Cast-in-drilled-hole (CIDH) piles are often constructed to depths that are inaccessible to internal vibration of the concrete. Internal vibration is necessary to consolidate the concrete and, if not performed, then typically inspection pipes are necessary to detect the presence of voids in CIDH piles. Void detection is critical to assessing whether or not the CIDH pile will provide adequate support for the design loads. However, inspection pipes are often placed in line with congested reinforcement bars and can further congest the reinforcement. Highly congested reinforcement can cause concrete voids to occur. Because these CIDH piles are inaccessible and have congested reinforcement a highly workable concrete mixture is necessary to decrease the potential of concrete voids from occurring. Flowing concrete (FC) is required for CIDH piles.
FC is a concrete mixture with a slump greater than 7.5 inches (178 mm). Little research has been performed on the variables that influence FC workability. However, much attention and research has been performed regarding the workability of conventional concrete (CC) and self-consolidating concrete (SCC). In fact, proportioning methods for these concrete types are well established. This is not the case for FC mixtures. Research is needed to proportion FC mixtures and assess the influence of coarse aggregate (CA) type and mixture proportions FC workability.
The research presented here proposes a new methodology for proportioning FC mixtures. This method uses a quantitative assessment of the coarse aggregate (CA) shape along with the combined aggregate void (AV) content to proportion FC mixtures. This research also provides information on the influence of various mixture constituents and proportions on workability: CA type, paste volume, fine aggregate (FA) to CA ratio (FA/CA), and paste volume to AV content ratio (PV/AV). Results from this study indicate that FC mixtures with adequate flowability, stability, and passing ability can be proportioned using this newly developed mixture proportioning method. Results also indicate that PV/AV significantly influences FC flowability and stability and more importantly a range of PV/AV can be identified to achieve adequate flowability and stability. In some cases, the results indicated that FA/CA significantly influences slump flow and in all cases FA/CA influences stability.