Freezing and Thawing Durability and Early Set and Strength Development of CLSM

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Title: Freezing and Thawing Durability and Early Set and Strength Development of CLSM

Author(s): T. E. Nantung and C. F. Scholer

Publication: Special Publication

Volume: 150

Issue:

Appears on pages(s): 53-86

Keywords: controlled low-strength material (CLSM); freeze-thaw durability; scaling; setting (hardening); strength; voids; Materials Research

Date: 6/1/1994

Abstract:
Most CLSM applications are designed not to resist freeze and thaw. However, in some applications, CLSM is susceptible to freeze-thaw deterioration. The failure of CLSM specimens in freeze and thaw is due mostly to surface scaling. Using a foam generator air-entraining admixture to distribute the voids throughout the mix yields good results. While the permeable void content of a typical CLSM mixture at 28 days is about 27 percent, low-strength CLSM has increasing pulse velocity but does not disintegrate into pieces. However, a typical higher strength CLSM (about 1.103 MPa or 160 psi at 28 days) with the same permeable voids has an almost constant pulse velocity during the freeze-thaw test with a slow rate of cooling. Typical 28-day compressive strength of CLSM ranges from 0.345 to 1.379 Mpa (50 to 200 psi), which is higher than that of most compacted soil or granular fills. The most important property of CLSM at early age is strength development, so that several hours after placement, the structure or facility can resume operation. The results show that there are two important stages in CLSM strength development: the stiffening stage, which indicates that the CLSM is beginning to develop cohesion; and the hardening stage, which indicates that the CLSM has hardened to the point at which it can sustain some load. Presently, only the hardening stage is recognized. CLSM can sustain foot traffic without surface depression 2 to 3 hr after the cement is in contact with the water. However, every CLSM develops strength differently, so that the hardening stage based on time in hours is inappropriate. Using penetration-resistance members is more appropriate for CLSM.