Soil-Cement Base Course Art. 352.03 165
351.12Basis 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.
352.01Description. This work shall consist of constructing a soil-cement
base course composed of soil, portland cement, and water.
352.02Materials. Materials shall be according to the following
Item Article/Section
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.
352.03Equipment. Equipment shall be according to the following
Item Article/Section
Note 1. The tampers shall be long enough to penetrate within 1 in. (25 mm) of the subgrade on the initial rolling.
Art. 352.03 Soil-Cement Base Course 166 Note 2. Steel wheel 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) width of roller.
Note 3. When more than 12,000 sq yd (10,000 sq m) of soil-cement base course are to be processed, a traveling mixing plant will be required together with any machine, or combination of machines, or equipment which will produce in one pass completed soil-cement base course meeting the requirements of these Specifications. Mixing devices approved by the Engineer may be used when less than 12,000 sq yd (10,000 sq m) of soil- cement base course are to be processed.
CONSTRUCTION REQUIREMENTS
352.04General. The soil-cement base course shall be constructed only when
the temperature of the subgrade, measured 6 in. (150 mm) below the surface, is above 50 F (10 C) and the ambient air temperature in the shade is above 45 F (7 C).
352.05Proportioning. Proportioning shall be as follows
and submitted to the Engineer at least 90 days prior to the construction of the soil-cement base course. Sample sizes shall be a minimum of 25 lb (11 kg) for the cement and 200 lb (91 kg) for the project soil(s).
determined by the Engineer prior to construction using the submitted samples. The Engineer reserves the right to make such adjustments in proportions as are considered necessary during the progress of the work.
In no case shall proportions or type of cement be changed during the progress of the work without permission from the Engineer.
352.06Preparation of Subgrade. The area to be processed shall be shaped
to the proper grade and cross section and shall be void of all vegetation and other objectionable material. In cut or at grade sections, the subgrade shall be prepared according to Articles 301.03 and 301.04; except the minimum immediate bearing value (IBV) of the soil, below the soil to be processed, shall be 3.0.
352.07Pulverizing. The soil to be processed shall be scarified and
pulverized prior to the application of the cement. Pulverizing shall be continued until the soil meets the gradation requirement specified in Article 352.10 and the moisture content of the soil does not exceed that which will permit a uniform mixture of soil and cement.
352.08Application of Cement. The cement shall be applied uniformly on the
soil. The application of cement shall be limited to such an area that all the operations specified in Articles 352.08 to 352.11, inclusive, will be continuous and completed during daylight hours; and the operations specified in Articles 352.09 to 352.11 inclusive, completed in six hours.
Soil-Cement Base Course Art. 352.10 167
No equipment, except that used in spreading and mixing, will be allowed to pass over the spread cement, and this equipment shall be operated in such a manner as to avoid displacement of cement.
Cement which has been damaged by hydration due to rain prior to or during the mixing operations, has been damaged while spread contrary to the above mentioned requirements, or has been displaced by the Contractor’s equipment or other traffic, shall be replaced.
352.09Dry Mixing. Dry mixing of soil and cement will be required when
mixing equipment other than a traveling mixing plant is used. Mixing shall be confined to the area and depth shown on the plans and shall be continued until the resulting mixture is homogeneous and uniform in appearance.
When any of the operations from the start of soil and cement mixing through final compaction are interrupted for more than 30 minutes for any reason, the entire thickness of the base course shall be thoroughly loosened, reprocessed, and shall be completed within the specified time limits for these operations. When the uncompacted soil-cement mixture is wet by rain so that the average moisture content exceeds the tolerance given in Article 352.10 at the time of final compaction, the portion being processed shall be reconstructed according to this Specification.
352.10Moist Mixing. Moist mixing shall be as follows
plant is not used, water shall be immediately applied uniformly and incorporated into the dry-mixed soil and cement in quantities which will produce the required moisture content for the soil-cement mixture.
Water supply and pressure distributing equipment shall be provided which will ensure the application of all water required on the section being processed within three hours. Each application or increment of water shall be at least partially incorporated into the mixture, if necessary, to avoid excessive concentration of water on and near the surface.
After the last increment of water has been added, mixing shall be continued until a uniform mixture of soil, cement, and water is obtained. Particular care shall be exercised to ensure satisfactory moisture distribution along the edges of the section and for the full depth of treatment.
When water application and moist mixing is completed, the percentage of moisture in the fraction of the mixture passing a 1 in. (25 mm) sieve, on a basis of dry weight (mass), shall be between 80 and 100 percent of the optimum moisture content for sandy soils, and between 100 and 120 percent of the optimum moisture content for silty and clayey soils. At completion of moist mixing, 100 percent of the soil shall pass a 1 in. (25 mm) sieve and at least 80 percent shall pass a No. 4 (4.75 mm) sieve, exclusive of gravel or stone retained on these sieves.
with soil and water with the traveling mixing plant. No mixing shall be done
Art. 352.10 Soil-Cement Base Course 168 below the desired depth. Mixing shall be at such rate that, or shall be repeated until, a uniform mixture of soil, cement, and water is obtained. Particular care shall be exercised to ensure a satisfactory mixture along the edges of the section and for the full depth of treatment. At the completion of the mixing operation, the moisture content and gradation of the mixture shall be as specified in Article 352.10(a).
