Benefits and Costs of Roller-Compacted Concrete
Roller compacted concrete or RCC was originally limited to the sub-base of roads and airfield pavements, being called lean concrete or dry lean concrete. 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. RCC mix contains a low cement content, about 110 to 120 kg/m3, uses washed aggregate of concreting quality, and has been defined by the American Concrete Institute (ACI) section 207.5R-89 as concrete compacted by rollers.
Cost and Techniques
The process of RCC itself will reduce your construction costs as there is no need to use rebars or forms, and the application process is very easy and can be done quickly. As an average, the cost per yard of RCC is about $75 per cubic yard while the cost of Hot-mix Asphalt pavement is about $90 per cubic yard, so you will already notice there are some savings by using RCC. Not only that, there are certain products used to improve RCC surface and applied to the RCC mix such as RCC Surface Pro that improves surface appearance and durability while ACEiT admixture can improve workability.
Follow these helpful tips for better results:
- Water quantity shall be carefully monitored and no water shall be added once it has been mixed thoroughly
- Dump trucks are normally used to place concrete along with paver equipment
- RCC shall be placed within 60 minutes otherwise, joints could have problems later on
- A 4-inch layer shall be the minimum thickness applied and 10 inches thick should be the thickest you can go on a single lift.
- RCC shall be compacted to 98% modified Proctor
- The concrete shall be finished with a small steel roller
- Joints shall be fresh and moist to adhere to the next concrete section
- Saw cuts shall be at a minimum 1/4 inch and spaced at least two times the thickness of the section, in feet.
- Curing concrete is critical for good results
The high strength of RCC pavements eliminates common and costly problems traditionally associated with asphalt pavements. Some of the benefits of using Roller Compacted Concrete are:
- No need to use forms
- Rebar is not required
- It provides great strength
- High Volume Placement
- It can be used as a roadway after only 24 hours of being placed
- Span soft localized subgrades
- Will not be affected by oil spills, fuels and/or hydraulic fluids
- Can withstand high temperatures
This concrete solution can be used to maintain traffic open and large volumes of RCC can be placed easily. Normally, RCC will be mixed at or near construction sites, and then transported using dump trucks and placed into an asphalt paver equipment. Then the RCC can be placed in lifts of almost 40 feet wide and 10 inches thick. The placing of the concrete is made of continuous layers and is consolidated by vibrating rollers. Other benefits are:
- Reduce cement consumption as the leaner concrete mix can be used.
- Formwork costs are minimized or eliminated because of the layer placement method.
- No concerns about high heat release while the concrete is drying.
- The cost of transporting, placement, and compaction of concrete are minimized because concrete can be hauled by dump trucks; spread by bulldozers and compacted by vibratory rollers.
Once the product has been placed, compaction process should start until the concrete pavement meets density requirements. A water cure spray or irrigation systems must be used to keep the concrete wet and providing a smooth surface. For proper workability, the concrete mix must be dry enough to prevent the sinking of the vibratory roller.
This process allows the chemical reaction that causes concrete to harden and gain strength to begin and complete. Once cured, the pavement is ready for use while sometimes an extra layer of asphalt surface is applied over the concrete for greater smoothness or as a riding surface for high-speed traffic.
Generally speaking, yes, it can be used at your site, and there is an increase in the demand for roller-compacted concrete lately in both private and public projects. Although RCC has been used almost and exclusively in new dam construction and the rehabilitation of existing dams, it can be used for the following applications:
- Highway shoulders
- Parking facilities
- Multi-modal yards
- Distribution centers