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Gulf States Materials, Inc.
Specifications for Item GS-50


1.1 This material shall consist of a combination of several classes of calcium sulfate that when blended, the final product shall be 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.


2.1 Blend

The material shall be calcium sulfate. The binder shall be material obtained from the crushing operation and from the fines intermixed with the material.
The calcium sulfate blend material shall consist of durable particles or fragments of calcium sulfate free from objectionable matter and shall not contain an excessive amount of flat or elongated pieces.

2.2 Physical Requirements

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

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





Sieve Size

Percent Retained

Sieve Size

Percent Retained



1 ¾”


1 ¾”




No. 4


No. 4




No. 40


No. 40




2.2.2 The binder, or the portion of the blend material passing the No. 40 mesh sieve, shall have a liquid limit of not more than 35 and a plasticity index of not more than 10.

2.2.3 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 35 after a period of 30 days when tested in general accordance with ASTM D 1883.

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


3.1 Preparation of the Subgrade or Existing Base

The subgrade or existing base course shall be Proof Rolled. Any soft spots, ruts or inadequately compacted areas shall be corrected in accordance with applicable specifications or as directed by the Engineer. Proper compaction and grade shall be accepted by the Engineer prior to placement of the GS-50 base course. Attention should be given to stabilizing the subgrade when excessively plastic or organic soils are encountered. Proper drainage of the subgrade or existing base is required.

When new GS-50 is required to be mixed with existing base, deliver, place, and spread the calcium sulfate in the required amount per station. Manipulate and thoroughly mix the new GS-50 with existing material to provide a uniform mixture to the specified depth before shaping.

3.2 Base Course Placement

The GS-50 shall be delivered to the job site in dump trucks with the dump beds thoroughly cleaned of any objectionable matter. Deposit and spread the calcium sulfate in a uniform layer without segregation. The base shall be spread to a loose depth not greater than 12 inches. Maintain the shape of the course. Control dust by sprinkling, as directed. Correct or replace segregated areas as directed.

3.3 Base Course Compacting

Compact GS-50 using any type of roller, or any combination of rollers, that meets the production rates and quality requirements of the contract unless otherwise shown or as directed by the Engineer. Gulf States does not recommend using a vibratory steel wheel roller for more than one complete pass for compaction.

Compact using density control unless otherwise shown on the plans. Multiple lifts are permitted when shown on the plans or approved. Bring each layer to the moisture content directed. When necessary, sprinkle the material to maintain optimum moisture.

Begin rolling longitudinally at the sides and proceed towards the center, overlapping on successive trips by at least ½ the width of the roller unit. On super-elevated curves, begin rolling at the low side and progress toward the high side. Offset alternate trips of the roller. Operate rollers at a speed between 2 and 6 mph as directed. Compaction with a pneumatic roller shall be completed within 6 hours from the time compaction was started.

Rework, re-compact, and refinish material that fails to meet or that loses required moisture, density, stability, or finish before the next course is placed or the project is accepted. Continue work until specification requirements are met.

a.     Ordinary Compaction. Roll with approved compaction equipment as directed. Correct irregularities, depressions, and weak spots immediately by scarifying the areas affected, adding or removing approved material as required, reshaping, and re-compacting.

b.    Density Control. Compact to at least 95% of the maximum dry density determined by the Modified Proctor (ASTM D 1557) or 100% of the maximum dry density determined by Tex-113-E, unless otherwise shown on the plans. Determine the moisture content of the material at the beginning and during compaction by drying in an oven at a temperature not to exceed 45°C.

3.4 Finishing

After compaction has been completed, use a maintainer or subgrade trimmer to clip, skin, or tight-blade the surface to a depth of approximately ¼-inch. Remove loosened material and dispose of it at an approved location. Seal the clipped surface immediately by rolling with a pneumatic tire roller until a smooth surface is attained. Add small increments of water as needed during rolling. Shape and maintain the course and surface in conformity with the typical sections, lines, and grades as shown on the plans or as directed.

In areas where surfacing is to be placed, correct grade deviations greater than ¼-inch in 16 feet measured longitudinally or greater than ¼-inch over the entire width of the cross-section. Correct by loosening, adding, or removing material. Reshape and re-compact in accordance with 3.3 above.

3.5 Curing

Cure the finished section until the moisture content is at least 2 percentage points below optimum or as directed before applying the next successive course or prime coat.


The GS-50 shall be measured by the ton on certified scales.

The amount of accepted blend material measured as specified will be paid for at the     unit contract price per ton of "Calcium Sulfate Blend Material, ITEM GS-50". This     price shall be full compensation for all labor, materials, equipment, and incidentals     necessary to complete the work.
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