CATEGORY 500 PAVING SECTION 501 — UNTREATED AGGREGATE BASE COURSES
501.01 Description
Construct base courses using one of the following:
a.Graded aggregate without a stabilizing agent.
b.Recycled Concrete Graded Aggregate
501.02 Materials
Graded Aggregate for Base Course 901.01 Recycled Concrete, Graded Aggregate 900.03.02 Production Plant Section 915 Water 921.01 Moisture and Dust Control Agents 921.02
501.03 Construction
At least 30 days prior to the start of constructing the base course, submit the proposed plants, equipment, and material sources for approval. Protect the subgrade and base against damage from all causes. Repair or replace damaged areas. Unless protected by a concrete traffic barrier, limit excavation for widening to an area that can be wedged the same day using graded aggregate base. Refer to Standard No. 104.01-28 for the area to be wedged. Maintain the temporary graded aggregate base wedge with a 4:1 or flatter fill slope when there is no barrier. Compact the material as indicated elsewhere in this specification. Leave the graded aggregate base wedge in place until placement of the next layer.
501.03.01 Equipment. All equipment, including the production plant and on-site equipment, is
subject to approval. Have the plant ready for inspection at least 48 hours prior to the start of construction operations. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS
501.03.02 Weather Restrictions.
a.Temperature and Surface Conditions. Place graded aggregate base when the ambient air and surface temperatures are at least 32 F and rising. Do not ship the material from plant at freezing temperature (32 F) and below. Do not place material on a frozen subgrade.
b.Precipitation. Do not place material during precipitation. When precipitation has occurred during the previous 24 hours, the Engineer will determine if the subgrade is sufficiently dry. If precipitation occurs during placement, placement of material enroute from the plant to the job site shall be at the Contractor’s risk.
501.03.03 Subgrade Preparation. Before beginning base course construction, complete the
approved subgrade to final line and grade at least 500 ft ahead. Construct the foundation as specified in Section 204 and Section 208. If traffic, including construction equipment, is allowed to use the subgrade foundation or preceding layer, distribute the loading over the entire width of the course to obtain uniform and thorough compaction. Remove rutting by reshaping and recompacting the affected area as specified in Section 204.
501.03.04 Transportation. Handle and transport mixed base materials in a manner that
minimizes segregation and loss of moisture. Cover all loads in accordance with State laws unless hauling is off road and is approved. Do not haul over areas that have met the grade and compaction requirements until its ready for the next layer.
501.03.05 Stockpiling. Stockpiling of the untreated aggregate base is prohibited, unless approved
by the Engineer. In addition, a Quality Control Plan to stockpile the untreated aggregate base material must be submitted by the contractor and be approved by the Soils and Aggregate Technology Division. The Quality control plan should include how the contractor will ensure the correct moisture content, minimize segregation, and how long they will be stockpiling the untreated aggregate base.
501.03.06 Spreading. Spread the base material uniformly and in layers of approximately equal
thickness, to provide the specified planned depth. Avoid segregation of coarse and fine particles. Build shoulders or berms at least 2 ft wide on each side of the base and to the top elevation of each uncompacted layer, except when placing the base against concrete curbs or gutters.
501.03.07 Grade or Finished Surface Control. Shape the surface of the base material to the
specified line, grade, and cross section. Set grades longitudinally and transversely with fixed controls spaced no greater than 25 ft. Compact and smooth the surface over its full width using a smooth faced steel-wheeled roller, or if rolling is not feasible, by mechanical tampers and vibratory compactors, as approved. Maintain the finished grade within 1/2 in. from the established grade.
501.03.08 Compaction. Immediately after placement, compact the material to the required
density. During compaction operations, maintain the moisture content of the material to within 2 percent of optimum moisture. Determine the optimum moisture content and maximum dry density as follows: 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS price per square yard or per ton as specified. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS
a.Graded Aggregate Base according to T 180 with oversize particle correction applied.
b.Compact graded aggregate base to at least 97 percent of the maximum dry density. Measure in place density according to MSMT 350 or MSMT 352 . Begin compaction operations, except on superelevated curves, at the sides of the course. Overlap the shoulder or berm at least 1 ft and progress toward the center parallel to the center line of the roadway. On superelevated curves, begin compaction at the low side and progress toward the high side. Continue compaction operations until all compaction marks are removed.
501.03.09 Moisture and Dust Control Agents. When specified, add calcium or magnesium
chloride at the plant or apply it to the surface of the material at the project site. Apply calcium chloride at the rate of 1 lb./yd
2.Apply magnesium chloride at the rate of 1 lb./yd2 or as a solution at the rate of 1/2 gal/yd2.
501.03.10 Maintenance. During construction and after completion of the base course, maintain
the grades and protect the base from damage until the next layer is placed. When unacceptable work cannot be repaired, replace it for the full depth of the base.
501.04 Measurement and Payment
The payment will be full compensation for all aggregate, furnishing, hauling, placing, and for all material, labor, equipment, tools, and incidentals necessary to complete the work.
501.04.01 Graded Aggregate Base Course will be measured and paid for at the Contract unit price
per square yard for the specified thickness. Surface area measurements will be based on the specified width of the base and the actual length measured along the center line of the base surface. The temporary graded aggregate base wedge constructed in conformance with Standard No. MD 104.01-28, maintaining the 4:1 or flatter slope, compaction, and removal of the material, will not be measured but the cost will be incidental to the Graded Aggregate Base Course.
501.04.02 Calcium or Magnesium Chloride will be measured and paid for at the Contract unit
502 — CEMENT TREATED BASE COURSE AND CEMENT MODIFIED SUBGRADE CATEGORY 500 PAVING SECTION 502 — CEMENT TREATED BASE COURSE AND CEMENT MODIFIED SUBGRADE
502.01 Description
Construct Cement Treated Base (CTB) course or Cement Modified Subgrade (CMS) using a combination of soil or graded aggregate base and Portland cement, uniformly mixed, moistened, compacted, shaped and sealed to the required depth and widths specified. Mix the CTB or CMS in place.
502.02 Materials
Graded Aggregate Base 901.01 Portland Cement 902.03 Emulsified Asphalts 904.03 Select or Capping Borrow for CTB 916.01 Soil for CMS 916.01 Water 921.01
502.03 Construction
Submit the equipment and material sources for approval at least 30 days prior to the start of construction of the CTB or CMS. For mix design approval time frame, refer to 502.03.04. Protect the subgrade and/or base against damage from all causes.
502.03.01 Equipment.
Reclaimer. A self-propelled rotary machine capable of cutting through material to depths equal to or greater than the planned lift thickness as specified in Contract Documents. The reclaimer shall be capable of pulverizing the material at a minimum width of 8 ft and mix water, dry additives, and the pulverized unbound materials into a homogenous mixture to the specified depth. The reclaimer shall be equipped with a computerized integral liquid proportioning system capable of regulating and monitoring the water application rate relative to depth of cut, width of cut, and speed. The reclaimer shall have a mounted spray bar to allow the water to be injected directly into the cutting drum/mixing chamber. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS
Source: Maryland Standard Specifications for Construction and Materials, 2025 Edition. Pages 619–621 of 1,113.