ITEM 613 LOW STRENGTH MORTAR BACKFILL
613.01
Description
613.02
Materials
613.03 Mix
Proportioning
613.04 Mix
Adjustment
613.05
Alternate Mixes
613.06 Mixing
Equipment
613.07 Mixing
the Materials
613.08 Placing
Mortar
613.09 Method
of Measurement
613.10 Basis of
Payment
613.01 Description. This work consists of
placing a low strength mortar backfill around conduits and at other
locations. Perform the work for this item according to Items 611 and 499, except as modified
below.
613.02 Materials. Furnish materials conforming to:
Cement....................................................
701.01 or 701.04
Fly
Ash.................................................................... 701.13
Furnish
fine aggregate consisting of foundry sand, natural sand, sand manufactured from
stone, gravel, or air-cooled blast furnace slag. Conform to the fine
aggregate gradation requirements of 703.05. Use fine aggregate that is
fine enough to stay in suspension in the mixture to ensure proper flow.
Furnish
an air-entraining admixture that is designed for use in low strength mortar mixtures
(also called controlled density fill or flowable
fill).
613.03 Mix Proportioning. Furnish a
low strength mortar mixture listed below or provide an alternate mix conforming
to 613.05.
|
Type 1[1] |
Type 2 |
Type 3 |
|||
lb/yd³ |
kg/m³ |
lb/yd³ |
kg/m³ |
lb/yd³ |
kg/m³ |
|
Cement |
50 |
30 |
100 |
59 |
0 |
0 |
Fly Ash, Class F |
250 |
148 |
[2] |
[2] |
1500 |
890 |
Fly Ash, Class C [4] |
0 |
0 |
0 |
0 |
297 |
297 |
Fine Aggregate [3] |
2910 |
1726 |
2420 |
1436 |
0 |
0 |
Water (Target) |
500 |
297 |
210-300 |
125-178 |
850 |
504 |
[1] The Contractor may add
an air-entraining agent specifically designed for the use in the low strength
mortar mixture. [2] Entrained air is substituted
for fly ash in this mix. (Approximately 25 percent) [3] Saturated Surface Dry [4] Class C Fly Ash may be
substituted for Class F Fly ash in Type 1 mixes with an approved mix design
meeting the alternate mix design criteria of this specification. |
These
mixtures of materials are expected to yield approximately 1 cubic yard (1 m3)
of material of a flowable consistency. Make
small adjustments, as necessary, in the amounts of the materials in a mix to
achieve the final product.
613.04 Mix Adjustment. Make one or more 1 cubic
yard (1 m3) trial batches at different water contents to ensure
a flowable material. The mixture is too dry if
cracks develop in the mixture as it flows into place.
Adjust
the proportions to maintain the total absolute volume. For large
adjustments, see 613.05.
In
order to expedite the settlement of a Type 1 mixture without entrained air,
bleed water may appear on the surface immediately after the material is struck
off. A delay in bleeding indicates there are too many fines in the
mixture. The Contractor may reduce the fly ash quantity in increments of
50 pounds (30 kg) until the mixture is bleeding freely. Add approximately
60 pounds (36 kg) of sand to replace each 50 pounds (30 kg) increment of fly
ash to maintain the original yield.
613.05 Alternate Mixes. The Contractor may submit
alternate mixes for approval. Furnish the mix design and test data from
an independent test laboratory 30 days before the intended usage for approval.
Submit
an alternate mix design for all mixes that:
A.
Vary more than 300 pounds (178 kg) in fine aggregate, 100 pounds (59 kg)
in water, 20 pounds (12 kg) in cement, or 200 pounds (119 kg) in fly ash from
the 613.03 mixes. These are considered
large adjustments.
B.
Have less than 50 pounds (30 kg) of cement in the Type 1 mixes or less than 100
pounds (59 kg) of cement in the Type 2 mixes.
C.
Use alternate materials.
D.
Contain foundry sand.
E.
Contain fly ash not conforming to 701.13.
F.
Use fine aggregate gradations other than 703.05.
The
Contractor may use foundry sand if it meets the requirements of the Division
of Surface Water Policy 400.007 “Beneficial Use of Non-Toxic Bottom Ash, Fly
Ash and Spent Foundry Sand and Other Exempt Wastes,” and all other
regulations. Ten days before using a mixture containing foundry sand on
the project, submit written permission from the Ohio EPA to the Engineer.
The Contractor may elect to have an independent ODOT consultant pre-qualified in
remedial design environmental site assessment review the proposed usage.
The consultant will provide all documentation utilized to ensure that the
proposed usage obeys all Ohio EPA regulations. The consultant shall
coordinate all EPA required meetings, documentation, and testing
requirements. The consultant shall certify the report or reports to the
Department.
Provide
alternate mixes with an unconfined compressive strength between 50 and 100
pounds per square inch (345 and 689 kPa) at 28
days when tested according to ASTM
D 4832. Ensure that the long term (12-month) unconfined compressive
strength is less than 100 pounds per square inch (689 kPa).
Ensure
that the final mix has the required strength, fills the voids of the intended
usages and sets up within 12 hours (4 hours for Type 3 or Type 3 alternate
mixes). The proportioning, yield, consistency, workability, compressive
strength, and all other requirements are the sole responsibility of the Contractor.
613.06 Mixing Equipment. Provide
the mixing capacity and delivery equipment to place the material without
interruption as much as practical. Deliver and place Type 1 and 2 mixes
or Type 1 and 2 alternate mixes from ready mixed concrete trucks, or deliver
them from a batch plant.
Deliver
and place Type 3 mix using volumetric mobile mixers. Calibrate volumetric
mixers properly and sufficiently mix the materials in the mixer to produce a
uniform material.
613.07 Mixing the Materials. Discharge
the mixture within 2.5 hours after adding water.
613.08 Placing Mortar. Unless specifically shown
on the plans, do not place the mortar within 3 (1 m) feet of the subgrade
elevation. Discharge the flowable material from
the mixer by any reasonable means into the space of the plan intended
usage. Bring the fill material up uniformly to the fill line shown on the
plans. The Contractor may begin placing the other fill material over low
strength mortar backfill material as soon as the surface water is gone.
The Engineer reserves the right to reject the mix if a flowable
mixture is not produced.
Before
placing the low strength mortar backfill as backfill for 611
Conduit, secure the conduit to prevent it from floating during placement of the
flowable material.
613.09 Method of Measurement. The
Department will measure Low Strength Mortar Backfill by the number of cubic
yards (cubic meters) completed and accepted in place, computed from the plan
lines. The Department will not pay additional compensation for over excavated
areas or for a change in the material blends.
613.10 Basis of Payment. The
Department will pay for accepted quantities at the contract prices as follows:
Item
Unit
Description
613
Cubic Yard
Low Strength Mortar Backfill
(Cubic Meter)
613
Cubic
Yard
Low Strength Mortar Backfill
(Cubic
Meter)
(Type ___)