Section 2506. Flowable Mortar.

2506.01 DESCRIPTION.
This work shall consist of placing a flowable mortar fill material. Uses include, but are not limited to, placement under existing bridges, around or within box culverts or culvert pipes, in open trenches, or at other locations as shown in the contract documents.

2506.02 MATERIALS.
All materials shall meet requirements for the respective items in Division 41 with the following exceptions:

A. Cement.
Cement shall meet the requirements of Section 4101.

B. Fly Ash.
Fly ash shall meet requirements of Section 4108 and shall come from a source approved by the Engineer.

C. Fine Aggregate.
Fine aggregate for flowable mortar shall be natural sand consisting of mineral aggregate particles or foundry sand from the castings of ferrous material. The gradation of this material shall be as follows:

Sieve Size Percent Passing
3/4 inch (9.5 mm)
No. 200 (75 µm)		 100
0-10

It is intended that the sand be a fine sand that will stay in suspension in the mortar to the extent required for proper flow. For the Contractor's information, uniformly graded sand in the following gradation range has generally shown good flow characteristics when using the normal amount of fly ash (300 pounds per cubic yard (180 kg/m3)). Concrete sand normally does not produce the desired flowability.

Informational Gradation Limits
Sieve Size Percent Passing
3/8 inch (9.5 mm)
No. 8 (2.36 mm)
No. 16 (1.18 mm)
No. 30 (600 µm)
No. 50 (300 µm)
No. 100 (150 µm)
No. 200 (75 µm)		 100
80-100
60-100
45-80
12-40
1.5-25
0-5

Fine aggregate meeting the above informational gradation limits may be used in the basic proportions shown in Article 2506.02, E, without initial mix design, provided the flowable mortar is used in noncritical fluidity locations described in Article 2506.02, F. The Engineer reserves the right to reject the intended sand if a flowable mortar cannot be produced using the specified proportions.

The Contractor shall not be responsible for certified aggregate testing. The Engineer will provide appropriate inspection, that is normally source approval, followed by visual inspection. Foundry sand shall meet the requirements of Iowa Administrative Code 567 IAC Section 108. Suppliers of foundry sand shall submit a processing plan to the District Materials Engineer for review and approval.

D. Admixtures.
Air entraining admixture may be added at a rate not to exceed 2 fluid ounces per cubic yard (75 mL/m3) to increase the fluidity of flowable mortar.

E. Mix Design.
The basic proportioning for flowable mortar is as follows:

Quantities of Dry Materials Per Cubic Yard (Cubic Meter)

Cement
Fly Ash
Fine Aggregate

100 pounds (60 kg)
300 pounds (180 kg)
2,600 pounds (1545 kg)

The Contractor shall submit samples of fine aggregate, cement, and fly ash intended for use to the Engineer before the work begins for mix proportions to produce the required efflux time.

The mix design will be determined by the Engineer. The cement content shall not exceed 100 pounds per cubic yard (60 kg/m3). The total amount of cementitious material shall not exceed 500 pounds per cubic yard (295 kg/m3).

These quantities of dry materials, with approximately 70 gallons (345 L) of water (mixes utilizing foundry sand may require more water), will yield approximately 1 cubic yard (1 m3) of flowable mortar of the proper consistency. The quantity of water used for the trial mix or at the project may require adjustment to achieve proper solids suspension and optimum flow ability.

For information, volume loss during the cure period resulting from surface evaporation, moisture migration away from the flowable mortar unit, and hydration have been observed to be less than 4% of the original volume determined in the fluid condition. In mixes utilizing foundry sand, additional fly ash may be required and the limit of total cementitious material will not apply.

F. Fluidity.
Fluidity of the flowable mortar shall be measured by the Corps of Engineers flow cone method according to their specification CRD-C611-80. Prior to filling the flow cone with flowable mortar, the mixture shall be passed through a 1/4 inch (6.3 mm) screen. In locations where fluidity is critical such as inside existing culverts and between the beams under existing bridges, the time of efflux shall be 10 seconds to 16 seconds, and will be measured by the Engineer prior to placement and at least once every 4 working hours until work is complete. In locations where fluidity is not critical such as for backfilling open trenches or placement below the beams under existing bridges, the time of efflux shall be 10 seconds to 26 seconds, and will be visually monitored.

G. Granular Backfill.
Granular backfill for use under flowable mortar shall meet the requirements of Section 4133.

2506.03 PROPORTIONING AND MIXING EQUIPMENT.
This equipment shall meet requirements of Articles 2001.20 and 2001.21. Sufficient mixing capacity or mixers shall be provided to permit the intended placement without interruption.

2506.04 FLANGE FILLER MATERIAL.
When the flowable mortar is to be placed under a bridge, the bridge beams shall be covered with a filler material, as shown in the contract documents, to fill the flange areas in a manner that will minimize intrusion of the mortar into the flange area of the beams. Construction insulation board or any other suitable material may be used.

2506.05 PLACEMENT OF MORTAR UNDER EXISTING BRIDGES.
The shoulder area shall first be constructed as shown in the contract documents, and with the drainage system also shown. This work shall be done in conjunction with pipe placement, if a pipe culvert is required.

