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Specialty Materials Testing

Thermal Testing for Flowable Fill, CLSM & FTB

Calicore and Soil Tests Laboratory provide thermal resistivity and conductivity testing for flowable fill, controlled low-strength material (CLSM), fluidized thermal backfill (FTB), thermal slurry, and suitable cementitious grout.

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Service overview

Test the proposed thermal backfill mix

A flowable material can fill the space around conduits, but its name alone does not establish thermal performance. A conventional CLSM or flowable-fill mix should not be assumed to meet a thermal backfill specification. Test the proposed mix under the condition required by the project.

Laboratory programs can include a specified-condition measurement, an oven-dry endpoint, or a measured dry-out curve. Identify the supplier, mix designation, casting date, curing record, and intended use so each result can be traced to the material proposed for placement.

This service supports suppliers qualifying mixes and engineers reviewing thermal data for duct banks and underground cable systems. We confirm specimen suitability and the applicable ASTM D5334 or IEEE 442 requirements before work begins.

Flowable fill, FTB, and thermal grout

Fluidized thermal backfill is supplied for applications where heat transfer is part of the performance requirement. Flowable fill and CLSM describe broader material categories whose proposed formulations still need evaluation when a thermal limit applies. Include the actual specification rather than relying only on the product label.

Thermal slurry and cementitious grout samples also need a defined curing and testing basis. Explain whether the material will be used for conduit encasement, filling a cable casing, or another application. The thermal test adds measured heat-transfer data to the separate strength, flow, settlement, and excavatability requirements.

Why test beyond the initial wet condition?

Water introduced during mixing and placement can influence a fresh or wet specimen’s thermal response. The cured material may perform differently as it loses moisture. A drying program measures that change instead of treating the first favorable result as a description of every later condition.

For a mix comparison, agree on the curing period, specimen geometry, moisture basis, units, and measurement program. Record material substitutions and mix revisions. The engineer can then review comparable results against the intended installation and acceptance criteria.

Connect qualification testing to delivered material

A qualifying specimen represents an identified formulation and test condition. Production verification should connect later specimens to the batch, placement, and approved mix record. Sampling frequency and acceptance decisions belong in the project’s quality-control plan.

If the project calls for testing installed backfill, define that as a separate field scope. Laboratory specimens and in-place measurements provide different information. We can discuss the appropriate combination when reviewing the request.

Step by step

How the process works

The exact scope is matched to the project, but a typical assignment follows these steps.

  1. 01

    Identify the proposed fill

    Share the formulation or mix reference, source, placement application, and thermal acceptance requirement.

  2. 02

    Plan casting and conditioning

    Confirm the appropriate specimen quantity, geometry, curing history and testing condition before shipment.

  3. 03

    Measure the specified points

    Test suitable specimens at the agreed condition or through a drying program, preserving mix and batch traceability.

  4. 04

    Deliver the qualification data

    Provide the thermal results and condition record for project review and comparison with later production samples.

Review criteria

A useful FTB or CLSM thermal testing record

Keep the proposed mix, tested specimen and project requirement connected throughout qualification and construction.

What you receive

Typical project deliverables

  • Thermal resistivity or conductivity data with stated units
  • Traceable supplier, mix and specimen identification
  • Documented curing, preparation and measurement conditions
  • Dry-out points and curve when included in the program

Common project needs

When this service is useful

  • FTB and flowable-fill suppliers
  • CLSM mixes with project thermal requirements
  • Cementitious thermal grout qualification
  • Duct-bank contractors verifying proposed backfill

Frequently asked

Thermal Testing for Flowable Fill, CLSM & FTB questions

Is every flowable fill a thermal backfill?+

No. Flowability alone does not establish a material’s thermal resistivity or conductivity. The actual mix should be evaluated against the project’s thermal requirement at the specified condition.

Can you perform CLSM thermal resistivity testing?+

Yes, for suitable specimens and an agreed test program. Send the proposed mix, test requirement, casting and curing information, and intended use so specimen preparation can be confirmed.

Do you test fluidized thermal backfill dry-out curves?+

Yes. A dry-out program can document how a suitable FTB specimen’s thermal response changes during drying. Test age, conditioning, specimen geometry, and reporting basis must be established before testing.

Can thermal grout be submitted for conductivity testing?+

Suitable cementitious grout specimens can be evaluated for thermal conductivity or resistivity. Contact the laboratory with the formulation and intended specimen condition before shipping fresh slurry or casting samples.

Does a low wet rho guarantee that the mix will meet the dry requirement?+

No. Results at different moisture conditions are not interchangeable. Test at the specified acceptance condition or request a curve that includes the needed range.

Technical guides

Learn more about thermal testing for flowable fill, clsm & ftb.

Use these technical articles to understand the methods, limitations, evidence, and decisions behind the service.

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What to send us to begin

Send the material or product name, mix designation, intended application, required thermal limit and units, specimen age and condition, and number of mixes. Include the specification and report deadline so we can confirm the testing and shipment plan.

Request a proposal