Development of a Recommended Practice for Use of Controlled Low-Strength Material in Highway Construction (2008) / Chapter Skim
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Appendix C - Recommended Specifications for CLSM
Appendix C - Recommended Specifications for CLSM
Pages 110-128
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From page 110... ...
For the purposes of this report, the CLSM is the alternative of an infill material that is typically a compacted granular structural fill. Backfill is not the same as utility bedding, although it can be contiguous with such bedding.
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From page 111... ...
That is, additional construction activities are performed overtop or adjacent to the backfilled area. Accordingly, it is desirable that the CLSM mixture has a setting time consistent with the overall construction schedule.
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From page 112... ...
Whenever such an interface exists, it is important to specify either a cathodic protection scheme or a physical protection scheme, such as coating or covering the pipe with a protective layer in this interface region. Subsidence In cases where interim and final grades of construction materials are important, such as in a trench transverse to a roadway (where subsidence could cause a dip in the final roadway surface, or even worse, cracking in an asphalt or portland cement concrete surface or a chip seal because of uneven support conditions)
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From page 113... ...
mm below the designed trench grade. If utility bedding is present, ensure that the bedding is not covered by rock, soil, or deleterious material.
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From page 114... ...
Placement shall bring the material up uniformly to lines or limits as shown on plans. For cases in which subsidence effects on the final grade are critical, place a final lift that will account for estimated subsidence or otherwise ensure that the final grades on the plans can be achieved and maintained.
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From page 115... ...
Definition and Types of Utility Bedding Utility bedding as intended in this report and recommended specification relates to the preplaced or infill material to provide support strength for utilities (usually underground)
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From page 116... ...
Setting Time Frequently, utility bedding is an interim operation in construction. That is, additional construction activities are performed overtop the bedding area.
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From page 117... ...
Corrosivity Corrosion issues come into play in bedding applications when pipe cross sections run through CLSM and soil. The soilCLSM interface can cause an electrochemical potential difference leading to corrosion of metallic pipe in this area.Whenever such an interface exists, it is important to specify either a cathodic protection scheme or a physical protection scheme, such as coating or covering the pipe with a protective layer in this interface region.
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From page 118... ...
Air Content For jobs where long-term freeze-thaw durability has been indicated as a concern, the air content of fresh CLSM will be determined using AASHTO X 2 prior to installation of the material as backfill. The CLSM must have an air content no less than [6]
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From page 119... ...
If standing water exists, it must be removed through appropriate water control measures. Soil shall be dried until suitable for placement of CLSM as approved by the engineer.
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From page 120... ...
compressive strength, or as dictated by the anticipated removal methods and as specified by the engineer, or as based on documented local experiences of excavation as provided by the contractor 2X2.06 Measurement. Measurement shall be based on the payment lines indicated on the plans.
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From page 121... ...
For example, the weight of void fill may cause disturbance to foundations of adjacent structures. Performance criteria related to these and other items shall be specified by the engineer, with the appropriate test methods indicated as discussed previously in this report.
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From page 122... ...
cylinders will be required, with three (3) cylinders tested according to AASHTO X 3 at 28 days and three (3)
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From page 123... ...
For the purposes of this report, the CLSM is the alternative of an infill material that is typically a compacted granular structural fill. Bridge approach fill is not the same as utility bedding, backfill, or void fill; the primary difference is that bridge approach fill is placed against a structure with the purpose of providing adequate structural resistance to loads.
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From page 124... ...
For bridge abutments fill, the fill is providing support for the wall, usually acting as a bridge between the wall and the area of embankment. Because of the various applications and needs for bridge approach fill, the criteria noted below have been deemed important.
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From page 125... ...
Furnish and install bridge approach fill to provide adequate structural support and less settlement bridge approaches. 2X2.02 Material.
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From page 126... ...
. Air Content For jobs where long-term freeze-thaw durability has been indicated as a concern, the air content of fresh CLSM will be determined using AASHTO X 2 prior to installation of the material as backfill.
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From page 127... ...
For bridge abutment fill, ensure and maintain the appropriate horizontal and vertical alignment of abutment walls prior to and during the placement procedure, and until such time as the CLSM has set to sufficient stiffness to exert minimum forces on the walls. Use soil counter fill or other approved means of restraint.
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From page 128... ...
compressive strength, or as dictated by the anticipated removal methods and as specified by the engineer, if future excavation is expected, or as based on documented local experiences of excavation as provided by the contractor. 2X2.06 Measurement.
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