Hong Kong International Airport represents the largest single airfield installation of interlocking concrete pavements. Since most of the airport is on reclaimed land, anticipated settlement required that flexible asphalt pavement be used instead of rigid concrete for runways. Concrete pavers also provide a more fuel-resistant surface than asphalt.

This lesson introduces and then tests the viewer on the variables that must be considered when using segmental pavements to support pedestrian and vehicular loads on municipal streets. According to the American Society of Civil Engineers (ASCE), the following four variables are critical to consider:

An ESAL is a standard unit that is used to measure the amount of damage vehicles inflict on a surface. 1 ESAL = the impact from a single 18,000-lb axle load. The damage to a pavement caused by one pass of a large tractor-trailer in exponentially greater than that caused by a two door sedan.

It takes roughly 20,000 passes of the sedan to cause the same amount of same amount of damage as one pass of a tractor-trailer. In these scenarios, the design ESALs will be predetermined. This is usually based on the expected traffic mix. Reference ASCE and ICPI Tech Spec 4 to calculate the appropriate ESAL rating to a design.

Aggregate bases stabilized with asphalt or cement are recommended under very heavy loads, and over weak or saturated soil subgrades. These are sometimes used when adequate aggregates are not available or when a stabilized base is more economical than unstabilized aggregate. Poor subgrade should be avoided if possible, but when it is necessary to build over weak soils there are several methods available to improve subgrade performance.

Soil characteristics play a major factor in the design of pavements. It is important to accurately assess the type of soil on a site. Soils are classified by the Unified Soils Classification method  (ASTM D2487, 2006a). Soils that have a course grain and good drainage are generally stronger than fine grained soils with poor drainage. For example a gravel soil with good drainage is significantly stronger than a clay soil with poor drainage.

Dimensional tolerances are important on a paver’s structural efficiency. Rectangular and shaped blocks need to be designed to include their surrounding space; and their length to width ratio depends upon the final laying pattern. To optimize the block surfacing structural efficiency then every block must be specified and controlled within strict tolerances.

This video demonstrates the flexing properties of interlocking concrete pavers. This flexing pattern allows for weight and pressure to be distributed evenly over the pavers, which as a result provides for a higher PSI (Pounds per Square Inch) and a material that is more durable than Asphalt or Poured Concrete. Interlocking pavers are proving to be a huge money saver with very little maintenance costs. The strength and durability of ICP can be seen in shipping ports, airports and other high density/heavy load areas.

This study is focused on the implementation of interlocking pavers in marshy roads and high groundwater table terrain. Permeable interlocking concrete pavers were used to combat intrusion of underground/saline water for the road of case study (Akin-Adesola Street, Victoria Island, Lagos). Hydrogeologic data, i.e., groundwater level information for marshy roads terrain including the area of case study was obtained in form of investigation hole/borehole data. Different scientific tests and researches put together show the effectiveness and durability of the modified exfiltration system type of permeable pavement for high ground water table terrain. 

Although interlocking concrete block pavements are used extensively in tropical and temperate regions, they have as yet been little used in cold climates. The nature of interlocking  concrete block pavements is briefly presented. The key elements constituting a high quality block pavement, to support traffic or industrial loads, are described and the approach to their design summarized. The problems posed by the construction and maintenance of pavements over permafrost and some of the special techniques evolved to overcome these problems are reviewed. In the context of these particular problems of pavements in the northern environment, the advantages and design of interlocking concrete block pavements are discussed and a typical cross-section (like the one in the picture above), for use in permafrost areas, is proposed.

The successful transferal of any vertical load through a segmental paved area requires the incorporation of three principles. These principles must be utilized when installing open grid as well as solid interlocking pavers. It is also important to note that all three principles are equally important.

Vertical loads are transferred through an assembly of units through the development shear between the units. When the units are placed next to each other in a tight arrangement, friction between the units is developed thereby mobilizing a large portion of the paved plane for load resistance. In order to develop the friction which develops the shear, the units must be continuous and contiguous within an arrangement. 

In order to develop the friction between neighboring units, the units within a paved surface must be restrained from drifting away from one another. This is accomplished through the use of edge restraints that keep the pavers in a contiguous arrangement. It is ideal to have all of the edges of a paved surface restrained as this will result in load transferring in more than a single direction. 

The preparation of the base is the final element in the successful load carrying capacity of concrete pavers. Although this is not a visible “design” element it is an important general principle that must be considered during initial conceptual design phases. The previous two principles deal primarily with the surface layer which is the top layer of the five total. The remaining four exist below the surface of the pavers.

When it comes to permeable paver design, several factors go into making a functional system.  One must size the system appropriately taking rainfall, infiltration rates, available area, void space, layer depth, and time all into consideration.  This lesson will introduce you to all those critical factors in these three lesson components:

Successful permeable interlocking concrete pavements (PICP) rely on an adequately designed sub-surface retention system, properly sized to handle the amount of water both falling on and running into the PICP system.  Proper depth and open-graded material selection (void space) are essential. The formula listed below is used to determine base/subbase depth. 

This learning animation walks you through many of the considerations for designing a ICP system.  Topics range from rainfall events, geographic range, soils, and substrates.  After completing the learning section, an interactive site allows your to choose different combinations of parking surface areas and base depth to hold a particular rain event. 

The Principle of Interlock:
Interlock is the inability of a paver to move independently from its neighbors. It is critical to the structural performance of interlocking concrete pavement. When considering design and construction, three types of interlock must be achieved: vertical, rotational, and horizontal interlock. These are illustrated in Figure 1.

The goals of this exercise are to investigate, design and fabricate an interlocking concrete pavement module to assist in understanding structural and aesthetic considerations of connections (edge and unit-to-unit condi- tions) and/or innovative environmental function(s). The exercise’s learning objectives include the following:
• Gain exposure to the technical aspects needed to develop a unique and innovative interlocking concrete pavement module to achieve the desired look, feel and function of a related site design proposal.
• Achieve technical accuracy, environmental and structural function, and the desired aesthetic outcome(s) of a construction detail through real-time fabrication and troubleshooting.

Most jobs will fail from improper base compaction. Learn how to compact your base in lifts and some helpful tips to determine if you have the proper compaction before you install pavers.

The goals of this exercise are to investigate, design and fabricate an interlocking concrete pavement module to assist in understanding structural and aesthetic considerations of connections (edge and unit-to-unit condi- tions) and/or innovative environmental function(s). The exercise’s learning objectives include the following:

This project represents part two of the Implementation Studio Section.  The student will achieve the following goals and objectives: 1. Develop and refine your ability to conceptualize, graphically construct, and properly coordinate construction documents that clearly communicate the desired three-dimensional look, feel, and function of your final design. 2. Achieve technical accuracy and the desired aesthetic outcome(s) of each detail condition.

After completing the final project with the Design Abstraction Sequence, you are ready to begin a series of studies that will translate your Systems Abstraction Design Proposal from schematic rendering into buildable elements. This process is known as Design Development, the products are known as Construction Documents.