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Gulf States Materials, Inc.
Specifications for Item GS-200
FLY ASH STABILIZED BASE MATERIAL

1. DESCRIPTION


1.1 This material shall consist of a fly ash stabilized base course composed of crushed calcium sulfate aggregate 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 Fly Ash

Fly Ash shall be a Class C Fly Ash, meeting the requirements of ASTM C 618, and shall also have a minimum compressive strength of 1000 psi when tested in accordance with ASTM C 593.


2.2 Water

Water shall be free of industrial waste and other objectionable material. Do not use salt water.


2.3 Base Material

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

The base 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.


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

Unscreened

Screened

Sieve Size

Percent Retained

Sieve Size

Percent Retained

1 ¾”

0-10

1 ¾”

-0-

No. 4

15-65

No. 4

15-65

No. 40

30-85

No. 40

30-80



2.4.2 The binder, or the portion of the base 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.


2.4.3 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 100 after a period of 30 days when tested in general accordance with ASTM D 1883.

3. PROPORTIONING OF MIXES


3.1 Strength Design

The mix will be designed with the intention of producing a minimum average compressive strength of 200 psi at an age of 14 days. Fly ash stabilized specimens shall be prepared, cured, and tested as outlined in ASTM D 1632 and D 1633.


3.2 Fly Ash Factor Design

The fly ash content shall not be less than 10% of the dry weight of the base material mixture.

4. CONSTRUCTION METHODS


4.1 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-200 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 GS-200 is required to be mixed with existing base, deliver, place, and spread the GS-200 in the required amount per station. Manipulate and thoroughly mix the GS-200 with existing material to provide a uniform mixture to the specified depth before shaping.


4.2 Base Course Placement

The GS-200 shall be delivered to the job site in dump trucks with the dump beds thoroughly cleaned of any objectionable matter. Deposit and spread the GS-200 in a uniform layer without segregation. The depth of layers shall be as approved by the Engineer but not in lifts of less than six inches (6”). Construction joints between new GS-200 and previously placed GS-200 that has been in place four (4) hours or longer shall be vertical. The plane of the joint may be formed by a header which shall be removed immediately prior to placing the subsequent base or the base placed first may be cut to a vertical face, free of loose and shattered material before placing subsequent base.

GS-200 shall not be placed when the air temperature is below 40º F and is falling, but may be placed when the air temperature is above 35º F and is rising. GS-200 shall be mixed or placed only when weather conditions in the opinion of the Engineer are stable for such work. Control dust by sprinkling, as directed. Correct or replace segregated areas as directed.


4.3 Base Course Compacting
Compact base 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. The moisture content of the mixture within each layer shall be maintained within a range of + or - 2% of the optimum moisture content before and during compaction operations. 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.  The compaction shall be completed within four (4) hours of the time water is added to the mixture. No vibratory compaction should be done after two (2) hours from the time moisture is added and compaction starts. If any reshaping needs to be done; scarify the base material to full depth maintaining optimum moisture and re-compact to achieve maximum density. This has to be done within the four (4) hours after the time moisture is added. Final grade should be approximately ¼-inch above grade.

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.



4.4 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 4.3 above.


4.5 Curing

The GS-200 shall be kept wet for a period of seventy-two (72) hours after completion of compaction. The GS-200 shall be opened to traffic as specified on the plans or as directed by the Engineer. Asphalt should not be placed on the GS-200 before being cured at least 72 hours.


4.6 Re-Working

Unlike cement-stabilized material, the GS-200 can be re-worked. Before reworking, proper aggregate sizing and moisture must be added to achieve maximum density. The Type C Fly Ash used in GS-200 has the ability to react a second time as long as the material is at optimum moisture or above. Repairs to GS-200 shall be done by replacing the base for its full depth rather than by adding a thin layer of GS-200 to the base in need of repair. All joints where the GS-200 is removed shall be vertical joints before new base is added.

The same compacting and finishing methods should be used as discussed in 4.2, 4.3 and 4.4. NOTE: Some strength will be lost, but in most cases it will continue to meet GS-200 specifications.


4.7 Stockpiling

Stockpiling GS-200 is not recommended, but if it is necessary for a short period not to exceed 36 hours, care must be taken to assure that the stockpile is stacked in its loose state.  Additional moisture will be necessary to obtain optimum density (ASTM D 1557) when material is placed for compaction. Use the same methods as discussed in 4.2, 4.3 and 4.4. Note:  Some strength will be lost, but in most cases it will continue to meet GS-200 specifications.

5. MEASUREMENT


The GS-200 shall be measured by the ton on certified scales.

6. PAYMENT


The amount of accepted base material measured as specified will be paid for at the unit contract price per ton of "Fly Ash Stabilized Base Material, ITEM GS-200". This price shall be full compensation for all labor, materials, equipment, and incidentals necessary to complete the work.
Copyright © 2012 Gulf States Materials, Inc. - All rights reserved. 555 Sens Rd. P.O. Box 1425 * La Porte, TX 77572
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