Art. 312.01 Stabilized Subbase SECTION 312. STABILIZED SUBBASE
312.01 Description. This work shall consist of furnishing, placing, and
compacting a stabilized subbase composed of hot-mix asphalt (HMA) or cement aggregate mixture II (CAM II) on a prepared subgrade.
312.02 General. When a particular material is not specified, the Contractor
shall have the option of selecting the type of stabilized subbase. Prior to placing the stabilized subbase, the subgrade shall be prepared according to Section 301, except Articles 301.05 and 301.06 will not apply, or according to Section 302 when soil modification is used. Stabilized subbase shall not be placed on frozen or muddy subgrade. The amount of stabilized subbase constructed will be limited to that which can be surfaced during the current construction season. The Contractor shall have at all times one day’s production of stabilized subbase prepared ahead of the paving location. HOT-MIX ASPHALT
312.03 Materials. Materials shall be according to Section 1030.
312.04 Equipment. Equipment shall be according to the following.
Item Article/Section
a.Steel Wheel Rollers .................................................................................. 406
b.Self-Propelled Pneumatic-Tired Roller ...................................................... 406
c.Vibratory Roller ......................................................................................... 406
d.Spreading and Finishing Machine ...................................................... 1102.03
e.Trench Roller ..................................................................................... 1101.01
f.Subgrade Machine ............................................................................. 1103.09 CONSTRUCTION REQUIREMENTS
312.05 Placing and Compacting. Prior to placing the initial lift of the HMA
stabilized subbase, trimmings and other loose material shall be removed from the prepared subgrade. HMA stabilized subbase shall be placed according to
Article 406 — 06 and compacted according to Article 406.07. The maximum compacted
thickness of each lift shall be 4 in. (100 mm), provided the required density is obtained.
312.06 Finishing. The compacted subbase shall meet the lines and grades
shown on the plans. Stabilized Subbase Art. 312.09 CEMENT AGGREGATE MIXTURE II
312.07 Materials. Materials shall be according to the following.
Item Article/Section
a.Coarse Aggregate (Note 1) .................................................. 1004.01-1004.02
b.Fine Aggregate (Note 2) ...................................................... 1003.01-1003.02
c.Portland Cement ..................................................................................... 1001
d.Water ...................................................................................................... 1002
e.Concrete Curing Materials (Note 3) ........................................................ 1022
f.Emulsified Asphalts (Note 4) ............................................................. 1032.06
g.Concrete Admixtures .............................................................................. 1021
h.Fly Ash .................................................................................................... 1010 Note 1. Coarse aggregate shall be gradation CA 6, CA 7, CA 9, CA 10, or CA 11, Class D quality or better. Article 1020.05(d) shall apply. Note 2. Fine aggregate shall be FA 1 or FA 2. Article 1020.05(d) shall apply. Note 3. Membrane Curing Compound shall be Type Ill. Note 4. RS-2 or CRS-2 shall be used.
312.08 Equipment. Equipment shall be according to Article 420.03 and
Article 1101 — 09.
CONSTRUCTION REQUIREMENTS
312.09 Proportioning and Mix Design. At least 60 days prior to start of
placing CAM II, the Contractor shall submit samples of materials to be used in the work for proportioning and testing. The mixture shall contain a minimum of 200 lb (120 kg) of cement per cubic yard (cubic meter). Portland cement may be replaced with fly ash according to Article 1020.05(c)(1), however the minimum portland cement content in the mixture shall be 170 lbs/cu yd (101 kg/cu m). Blends of coarse and fine aggregates will be permitted, provided the volume of fine aggregate does not exceed the volume of coarse aggregate. The Engineer will determine the proportions of materials for the mixture according to the “Portland Cement Concrete Level III Technician Course” manual. However, the Contractor may substitute their own mix design. Article 1020.05(a) shall apply and a Level III PCC Technician shall develop the mix design. Air-entraining admixture and water-reducing admixture shall be added to the CAM II mixture according to Article 1020.05(b). The final CAM II mix design shall be based upon trial mixes. The mixture shall have a relative durability of 80 percent at 100 cycles when tested according to Illinois Modified AASHTO T 161. The percentage of air-entrainment shall not be less than seven percent nor more than ten percent. Air content shall be determined according Art. 312.09 Stabilized Subbase to Article 1020.08. The mix shall have a slump of 1 to 3 in. (25 to 75 mm). Slump shall be determined according to Article 1020.07.
