850 Cement Treated Free Draining Base

Be advised SS850 dated 4/18/2008 is included in its entirety at the end of this document for reference only; the official version is available online.

Materials (850.02)

The cement treated free draining base (CTFDB) is to be a mixture of coarse aggregate, Portland cement and water.

Cement used must be Type 1A (701.01) or Type I (701.04) conforming to ASTM C 150.

The coarse aggregate used can be either No. 57 or No. 67 size per Table 703.01-1.

Proportioning, Mixing, and Transporting (850.03)

The Contractor must proportion, mix, and transport the CTFDB according to Item 499.

The mix is to be prepared as follows:

The minimum cement content must be 250 pounds per cubic yard (148 kg/m³) when using No. 57 size coarse aggregate. The minimum cement content must be 220 pounds per cubic yard (130 kg/m³) when using No. 67 size coarse aggregate.

The water to cement ratio is 0.36.

A water-reducing admixture meeting 705.12 can be used.

Verification of Design (850.04)

The Contractor must submit a mix design for the proposed CTFDB 30 days prior to the start of production. This mix design must describe the proposed aggregate size, the cement content, and the water content by weight. A private laboratory must perform tests on the proposed mix to verify the yield of the mix design.

Inspection should include random sampling of the CTFDB material delivered to the project to ensure conformance to the mix design. The unit weight of the mix must be determined and the yield checked.

Equipment (850.05)

The Contractor must provide all equipment necessary to mix, transport, place, compact, and finish the CTFDB. Equipment must be approved before the work begins.

A spreader must be used if the width being placed is more than 12 feet (3.6 m) or the total area of any given width exceeds 5,000 square yards (4,000 m²) of area. The spreader could be a concrete spreader or an asphalt paving machine.

Initial compaction may be done by using a steel wheel roller, a modified slip-form paving machine with vibratory plates, or high-density screed pavers. Compaction must not crush aggregate particles or cause segregation. Final compaction must be done with steel wheel rollers weighing 6 to 10 tons (5 to 9 metric tons). If vibratory rollers are used, do not use them in vibratory mode.

Figure 850.A – Spreading with an Asphalt Paving Machine

Figure 850.B – Spreading CTFDB with a Concrete Spreader

Placing and Spreading (850.06)

The Contractor must thoroughly moisten the base if there is no prime coat specified in the Contract prior to placing the CTFDB. Workers must not contaminate the CTFDB by walking through it with mud or other foreign material on their work shoes.

The CTFDB must be spread in a smooth, uniform layer prior to compacting it.

Inspection should include sampling the CTFDB mixture and testing for in-place gradation after it is spread and before compaction. This testing is to be done in accordance with Supplement 1090.

Limitations on Placing Operations (850.07)

Minimum temperature is required to be 35 ºF (2 ºC) and rising.

The material is not placed on frozen material or on rain softened subgrade or base.

Figure 850.C – Vibrating Plate behind Concrete Spreader

Figure 850.D – Steel Wheel Roller Compact the CTFDB

Compaction and Shaping (850.08)

The CTFDB is to be shaped to produce a uniform density and cross-section. Compaction must not cause crushing of the aggregate particles.

The Contractor must make a minimum of two passes over any given area with the required steel wheel rollers.

Construction joints between each day’s work must be made by cutting transversely across the hardened CTFDB with diamond saws or the Contractor is permitted to use forms to form the construction joints.

Figure 850.E – Curing CTFDB with 6 mil White Opaque Polyethylene Sheeting

Curing (850.09)

Curing of CTFDB is to be done by placing 6 mil (150 μm) white opaque polyethylene sheets over the completed work. These coverings must be left in place for a minimum of 3 days. A cure day is defined as 24 consecutive hours of time in which the temperature is above 40 ºF (5 ºC). Add a cure day for each day the temperature falls below 40 ºF (5 ºC). Do not allow the use of liquid concrete curing membranes for curing.

