Roller Compacted Concrete (Rollcrete): A Comprehensive Guide to Ultra-Tough Pavement Construction

Roller Compacted Concrete

Roller Compacted Concrete also know as Rollcrete. Roller Compacted Concrete takes its name from the construction method used to build it. It’s placed with conventional or high-density asphalt paving equipment, and then compacted with rollers.

Roller-compacted concrete has the same basic ingredients as conventional concrete: cement, water, and aggregates, such as gravel or crushed stone. But unlike conventional concrete, it’s a drier mix stiff enough to be compacted by vibratory rollers.

Typically, Rollcrete is constructed without joints. It needs neither forms nor finishing, nor does it contain dowels or steel reinforcing. These characteristics make roller-compacted concrete simple, fast, and economical.

What Is Roller Compacted Concrete?

Roller-compacted concrete (Rollcrete) is an ultra-tough, zero-slump concrete with compressive strengths greater than 4,000 psi.

It is placed with asphalt pavers to form a nonreinforced, concrete pavement. Roller-compacted concrete successfully and economically combines strength and durability with ease of construction.

Roller Compacted Concrete Process

Rollcrete takes its name from the method used to build it.

Mixing of Roller-compacted concrete

A Roller-compacted concrete (Rollcrete) mixing facility, such as a pug mill, tilt drum, or dry batch ready-mixed plant, must have the efficiency to evenly disperse the relatively small amount of water present in the stiff, dry mix which resembles damp gravel.

Transport of Roller-compacted concrete

Dump trucks transport the roller-compacted concrete (Rollcrete) mix from the plant to the conventional or high-density asphalt pavers.

Placement of Roller-compacted concrete

The mix is placed in layers (or lifts) 4-9 inches thick.

Compaction of Roller-compacted concrete

Steel drum vibratory rollers compact the concrete.

Compaction is the most important step in Roller-compacted concrete (Rollcrete) construction because it provides density, strength, smoothness, and surface texture.

The process begins immediately after placement and continues until the pavement meets density requirements. The pavement must be cured to ensure proper strength gain.

Characteristics of Roller-Compacted Concrete

Compressive Strength

• Compressive strengths of Roller-compacted concrete (Rollcrete) are usually similar to those of conventional concrete (i.e. 4,000 – 6,000 psi).
• The dense-graded aggregate structure and effectively low water-to-cementitious materials ratio (w/cm) help roller-compacted concrete achieve high compressive strengths.

Flexural Strength

• Flexural strength is directly related to the density and compressive strength of the Roller-compacted concrete mixture.
• In properly constructed roller-compact concrete pavements, the aggregates are densely packed and minimize the development of fatigue cracking.
• The density of the paste and the strength of its bond to the aggregate particles are high due to its low w/cm ratio.
• As a result, the flexural strength of Roller-compacted concrete, depending on the mix design, is generally high ranging from 500 to 1,000 psi.
• Based on beams and cores obtained from a test section, the relationship between the compressive and flexural strengths of Roller Compacted Concrete appears to be similar to that for conventional concrete and can be represented by the equation below:

fr = C. fc

where:

fr = Flexural Strength (Third-Point Loading), Psi
fc = Compressive Strength, Psi
C = A Constant Between 9 and 11 Depending on Actual Roller Compacted Concrete Mix

Modulus of Elasticity

• Modulus of elasticity represents a material’s propensity to undergo reversible elastic deformation in response to stress.
• Limited tests on Roller Compacted Concrete cores obtained from a full-scale test section indicate that Roller Compacted Concrete modulus of elasticity values are similar to or slightly higher than those of conventional concrete when the mixes have similar cement contents.
• The modulus of elasticity expresses the ratio between the applied stress and strain, as shown below:

E = σ / ε

where:

E = Modulus of Elasticity (psi)
σ = Stress (psi)
ε = Strain (in./in.)

Freeze-Thaw Durability

• Two sets of roller-compacted concrete (Rollcrete) samples cured for 28 days were subjected to freeze-thaw (F-T) cycles and immersion in laboratory conditions.
• The compressive strength of Rollcrete immersed in KAc solution decreases by 18.8% and 32.8% after 6 and 12 months.

