607PAVING GEOTEXTILES

480

at open joints. The remainder of the filter material shall then be placed and compacted to the required height. Any remaining portion of trench above the filter material shall be filled with granular or impervious material, as may be directed, and thoroughly compacted, consistent with the location of the trench within the work.

Trenches for underdrain outlets shall be excavated to the width and depth shown on the plans. Pipe shall be laid in the trench with all ends firmly joined by applicable methods and means. Perforated pipe shall be laid with holes up and covered with roofing paper, or non-perforated pipe meeting the same requirements of the perforated pipe may be used. After inspection and approval of the pipe installation the trench shall be backfilled with suitable soil in layers and compacted as provided for drainage pipe. Filter material will not be required for outlet trenches unless specified on the plans, or ordered by the Engineer.

606.04Method of Measurement

The accepted length of pipe underdrain, complete in place, of each specified size and type will be measured in linear feet {meters} along the center of each line or lateral, center to center of junctions and fittings.

606.05Basis of Payment

unit price for pipe underdrain, complete in place for a depth of 3 feet {1 meter} and less below existing ground line to bottom of trench which shall be payment in full for all excavation and its disposal, foundation preparation, backfilling, furnishing, hauling and placing of all materials including fittings, cutting for connections, joint material, bands, geotextile filter fabric, and aggregate filter material (or cover and bedding layer materials.)

below the ground line shall have an adjusted unit price, arrived at by increasing the contract price bid by the percentage indicated in the table below. The unit price coverage provided in Item 1 above shall govern for such adjusted unit price. Depth Underdrain Installed Below Existing Ground Line Extra Percentage Contract Unit Price Bid to be Increased More than 3 feet {1 meter}, but less than 6 feet {2 meter} 20 6 feet {2 meter} and more, but less than 9 feet {3 meter} 50 9 feet {3 meter} and more, but less than 12 feet {4 meter} 75 12 feet {4 meter} or more 100

applicable to this Section.

606-A ___ inch {mm} Underdrain Pipe, Type * - per linear foot {meter} * Note specific type or types of pipe if required. See Article 606.01 for approved types. PAVING GEOTEXTILES

607.01Description

This section shall cover the work of furnishing and placing a geotextile between pavement layers for the purpose of incorporating a waterproofing and stress relieving membrane within the pavement structure. This specification is applicable to geotextile membranes used for full coverage of the pavement, or as strips over transverse and longitudinal pavement joints. It is not intended to describe membrane systems specifically designed for pavement joints and localized (spot) repairs. PAVING GEOTEXTILES 481

607.02Materials

The geotextiles used in this work shall be constructed of non-woven synthetic fibers meeting the requirements of AASHTO M 288 for Paving Fabric, Type II, and Section 810 of these specifications. The geotextile shall be selected from List II-3, of the Department's manual titled "Materials, Sources, and Devices With Special Acceptance Requirements". Information concerning this list is given in Subarticle

106.01(f) and ALDOT-355

The material used to impregnate and seal the geotextile, as well as bond it to both the base pavement and overlay, shall be a paving grade asphalt recommended by the geotextile manufacturer and approved by the Engineer. Cutbacks and emulsions which contain solvents shall not be used. Uncut asphalt cements or cationic and anionic emulsions may be used provided these emulsions are used as outlined in Article

607.04of these specifications

If the ambient temperature is high enough to cause a bleed-through of the asphalt sealant, washed concrete sand may be spread over asphalt-saturated geotextiles to facilitate movement of equipment during construction or to prevent tearing or delamination of the geotextile. Excess quantities shall be removed from the geotextile prior to placing the surface course. A hot asphalt mix broadcast in front of construction vehicle tires may also be used.

607.03Equipment

The distributor shall be capable of spraying the asphalt sealant at the prescribed uniform application rate. No streaking, skipping, or dripping will be permitted. The distributor shall also be equipped with a hand spray having a single nozzle and positive shut-off valve.

Mechanical or manual laydown equipment may be used provided the laydown is smooth and without wrinkles or creases.

