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2020 / 2021 Edition

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Rapid International equipment selected for roller compacted concrete paving in US

Northern Irish concrete machinery assists in the growing increase of roller compacted concrete paving in Columbus, Ohio, USA

Using mobile continuous mixing plants, supplied by Rapid International Ltd based in Tandragee, Co. Armagh, contractors such as Complete General Construction and Nickolas Savko & Sons, Inc., in Ohio, USA are increasingly switching over to roller-compacted concrete (RCC) applications for roads and pavements.

The city of Columbus, Ohio, has experienced a rapid growth in recent years in the use of RCC for the city streets and highways since RCC construction procedures were first introduced to the area in 2001. Using Rapid International mobile continuous twin-shaft plants to mix the concrete and high-density pavers and rollers to lay it, RCC is becoming a popular choice for projects due to its strength, the speed of its construction and its economic value in comparison to asphalt.

For many years Columbus has made use of ‘composite’ pavement designs, where concrete is used as the pavement base, and asphalt for the pavement surface, but with the introduction of RCC, dozens of successful projects have been completed.

Contractors, Complete General Construction, have commenced work on a highway network in the city. Using a mobile continuous mixing plant, supplied by Rapid International Ltd, along with specialized paver and vibratory rollers, they have started laying the RCC which will provide long serviceability with minimal maintenance.

Why choose RCC over asphalt?

Although RCC has the same ingredients as conventional concrete, it is a drier mix and stiff enough to be compacted by vibratory rollers.

It has a high flexural strength (500-1,000 lb/in2) (3.5-7.0 MPa) meaning it can support heavy, repetitive loads without failure and spans localized soft subgrade areas, which reduces maintenance costs and down time.

It also has a high compressive strength (4,000-10,000 lb/in2) (28-69 MPa) allowing it to withstand high concentrated loads and impacts from heavy industrial, military, and mining applications. Its high density and low absorption provides durability, even under freeze-thaw conditions and eliminates seepage through pavement.

As RCC is constructed with no joints, there is no requirement for steel reinforcing or dowels, forms or finishing or sawed joints. Construction is speedy and simplified - reducing costs, minimizing labour and eliminating the need for preventative measures taken to minimize corrosion of reinforcing steel.

RCC itself is as economical and simple to use as asphalt. Companies like Complete General Construction and Nickolas Savko & Sons, Inc., who are involved in many RCC projects, recognize the life-cycle cost savings you get when using concrete as opposed to asphalt.

The high strength of RCC pavements eliminates common and costly problems traditionally associated with asphalt pavements. The RCC has the durability to resist freeze-thaw damage. The pavements will not deform under heavy, concentrated loads and do not deteriorate from spills of fuels and hydraulic fluids. They will also not soften under high temperatures.

Stages of RCC and use of the mobile continuous mixing plant

The Rapidmix mobile continuous twin-shaft plant is a key machine to ensure that RCC projects are carried out on time and within budget. It produces high outputs of up to 400 and 600 tonnes from both models. It provides the mixing efficiency needed to evenly disperse the relatively small amount of water used in the mixing of RCC. Dumptrucks then transport the RCC and discharge it into a paving plant, which places the material in layers up to 10in (250mm) thick and 42ft (13m) wide.

Compaction begins immediately after placement, which is how the concrete attains its level of smoothness, density, surface texture and strength. This stage continues until the density requirements are met.

The final stage is curing where moisture is applied, allowing hydration of the concrete, thus causing it to harden and strengthen.

The machine can work on a variety of applications such as bentonite landfill sealing, dam construction, contaminated soil stabilisation as well as cement treated base for road construction.

Applications of RCC

Due to its superior strength, RCC can be used in industrial applications where strong pavement is required to stand up to massive loads and specialized equipment. Airport runways and aprons are well suited to RCC. Also suited are: parking, storage and warehouse floors; container storage and handling; and port pavements etc.

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