![UserKTrimble-AP Taum Sauk Reservoir UnderConstruction Nov 22 2009 crop1](https://upload.wikimedia.org/wikipedia/commons/4/41/UserKTrimble-AP_Taum_Sauk_Reservoir_UnderConstruction_Nov_22_2009_crop1.jpg)
Roller-compacted concrete (RCC) or rolled concrete (rollcrete) is a special blend of
concrete
Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wi ...
that has essentially the same ingredients as conventional concrete but in different ratios, and increasingly with partial substitution of
fly ash
Fly ash, flue ash, coal ash, or pulverised fuel ash (in the UK) plurale tantum: coal combustion residuals (CCRs)is a coal combustion product that is composed of the particulates (fine particles of burned fuel) that are driven out of coal-fired ...
for
Portland cement
Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-specialty grout. It was developed from other types of hydraulic lime in England in the early 19th c ...
. The partial substitution of fly ash for Portland Cement is an important aspect of RCC dam construction because the heat generated by fly ash hydration is significantly less than the heat generated by Portland Cement hydration. This in turn reduces the thermal loads on the dam and reduces the potential for thermal cracking to occur. RCC is a mix of cement/fly ash, water, sand,
aggregate and common additives, but contains much less water. The produced mix is drier and essentially has no
slump. RCC is placed in a manner similar to
paving; the material is delivered by
dump truck
A dump truck, known also as a dumping truck, dump trailer, dumper trailer, dump lorry or dumper lorry or a dumper for short, is used for transporting materials (such as dirt, gravel, or demolition waste) for construction as well as coal. A typi ...
s or
conveyor
A conveyor system is a common piece of mechanical handling equipment that moves materials from one location to another. Conveyors are especially useful in applications involving the transport of heavy or bulky materials. Conveyor systems allow ...
s, spread by small
bulldozer
A bulldozer or dozer (also called a crawler) is a large, motorized machine equipped with a metal blade to the front for pushing material: soil, sand, snow, rubble, or rock during construction work. It travels most commonly on continuous track ...
s or specially modified
asphalt paver
A paver (road paver finisher, asphalt finisher, road paving machine) is a piece of Heavy equipment, construction equipment used to lay asphalt concrete or Road_surface#Concrete, Portland cement concrete on roads, bridges, parking lots and other su ...
s, and then compacted by
vibratory rollers.
In dam construction, roller-compacted concrete began its initial development with the construction of the
Alpe Gera Dam near Sondrio in North Italy between 1961 and 1964. Concrete was laid in a similar form and method but not rolled. RCC had been touted in engineering journals during the 1970s as a revolutionary material suitable for, among other things, dam construction.
Initially and generally, RCC was used for backfill, sub-base and concrete pavement construction, but increasingly it has been used to build concrete
gravity dam
A gravity dam is a dam constructed from concrete or stone masonry and designed to hold back water by using only the weight of the material and its resistance against the foundation to oppose the horizontal pressure of water pushing against it. ...
s because the low cement content and use of fly ash cause less heat to be generated while curing than do conventional
mass concrete Mass concrete is defined by American Concrete Institute Committee 207 as "any volume of concrete with dimensions large enough to require that measures be taken to cope with the generation of heat from hydration of cement and attendant volume change ...
placements. Roller-compacted concrete has many time and cost benefits over conventional mass concrete dams; these include higher rates of concrete placement, lower material costs and lower costs associated with post-cooling and
formwork
Formwork is Molding (process), molds into which concrete or similar materials are either precast concrete, precast or cast-in-place concrete, cast-in-place. In the context of concrete construction, the falsework supports the shuttering mold ...
.
Dam applications
For dam applications, RCC sections are built lift-by-lift in successive horizontal layers resulting in a downstream slope that resembles a concrete staircase. Once a layer is placed, it can immediately support the earth-moving equipment to place the next layer. After RCC is deposited on the lift surface, small dozers typically spread it in one-foot-thick (about 30 cm) layers.
[Portland Cement Association]
The first RCC dam built in the USA was the
Willow Creek Dam on Willow Creek, a tributary in
Oregon
Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...
of the
Columbia River
The Columbia River (Upper Chinook: ' or '; Sahaptin: ''Nch’i-Wàna'' or ''Nchi wana''; Sinixt dialect'' '') is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia, C ...
. It was constructed by the
Army Corps of Engineers between November 1981 and February 1983.
[ (start date conflicts with USACE source)] Construction proceeded well, within a fast schedule and under budget (estimated $50 million, actual $35 million). On initial filling though, it was found that the leakage between the compacted layers within the dam body was unusually high. This condition was treated by traditional remedial
grouting at a further cost of $2 million, which initially reduced the leakage by nearly 75%; over the years, seepage has since decreased to less than 10% of its initial flow. Concern over the dam's long-term safety has continued however, although only indirectly related to its RCC construction. Within a few years of construction, problems were noted with stratification of the reservoir water, caused by upstream pollution and anoxic decomposition, which produced
hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...
gas. Concerns were expressed that this could in turn give rise to sulfuric acid, and thus accelerate damage to the concrete. The controversy itself, as well as its handling, continued for some years. In 2004 an aeration plant was installed to address the root cause in the reservoir, as had been suggested 18 years earlier.
![Omo Gibe III, Wolayita 3](https://upload.wikimedia.org/wikipedia/commons/9/99/Omo_Gibe_III%2C_Wolayita_3.jpg)
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; by 2008, about 350 RCC dams existed worldwide.
[Brian Forbes]
RCC – New Developments and Innovations
Brazilian International Roller Compacted Concrete (RCC) Symposium, Salvador, Brazil, 7Sept. 2008 Currently the highest dam of this type is the
Gilgel Gibe III Dam
The Gilgel Gibe III Dam is a 250m high roller-compacted concrete dam with an associated hydroelectric power plant on the Omo River in Ethiopia. It is located about west of Sodo in the Southern Nations, Nationalities, and Peoples' Region. Once f ...
in Ethiopia, at 250 m, with the Pakistani
Diamer-Bhasha Dam
Diamer-Bhasha Dam is a concreted-filled gravity dam, in the preliminary stages of construction, on the River Indus between Kohistan district in Khyber Pakhtunkhwa and Diamer district in Gilgit Baltistan, Pakistan administered Kashmir. Its founda ...
under construction at 272 m.
Use
Concrete canvas field of application extends from landscape construction to prefabricated buildings:
* at channel creation - concrete canvas makes it possible to fix and concrete internal surface using water collecting channels;
* to protect the walls of pits and cuts from erosion, to prevent the collapse of slopes;
* for embankment of dirt fills enclosing sludge ponds at sewage treatment plants;
* at concrete construction repair - supporting walls, stairs, collision walls;
* in the construction, reconstruction and repair of hydraulic facilities, primarily in the repair of structures that secure the coastline.
Concrete canvas is used for construction of prefabricated buildings - shelters in the areas of emergency situations - the canvas is drawn on the light carcase, poured with water and within several hours window and door units may be inserted into the made-up house.
Advantages
* simple usage - specially qualified workers are not required;
* easy to transport;
* environmental safety and nonflammability;
* no need for care after installation;
* it's possible to use in different climate conditions - in the rain, at high and low temperatures.
See also
*
List of roller-compacted concrete dams
*
Asphalt concrete
Asphalt concrete (commonly called asphalt, blacktop, or pavement in North America, and tarmac, bitumen macadam, or rolled asphalt in the United Kingdom and the Republic of Ireland) is a composite material commonly used to surface roads, parkin ...
Further reading
*
*
References
External links
History of ConcreteDatabase of Worldwide Roller Compacted Concrete Dams
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