Stiff bristle brooms or squeegees shall be provided to smooth the geotextile, scissors or blades for cutting same, and brushes for applying asphalt sealant at the geotextile overlaps. When the ambient temperature is so low that the normal wicking of the asphalt sealant into the geotextile does not occur, a pneumatic roller may be used to ensure geotextile bond to the adjoining pavement layers, especially where thin lifts or chip seals are being placed.

Construction Requirements

Neither the asphalt sealant nor geotextile shall be placed when weather conditions, in the opinion of the Engineer, are not suitable. Air and pavement temperatures shall be sufficient to allow the asphalt sealant to hold the geotextile in place. For asphalt cements, the minimum air temperature shall be 50 °F {10 °C} and rising. When using asphalt emulsions, the minimum air temperature shall be 60 °F {15 °C} and rising.

The surface on which the geotextile is to be placed shall be free of dirt, water, vegetation, or other debris. Cracks exceeding 1/8 inch {3 mm} in width shall be filled with a rubberized joint sealer meeting the requirements of ASTM D 6690, for Type II sealant. Potholes shall be properly repaired as directed by the Engineer. The joint sealer shall be allowed to cure prior to geotextile placement.

The asphalt sealant shall be spray applied uniformly to the prepared dry pavement surface at the rate of 0.20 to 0.30 gallons per square yard {0.9 to 1.36 L/m²} or as recommended by the geotextile manufacturers and approved by the Engineer. The recommended application for asphalt cements is 0.20 gallons per square yard {0.9 L/m²} with rough and ravelled surfaces requiring a higher application. When using emulsions, the application rate shall be increased to offset the water content of the emulsion. GEOTEXTILES IN SEPARATION APPLICATIONS 482

Application of the sealant shall be by distributor spray bar, with hand spraying kept to a minimum. Temperature of the sealant shall be sufficiently high to permit a uniform spray pattern. For asphalt cements, the minimum temperature shall be 290 °F {143 °C}. To avoid damage to the geotextile, however, distributor tank temperatures shall not exceed 325 °F {163 °C}. Spray patterns for asphalt emulsion can be improved by heating. Temperatures in the 130 to 150 °F {54 to 71 °C} range are recommended. A temperature of 160 °F {71 °C} shall not be exceeded since higher temperatures may break the emulsion. The target width of asphalt sealant application shall be 6 inches {150 mm} wider than the geotextile width. The sealant shall not be applied any farther in advance of geotextile placement than the distance which the Contractor can maintain free of traffic. Asphalt spills shall be cleaned from the road surface to avoid flushing and geotextile movement. When asphalt emulsions are used, the emulsion shall be cured (essentially no water remaining) prior to placing the geotextile and final wearing surface.

The geotextile shall be placed into the asphalt sealant with minimum wrinkling prior to the time the asphalt has cooled and lost tackiness. As directed by the Engineer, wrinkles or folds in excess of 1 inch {25 mm} shall be split and laid flat. Brooming and/or pneumatic rolling will be required to maximize geotextile contact with the pavement surface. Overlap of geotextile joints shall be sufficient to ensure full closure of the joint, but should not exceed 6 inches {150 mm}. Transverse joints shall be lapped in the direction of paving to prevent edge pickup by the paver. A second application of asphalt sealant to geotextile overlaps will be required, if in the judgement of the Engineer, additional asphalt sealant is needed to ensure proper bonding of the double geotextile layer. Removal and replacement of damaged geotextile will be the responsibility of the Contractor. Trafficking the geotextile will be permitted for emergency or construction equipment only.

Placement of the hot mix overlay shall closely follow geotextile laydown. The temperature of the mix shall not exceed 325 °C {163 °C}. In the event asphalt bleeds through the geotextile causing construction problems before the overlay is placed, the affected areas shall be blotted by spreading sand or hot-mix. To avoid movement or damage to the geotextile membrane, turning of the paver and other vehicles shall be gradual and kept to a minimum.

Prior to placing a seal coat (or thin overlay such as an open-graded friction course), the geotextile shall be lightly sanded at a spread rate of 1.5 to 2.0 pounds per square yard {0.8 to 1.1 kg/m²} and pneumatically rolled so as to embed the geotextile tightly into the sealant.

