Screen, crushers and stackers are used to separate various gradations of the materials.

Specifications for Item GS-100
FLEXIBLE BASE MATERIAL

1. DESCRIPTION

1.1 This construction shall consist of a base course composed of crushed calcium sulfate in accordance with these specifications and shall conform to the dimensions, lines and grades as shown on the plans, or as directed by the Engineer.

2. MATERIALS

2.1 Aggregate

The aggregate shall be crushed calcium sulfate. The binder shall be material obtained from the crushing operation and from the fines intermixed with the material.

The crushed material shall consist of hard, durable particles or fragments of calcium sulfate free from objectionable matter and shall not contain an excessive amount of flat or elongated pieces. The method used in production of the crushed material shall be such that the finished product is uniform.

2.2 Physical Requirements

The process material, when properly sampled and tested by standard laboratory procedures, shall meet the following requirements:

2.2.1 The crushed Calcium sulfate material shall be within the following gradation:

Screened		Unscreened
Sieve Size	Percent Retained	Sieve Size	Percent Retained
1 3/4"	-0-	1 3/4"	0-10
7/8"	5-35	No. 4	15-65
3/8"	25-50	No. 40	30-70
No. 4	35-65
No. 40	55-85

2.2.2 The amount of the fraction of material passing the No. 200 mesh sieve shall not exceed two-thirds the fraction passing the No. 40 mesh sieve.

2.2.4 The crushed aggregate shall have a percent wear of not more than 75 (Los Angeles Abrasion Test).

2.2.5 The processed material, when compacted to 95 percent of the modified proctor density (ASTM D 1557), shall have a CBR value of not less than 100 after a period of 30 days when tested in general accordance with ASTM D 1883.

2.2.6 The specific gravity of the processed material shall be a minimum of 1.90 as determined by ASTM C 127.

3. CONSTRUCTION METHODS

The underlying course shall be Proof Rolled. Any soft spots, ruts or inadequately compacted areas shall be corrected and compacted to the required 95 percent of standard proctor density (ASTM D 698) before the fill course is placed. Proper compaction and grade, shall be accepted by the Engineer prior to placement of the base course. Attention should be given to the underlying course and to the modification of excessively plastic or organic soils with stabilizing agents. Proper drainage is a must for the underlying coarse and base material.

3.2 Base Course Placement

The crushed calcium sulfate material shall be delivered to the job site in dump trucks, then deposited and spread in a uniform layer without segregation. The base shall be spread to loose depth not greater than 10 inches.

The Engineer shall perform laboratory tests to determine the maximum density and the optimum moisture content of the base material (ASTM D 1557). This information will be made available to the contractor. The base material shall have the proper moisture content when rolling is started and shall be corrected, if necessary by sprinkling or aerating.

3.3 Base Course Compacting and Finishing

The roller used for compacting the material to the required density may be a sheep foot, pad foot, pneumatic roller, or any combination, or as directed by the Engineer. Gulf States does not recommend a steel flat wheel for compaction or finishing. Rolling operations shall start as soon as moisture is determined after the material is spread over an area large enough for efficient operation. The roller shall start at the side and work towards the center, overlapping on successive trips by one-half the width of each rear wheel. Rolling shall be done longitudinally with the sub grade. If directed by the Engineer successive rolling shall be perpendicular or diagonal to the direction of the first rolling. Rolling shall continue until the material is thoroughly compacted, voids are reduced, and indentions from the roller are no longer visible. Vibratory compaction should be completed within the first 2 hours of compaction and a pneumatic roller after 6 hours from the time compaction was started. The base material shall be placed at least 1/4 inch above finish grade. After completing compaction tight-blade surface with maintainer to 1/4 inch or finish grade. Remove loosened material and dispose at an approved location.

4. MEASUREMENT

5. PAYMENT