This paper describes how flowable fill is a self-compacted, cementitious material and it 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, and safer than other forms of fill. One approach to predict whether or not a flowable fill mix is excavatable is to develop a correlation using the early age strength and long-term strength. Flowable fill mixture exhibiting strength less than 0.689 Mpa (100 psi) would be classified excavatable. Mixtures resulting in strengths higher than 0.689 Mpa would be very difficult to excavate and would be termed non-excavatable. Because flowable fill is generally used for backfill and is placed underneath pavement, literature review shows few studies done where one evaluates the effect of moisture on the long term strength of flowable fill while underneath the pavement. This paper presents the results of a laboratory study that evaluated the effects of moisture on long term strengths of flowable fill and assessed an accelerated method for predicting the 28-day strength of flowable fill. Samples were cast in LBR cylinders and rectangular wooden molds. Samples were categorized as undrained and drained. Promising results were obtained with respect to how moist environments impact the long term strength of flowable fill mixtures. Results showed for early curing period, the undrained samples exhibited lower strength than the drained samples. However, the strength of the undrained samples increased with longer periods and to some extent exceeded the drained samples at 28 days curing period. The accelerated samples had the potential to predict the 28 day strength using an accelerated method.
Abstract