607.05Method of Measurement

The paving geotextile will be measured by the square yard {square meter}. Asphalt sealant for the paving geotextile will be measured by the gallon {liter}.

607.06Basis of Payment

The accepted quantities of paving geotextiles will be paid for at the contract unit price per square yard {square meter} in place. Accepted quantities of asphalt sealant for the paving geotextile will be paid for at the contract unit price per gallon {liter} complete in place.

607-D Paving Geotextile - per square yard {square meter} 607-E Asphalt Sealant - per gallon {liter} GEOTEXTILES IN SEPARATION APPLICATIONS

608.01Description

This section shall cover the furnishing and placing of geotextiles for use as a permeable separator to prevent mixing of dissimilar materials such as subgrades and surfaced and unsurfaced pavement GEOTEXTILES IN SEPARATION APPLICATIONS 483

structures, zones in embankments, foundations, and select fill materials. The geotextiles shall be designed to allow passage of water while retaining in situ soil without clogging. When used as a soil stabilizer, a detailed design process shall be followed taking into consideration the separation function of the geotextile, along with its filtration and reinforcement functions.

608.02Materials

The geotextile shall meet the requirements of AASHTO M 288 for Separation Applications, Class 2, and Section 810 of these Specifications. The geotextile shall be selected from List II-3, of the Department's MSDSAR manual. Information concerning this list is given in Subarticle 106.01(f) and ALDOT- 355.

608.03Construction Requirements

The installation site shall be prepared by clearing and grading the area as required. All sharp objects and large stones shall be removed and trees and shrubs shall be cut flush with the subgrade. The removal of topsoil and vegetation is not necessary. When appropriate, soft spots and unsuitable areas shall be identified during site preparation or subsequent proof rolling. These areas shall be excavated and backfilled with select material which is compacted to a depth such that the area provides equal stability as the adjacent area. Stabilization of these areas may be enhanced by use of a geotextile at the bottom of the excavation before backfill.

608.04Installation

The geotextile shall be unrolled as smoothly as possible on the prepared subgrade in the direction of the construction traffic. Adjacent geotextile rolls shall be overlapped in the direction of subbase placement using the following guide: Required Overlaps Soil Strength (CBR) Unsewn Overlap (inches {mm}) Sewn Overlap (inches {mm}) < 1 - - 9 {225} 1 - 2 38 {950} 8 {200} 2 - 3 30 {750} 3 {75} > 3 24 {600} - - Unless shown otherwise on the plans, the required overlap shall be as shown for a CBR value of 1 - 2. The geotextile may be held in place prior to subbase placement by pins, staples, or piles of fill or rock. Geotextiles may be folded or cut to conform to any curvature of the area. A fold or overlap shall be in the direction of construction and held in place as prescribed above.

608.05Seams

Both factory and field sewn or sealed seams shall conform to the strength requirements of Table 1 as outlined in AASHTO M 288 for Separation Applications. All seams shall be subject to the approval of the Engineer.

608.06Subbase Placement

The subbase shall be placed by end dumping onto the geotextile from the edge of the geotextile, or over previously placed subbase aggregate. On subgrades having a CBR of 1, the subbase aggregate shall be spread simultaneously with dumping to minimize the potential of a localized subgrade failure. Direct traffic on the geotextile, along with any sudden stops, starts, or turns on the subbase material by construction equipment, shall be avoided where possible. Using whatever means, the subbase material shall be spread from the back dumped pile. Except in the case of low volume roads (ADT < 200), a minimum thickness of 6 inches {150 mm} shall be maintained. In the case of low volume roads, this thickness shall be 4 inches {100 mm}. A smooth drum roller shall be used to achieve the specified density. Any ruts occurring during construction shall be filled with additional subbase material and compacted to the specified density. The use of vibratory compaction will not be allowed as it may cause damage to the geotextile.

608.07Damage Repair

Damaged geotextiles, as identified by the Engineer, shall be repaired immediately. The damaged area, plus an additional 3 feet {1 m} around the area, shall be cleared of all fill material. This area shall be covered with a geotextile patch extending 3 feet {1 m} beyond the perimeter of the damage. The removed subbase material shall be replaced and compacted to the specified density.