详情

原文传递 Characterization of Passing Ability of Concrete in CIDH Piles with Wet Conditions.

题名：	Characterization of Passing Ability of Concrete in CIDH Piles with Wet Conditions.
作者：	Sun, J.; Shing, P. B.
关键词：	Concrete mixtures, Concrete workability, Non-destructive evaluation, Reinforcement spacing, Wet holes, Slurry displacement method, Inspection tubes, Concrete flowability, Voids, Cavities, Concrete mixes
摘要：	In the presence of ground water or caving soils, the slurry displacement method may be used to place concrete for CIDH piles to ensure the stability of the drilled hole. As concrete is placed under slurry, anomalies may occur around the reinforcement, affecting the structural integrity of the pile. Hence, the construction of CIDH piles under wet conditions requires the installation of inspection tubes for the non-destructive detection of potential anomalies in concrete. Current Caltrans practice requires that the clear spacing between an inspection tube and an adjacent longitudinal bar be at least three inches, which is less than the 5-in. minimum clear spacing required for rebar cages of piles. Hence, concrete mixtures used for CIDH piles must have good passing ability to avoid anomalies or voids. Caltrans developed a field test method, called the California Bar (C-Bar) test, for assessing the passing ability of concrete used in CIDH piles poured with the slurry displacement method. This study was to examine if results of C-Bar tests could be used to determine whether the concrete mix has sufficient passing ability to result in good quality concrete in CIDH piles. L-Box tests were also conducted for comparison purposes. The passing ability of several concrete mixes was tested with trial batches, and mixes with different levels of passing ability were selected for trial pours of pile specimens. Twelve 24-in. diameter piles were cast with the selected mixes using the slurry displacement method. The quality of the cast concrete piles was inspected visually, and the passing ability of the mixes was assessed with C-Bar and L-Box tests. The study has found that concrete mixes with C-Bar passability ratios of 1.82 or lower resulted in piles that were free of voids on the exterior surface except for some small voids near the base of the piles. However, the concrete mix that had a passability ratio of 1.82 barely flowed beyond the rebars in the C-bar test. The results have shown that 1.80 is a reasonable upper limit for the passability ratio. Furthermore, the concrete should have a minimum slump of 10 inches. None of the concrete mixes used for the pile specimens passed the L-Box tests. Hence, this is not a good test for the passing ability.
报告类型：	科技报告