SECTION 603 — CONTROLLED LOW STRENGTH MATERIAL (CLSM) SECTION 603 — CONTROLLED LOW STRENGTH MATERIAL (CLSM)
603.01 Description.
This work includes furnishing and placing Controlled Low Strength Material (CLSM) as a self- consolidating, self-leveling, rigid setting, low density material to be substituted for compacted gravel, structural fill, and any incidental construction directed by the Engineer. CLSM consists of a homogenous mixture of Portland cement, fine aggregate, water, and mineral admixtures (when used), mixed in proportions to attain the specified properties. Classification. There are two main categories for CLSM ― excavatable and non-excavatable. The consistency of these two main categories can be subdivided as flowable and very flowable. The following Table presents each classification required for the specific work. Description Flowable Very Flowable Excavatable Class I Class II Non-Excavatable Class III Class IV
a.Definitions. ● Very Flowable. Exhibits characteristics needed for small or confined areas and required to flow over long distances. ● Flowable. Where the above flowability characteristics are not required. ● Classes I and II. Excavatable, that may be removed in the future if required, may be used (but not limited to) in types of applications such as backfill, void filler, fill around manholes and catch basins, and utility cut backfill. ● Classes III and IV. Non-excavatable, used in areas not expected to be removed in the future, such as (but not limited to) fill between median barriers, under approach slabs, and mat foundations.
603.02 Materials.
Provide materials that conform to SECTION 601. Chemical Admixtures. In addition to the requirements of SECTION 601, the CLSM may contain air entrainment. The amount and type of air entraining admixture is dependent upon the design of the CLSM. Submit the type of air entrainment to be used, and specify if an air entrainment admixture is used or if a high-range, air-inducing, or foaming type of admixture is used within the mix design.
Part 600 — Concrete August 2025
SECTION 603 — CONTROLLED LOW STRENGTH MATERIAL (CLSM) 600-29 Mineral Admixtures. Provide a mineral admixture, if used, that consists of, but is not limited to, Fly Ash Type F that complies with ASTM C618, including the supplemental chemical and physical requirements. The use of high or low carbon content (i.e., loss of ignition) fly a sh may be allowed if submitted for approval to the Engineer on a project specific basis. Ensure that the lime (CaO) content is less than 10 percent by weight for Classes I and II.
603.03 Construction Methods.
General. Ensure that the CLSM produced by a Department-approved ready-mix concrete supplier familiar with the design, production, and transport of CLSM. Follow the guidelines in the ACI 229R Report “Controlled Low Strength Materials (CLSM),” except do not use non-standard materials (Section
3.7 of the ACI Report). Ensure that the methods and tolerances conform to SECTION 601.
Proportions.
a.General. Design the CLSM to conform to the following end result properties (AASHTO test method referenced if applicable): Property Criteria Modified Slump; performed in accordance with Para. b. below Class I and III: 6 in. to 8 in. diameter Class II and IV: 9 in. to 14 in. diameter Air Content (T 152) 0 percent to 35 percent* (see below) Unit Weight (T 121) ±5.0 pcf from that stated on mix design * The maximum air content may be adjusted, if it is demonstrated to the Engineer that no deleterious effects would be incurred. Ensure that the air content in the mix design is within ±5 percent. Ensure that the CLSM develops a 28 -day compressive strength (T22, T23, or T106) as indicated below: Mix Specification Range (psi) Maximum psi Classes I and II 30 - 100 100 at 28 days; 200 at 6 months Classes III and IV 100 - 1200 1200 at 28 days
b.Modified Slump Test. Ensure that the test is performed according to ASTM C1611.
Part 600 — Concrete August 2025
600-30 SECTION 603 — CONTROLLED LOW STRENGTH MATERIAL (CLSM) CLSM Mixing, Delivery, and Discharge. In addition to the requirements of Subsection 601.03.3, ensure that CLSM is discharged within three hours from the original batching. Curing. Protect the CLSM from freezing until it is hardened. Ensure that the temperature of the CLSM is a minimum of 40°F upon placement. Otherwise, no curing is required. Testing of CLSM. In addition to the requirements of Subsection 601.03.7(b), cast six, 4 -in. × 8-in. cylinders per each day’s production and type of mix used (6-in. × 12-in. cylinders are also acceptable). Rodding of specimen is not required. Once the specimen is full, lightly strike the exterior of the mold 8 to 12 times to consolidate the CLSM. Ensure that specimens remain in the molds until time of testing. Exer cise care in the handling and transportation of CLSM specimens. The age of compressive strengths will be tested at the discretion of the Engineer. Paras. c, d, e, f, and g of Subsection 601.03.8 do not apply to CLSM. Plant Field Laboratory. Ensure that the plant field laboratory conforms to Subsection 930.03.7, except for the following which do not apply: • The 45-kg digital platform beam scale • The gravity drying oven • The Gilson TS-1 sieve shaker • The sample splitter 2½-in. chute width Placing CLSM by Pumping. Ensure that the requirements for pumping CLSM conform to Subsection 808.03.6 with the following exception: The discharge height may exceed 5 ft and is limited only if the mixture becomes segregated. Pumping may be suspended if the Engineer observes any deleterious materials in the discharge. Ensure that the CLSM can be pumped without appreciable loss or consistency of air content. Traffic/Paving. Resumption of traffic onto CLSM or the asphalt paving over CLSM, when required by the Engineer to expedite the overall operation , will require an initial set time and early strength development. The initial time for the CLSM to set will be a maximum of three hours. During the mix design approval process, demonstrate that the mix design will achieve the initial set time and early strength development for opening to traffic.
Part 600 — Concrete August 2025
SECTION 603 — CONTROLLED LOW STRENGTH MATERIAL (CLSM) 600-31 The Engineer may require that the area be completely covered by steel plating or protected according to the latest edition of the MUTCD.
603.04 Method of Measurement.
Controlled Low Strength Material will be measured by the number of cubic yards placed.
603.05 Basis of Payment.
The accepted quantity of Controlled Low Strength Material will be paid for at the Contract unit price per cubic yard. The price constitutes full compensation for all labor, materials, equipment, testing, and all other incidentals required to finish the work, complete and accepted.
Part 600 — Concrete August 2025
600-32 SECTION 604 SECTION 604 This Section has been Reserved for Future Use.
Part 600 — Concrete August 2025
SECTION 605 600-33 SECTION 605 This Section has been Reserved for Future Use.
Part 600 — Concrete August 2025
600-34 SECTION 606 SECTION 606 This Section has been Reserved for Future Use.
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Source: Standard Specifications for Road and Bridge Construction (Blue Book), 2022 (Aug 2025 compilation) Edition. Pages 307–313 of 951. View official source ↗