Art. 351.01 Aggregate Base Course SECTION 351. AGGREGATE BASE COURSE
351.01 Description. The base course shall consist of furnishing one or more
courses of aggregate on a prepared subgrade or subbase.
351.02 Materials. Materials shall be according to the following.
Item Article/Section
a.Coarse Aggregate .............................................................................. 1004.04
351.03 Equipment. Equipment shall be according to the following.
Item Article/Section
a.Tamping Rollers ................................................................................. 1101.01
b.Pneumatic-Tired Rollers .................................................................... 1101.01
c.Steel Wheel Rollers (Note 1) ......................................................... 1101.01(e)
d.Aggregate Spreaders ......................................................................... 1102.04
e.Vibratory Machine (Note 2) Note 1. Three-wheel or tandem rollers shall weigh from 6 to 10 tons (5.5 to 9 metric tons) and shall weigh not less than 200 lb/in. (35 N/mm) nor more than 325 lb/in. (57 N/mm) of width of the roller. Note 2. The vibratory machine shall meet the approval of the Engineer. CONSTRUCTION REQUIREMENTS
351.04 Subgrade. The subgrade shall be prepared according to Section 301,
351.05 Base Course. The aggregate shall be uniform in gradation. Wetting
the aggregate in cars, bins, stockpiles, or trucks will not be permitted. The base course shall be constructed in lifts not more than 4 in. (100 mm) thick when compacted, except that if tests indicate that the desired results are being obtained, the compacted thickness of any lift may be increased to a maximum of 8 in. (200 mm). The aggregate shall be deposited full-lane width, directly on the prepared subgrade or on the preceding lift of compacted aggregate with a spreader. When placed, it shall be free from segregation and shall require minimum blading or manipulation. Immediately after the material has been placed, it shall be compacted with a tamping roller, or with a pneumatic-tired roller, or with a vibratory machine, or with a combination of any of the three. The top lift shall be given a final rolling with a steel wheel roller. The manner of compaction shall be approved by the Engineer. If any subgrade material is worked into the base material during the compacting or finishing operations, all granular material within the affected area shall be removed and replaced with new aggregate. The Engineer may restrict hauling over the completed or partially completed work after inclement weather or at any time when the subgrade is soft and there is a tendency for the subgrade material to work into the base material. Aggregate Base Course Art. 351.07 Specific requirements for Type A and Type B aggregate base course shall be as follows.
a.Type A. The aggregate shall have a bearing ratio of not less than 80, except that if the aggregate used is crushed gravel, crushed stone, crushed concrete, or crushed slag, the bearing ratio will not be required. The bearing ratio will be determined according to the Standard methods adopted by the Department. A sample of the aggregate to be used shall be submitted to the Engineer at least 15 days prior to starting construction. The sample so submitted will be tested by the Department for acceptance. Before the aggregate is deposited on the subgrade, it shall contain the amount of moisture required for compaction. The amount of moisture required shall be that determined by the Engineer for the material and compaction methods being used. The water and aggregate shall be mixed through a controlled aggregate mixing system. The system shall consist of a mechanical mixing device, and aggregate and water measuring devices, meeting the approval of the Engineer. The granular material shall be compacted to not less than 100 percent of the standard laboratory density. The standard laboratory density shall be the maximum dry density determined according to Illinois Modified AASHTO T 99 (Method C). A coarse particle correction according Illinois Modified AASHTO T 99 (Annex A1) shall be used. The dry density of the compacted base course, will be determined by the Engineer at regular intervals according to Illinois Modified AASHTO T 191, Illinois Modified AASHTO T 310 (Direct Transmission Density/Backscatter Moisture), or by other methods approved by the Engineer. If these tests indicate that the base course does not comply with the density requirements, additional wetting, if necessary, and rolling will be required until the density is obtained. Moisture shall be added to the material during compaction only when it is necessary to increase the percentage of moisture to obtain the required density.
b.Type B. The moisture content shall be sufficient to prevent segregation of the aggregate. Water shall be added as required by the Engineer to obtain compaction satisfactory to the Engineer.
351.06 Tolerance in Thickness. The base course shall be constructed to the
thickness shown on the plans. Thickness determinations will be made at such points as the Engineer may select. When the constructed thickness is less than 90 percent of the specified thickness shown on the plans, aggregate shall be added to obtain the required specified thickness.
351.07 At Bridges, Railroad Grade Crossings, and Existing Pavement.
The base course adjacent to bridges, railroad grade crossings, and existing Art. 351.07 Aggregate Base Course pavement shall be 3 in. (75 mm) (compacted) greater in depth than the typical section, with the surface at the established grade. The width at bridges and railroad grade crossings shall be the same as the typical section. At existing pavement, the width shall be as shown on the plans or as directed by the Engineer. This 3 in. (75 mm) increase in depth shall be made at a uniform rate in a distance of 50 ft (15 m). The cost of excavation in this transition shall be considered as included in the cost of the base course.
