The Table of Contents for this section is available.
The work covered by this section consists of constructing and curing a cement treated base composed of aggregate, cement and water, mixed on the roadway and compacted in accordance with these specifications and in conformance to the lines, grades, depths, and typical sections shown on the plans or established by the Engineer.
All materials shall meet the requirements of Division 10 shown below:
Portland cement, Type I Article 1024-1
Water Article 1024-4
Aggregate shall meet the requirements of Article 10101 and Article 10102 or Article 10103, except that the gradation shall meet the requirements of Table 10104.
Cement treated base shall not be constructed from November 1 to March 31 inclusive. Base shall not be constructed when the air temperature is less than 40F. in the shade nor when conditions indicate that the temperature may fall below 40F within 24 hours. No frozen materials shall be incorporated into the mixture and no material shall be placed on frozen subgrade. The base shall be protected from freezing for a period of 7 days after completion. Work shall be performed only during daylight hours unless otherwise provided by the provisions of the traffic control plans.
No cement treated base shall be placed that will not be covered with pavement by December 1 of that year. Failure of the Contractor to cover the cement treated base as required above will result in the Engineer notifying the Contractor in writing to cover the cement treated base with a sand seal. The sand seal shall be applied in accordance with the requirements of Section 660 except that Articles 6603, 66011, and 66012 will not apply. This work shall be performed by the Contractor at no cost to the Department. In the event the Contractor fails to apply the sand seal within 72 hours after receipt of such notice, the Engineer may proceed to have the work performed with other forces and equipment. The cost of such work performed by other forces will be deducted from monies due or to become due the Contractor. The application of the sand seal by the Contractor or other forces will in no way relieve the Contractor of the responsibility to maintain or repair the damaged base, no matter what the cause of damage, at no cost to the Department.
Any combination of machines or equipment that are in good, safe working condition and that will produce results meeting these requirements may be used upon approval of the Engineer. Equipment necessary for proper prosecution of the work shall be on the project and approved by the Engineer prior to its use in the construction operations. A cement spreader shall be used which has an adjustable rate of flow and the capability of spreading the required amount of cement in one pass. A self-propelled rotary mixer will be required for mixing. All mixing equipment shall be capable of mixing to a compacted depth of at least 10 inches. The machines and equipment shall be maintained in a satisfactory operating condition at all times during use. Leakage of water, oil, grease, or other objectionable materials shall be corrected promptly or the Engineer may order such equipment removed from the project and replaced with satisfactory equipment.
541-5 PREPARATION OF SUBGRADE.
The subgrade shall be prepared in accordance with Section 500. The subgrade shall be firm and able to support, without displacement, the construction equipment and the compaction operations hereinafter specified. Soft or yielding subgrade shall be corrected and made stable before construction proceeds. The subgrade shall be moistened as needed prior to spreading the base material.
The required quantity of aggregate shall be placed on the prepared subgrade in a uniform layer. Aggregate shall be spread on the subgrade in advance of the mixing operations only to the extent that processing can be completed within one week. The required quantity of cement shall then be applied in a uniform spread on the aggregate in place and immediately blended until the cement is uniformly distributed throughout the aggregate. At the time of application of the cement, the moisture content of the aggregate shall not exceed optimum moisture. Cement shall not be applied on excessively windy days and shall be applied only to such an area that all operations shall be completed on the same day during daylight hours.
The approximate cement content of the mixture shall be 4.0% based on the dry weight of the aggregate. The actual cement content will be established during construction by the Engineer.
Immediately after the aggregate and cement have been thoroughly blended, water shall be applied as needed and incorporated into the mixture. The application of the water shall be controlled so that there is no excessive concentration on or near the surface of the mixture. After the necessary water has been applied, mixing shall continue until a thorough and uniform mixture is obtained.
The moisture content at the time of final mixing and during compaction shall be maintained within a range of optimum to optimum plus 1.50% as determined by the Engineer. In no case shall the moisture content in the mix exceed the quantity that will cause the base course to become unstable during compaction or finishing operations.
The compacted thickness of any one layer of base shall not exceed 8 inches and shall not be less than 4 inches.
After spreading, the moisture content of the material shall be maintained within a range of optimum to optimum plus 1.5% moisture during compaction.
