307Permeable Bases

307.01 DESCRIPTION. Construct a permeable asphalt base or

permeable concrete base on a prepared subgrade in accordance with these specifications and in conformity with the lines, grades, thicknesses, and typical sections shown on the plans or as directed. When including a permeable base in the contract, furnish either a permeable asphalt base or a permeable concrete base unless otherwise specified. Use the same type of base throughout the project unless otherwise specified on the plans or approved in writing. The permeable asphalt base shall consist of a mixture of aggregate, polymer modified asphalt cement, and approved anti-strip additive. The permeable concrete base shall consist of a mixture of aggregate, portland cement, admixtures, and water.

307.02 MATERIALS. Materials shall comply with the following

requirements.

307.02.1 Aggregates: The aggregates for both the permeable

asphalt base and the permeable concrete base shall be 100 percent crushed stone conforming to the requirements of 1003.03.4.

307.02.2 Asphalt: The asphalt for asphalt treated permeable base

shall be an approved polymer modified asphalt cement, or, complying with Section 1002. The percentage of asphalt cement shall be 2.0 percent to 4.0 percent by weight of the total mixture. Asphalt cement content and mixing process shall be such that all aggregates are visibly coated. The mixture shall retain 90 percent coating when tested in accordance with DOTD TR 317. Submit a job mix formula for approval in accordance with Section 502.

307.02.3 Anti-Strip Additive: Use an Approved Materials List anti-

strip additive complying with 1002.02.1 for the permeable asphalt base. Add the anti-strip additive at the minimum rate of 0.5 percent by weight of asphalt and thoroughly mix with the asphalt cement at the plant. Additional anti-strip additive may be up to 1.2 percent by weight. The proposed job mix formula shall indicate a single anti-strip additive rate, which is 0.1 percent greater than the percentage that will yield a minimum of 90 percent coating when tested in accordance with DOTD TR 317. The approved range shall be 0.2 percent by weight of asphalt, with the lower limit being the quantity determined in accordance with DOTD TR 317 and the maximum limit not to exceed 1.2 percent by weight of asphalt.

307.02.4 Permeable Portland Cement Concrete: Use a Type I

portland cement complying with Section 1001 for permeable concrete base. Provide a minimum cement content of 235 pounds of portland cement per cubic yard of concrete. The water cement ratio of the mixture shall be not more than 0.37. Submit a mix design for approval in accordance with Section 901.

307.02.5 Admixtures: Admixtures for the permeable concrete base

shall be from the Approved Materials List complying with 1011.02. The rate shall be as indicated in the Approved Materials List.

307.03 Construction

307.03.1 Permeable Asphalt Base: Place the permeable asphalt

base in accordance with Section 502. Compact with a minimum of three passes of a 5- to 10-ton smooth steel-wheel roller conforming to Section 503 until no further displacement is noted. Place permeable asphalt base at a temperature between 200°F to 260°F when measured in the hopper of the paving machine. Begin compaction when the temperature of the permeable asphalt base has cooled to approximately 160°F and complete before the temperature falls below 100°F.

307.03.2 Permeable Concrete Base: Place the permeable

concrete base by slip forming in accordance with Section 601 or by an asphalt concrete paver in accordance with Section 503. Compact by using vibrating screeds or plates as directed. No construction joints will be required. Immediately after concrete placement, cure the permeable concrete base by covering the entire surface and exposed edges with white pigmented curing compound in accordance with 601.03.10.

307.04 PROTECTION. Protect the permeable asphalt and permeable

concrete bases from severe weather conditions and contamination by dust, dirt, mud, or other fine grained material. Protect by an approved method from the time of placement until placement of the following pavement layer. Do not permit traffic on the permeable asphalt base or permeable concrete base. Equipment required to place the pavement will be allowed, provided that it enters and exits as near as possible to the paving operation. Repair all damage to the permeable bases caused by the contractor’s equipment at no direct pay. Remove and replace at no direct pay all portions of the permeable bases that become contaminated to the extent that drainage is reduced or inhibited. Cover the permeable bases with the pavement within 15 working days after placement.

307.05 TOLERANCES. The finished surface of permeable asphalt base

and permeable concrete base shall be uniform and shall not vary at any point more than 0.05 foot above or below the established grade. The cross- slope shall not vary by more than ±0.003 foot/foot. Permeable asphalt base or permeable concrete base with a surface higher than 0.05 foot above the established grade shall be removed and replaced with permeable base which complies with these specifications or, when permitted, the high spots may be removed to within specified tolerance by any method that does not produce contaminating fines nor damage the base to remain in place. Grinding will not be permitted. Permeable base with a surface lower than 0.05 foot below the established grade shall be removed and replaced with permeable base which complies with these specifications. When permitted, low areas not exceeding 1 inch shall be filled with subsequent roadway pavement at the time and in the same operation in which the pavement is placed at no direct pay.

307.06 TESTING. Before placing surfacing, core the permeable bases at

the locations determined by the engineer in accordance with DOTD TR 602. All cores shall be taken in the presence of and given to the engineer for verification of base thickness.

307.07 MEASUREMENT. Permeable base will be measured by the

square yard from the design quantities shown on the plans. Design quantities will be adjusted if the engineer makes changes to adjust to field conditions, plan errors are proven, or design changes are necessary. Determine design areas using the horizontal dimensions shown on the plans, the length being along the centerline of the base.

307.08 PAYMENT. Payment for permeable base will be made at the

contract unit price per square yard, which shall include all materials, tools, incidentals and the performance of work necessary to complete these items. Payment will be made under: Item No. Pay Item Pay Unit 307-01 Permeable Base ___ in Thick Square Yard Section 308 Vacant