Protection of the Underdrains (850.10)

Care must be exercised by the Contractor so as not to damage any installed underdrains during placing or compacting of the CTFDB. The Contractor must ensure positive connection between the underdrain backfill and the CTFDB at all times during construction.

Protection of the Cement Treated Free Draining Base (850.11)

The Contractor is permitted to haul materials or operate equipment on completed CTFDB, provided there is no significant displacement, breakup, or contamination. If any of this occurs, the Contractor must stop using the completed CTFDB for such purposes until the Contractor can demonstrate to the Department that it will not happen again in the future. Any damage to the CTFDB must be corrected by the Contractor at no cost to the state.

The Contractor must protect the completed CTFDB from contamination of fine material at all times.

The Contractor must use track mounted asphalt paving machines for placing the first lift of asphalt concrete on top of completed CTFDB. This first course must cure at least over-night before placing succeeding lifts of asphalt concrete.

Thickness Tolerances (850.12)

The compacted depth of the CTFDB is to be 4 inches (100 mm) with a tolerance of ± 1/2 inch (13 mm). Depth checks must be made every 2,000 square yards (1650 m²). Areas found to be out of this tolerance must be removed and replaced at no cost to the Department and retested for proper thickness.

Surface Tolerance (850.13)

The CTFDB must be constructed to the proper elevation and have the plan specified cross-slope. Checks should be made periodically to verify these parameters. The surface tolerance of the finished surface must not vary more than 1/2 inch from a 10-foot (13 mm from a 3 m) straightedge. Any irregularities exceeding this amount must be corrected by the Contractor.

Exposure to the Elements (850.14)

The Contractor is required to place the next pavement layer on top of the CTFDB within 40 days from the end of the curing period. In addition, the Contractor must plan the work so that the CTFDB is completely covered with the next pavement layer and have the underdrain system in place and functioning by the end of the construction season in any calendar year.

Method of Measurement and Basis of Payment (850.15 & 850.16)

The project will measure and calculate the area in square yards (square meters) based on the typical sections shown on the plans. Payment will be made at the contract bid price for work that is accepted in place.

Documentation Requirements - 850 Cement Treated Free Draining Base

1. Materials.

2. Verify design.

3. Proportioning and mixing as per 850.03.

4. Prime base or sprinkle base with water.

5. Temperature must be above 35 °F (1.6 °C).

6. Use a spreader if project quantity exceeds 5,000 square yards (4,000 square meters).

7. Compact and cure in accordance with 850.08 and 850.09.

8. Check segregation and thickness.

9. Curing and protection.

10. Pay and measure according to 850.15 and 850.16.

11. Document on CA-EW-12, CA-D-1, and CA-D-2. Do not duplicate the information on these forms unless necessary.

SUPPLEMENTAL SPECIFICATION 850

CEMENT TREATED FREE
DRAINING BASE

April 18, 2008

850.01 Description

850.02 Materials

850.03 Proportioning, Mixing, and Transporting

850.04 Verification of Design

850.05 Equipment

850.06 Placing and Spreading

850.07 Limitations on Placing Operations

850.08 Compaction and Shaping

850.09 Curing

850.10 Protection of the Underdrains

850.11 Protection of the Cement Treated Free Draining Base

850.12 Thickness Tolerances

850.13 Surface Tolerance

850.14 Exposure to the Elements

850.15 Method of Measurement

850.16 Basis of Payment

850.01 Description. This work consists of constructing a cement treated free draining base (CTFDB) on a prepared base course.

850.02 Materials. Use CTFDB which is a mixture of aggregate, portland cement, and water. Use portland cement conforming to 701.01 or 701.04. Do not substitute pozzolans for portland cement. Furnish aggregate conforming to the following:

Furnish aggregate consisting of CCS, crushed gravel, or ACBFS according to the following:

A. Use aggregate for cement treated free draining base with the gradation of No. 57 or 67 conforming to Table 703.01-1.

B.Provide aggregate with physical properties of

	Maximum
Percent of wear, Los Angeles test, (stone or gravel)	40
Loss, sodium sulfate soundness test, percent	15
Shale and shaly material, percent	5
Chert that disintegrates in 5 cycles of the soundness test, percent	5
Liquid limit^[1]	25
Plastic index^[1]	6
Fractured pieces^[2], percent	90
[1] The portion of the material passing the No. 40 (425 µm) sieve.
[2] If gravel is used, ensure that the aggregate retained on the No. 8 (2.37 mm) sieve has at least two mechanically fractured faces. Ensure that the gravel is crushed from material retained on the 1/2 inch (12.5 mm) sieve.

