ACI 309.1R-08 Report on Behavior of Fresh Concrete During Vibration

ACI 309.1R-08 Report on Behavior of Fresh Concrete During Vibration. Reading (1967) observed that for most ordinary mixtures, the stickiness imparted by air entrainment makes it difficult to release entrapped air; consequently, more vibration may be necessary for certain mixtures. Ritchie (1968) reviewed such concepts as workability and described such factors as stability, compactahility, and mobility and the corresponding methods of measurements. Shiaerman (1970) reported that ultra-high- frequency vibration increases the hydration of the cement and improves the properties of concrete. High energy input and heat generation, and the small depth of penetration of the vibration, however, are drawbacks to this method. Wilde (1970) discussed the basic parameters involved in the vibrator-concrete interaction and presented formulas for computing the radius and volume affected and the time required for consolidation. ACI Committee 309 (1982) published a report that explained the basic principles of consolidation and gave recommendations for proportioning concrete mixtures, equipment, and procedures for different types of construction, quality control, vibrator maintenance, and consolidation of test specimens. A RILEM symposium at the University of Leeds in 1973 included papers by Smalley and Ahmad (1973), Bache (1973), and Popovics (1973) that addressed rheological properties and consolidation of concrete. Cannon (1974) reported on the compaction of zero-slump concrete with a vibratory roller. Later, AC! Committee 207 (1980) prepared a state-of-the-art report on this subject. Tattersall (1976) reported on the mobility of concrete by determining power requirements for mixing at various speeds. Taylor(1976) published the results of extensive laboratory tests on the effect of different parameters on the effectiveness of internal vibrators. Gamma ray scanning was used to determine the density of the concrete and, hence, the radius of action of the vibrators. Acceleration and amplitude were found to be the most important parameters. Alexander (1977) reported basic research on the mechanics of motion of fresh concrete. It was found that the response of concrete to vibration under low applied forces can be expressed in terms of stiffness, damping, and mass. During vibration, stiffness and damping practically disappear, and only mass is involved. Tuthill (1977) summarized knowledge of the effects of revibration. Revibration may produce benefits, particularly for the wetter mixtures, by eliminating water that collects under reinforcing bars and reducing bugholes, especially in the upper portion of deep lifts, which increases the strength of the concrete.ACI 309.1R pdf download.