607.01 Description.
Depth Underdrain Installed Below Existing Ground Line Extra Percentage Contract Unit Price Bid to be Increased More than 3 feet {1 m eter}, but less than 6 feet {2 m eter} 20 6 feet {2 m eter} and more, but less than 9 feet {3 m eter} 50 9 feet {3 m eter} and more, but less than 12 feet {4 m eter} 75 12 feet {4 m eter} or more 100
3.No separate payment will be made for excavation. The provisions of Article 214.04 are not applicable to this Section.
b.Payment will be made under Item No .: 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
607.01 Description.
a.General . 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.
607.02 Materials.
a.Paving Geotextiles . The geotextiles u sed 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 ti tled "Materials, Sources, and Devices With Special Acceptance Requirements". Information concerning this list is given in Subarticle 106.01(f) and ALDOT -355.
b.Asphalt Sealant . The material used to impregnate and seal the geotextile, as well as bond it t o 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 e mulsions may be used provided these emulsions are used as outlined in Article
607.04 of these specifications.
c.Aggregate . 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 bro adcast in front of construction vehicle tires may also be used.
607.03 Equipment.
a.Asphalt Distributor . 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.
b.Geotextile Handling Equipment. Mechanical or manual laydown equipment may be used provided the laydown is smooth and without wri nkles or creases.
607.04 Construction Requirements.
c.Miscellaneous Equipment . 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 temperat ure 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.
607.04 C onstruction Requirements.
a.Weather Limitations . 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.
b.Surface Preparation . The surface o n 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.
c.Application of Asphalt Sealant . 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. Applicat ion 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 a void 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 cur ed (essentially no water remaining) prior to placing the geotextile and final wearing surface.
d.Geotextile Placement . The geotextile shall be placed into the asphalt sealant with minimum wrinkling prior to the time the asphalt has cooled and lost tackin ess. 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 geot extile will be permitted for emergency or construction equipment only.
e.Asphalt Overlay . 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 t hrough the geotextile causing construction problems before the overlay is placed, the affected areas shall be blotted by spreading
607.05 Method of Measurement.
sand or hot -mix. To avoid movement or damage to the geotextile membrane, turning of the paver and other vehicles shall be gra dual and kept to a minimum.
f.Seal Coats . 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 pneumatic ally rolled so as to embed the geotextile tightly into the sealant.
607.05 Method 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}.
607.06 Basis of Payment.
a.General . 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.
b.Payment will be made under Item No .: 607-D Paving Geotextile - per square yard {square meter} 607-E Asphalt Sealant - per gallon {liter} SECTION 608 GEOTEXTILES IN SEPARATION APPLICATIONS
608.01 Description.
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 un surfaced pavement 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.
608.02 Materials.
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 manual titled "Materials, Sources, and Devices With Special Acceptance Requirements". Information concerning this list is given in Subarticle 10 6.01(f) and ALDOT -355.
608.03 Construction 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 top soil 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.
608.04 Installation.
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:
Source: Alabama Standard Specifications for Highway Construction, 2022 Edition. Pages 483–484 of 934.