Roller Compacted Concrete
...strong, dense and durable.
RCC: Roller Compacted Concrete Is Here To Stay
What is roller compacted concrete?
Roller Compacted Concrete pavement is an ultra-tough best described as a zero slump concrete with compressive strengths greater than 30n/mm2 , and is placed with standard or high-density paving equipment and consolidated/compacted using steel-drum or rubber-tired rollers to achieve a durable, wear resistant surface.
Roller compacted concrete (RCC) is a tough, durable type of concrete pavement that is well suited for heavy industrial applications, as well as low-speed roads and arterial roads. Roller compacted concrete draws its name from the construction practices used to place and finish the material. Similiar to what the industry knows as conventional concrete(stone, sand, cement, and water), RCC however, is composed up of different proportions and placing methods. Roller compacted concrete pavement (RCCP) is a dry mix that is rigid enough to bear the weight of 20 ton rollers and stiff enough to be compacted by high density pavers. The standard means of placing RCCP is by first being placed through a standard or high density paver and subsequently compacted by a non-vibratory or vibratory roller. Most of the time, RCC is constructed without joints, formwork, finishing, steel reinforcement, or dowels. Making a significant economic impact in those areas for the job at hand.
RCC is NOT a new product…
In North America, RCC has been around since the 1960’s and was used primarily in the construction of dams. The use of RCC in dam building became so prevalent through the economic benefits that it brought to that application. Quicker, easier placement methods coupled with lower costs made RCC the standard practice for dam building in the 1960’s and 1970’s. The lower cement content in RCC, compared to that of conventional concrete, enable the construction process to be overhauled due to the lower heat of hydration that occurs in curing of the material. Meaning that one can place more RCC at a time than conventional concrete.
The need at hand was that of a strong pavement capable of bearing severe loads from logging trucks and other specialized equipment. The economic benefits that RCC brought were the perfect fit for the industry, the lower material costs and resources needed for placement helped spring RCC from the logging industry to other industrial applications around the world.
RCCP is a product that doesn’t fit any and all applications, but does excel when used in heavy load, low speed, and cold weather uses. With the material becoming more and more prominent in the marketplace, there is an increase in the use of RCCP in areas such as; industrial parking, local streets, highway shoulders, as well as other low volume roads. To go along with the above stated, RCCP has entered the urban paving market, with applications like low-maintenence roads, subdivision residential streets, and various other arterial roads. With the use of an asphalt overlay, RCC has been used in trucking roads, highway shoulder rehabilitation, as well as intersection approach lanes.
Benefits of Roller-Compacted Concrete
Speed of Construction
Perhaps the biggest benefit of Roller Compacted Concrete pavement is that it can be constructed more quickly and cost-effectively than conventional concrete or most asphalt pavements. Roller Compacted Concrete is placed with conventional or high-density asphalt-type paving equipment and compacted with rollers, eliminating the need for forming and finishing. In most cases, Roller Compacted Concrete can be competed in one pass. Extremely heavy-duty pavements requiring thicknesses greater than 10 inches may require two lifts. Because of its density and compaction, Roller Compacted Concrete can achieve sufficient load carrying capacity quickly and has, in some instances, been open to traffic within 24 hours after placement
Roller Compacted Concrete is a rigid pavement which will easily withstand the load form repetitive traffic. Because it can more evenly carry heavy loads, Roller Compacted Concrete will not rut from heavy axle loads, nor will it shove or tear from turning or braking vehicles. Additionally, Roller Compacted Concrete has all of the durability of conventional concrete pavement including resistance to fuels, oils, solvents and other fluids, and the ability to withstand the extremes of summer heat and winter cold. A properly designed Roller Compacted Concrete pavement will easily provide 20+ years of service.
Similar to conventional concrete, Roller Compacted Concrete has fewer repairs over its service life. There is no seal coating or resurfacing required. Aside from an occasional cleaning with a sweeper/vacuum, Roller Compacted Concrete maintenance requirements are minimal.
There are numerous cost savings associated with Roller Compacted Concrete. Historically, Roller Compacted Concrete has been comparable in cost to asphalt pavement. With rising oil/asphalt costs, Roller Compacted Concrete may actually be lower in initial paving costs. When compared to conventional concrete paving costs, Roller Compacted Concrete can provide savings of 25% to 30%. And owners will appreciate the lower Life-Cycle cost associated with Roller Compacted Concrete’s low maintenance requirements.
You have probably read much about the economic benefits that RCC possesses. So what are those benefits? Let’s identify them.
Lower material costs. This refers to the lower cement content in RCC than that of conventional concrete, and in conventional concrete, cement is the most expensive ingredient. This is accomplished through the replacement of Portland cement with fly ash.
Simpler construction practices. Again, compared to conventional concrete, RCC requires no materials for formwork, calls for no joints or dowels, significantly less manpower for the application, and time saved in opening a recently completed project. Once RCC is rolled and compacted fully, the material is capable of withstanding traffic and bearing stress immediately. Although not recommended, that is where one can save a considerable amount of time in the construction process.
High strengths. RCC is one material of great strength and durability. These describing factors are also achieved in a short amount of time. Compressive strenghs for roller compacted concrete can be in the upwards of 9000 psi! The mix design of RCC will 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 drier mix allows a high psi to form much quicker than that of a more fluid, hydrated mix.
Roller Compacted Concrete pavements are environmentally friendly. Supplementary cementitious materials such as fly ash and ground granulated blast furnace slag can be used, reducing the amount of Portland cement and thus lowering the embodied energy of an Roller Compacted Concrete mix.
Roller Compacted Concrete’s lighter color provides greater light reflectivity, which means brighter and safer surroundings as well as lower lighting requirements. In fact, Roller Compacted Concrete pavement can reduce energy consumption by as much as 37% by either reducing the number of light fixtures needed or by allowing lower wattage light.
The lighter color of Roller Compacted Concrete also means less heat is absorbed, resulting in cooler communities. Utilizing a lighter colored pavement such as Roller Compacted Concrete can reduce ambient air temperatures by as much as 7-10 degrees.
Roller Compacted Concrete pavements have a solar reflectance index (SRI) greater than the minimum 29 that is necessary to obtain the appropriate credits for heat island mitigation – non-roof in the USGBC’s LEED Green Building Rating System.
Subgrade/Subbase Preparation by RCCP
RCCP calls for most of the same guidelines and procedures for subgrade preparation as that of conventional concrete pavement. The bottom line is that the subbase should provide sufficient strength throughout the entire thickness of the pavement to support the compaction process. Incorrect subbase preparation can cause inconsistent surface conditions and potentially shorten the life span of the pavement itself. The target density grade of RCCP after it has been compacted is right at 95% of the total compaction. Prior to paving, the subgrade should be adequately moistened, wet but no standing water or puddling, as well as kept free of foreign material like garbage or other debris. There are drawbacks from oversaturating the subbase or having the subgrade too dry. If the subbase is too dry, it can draw moisture from the RCC on top of it, causing improper compaction and a failed product. For a subgrade that is too wet, the RCC can swell and lead to another failed end result. Adequate time should be invested to ensure that the subbase is properly moistened, this is another aspect that can lead to a successful application of RCCP.
Construction Process Photos of RCCP
Construction Process Photos of RCCP