351.08 At Side Roads, Entrances, and Mailboxes. The material used at
side roads, entrances, and mailbox turnouts shall be the same as that used to construct the base course. After the shoulders have been completed, the subgrade shall be excavated and the bottom of the excavation shall be compacted in a manner approved by the Engineer. The earth excavated in preparing the subgrade shall be disposed of within the right-of-way, as directed by the Engineer, within a distance of 1000 ft (300 m) from the place of excavation. The excavation, preparation of subgrade and disposal of surplus excavation shall be considered as included in the cost of the base course.
351.09 Shaping, Trimming, Finishing, and Opening to Traffic. All shaping,
trimming, and finishing shall be according to Section 212. The road shall be opened to traffic according to Article 701.17(b)(1).
351.10 Maintaining. The Contractor shall maintain the base course until the
entire section is accepted. In no case shall the maintenance period be less than ten days for any portion of the road. In lieu of the above specified minimum ten day maintenance period, the Contractor, at his/her option, may elect to proof roll the completed aggregate base course. The test vehicle for proof rolling shall consist of a tandem axle truck loaded to a minimum gross weight of 40,000 lb (18,100 kg). Proof rolling shall consist of 40 passes in each lane of the completed aggregate base course. Any failures in the base that occur during the proof rolling shall be immediately repaired and shall be subjected to an additional five passes of the test vehicle after the initial 40 passes are completed. This process shall be repeated, if necessary, until all failed areas pass the proof rolling.
351.11 Method of Measurement. Aggregate used for base course will be
measured for payment in tons (metric tons), cubic yards (cubic meters), or square yards (square meters) of the thickness specified. Aggregate used for maintenance will be measured for payment in tons (metric tons). The unit of measurement will be shown on the plans. Water required to be added for compaction on the grade will not be measured for payment, but shall be considered as included in the cost of the item of work being constructed. The requirements for the use of contract quantities and measured quantities shall be according to Articles 311.08(a) and 311.08(b), respectively. Soil-Cement Base Course Art. 352.03
351.12 Basis of Payment. This work will be paid for at the contract unit price
per ton (metric ton), or cubic yard (cubic meter), for AGGREGATE BASE COURSE, TYPE A, or AGGREGATE BASE COURSE, TYPE B, or at the contract unit price per square yard (square meter) for AGGREGATE BASE COURSE, TYPE A or AGGREGATE BASE COURSE, TYPE B, of the thickness specified. Additional aggregate required for maintenance will be paid for at the contract unit price per ton (metric ton) for AGGREGATE BASE COURSE, TYPE A or AGGREGATE BASE COURSE, TYPE B. Except as specified above for the additional aggregate required for maintenance, the work of maintaining or proof rolling the completed aggregate base will not be paid for separately, but shall be considered as included in the unit prices bid for the construction items involved, and no additional compensation will be allowed. SECTION 352. SOIL-CEMENT BASE COURSE
352.01 Description. This work shall consist of constructing a soil-cement
base course composed of soil, portland cement, and water.
352.02 Materials. Materials shall be according to the following.
Item Article/Section
a.Portland Cement (Notes 1 & 2) ............................................................... 1001
b.Soil for Soil-Cement Base Course ..................................................... 1009.03
c.Water ...................................................................................................... 1002
d.Bituminous Materials (Note 3) ................................................................ 1032 Note 1. Bulk cement may be used for the traveling mixing plant method if the equipment for handling, weighing, and spreading the cement is approved by the Engineer. Note 2. Either Type I or Type IA portland cement shall be used. Note 3. The bituminous materials used for curing shall be emulsified asphalt RS-2, CRS-2, HFE 90, or HFE 150; rapid curing liquid asphalt RC-70; or medium curing liquid asphalt MC-70 or MC-250.
352.03 Equipment. Equipment shall be according to the following.
Item Article/Section
a.Pneumatic-Tired Rollers .................................................................... 1101.01
b.Tamping Rollers (Note 1) ................................................................... 1101.01
c.Steel Wheel Rollers (Note 2) ............................................................. 1101.01
d.Traveling Mixing Plant (Note 3) ......................................................... 1101.07 Note 1. The tampers shall be long enough to penetrate within 1 in. (25 mm) of the subgrade on the initial rolling.
Referenced in this section
AGGREGATE BASE COURSE in other states
Get an email when 351 changes
Illinois revises spec sections through supplementals and new editions. We check this one every week and email you the day it changes. Free, no account.
Source: Illinois Standard Specifications for Road and Bridge Construction, 2022 Edition. Pages 179–182 of 1,217. View official source ↗