Furnish ACBFS according to Supplement 1027.

850.03 Proportioning, Mixing, and Transporting. Proportion, mix, and transport CTFDB according to Item 499, except prepare a mix design conforming to the following requirements:

A. Ensure that the minimum cement content by weight is 250 pounds per cubic yard (148 kg/m³) when using No. 57 gradation and 220 pounds per cubic yard (130 kg/m³) when using No. 67 gradation.

B. Ensure that the water-cement ratio is approximately 0.36. This ratio is the amount of water, exclusive of that absorbed by the aggregates, to the amount of cement, by weight. The Contractor may change this water-cement ratio depending on the workability of the mixture.

C. The Contractor may use water-reducing admixtures according to 705.12.

D. Prewet, as necessary, the mixer fins and chute to allow discharge of the CTFDB.

850.04 Verification of Design. A minimum of 30 days before the production of CTFDB, submit a computed blend of aggregates, cement content, admixture, and water content for the necessary testing to determine the mix design acceptance. Have an independent private laboratory perform the required tests to check the yield of the mix design.

The Department will take random samples of the material at the discharge of the mixer and following the spreading operation to ensure conformance to the mix design. The Department will check the yield using a bulk density test for aggregate (ASTM C 29) to determine the unit weight of the mix.

850.05 Equipment. Provide all equipment necessary to mix, transport, place, compact, and finish CTFDB. Receive approval for this equipment before work can start.

850.06 Placing and Spreading. When the Contract Documents do not require the base to be primed, sprinkle it with water so it is thoroughly moistened when CTFDB is placed.

Do not allow workers to walk in freshly mixed CTFDB with boots or shoes coated with earth or other foreign material.

Before compaction, spread the mixed CTFDB to produce a smooth uniform layer.

If the width of the CTFDB being placed in one operation is more than 12 feet (3.5 m) or the total area of any given width on the project exceeds 5000 square yards (4000 m²), use a spreader.

The Department will test for in place gradation after spreading, but before compaction testing, according to Supplement 1090.

850.07 Limitations on Placing Operations. Spread CTFDB only when the atmospheric temperature is above 35 °F (2 °C). Do not spread on frozen material.

Do not place the CTFDB when rain is imminent. If rain occurs during placement of the CTFDB, cease all operations. Do not place the CTFDB when rain has softened the underlying base course or subgrade.

Do not place the CTFDB during any weather conditions that would cause its degradation, segregation, or contamination.

850.08 Compaction and Shaping. Compact and shape CTFDB to produce uniform density and cross-section. Use approved methods of compaction and shaping.

Compact the CTFDB using steel wheel rollers, modified slip-form pavers (using vibratory plates), or high-density screed pavers. Firmly seat the CTFDB into place by using the above equipment or combination thereof. Compact the CTFDB without crushing the aggregate or segregating the materials.

Perform the final compaction using steel wheel rollers weighing from 6 to 10 tons (5 to 9 metric tons). The Contractor may use vibratory rollers meeting the above requirements provided the vibration is turned off. Make at least two passes over any given point on the surface with the rollers. More passes may be required to ensure compaction.

Begin compaction within 1/2 hour of the spreading operation. Provide sufficient spreading and compaction equipment to complete compaction within 1-1/2 hours after water is added to the aggregate and cement.

Make construction joints by cutting a straight transverse joint in the completed work to form a vertical face at the end of each day’s work or when work is suspended for more than 3 hours. Cut the CTFDB using a diamond blade saw. The Contractor may use a bulkhead instead of this procedure.

