308—SUBBASE COURSE

308.01 Description

This work shall consist of furnishing and placing one or more courses of mineral aggregate on a prepared subgrade in accordance with the required tolerances within these specifications and in conformity with the lines, grades, typical sections, and cross sections shown on the plans or as established by the Engineer.

308.02 Materials

308.03 Procedures

Prior to placement of the subbase course, the subgrade shall be constructed in accordance with Section 304 and Section 305 as applicable. Subbase material shall be mixed in an approved central mixing plant of the pugmill or other mechanical type in accordance with Section 208.05. The Contractor shall place the mixed material on the subgrade by means of an approved aggregate spreader. The Engineer will not require the use of such spreader when the material is being applied solely for the temporary maintenance of traffic or where the width of the course shown on the plans is transitional and impracticable to place with a spreader box. The Contractor shall spread and compact the material in two or more layers of approximately equal thickness where the required thickness is more than 6 inches. The compacted thickness of any one layer shall be not more than 6 inches, however the Engineer may approve increasing the compacted depth of a single layer of the subbase course to 10 inches when vibrating or other approved types of special compacting equipment are used. Each layer of subbase course shall be compacted at optimum moisture, within ±2 percentage points of optimum. The density of each layer of subbase aggregate material, when compared to the theoretical maximum density as determined in accordance with VTM-1, shall conform to the following: % Material Retained on No. 4 Sieve Min. % Density 0-50 100 51-60 95 61-70 90 Percentages shall be reported to the nearest whole number.308.01 377Not more than one sample in every five shall have a density less than that specified, and the density of such a sample shall be not more than 2 percent below that specified. The Contractor shall scarify, reshape, and recompact the surface of the subbase if it becomes uneven or distorted and sets up in that condition. If the subbase when compacted and shaped shows a deficiency in thickness or if depressions occur in the surface, the Contractor shall scarify such sections at his own expense before additional material is added. The Department will perform field density determinations with a portable nuclear field density testing device using the density control strip as specified in Section 304 and VTM-10, or by other approved methods as directed by the Engineer.

308.04 Tolerances

The Engineer will determine the thickness of the subbase course by the depth measurement of holes dug in the subbase in accordance with VTM-38B. The Engineer’ s acceptance of the subbase course for the physical property of depth will be based on the mean result of tests performed on samples taken from each lot of material placed. A lot of material is defined as the quantity being tested for acceptance except that the maximum lot size will be 2 miles of paver application width. The Engineer will consider a lot acceptable for depth if the mean result of the tests is within the following tolerance of the plan depth for the number of tests taken except that each individual test shall be within ±1.00 inch of the plan depth; mean of two tests, ±0.75 inch; mean of three tests, ±0.60 inch; and mean of four tests, ±0.50 inch. If an individual depth test exceeds the ±1.00 inch tolerance, the Engineer will exclude that portion of the lot represented by the test from the lot. If the individual test result indicates that the depth of material represented by the test exceeds 1.00 inch, the Contractor will not be paid for that material in excess of the tolerance throughout the length and width represented by the test. If the individual test result indicates that the depth of the material represented by the test is deficient by more than 1.00 inch, The Contractor will be required to make correction of the subbase course represented by the test as specified herein. If the mean depth of a lot of material is in excess of the allowable tolerance, the Engineer will not pay the Contractor for that material in excess of the tolerance throughout the length and width represented by the test. If the mean depth of a lot of material is deficient by more than the allowable tolerance, the Engineer correction will not normally require the Contractor to make correction and the Contractor will be paid for the quantity of material that has been placed in the lot. For excessive depth subbase courses, when tonnage measurement is used, the Engineer will calculate the rate of deduction from the tonnage of subbase material allowed for payment at a weight of 110 pounds per square yard per inch of depth in excess of the tolerance. Areas that are deficient in depth by more than 1.00 inch and areas that do not provide a smooth uniform surface shall be scarified, material added or removed; reshaped; and recompacted to the specified density so as to conform to the depth tolerance and provide a smooth, uniform surface.308.04 378308.05—Measurement and Payment Subbase course will be measured in cubic yards or tons of aggregate material or aggregate base material as specified and will be paid for at the contract unit price per cubic yard or ton. When the cubic yard unit is specified in the contract, the quantity will be determined by compacted measurements on the road unless otherwise specified. When the ton unit is specified, the quantity will be determined in accordance with Section 109.01. This price shall include furnishing, hauling, placing, manipulating, and compacting subbase course; clearing and grubbing local pits; material royalties; and access roads. The Engineer will make a deduction from the net weight of both truck and rail shipments for moisture in excess of optimum + 2 percentage points. Payment will be made under: ————————————————————————————— Pay Item Pay Unit—————————————————————————————Aggregate material (No.) Cubic yard or ton Aggregate base material (Type and no.) Cubic yard or ton————————————————————————————— SECTION 309—AGGREGATE BASE COURSE

309.01 Description

This work shall consist of furnishing and placing one or more courses of aggregates and additives, if required, on a prepared surface in accordance with these specifications and in conformity with the lines, grades, and typical sections and cross sections shown on the plans or as established by the Engineer.

309.02 Materials

309.03 Equipment

The Engineer will approve the equipment used for the construction of aggregate base course prior to performance of such work. Any machine, combination of machines, or equipment that handles the material without undue segregation and produce the completed base in accordance with these specifications for spreading, moistening, mixing, and compacting will be acceptable to the Engineer.

309.04 Procedures

The Contractor shall prepare the surface or course upon which the base course is to be placed in accor - dance with the applicable provisions of Section 304 and Section 305.308.05