Concrete Road Design and Structures
APPLICATIONS FOR STRUCTURAL CONCRETE IN PAVEMENT DESIGN
On major highways and freeways where a long design life is imperative and/or has a high structural number requirement, concrete is a more durable choice for road pavement than asphalt. However, all pavements ultimately derive their support from the underlying subgrade, and where a roadway subgrade is poor, substantial reinforcement is necessary. Using structural concrete in pavement design offers a solution to this problem. Though often cost-prohibitive, the decision to use concrete in road pavement design typically stems from the existence of poor underlying subgrade.
Roadway design engineers consider concrete road design an option for projects intended to have a long design life. Structural concrete creates a ‘slab’ that distributes loads across a wider area. Considered a ‘rigid’ pavement, concrete pavement can be combined with an asphalt overlay for an improved riding experience. Concrete pavements are most commonly seen as the riding surface for major highways such as Interstates, but can also be used for reconstruction, resurfacing, restoration, or rehabilitation of other road structures.
Concrete pavement will undergo expansion and contraction with cyclic fluctuations in temperature, therefore concrete road design must include expansion joints to accommodate these volume changes. However, temperature is only one of several factors that can cause stress-induced pavement failure. Other factors are wheel load and loss of continuity of the subgrade or base course support. Stratum Logics always considers the improvement of the base course the most important factor in creating proper support reinforcement.
Benefits of concrete road design:
- Withstands high-loading traffic conditions – will perform for the design life when ESALs remain within projected limits
- Long service life – Concrete pavements have an average service life of 30 to 50 years, providing the design life is not accelerated by over-use, causing attrition of the road
- Low maintenance requirements and costs – reduced frequency of resurfacing, spot repairs or patching is expected
- Safety – Less susceptible to rut formation, provides greater visibility at night and facilitates shorter vehicle stopping distances in wet conditions
ADVANTAGES OF GEOSYNTHETICS IN CONCRETE ROAD DESIGN
As a geotechnical company, Stratum Logics strives to deliver the most innovative, cost-effective and sustainable solutions in pavement design. The field of pavement design is a dynamic concept that evolves and improves as new data and new technologies develop. Stratum’s approach is to apply innovative technologies to achieve sustainability in every project or application.
Stratum’s roadway design engineers utilize the unique properties of NPA geocells that can help reduce the amount of concrete necessary for concrete pavement construction by improving the modulus of base and subbase layers. Reinforcing the base or subbase course with NPA Geocells creates a ‘slab’ that will distribute the applied load stresses horizontally beneath the concrete layer. This stronger base course reduces the stress transferred to the subgrade, ultimately protecting it from damage and plastic deformation. For a given number of design ESALs, this support allows for a reduced concrete thickness on the surface and aids in minimizing surface cracking, further extending the service life of concrete roadways.
STRUCTURAL CONCRETE IN OTHER CIVIL ENGINEERING APPLICATIONS
With its durable and sustainable characteristics, concrete also presents a suitable solution for other high-loading applications. Sea and Air ports, runways and tarmacs, storage areas, container yards and similar slab-on-grade structures require heavy-duty load capacity, high quality aggregate layers, and effective surface drainage.
As concrete pavements are an expensive option, Stratum recommends it use only when other design solutions become unviable. Stratum’s standard practice examines multiple design options and recommends the best option based on merit. Both planar and three dimensional reinforcement, including NPA geocells, are compared, and an optimum design recommended.
The use of NPA geocells as a subbase reinforcement can offer a reduction in the costs associated with steel-reinforced concrete production or stabilized cement subgrade layers. Geocell reinforcement provides a strong base for the concrete slab which can result in reduced concrete thickness and a lower percentage of reinforcing steel required. Replacement of base layer infill with lower-quality locally available materials help project owners realize even greater savings over the long term life cycle of the structure.
This high-strength, 3-dimensional cellular containment system is uniquely suited for projects in which soil bearing capacity, quality of aggregates, and durability are critical. Geocells manufactured from innovative NPA materials provide extreme load support even while using inexpensive, marginal granular materials such as sand or clay for infill. Beyond concrete road design and high-load concrete pavement operations, other applications for NPA geocell-reinforced subgrade layers for structural concrete can include bridge beams, sea walls, and channels.