309.5R-00: Compaction of Roller-Compacted Concrete

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Title: 309.5R-00: Compaction of Roller-Compacted Concrete

Author(s): ACI Committee 309

Publication: Technical Documents

Volume:

Issue:

Appears on pages(s): 15

Keywords: compaction; consolidation; dams; pavements; roller-compacted concrete.

Date: 2/23/2000

Abstract:
Roller-compacted concrete (RCC) is an accepted and economical method for the construction of dams and pavements. Achieving adequate compaction is essential in the development of the desired properties in the hardened material. The compaction depends on many variables, including the materials used, mixture proportions, mixing and transporting methods, discharge and spreading practices, compaction equipment and procedures, and lift thickness. The best performance characteristics are obtained when the concrete is reasonably free of segregation, well-bonded at construction joints, and compacted at, or close to, maximum density. Compaction equipment and procedures should be appropriate for the work. In dam or massive concrete applications, large, self-propelled, smooth, steel-drum vibratory rollers are used most commonly. The frequency and amplitude of the roller should be suited to the mixture and lift thickness required for the work. Other roller parameters, such as static mass, number of drums, diameter, ratio of frame and drum mass, speed, and drum drive influence the rate and effectiveness of the compaction equipment. Smaller equipment, and possibly thinner compacted lifts, are required for areas where access is limited. Pavements are generally placed with paving machines that produce a smooth surface and some initial compacted density. Final density is obtained with vibratory rollers. Rubber-tired rollers can also be used where surface tearing and cracks would occur from steel-drum rolling. The rubber-tired rollers close fissures and tighten the surface. Inspection during placement and compaction is also essential to ensure the concrete is free of segregation before compaction and receives adequate coverage by the compaction equipment. Testing is then performed on the compacted concrete on a regular basis to confirm that satisfactory density is consistently achieved. Corrective action should be taken whenever unsatisfactory results are obtained. RCC offers a rapid and economical method of construction where compaction practices and equipment are a major consideration in both design and construction.