3-19 Section 305. HMA Base Crushing and Shaping
305.01 Description
This work consists of constructing an aggregate base from existing flexible pavement.
305.02 Materials
Provide material in accordance with the following section: Dense-Graded Aggregate 21A, 21AA, 22A ........................................... 902
305.03 Construction .
Crush and shape HMA to the depth and width shown on the plans. The plans will also show construction staging and shoulder treatment. Obtain the Engineer’s approval for the initial surfacing course HMA mix design before crushing begins.
A.Equipment . Provide a self -propelled rotary reduction crushing machine capable of crushing the pavement to the size required by the contract and mixing the crushed material with the underlying aggregat e base to the required depth. Use a water sprinkling system to suppress dust generated by the pavement crushing operations. Provide final grading equipment that includes automatic cross slope and crown control. If no plan grades are provided, provide an automated system for referencing and averaging the existing surface for longitudinal control.
B.Crushing and Shaping . Unless otherwise approved by the Engineer, crush, shape, compact , and grade the first side of the roadway to the referenced grade prior to crushing and shaping the second side. Reference the longitudinal crushed grade from the existing pavement surface or the new HMA pavement surface for the second side. The Contractor may blade the existing shoulder asphalt or seal coat material onto the mainline pavement before crushing. Uniformly crush existing asphalt pavement, including 1 to 2 inches of the aggregate base to the required width and depth. Ensure that 95% of the crush ed material has a maximum particle size of 1½ inches, and the remaining 5% contains no particles larger than 4 inches. Uniformly spread and compact the crushed material to the dimensions shown on the plans. Use salvaged crushed material, if available, or dense-graded aggregate to add material to attain the plan grade or cross MDOT Standard Specifications for Construction Section 305 3-20 section. Spread added aggregate uniformly before crushing or plac ing aggregate on the crushed surface and remix to the full crushed depth.
C.Compacting and Grading . Compact the crushed m aterial to at least 98 % of the maximum unit weight. The maximum unit weight is to be determined using a representative sample of material that has a moisture content short of saturation and a maximum top size of 1 inch. Repair base destabilized by overwatering or non- uniform water application, damaged by Contractor operations, or from maintaining traffic at no additional cost to the Department.
D.Surplus Crushed Material. The Contractor may use surplus crushed material as aggregate base or aggregate shoulder.
E.Weather Limitations. Do not crush HMA pavement if anticipated precipitation may destabilize the prepared base. Crush and shape HMA base in accordance with the weather limitations specified in section 501.
F.Acceptance Criteria. The Engineer will inspect crushing and shaping work and base acceptance on all of the following criteria:
1.Crushed material meets particle size requirements ;
2.After final grading, the surface does not vary by more than ½ inch when tested with a 10-foot straightedge;
3.Immediate ly before paving, undulations or variations are corrected to meet the criteria in subsection 305.03.B and subsection 305.03.C ; and
4.Required density is maintained until the HMA surface material application.
305.04 Measurement and Payment
Pay Item Pay Unit HMA Base Crushing and Shaping ................................................. Square Yard Salv Crushed Material, LM .............................................................. Cubic Yard Material, Surplus and Unsuitable, Rem, LM .................................... Cubic Yard
A.HMA Base Crushing and Shaping . The Engineer will base payment for HMA Base Crushing and Shaping on the width of the proposed HMA surface, in accordance with subsection 109.01.A, unless shown otherwise on the p lans, regardless of any variation in depth. The unit price for HMA Base Crushing and Shaping includes the cost of water to obtain the required density, and scarifying, crushing, grading, shaping, rolling, and compacting existing HMA. MDOT Standard Specifications for Construction Section 305 3-21 B. Salv Crushed Material, LM . The Department will pay for Salv Crushed Material, LM for use in other items of work only if surplus crushed material requires loading and hauling. The Engineer will measure, and the Department will pay for , surplus material that is loaded and hauled from locations on the project to attain the plan grade or cross section, in the final location as Salv Crushed Material, LM or as shoulder or approach in accordance with subsectio n 307.04.
C.Material, Surplus and Unsuitable, Rem, LM. The Department will pay for Material, Surplus and Unsuitable, Rem, LM only if the Contractor removes material from the project site and disposes of it in accordance with subsection 205.03.P.
D.Trenching. The Department will pay separately for Trenching in accordance with subsection 307.04.
E.Aggregate. The Department will pay separately for additional aggregate as Aggregate Base in accordance with subsection 302.04. If Aggregate Base is not included in the contract, the Department will pay for additional aggregate as extra work.
Source: Michigan Standard Specifications for Construction, 2020 Edition. Pages 194–196 of 1,146.