312.10 Mixing, Placing, Strike Off, Consolidation, and Finishing. CAM II
shall be mixed according to Article 1020.11(c). CAM II shall be placed when the air temperature in the shade is a minimum of 40 F (4 C). Forms and form setting shall be according to Article 420.06. Form removal shall be according to Article 420.11. Placing CAM II shall be according to the requirements of Article 420.07. Strike off, consolidation, and finishing shall be according to Articles 420.09(a)(1) or 420.09(a)(2). Screeds may be used without the restrictions indicated in
Article 1103 — 13(b)(2). Article 420.09(a)(3) shall apply in the event of breakdown of
mechanical equipment. Slipform paving methods may be used, provided the requirements of Article 420.14(c) are met.
312.11 Longitudinal Floating and Straightedging. After the CAM II
subbase has been struck off and consolidated, and finished, longitudinal floating shall be performed according to Articles 420.09 (b)(1) or 420.09(b)(2). Straightedging shall be performed according to Article 420.09(c). The surface including the paver trackline shall not have variations of more than 3/16 in. (5 mm) in 10 ft (3 m) measured parallel with the centerline of pavement. The finished surface shall not be textured but shall be closed. CAM II samples shall be furnished by the Contractor and shall be taken from unconsolidated material on grade to determine the slump and air content. Testing shall be according to Article 1020.07 and 1020.08.
312.12 Curing. Immediately after the finishing operations have been
completed, the surface shall be cured and protected for three days according to Articles 1020.13(a)(4) and 1020.13(c). All areas of membrane curing compound damaged within the required three day curing period shall be repaired by applying another coat.
312.13 Protection. Minor construction traffic will not be permitted on the
completed subbase for at least three days, and no batch or haul trucks will be permitted on the completed subbase unless approved by the Engineer. STABILIZED SUBBASE – ALL TYPES
312.14 Tolerance in Thickness. The stabilized subbase shall be constructed
to the thickness shown on the plans. Determination of thickness will be based on measurements taken at cored holes or at the edge of the subbase. When the constructed thickness is less than 90 percent of the specified thickness, the stabilized subbase shall be corrected. The method of correction shall be removal and replacement, except as follows.
a.HMA Stabilized Subbase. When HMA stabilized subbase is used, the deficient thickness may be corrected by placing additional HMA, provided the lift thickness requirements of Article 312.05 are met. Lime Stabilized Soil Mixture Art. 350.03
b.Portland Cement Concrete Pavement. When portland cement concrete pavement is to be constructed, the deficient thickness may be corrected by increasing the thickness of the pavement. This method of correction will not be allowed for continuously reinforced concrete pavement. The surface elevation of the completed stabilized subbase shall not exceed by more than 3/16 in. (5 mm) the surface elevation shown on the plans or authorized by the Engineer.
312.15 Method of Measurement. This work will be measured for payment as
follows.
a.Contract Quantities. The requirements for the use of Contract Quantities shall conform to Article 202.07(a).
b.Measured Quantities. This work will be measured for payment in place and the area computed in square yards (square meters). The width measured will be at the top of the final lift of the completed work as shown on the plans or as directed by the Engineer.
312.16 Basis of Payment. When the Contractor has the option of which
material type to use, this work will be paid for at the contract unit price per square yard (square meter) for STABILIZED SUBBASE of the thickness specified. When the Department requires a specific material type be used, this work will be paid for at the contract unit price per square yard (square meter) for STABILIZED SUBBASE – HMA or STABILIZED SUBBASE – CAM II of the thickness specified. BASE COURSE SECTION 350. LIME STABILIZED SOIL MIXTURE
350.01 Description. This work shall consist of the construction of a lime
stabilized soil mixture composed of soil, lime, and water which shall be considered as base course. This work shall be according to Section 310, except the lime stabilized soil mixture shall provide a minimum laboratory average compressive strength of 150 psi (1030 kPa), according to AASHTO T 208.
350.02 Method of Measurement. This work will be measured for payment
according to Article 310.14.
350.03 Basis of Payment. This work will be paid for according to
Article 310 — 15.
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Source: Illinois Standard Specifications for Road and Bridge Construction, 2022 Edition. Pages 175–178 of 1,217. View official source ↗