Development of a Recommended Practice for Use of Controlled Low-Strength Material in Highway Construction (2008) / Chapter Skim
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From page 5... ...
In 1984, ACI Committee 229 was formed, and the ACI-approved term "controlled low-strength material or CLSM" was adopted. In its 1999 committee report, ACI Committee 229 defined CLSM as a self-compacted, cementitious material used primarily as a backfill alternative to compacted fill (ACI Committee 229 1999)
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From page 6... ...
More specific information on types and dosages of fly ash used in typical CLSM mixtures is provided later in this chapter, and the laboratory and field evaluations described in Chapters 3 and 4 included the use of a range of different fly ashes. Other Supplementary Cementitious Materials Although fly ash is the most commonly used supplementary cementitious material (SCM)
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From page 7... ...
However, several fairly typical approaches to designing CLSM mixtures have emerged and can be grouped in broad classes. Regardless of the approach to mixture proportioning, key properties sought are fluidity with minimal segregation, acceptable setting times, and adequate strength gain (also a function of whether excavatability may be needed in the future)
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From page 8... ...
ASTM D 6103, "Flow Consistency of Controlled Low Strength Material," has gained some acceptance since its adoption by ASTM. The test method uses a 75 × 150 mm cylinder, which is lifted, allowing the CLSM to slump and increase in diameter.
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From page 9... ...
Flow 18 ASTM D 6103 (or similar) and ASTM C 143 Compressive strength 17 AASHTO T 22 and ASTM D 4832 Unit weight 14 AASHTO T 121 Air content 10 AASHTO T 152 Set time 7 ASTM C 403 Durability 2 pH and resistivity Shrinkage 1 Visual Geotechnical 1 Direct shear Temperature 1 Modified ASTM C 1064 Chlorides/sulfates 1 Determination of ion contents Permeability 0 None Source: Folliard et al.
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From page 10... ...
Concerns regarding machine capacity and accuracy, as well as curing conditions, cylinder mold types, and other aspects of compression testing were evident in the 1998 survey conducted under this project, and significant emphasis was placed in the laboratory phase of this project (Chapter 3) on improving the test method.
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From page 11... ...
This is especially important when considering CLSM for use in bridge approaches or whenever CLSM will serve as a functional base or subbase material. Common soil test methods that could potentially be applied to CLSM include AASHTO T 193, "Standard Method of Test for the California Bearing Ratio," AASHTO T 274, "Resilient Modulus of Unbound Granular Base/Subbase Materials and Subgrade Soils," AASHTO T 292, "Resilient Modulus of Subgrade Soils and Untreated Base/Subbase Materials" and AASHTO T 307, "Determining the Resilient Modulus of Soils and Aggregate Materials." Consolidation The consolidation of CLSM can be measured using ASTM D 2435, "One-Dimensional Consolidation Properties of Soil." This method is easy to perform, requires minimal equipment, and can be used to estimate both the rate and total amount of settlement for CLSM used in various applications.
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From page 12... ...
, often indicate that CLSM could be detrimental to the corrosion performance of pipes embedded in CLSM. Probably one of the most common methods used to determine the corrosivity of soils around ductile iron pipes is the ANSI/AWWA C105/A21.5, "American National Standard for Polyethylene Encasement for Ductile-Iron Pipe Systems." This standard, shown in Appendix B, assigns points for various soil backfill characteristics (such as pH, resistivity, moisture content, etc.)
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From page 13... ...
Test methods typically used to measure corrosion in concrete may be applied to CLSM, including ASTM G 109, "Determining the Effects of Chemical Admixtures on the Corrosion of Embedded Steel Reinforcement in Concrete Exposed to Chloride Environments"; ASTM G 59, "Conducting Potentiodynamic Polarization Resistance Measurements"; and ASTM G 1, "Preparing, Cleaning, and Evaluating Corrosion Test Specimens." In addition, Abeleirra et al.
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From page 14... ...
CLSM Applications CLSM is used as an alternative to compacted fill mainly for backfill, utility bedding, void fill, and bridge approach applications. Before summarizing the current practice of using CLSM for these applications, a brief overview of the general benefits of using CLSM in each application is provided.
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From page 15... ...
However, for utility bedding, the advantages of CLSM were recognized not only by state DOTs but also by city agencies. Void fill is another common application of CLSM products.
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From page 16... ...
A review of this information highlights some of the key research needs that existed prior to conducting the research described in the remainder of this report: • Lack of standardized test methods, specifications, and construction guidelines for CLSM • Concerns over long-term strength gain (and impact on excavatability) • Potential concerns over long-term durability of CLSM, especially related to corrosion of utilities It is hoped that the findings from this project (highlighted in Chapters 3 and 4)
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