Effects of Accelerating Admixture on Flowable Fill Strength


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Title: Effects of Accelerating Admixture on Flowable Fill Strength

Author(s): W. Lovencin and F.T. Najafi

Publication: Special Publication

Volume: 259


Appears on pages(s): 121-138

Keywords: applications; concrete; polymer concrete; polymer-impregnated concrete; polymer-modified concrete; polymers

Date: 2/1/2009

Flowable fill is a self-compacted, cementitious material used primarily as a backfill in lieu of compacted fill. It generally consists of sand, Portland cement, fly ash/slag and water. Flowable fill, does not settle, does not require vibration or other means of compaction, can be excavated, is fast to place, and safer than other forms of fill. Because of its versatile applications, the construction industry utilize flowable fill as a means of reducing cost and completion time for their projects. Among its many uses, flowable fill mixtures used for pavement base design for placement under flexible pavements received reviews due to its curing or setting time. Review of literature shows that flowable fill is highly considered and used by numerous state department of transportation (DOTs). In that study, state DOTs that were surveyed discussed problems of getting flowable fill to set and harden within a reasonable amount of time. Hardening time is the approximate period of time required for flowable fill to go from plastic state to a hardened state with sufficient strength to support the weight of a person. This paper presents the results of a laboratory study which evaluate the effects of accelerating admixtures on setting time and long term strength of flowable fill. Samples were cast in Limerock Bearing Ratio (LBR) cylinders and rectangular wooden molds. Samples were categorized as undrained and drained. Undrained samples contained plastic sheets in their interior and the drained samples contained geofabric or filter fabric in its interior. The results show flowable fill containing accelerating admixture hardened and set at somewhat earlier time than control mixtures containing no accelerating admixture. Thus, accelerating admixtures help reduce minimally both the setting and harden times in flowable fill. The findings from this study, show promising sign for field application. Such information, although small, can be of beneficial usage for engineers deciding on whether to add accelerator to a flowable fill mixtures for reducing the setting and hardening time.