slurry mixture except the asphalt emulsion. It shall include surface preparation, mixing, placing the mixture and furnishing all equipment, tools, and labor.

B. Slurry Wedge.

1. Aggregate for Slurry Wedge.
The Contractor will be paid the contract unit price for Slurry Wedge Aggregate, of the type specified, per ton (megagram) of aggregate used measured as provided above. This payment shall be full compensation for furnishing all materials except the asphalt emulsion and tack coat. It shall include all equipment and labor necessary to mix and apply the slurry.

2. Surface Preparation for Slurry Wedge.
For the number of miles (kilometers) of surface preparation satisfactorily completed, the Contractor will be paid the contract unit price per mile (kilometer).

C. Strip Slurry Treatment.

1. Aggregate for Strip Slurry Treatment.
The Contractor will be paid the contract unit price for Strip Slurry Treatment Aggregate, of the type specified, per ton (megagram) of aggregate used measured as provided above. This payment shall be full compensation for furnishing all materials except asphalt emulsion and tack coat. It shall include all equipment and labor necessary to mix and apply the slurry.

2. Surface Preparation for Strip Slurry Treatment.
For the number of miles (kilometers) of surface preparation satisfactorily completed, the Contractor will be paid the contract unit price per mile (kilometer).

D. Asphalt Emulsion for Slurry Mixtures.
For the number of gallons (liters) of asphalt emulsion used, measured as provided above, the Contractor will be paid the contract unit price per gallon (liter). This payment shall be full compensation for furnishing the asphalt emulsion.

E. Tack Coat for Slurry Wedge and Strip Slurry Treatment.
The undiluted asphalt emulsion used for tack coat shall be considered incidental to asphalt emulsion and the cost shall be included in the contract unit price for asphalt emulsion.