352.11Compaction and Finishing. Compaction of the soil-cement mixture
shall be a continuation of the moist mixing operation such that the soil-cement mixture does not remain undisturbed after mixing and before compacting for more than 30 minutes. Prior to the beginning of compaction, the mixture shall be in a loose condition for its full depth and width. The mixture shall then be uniformly compacted with tamping rollers in conjunction with other compaction equipment until the specified density has been obtained. Particular care shall be exercised to ensure satisfactory density along the edges of the section and adjacent to construction joints. The type, size, number of compactors, and the rate of their operation shall be such that the section being processed can be compacted within two hours.
When initial compaction of the soil-cement mixture is nearing completion, the surface of the base course shall be shaped to the required lines, grades, and cross section, and compaction continued until the required density is obtained. If necessary to attain satisfactory surface grade, the surface shall be lightly scarified with a nail drag, spike-tooth harrow, or weeder, and reshaped. The resulting surface then shall be thoroughly rolled with a steel wheel roller, a pneumatic-tired roller, or both. The moisture content of the surface material shall be maintained at or slightly above its specified optimum during all finishing operations and until the curing material is applied.
Surface compaction and finishing shall be done in such a manner as to produce a smooth, closely knit surface, relatively free from cracks, ridges, low spots, or loose material, conforming to the crown, grades, and lines shown on the plans. When directed by the Engineer, surface finishing methods may be varied, provided a smooth, dense, uniform surface, free of surface compaction planes is produced.
The compacted soil-cement base course shall have a minimum dry density of 95 percent of the laboratory standard dry density. The in-place dry density will be determined according to Illinois Modified AASHTO T 191, or Illinois Modified AASHTO T 310 (Direct Transmission Density/Backscatter Moisture). The laboratory standard dry density will be determined according to Illinois Modified AASHTO T 134 (Method B).
Any portion of the base course that has a density less than 95 percent of the standard laboratory density shall be corrected or removed and replaced.
352.12Compressive Strength. Prior to compaction, the Engineer will obtain
random samples from the field design mixture, to be tested for the compressive strength according to Illinois Modified AASHTO T 22. The samples will be compacted according to Illinois Modified AASHTO T 134 (Method B), moist cured for seven days, and will be capped and soaked four hours immediately prior to compression testing. The compacted, cured specimens shall have a minimum seven day compressive strength of 500 psi (3500 kPa) or a specified design strength, whichever is greater.
Soil-Cement Base Course Art. 352.18 169 Any portion of the base course that has less than the required compressive strength shall be corrected or removed and replaced.
352.13Protection and Cover. After the soil-cement base course has been
finished, it shall be protected against drying for a period of seven days by applying a bituminous material. The bituminous material shall be applied as soon as possible after the completion of final rolling, but in no event shall the finished soil-cement base course remain without cover for more than 14 hours unless prolonged rain intervenes.
The bituminous material shall be applied at the rate of approximately 0.20 gal/sq yd (1 L/sq m) uniformly to the surface of the base course by a pressure distributor to give complete coverage without excessive runoff. The exact rate of application and temperature will be specified by the Engineer. If needed, water shall be applied to fill the surface voids immediately before the bituminous cover is applied. The equipment used for wetting the finished soil-cement base course with water or to apply a bituminous protective cover shall be of such limited weight that its use will not cause marring or rutting of the base course. Should it be necessary for construction equipment or other traffic to use the bituminous covered soil-cement base course before the bituminous material has hardened sufficiently to prevent pickup, sufficient sand shall be applied to prevent pickup.
352.14Construction Joints. At the end of each day’s construction, a straight
transverse construction joint shall be formed by cutting back into the completed work to form a vertical face. Damage to completed work shall be avoided. The base course shall be constructed and finished full width each day without longitudinal joints.
352.15Opening to Traffic. The base course shall be opened to traffic
according to Article 701.17(b)(2).
352.16Maintenance. The Contractor shall maintain the entire base course in
a manner satisfactory to the Engineer until the surface course has been constructed. Maintenance shall include immediate repairs of any defective or damaged portions of the base course. Repairs or replacements shall be made in such a manner as to ensure restoration of a uniform surface and durability of the portion repaired or replaced.
352.17Tolerance in Thickness. Soil-cement base course shall be
constructed to the thickness shown on the plans. Determination of base thickness will be based on thickness measurements at cored points taken at locations selected by the Engineer. Any portion of the soil-cement base course that is less than 90 percent of the specified thickness shall be removed and replaced with new material to the correct thickness.
352.18Method of Measurement. This work will be measured for payment as
follows.
shall conform to Article 202.07(a).
Art. 352.19 Portland Cement Concrete Base Course 170
place and the area computed in square yards (square meters).
payment in hundredweights (kilograms), but payment will not be made for cement in excess of 105 percent of the amount specified by the Engineer.
measured for payment according to Article 202.07(b).
for payment according to Article 204.07(b).
Engineer, will be measured for payment according to (1) and (2) above.
352.19Basis of Payment. This work will be paid for at the contract unit
prices as follows.
COURSE, of the thickness specified.
according to Article 202.08.
Article 204.08.
Engineer, will be paid for at the contract unit prices for (a) and (b) above.
SECTION 353. PORTLAND CEMENT CONCRETE BASE COURSE
353.01Description. This work shall consist of constructing a portland cement
concrete base with or without reinforcement as specified.
353.02Materials. Materials shall be according to the following
Item Article/Section
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