If a culvert is required, engineering fabric, meeting requirements of Article 4196.01, B, shall be placed over all joints in the culvert, within the area to be backfilled with flowable mortar. The fabric shall be placed from the underlying ground line around the culvert, 1 foot (0.3 m) on each side of the joint.

Flowable mortar shall be discharged from the mixer by any reasonable means into the area to be filled.

The mortar fill shall be brought up uniformly to the elevation of the first stage fill line, if specified. Placement of mortar shall then cease for a period of 72 hours.

If there is only one stage of flowable mortar, granular backfill shall be placed in the lower part of the fill and around the pipe as specified. The granular backfill shall be compacted according to Article 2402.09 or shall be thoroughly and uniformly wetted with water in a quantity of approximately 10% of the granular backfill. Complete flooding may be required. Regardless of the method of consolidation, placement of flowable mortar shall not begin for 72 hours.

The flowable mortar shall then be placed in a sequential operation from side to side and longitudinally, beginning with fill in one shoulder area, then through each hole in the deck adjacent to the shoulder until mortar is expelled from the adjacent longitudinal hole. The last fill shall be placed on the opposite shoulder. Mortar placement through holes in the deck shall be with a suitable funnel which can create a 3 foot (1 m) head during filling.

The locations for holes in the deck will normally be shown in the contract documents. When not shown, a hole shall be drilled approximately 5 feet (1.5 m) from each end of the bridge in each area between bridge beams, and additional holes shall be drilled, as necessary, so the longitudinal spacing does not exceed 20 feet (6 m). Holes shall be no larger than necessary to accommodate filling equipment.

When placement of flowable mortar is completed and set, the mortar in the holes in the deck shall be removed and replaced with a suitable PCC mixture.

2506.06 PLACEMENT OF MORTAR AS CULVERT BACKFILL.
The shoulder area shall first be constructed with suitable soil as shown in the contract documents and with a drainage system also shown. This work shall be done in conjunction with the pipe placement, if the culvert is a pipe.

Engineering fabric, meeting requirements of Article 4196.01, B, shall be placed over all joints in the culvert, within the area to be backfilled with flowable mortar. The fabric shall be placed from the underlying ground line around the culvert, 1 foot (0.3 m) on each side of the joint.

Granular backfill, meeting requirements of Section 4133, shall be placed in the area to be backfilled to approximately mid-height of the culvert. This backfill shall proceed simultaneously on both sides of the culvert so that the two fills are kept at approximately the same elevation at all times. Compaction of the granular backfill is not necessary.

Flowable mortar shall be discharged from the mixer into the remaining area to be filled. Filling operations shall proceed simultaneously on both sides of the structure so that the two fills are kept at approximately the same elevation at all times.

If the culvert starts to float, the filling operation shall cease. An external load shall be applied to the culvert, sufficient to hold it in place, before the filling is continued. As an alternate, the filling may be suspended until the buoyancy effect of the mortar has ceased.

The flowable mortar shall be placed to the elevation shown in the contract documents. When not shown, the mortar shall be placed as follows:

Place mortar to 1 foot (0.3 m) below subgrade elevation if the subgrade elevation is not more than 5 feet (1.5 m) over the top of the culvert. If the subgrade is more than 5 feet (1.5 m) over the top of the culvert, mortar shall be placed to an elevation 2 feet (0.6 m) over the top of the culvert, and the remainder shall be backfilled with soil designated by the Engineer.

2506.07 LIMITATION OF OPERATIONS.

A. Flowable mortar shall not be placed on frozen ground.

B. Flowable mortar batching, mixing, and placing may be started, if weather conditions are favorable, when the temperature is at least 34°F (1°C) and rising. At time of placement, mortar must have a temperature of at least 40°F (4°C). Mixing and placing shall stop when the temperature is 38°F (3°C) or less and falling.

C. Each filling stage shall be as continuous an operation as is practicable.

D. Flowable mortar shall be kept out of streams and waterways.

2506.08 METHOD OF MEASUREMENT.
The Engineer will compute the volume of flowable mortar furnished and placed, from the nominal volume of each batch and a count of batches. Unused mortar will be estimated and deducted by the Engineer; however, deduction will not be made for a partial batch remaining at the completion of the operation.

Granular backfill used in the lower part of the fill area will be based on the contract document quantity.

When the flowable mortar elevation for backfilling of culverts is shown in the contract documents, payment for flowable mortar will be based on the quantity shown in the contract documents.

2506.09 BASIS OF PAYMENT.
The Contractor will be paid the contract unit price per cubic yard (cubic meter) for flowable mortar. This payment shall be full compensation for placing the flowable mortar, the flange filler material, for engineering fabric as required, for drilling and filling the bridge deck holes, and for furnishing all materials, equipment, and labor necessary to complete the work.

Payment for granular backfill used in the lower part of the fill area will be based on the quantity shown in the contract documents, and this will normally be included in the quantity of other granular backfill on the project.

Excavation, backfilling for construction of the shoulder area, and moisture control if designated necessary for this work, will be paid for separately. These items will be included in the quantities of other similar work on the project. Furnishing and placing the drainage system in the shoulder area will be considered incidental to the payment for flowable mortar.