Assessment of design and properties for flowable fill usage in highway pavement construction for conditions in Florida

Flowable fill, also known as controlled low-strength material (CLSM), is a self compacting cementitious material primarily used as a backfill in lieu of compacted soil. Flowable fill is an extremely versatile construction material that has been used in a wide variety of applications. There are two types of flowable fill, excavatable and nonexcavatable. An excavatable flowable fill mixture is considered excavatable when the 28-day compressive strength is 100 psi. Nonexcavatable mixtures are mixes in which the minimum design strength is at 125 psi or greater. The ability to control and predict the strength and volume change (shrinkage) is an important aspect to consider when designing a flowable fill mixture. Various studies have been conducted to better understand and predict quality control measures such as the strength and the occurrence of shrinkage in flowable fill. The aim of this research was to vary components of excavatable flowable fill mixtures. A 4 × 3 × 2 × 3 factorial design (i.e. , 4 levels of cement, 3 levels of mineral admixtures, 2 levels of air content, and 3 levels of water/cement ratio) was applied to evaluate the compressive strength, limerock bearing ratio (LBR) strength, and shrinkage. With this study’s objective in mind, a total of 58 mixtures were selected from the factorial design matrix and batched in a laboratory. The strength of the mixtures was evaluated at 6 hours, 1 day, 2 days oven cured, 3 days, 28 days and 56 days. Mathematical models were developed to predict the LBR, compressive strength, and volume change. An accelerated curing method, along with prediction models, was developed to help estimate long-term strength of flowable fill. Based on the performance of the statistical analysis, it was found that the models developed from this study provided good correlations for estimating strength and volume change of excavatable flowable fill mixture. Though the models were found to provide good correlations, the formula developed for estimating the volume change was found to be unacceptable for design application. This study provides a rational method for engineers to utilize when designing flowable fill mixture.