850.09 Curing. Place 6-mil (150 mm) white opaque polyethylene sheeting conforming to 705.06 over the completed CTFDB course immediately after compaction, and keep the sheeting in place for 3 days. Do not use concrete curing membranes.

If the next layer of pavement is placed without loading the CTFDB with construction or compaction equipment, the Engineer may allow a 2-day curing period. In this case, do not allow more than 4 hours to elapse between the removal of the curing and the placement of the pavement.

When the next layer of pavement is asphalt or a pavement layer that requires compaction equipment, cure the CTFDB for 3 days.

A cure day is defined as 24 consecutive hours. Maintain the temperature of the CTFDB above 40 °F (5 °C) during the curing period. For every day that the temperature of the CTFDB falls below 40 °F (5 °C) for any length of time, add an additional cure day.

850.10 Protection of the Underdrains. Do not allow equipment to crush any part of the underdrain system as a result of the placement or compaction of CTFDB. Repair or replace damaged underdrain pipe at no expense to the Department.

Ensure a positive connection between the underdrain backfill and the CTFDB at all times.

850.11 Protection of the Cement Treated Free Draining Base. The Department has not designed CTFDB for use as a haul road. Provided there is no significant displacement, breakup, or contamination, the Contractor may operate hauling units and other construction vehicles on the CTFDB.

If significant displacement, breakup, or contamination of the CTFDB is occurring, cease operating the hauling units and construction vehicles on the CTFDB. The Department will not allow hauling units and construction vehicles to travel on the CTFDB until the Contractor has satisfactorily demonstrated that displacement, breakup, or contamination is not expected to recur.

The use of the CTFDB by hauling vehicles or construction equipment is at the risk of the Contractor. Repair or replace all damage to the CTFDB, base, subgrade, or underdrains caused by the hauling units and construction vehicles at no expense to the Department.

Protect the CTFDB from fine material contamination at all times.

Provide adequate surface and subsurface drainage for the CTFDB, base, and subgrade at all times.

If constructing asphalt concrete pavement on the CTFDB, place the first course using a paver mounted on tracks. Allow the first course to cure overnight before placing the succeeding pavement courses.

850.12 Thickness Tolerances. Ensure that the compacted depth of CTFDB is 4 ± 1/2 inch (100 ± 13 mm). Ensure that the compacted depth conforms to the plans.

Verify the specified depth by randomly checking the CTFDB’s depth during construction for at least every 2000 square yards (1650 m²). If the depth is less than the specified depth by more than 1/2 inch (13 mm), remove and replace it with CTFDB within tolerance at no expense to the Department.

850.13 Surface Tolerance. Use templates, slope boards, or other devices to verify the surface tolerance.

Ensure that the finished surface is uniform and does not vary more than 1/2 inch (13 mm) from a 10-foot (3 m) straightedge applied to the surface parallel to the centerline of the pavement. If an area is out of tolerance, remove the areas and replace it with CTFDB within the specified tolerance at no expense to the Department.

850.14 Exposure to the Elements. Place the next layer of pavement within 40 days of the end of the CTFDB’s curing period.

The Contractor may construct the CTFDB at any time that complies with the temperature restrictions specified in 850.07. However, completely cover the CTFDB with the next layer of pavement, and place the underdrain system and have it functioning before the atmospheric temperature falls below 35 °F (2 °C) or by the end of the construction season in any given calendar year.

Remove and replace CTFDB, base, subgrade, and underdrain system damaged by exposure to temperatures below 35 °F (2 °C) at no expense to the Department.

850.15 Method of Measurement. The Department will measure the 4-inch (100 mm) Cement Treated Free Draining Base by the number of square yards (square meters) computed from the profile grade and typical sections accepted in place.

850.16 Basis of Payment. The Department will pay for accepted quantities at the contract price as follows:

Item Unit Description

850 Square Yard 4 inch (100 mm) Cement Treated Free Draining Base
(Square Meter)