Application of Roller Compacted Concrete

• Today, Roller-compacted concrete is used when strength, speed of construction, durability, and economy are primary needs.
• It is a type of concrete pavement that is well suited for heavy industrial applications, as well as low-speed roads and arterial roads.
• The roller-compacted concrete has been used to construct, repair, or maintenance of the following structures:

List of Application Roller Compacted Concrete

Roller Compacted Concrete Cost

• The process of Roller compacted concrete itself will reduce your construction costs as there is no need to use forms or rebars, and the application process is very easy and can be done quickly.
• As an average, the cost per yard of Roller compacted concrete 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 Roller compacted concrete.
• Not only that, there are certain products used to improve the Roller compacted concrete surface and applied to the Roller compacted concrete mix such as Roller compacted concrete Surface Pro that improves surface appearance and durability while ACEiT admixture can improve workability

Benefits of Roller Compacted Concrete

The high strength of Roller compacted concrete pavements eliminates common and costly problems traditionally associated with asphalt pavements.

Some of the benefits of using Roller Compacted Concrete are:

• Roller compacted concrete provides great strength
• Roller compacted concrete no need to use forms
• In this roller-compacted concrete rebar is not required
• Roller compacted concrete is high volume placement
• It can be used as a roadway after only 24 hours of being placed
• Will not be affected by oil spills, fuels and/or hydraulic fluids
• Span soft localized subgrades
• Can withstand high temperatures

Advantages of Roller-Compacted Concrete

• This roller-compacted concrete is cost-effective and fast construction.
• Roller-compacted concrete requires minimal maintenance.
• Roller compacted concrete plain surface and also no rutting, no potholes.
• The cost of formwork is minimized or eliminated due to the layer placement method.
• Roller-compacted concrete does not deform under heavy concentric loads.
• Also, reduces cement consumption as leaner concrete mixtures may be used.
• There is no concern about the release of high heat during the drying of concrete.
• Roller-compacted concrete resistance to shoving and pushing.
• Transportation costs, placement, and compaction of concrete are minimized, as a result, the concrete will be handled by dump vehicles; spread by the bulldozers and compressed by vibration rollers.
• Shorter haul distance.
• Rapid placement
• Small construction crew

Roller Compacted Concrete Disadvantages

• Smoothness is difficult to achieve.
• Revelling of Cracks.
• Skill person required.
• In roller compacted concrete dams, the drainage gallery often increases construction time and increases costs because the earth fill method being used does not easily accommodate such a construction.
• Situations, where Roller Compacted Concrete may not be appropriate, is when aggregate material is not reasonably available, the foundation rock is of poor quality or not close to the surface, or where foundation conditions can lead to excessive differential settlement.
• Dams constructed or repaired with roller-compacted concrete may suffer from water seepage. That is why water stoppage layers shall be considered.

Frequently Asked Questions (FAQ) about Roller Compacted Concrete (Rollcrete)

What is Roller Compacted Concrete (Rollcrete)?

Rollcrete is a type of ultra-tough, zero-slump concrete with compressive strengths greater than 4,000 psi, placed using asphalt pavers and compacted with vibratory rollers.

What materials are used in Rollcrete?

Rollcrete uses the same basic ingredients as conventional concrete: cement, water, and aggregates like gravel or crushed stone.

How is Rollcrete different from conventional concrete?

Unlike conventional concrete, Rollcrete is a drier mix that can be compacted by rollers. It typically does not require joints, forms, finishing, dowels, or steel reinforcement.

What are the main steps in the Rollcrete construction process?

The Rollcrete construction process includes mixing the concrete, transporting it, placing it in layers, and compacting it with steel drum vibratory rollers.

Why is compaction important in Rollcrete construction?

Compaction is crucial because it ensures the pavement achieves the necessary density, strength, smoothness, and surface texture.

What are the typical applications of Rollcrete?

Rollcrete is used in heavy industrial applications, low-speed roads, airports, distribution centers, industrial slab floors, dam construction, parking facilities, and more.

What are the benefits of using Rollcrete?

Rollcrete offers high strength, quick construction, minimal maintenance, resistance to oil spills and high temperatures, and cost savings compared to other paving materials.

What are the disadvantages of Rollcrete?

Some disadvantages include difficulty in achieving smoothness, potential for crack raveling, and the need for skilled labor. It may also be unsuitable for areas with poor aggregate availability or problematic foundation conditions.

How does the cost of Rollcrete compare to other paving materials?

Rollcrete costs about $75 per cubic yard, which is lower than the $90 per cubic yard for hot-mix asphalt, offering cost savings.

What is the typical compressive and flexural strength of Rollcrete?

Rollcrete generally has compressive strengths between 4,000 and 6,000 psi and flexural strengths ranging from 500 to 1,000 psi, depending on the mix design.

Is Rollcrete durable in freeze-thaw conditions?

Rollcrete can experience a reduction in compressive strength under freeze-thaw conditions, with a decrease of up to 32.8% after 12 months of immersion in KAc solution.

Can Rollcrete be used immediately after placement?

Rollcrete can be used as a roadway after only 24 hours of being placed, making it suitable for projects requiring quick turnaround times.