Compaction shall be accomplished by the use of approved self-propelled rollers except that a sheep-foot roller shall not be used for more that 2 passes. The base shall be compacted to a density of at least 97% of the maximum density obtained by compacting a sample of the material in accordance with AASHTO T180 as modified by the Department. Copies of these modified testing procedures are available upon request from the Materials and Tests Unit. The Engineer may, at his option, utilize nuclear methods as described in Article 52010 to determine the density of the base in lieu of the methods required above.
Final compaction, including that necessary due to correction of high or low areas, shall be completed within 3 hours after water has been added to the mixture. Any cement-aggregate mixture that has not been compacted and finished shall not remain undisturbed for more than 30 minutes. When rain causes excessive moisture, the entire section shall be reconstructed. When such reconstruction is necessary, the work of reconstruction and the cement required shall be furnished at no cost to the Department.
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. The base for large, wide areas shall be built in a series of parallel lanes of convenient length and width meeting the approval of the Engineer. Straight longitudinal joints shall be formed at the edge of each day's construction by cutting back into the completed work to form a vertical face free of loose or shattered materials. Where traffic considerations require that a longitudinal joint be exposed for an excessive length of time, the Engineer may require that it be covered with a curing seal in accordance with Section 543.
After final shaping and compacting of the base, the Engineer will check the surface of the base for conformance to the grade and typical section and determine the base thickness.
The thickness of the base shall be within a tolerance of plus or minus 1/2 inch of the base thickness required by the plans.
The maximum differential between the established grade and the base within any 100 foot section shall be 1/2 inch.
After the cement treated base has been finished as specified herein, it shall be cured in accordance with Section 543.
Completed sections of the base may be opened when necessary to lightweight local traffic, provided the base has hardened sufficiently to prevent marring or distorting of the surface, and provided the curing is not impaired. Construction equipment shall not use the base except as necessary to discharge into the spreader during paving operations.
The Contractor shall maintain the base in an acceptable condition until final acceptance of the project. Maintenance shall include immediate repair of any defects or damage that may occur. This work shall be performed by the Contractor at no cost to the Department and shall be repeated as often as may be necessary to keep the base in an acceptable condition. Repairs to the base shall be performed by replacing the base for its full depth rather than by adding a thin layer of cement stabilized material to the existing layer of base.
The quantity of base course to be paid for will be the number of square yards of base course which has been completed and accepted. In measuring this quantity, the width of the base course will be called for on the plans or as established by the Engineer measured across the top surface of the base. The length will be the actual length constructed, measured along the centerline of the surface of the base course.
The quantity of aggregate to be paid for will be the number of tons of aggregate that has been placed on the roadbed. The quantity will be measured by weighing in trucks on certified platform scales or other certified weighing devices. No deduction will be made for any moisture contained in the aggregate at the time of weighing. Measurement will not be made of any base mixture added or replaced for corrective measures during construction or for repairing damaged areas.
The quantity of portland cement to be paid for will be the number of tons of cement that has been incorporated into the mix. When bulk cement is used, the quantity will be measured by weighing in trucks on certified platform scales or other certified weighing devices. Measurement will not be made of any cement added or replaced for corrective measures during construction or for repairing damaged areas.
The quantity of base course, measured as provided in Article 54113, will be paid for at the contract unit price per square yard for "________Inch Road Mixed Cement Treated Base Course."
The quantity of aggregate, measured as provided in Article 54113, will be paid for at the contract unit price per ton for "Aggregate for Road Mixed Cement Treated Base Course."
The quantity of portland cement, measured as provided in Article 54113, will be paid for at the contract unit price per ton for "Portland Cement for Road Mixed Cement Treated Base Course."
Asphalt curing seal will be paid for as provided in Article 5436.
Blotting sand will be paid for as provided in Article 8185.
The above prices and payments will be full compensation for all work covered by this section including but not limited to the furnishing of water and aggregate; the mixing; proportioning, hauling, and spreading of the materials; furnishing portland cement at the point where it is incorporated into the mix; manipulating, compacting, and finishing the base; maintaining the base; making repairs or corrections to the base; and applying sand seal in accordance with Article 5413.
Payment will be made under:
________Inch Road Mixed Cement Treated Base Course Square Yard
Aggregate for Road Mixed Cement Treated Base Course Ton
Portland Cement for Road Mixed Cement Treated Base Course Ton