Mix design proportioning methods for roller compacted concrete rcc.
Roller compacted concrete mix design for dams.
Over the past two decades many design details and construction methods have been adapted to enhance the final product while maintaining the speed of construction that provides rcc its competitive edge.
Roller compacted concrete rcc continues to gain recognition as a competitive material for building new and rehabilitating existing dams.
The mixture of roller compacted concrete need to be dry enough to avoid sinking of the vibratory roller equipment but wet enough to allow sufficient distribution of.
The mix design of rcc usually consist of a high amount of stone portland cement with a replacement of fly ash a minimal amount of sand and of course water to hydrate the mix.
The soil compaction method consists of the following steps.
This proportioning method involves establishing a relationship between the density and moisture content of an roller compacted concrete mixture to obtain the maximum density by compacting samples over a range of moisture contents.
Roller compacted concrete rcc was originally limited to the sub base of roads and airfield pavements being called lean concrete or dry lean concrete.
In the quarter century since willow creek considerable research and experimentation have yielded innumerable improvements in concrete mix designs dam designs and construction methods for roller compacted concrete dams.
Different mixes of roller compacted concrete can be designed to meet the different requirements of the two applications.
Cement content is generally low typically 70 to 130 kg m3.
Whereas a roller compacted concrete pavement built to replace a failed pavement on a major route may require reaching 2 500 psi compressive strength and be opened for traffic within one or two days from placement.
Materials used in rcc mix design a cementitious materials.
Currently the highest dam of this type is the gilgel gibe iii dam in ethiopia at 250 m with the pakistani diamer bhasha dam.
The overriding criteria for these mixtures are the shear strength between the lifts and low permeability of concrete since no protective impermeable face is used upstream.
Properties of roller compacted concrete mix design.
By 2008 about 350 rcc dams existed worldwide.
Upper still water and elk creek dams are examples of dams that were built using this approach.
The concrete mixture used for construction should keep in an unhardened state to support the roller compaction.
This type of concrete has become very popular due to the fact that it is a simple material to produce and because it can be placed fast while producing a great surface.
The development of roller compacted concrete rcc was a major change in the construction practices of dams and other structures.
