BLOCK PAVING
A tough, Hard-Wearing block capable of handling heavy – use trafficking but with the size and colour range to meet most visual design criteria.
- Offers a high level of durability and good grip.
- Can be easily lifted to access services
- Wide range of shades including three mixed colors for aesthetic appeal.
- Comes in a wide range of variations to help meet your specification such as pencil edge and colour coatings.
- Also available as a mechanical lay option for increased speed and efficiency of installation.
Applications
Block paving is suitable for all pedestrianized areas, shopping precincts, HGV loading areas, docks and container loading bays, access roads and airports as well as farm and stable areas. Refer to our technical department for future guidance on suitability for given applications. For correct choice of block thickness to suit your application.
Advantages
Interlocking concrete pavements offer the advantages of concrete materials, but with flexible performance similar to asphalt pavement. As high strength concrete, the units have high resistance to freeze-thaw cycles and de-icing salts, high abrasion and skid resistance, no damage from petroleum products or from concentrated point loads or high temperatures. Load transfer is achieved through shear transfer through the various joints in the pavement. As with flexible asphalt pavement, an aggregate base accommodates minor settlement, however the difference with the interlocking pavement is that it will not crack. Another advantage to these pavements is access to underground utilities and the ability to re-instate the paving units, thereby reducing waste materials. The results of the life-cycle cost analysis for Main Street, North Bay, (JEGEL, 2000) indicate that when a discount rate of 4% is applied, interlocking concrete pavements are more cost-effective than asphalt pavements for this type of application.
Interlock
Critical to the structural performance of segmental concrete pavements is the concept of interlock between the units. Figure 1 demonstrates the three types of interlock that must be achieved; vertical, rotational, and horizontal. Vertical interlock relies primarily on shear transfer of loads to adjacent units through the jointing sand, rotational interlock relies mainly on paver thickness, unit spacing, and edge restraint, and horizontal interlock relies primarily on laying patterns that disperse braking, turning, and accelerating forces. Figure 2 shows a herringbone pattern that is universally recommended for areas subjected to vehicular traffic. Testing has shown that this laying pattern with the use of dentate (or non-rectangular) paver shapes offer the greatest structural capacity and resistance to horizontal creep.
Figure 1: The three types of interlock. Vertical, rotational, and horizontal Source: Interlocking Concrete Pavement Institute
Figure 2: Recommended laying patterns for vehicular traffic Source: Interlocking Concrete Pavement Institute
Typical Pavement Sections
Figure 3 shows typical pavement cross sections for interlocking concrete pavements. The pavers are laid on a one-inch (25 mm) thick sand bedding layer over a compacted bound or unbound base and a granular sub base as required. The base design and sub base requirement are determined by the severity of the applied loads and either the resulting vertical stresses and strains at the top of the subgrade or the horizontal strains in the base. Many pavements for city uses do not require an
Aggregate sub base except for very heavy use, or over a weak soil subgrade. In these situations it may be more economical to use asphalt or cement stabilized base layers. Often, they are placed over a sub base layer of unbound compacted aggregate.
The Interlocking concrete paving system also relies on the design and installation of adequate restraint in the form of an edge restraint (ICPI, 1994). The requirement for geotextile application over the subgrade is dependent on the soil conditions. Geotextile may be required to facilitate encapsulation of bedding and joint sands in applications with stabilized bases.
Figure 3: Typical Cross sections for interlocking concrete pavements
Source: Interlocking Concrete Pavement Institute
Concrete Paver Specifications
Concrete pavers are manufactured to CSA A231.2 specifications. In this specification, concrete pavers are defined by their aspect ratio (length over thickness) and by their total surface area. A concrete paver, by definition, must have an aspect ratio less than 4:1 and a surface area less than 100.25 in2 (0.065 m2). For areas subject to constant vehicular use the required aspect ratio is less than 2.5:1 and is assumed for the purposes of this paper. CSA specifies a minimum average compressive strength of 50 Mpa (7250 psi) and includes a durability requirement of a maximum loss of 200 g/m2 of surface area after 25 cycles of freeze and thawing in a 3% saline solution or 500 g/m2 loss after 50 cycles.
Joint sand provides vertical interlock and shear transfer of loads. It can be slightly finer than the bedding sand. Gradation for this material can have a maximum 100% passing the 1.25 mm sieve and more than 10% passing the 80µm sieve. Commonly the bedding sand is used for the joint sand for easier control of job site materials. This will require additional effort in filling the joints during compaction due to the coarser gradation. Joint sand should be dry when swept in to the joints to ensure that there is no bridging of sand in the joints, which would decrease interlock.
Consideration should also be given to joint sand stabilizers, which have been shown to reduce the long-term loss of joint sand.
Construction of Interlocking Pavements
Due to the similarities in flexible pavement performance, the soil subgrade and base materials are prepared and installed in a similar manner to asphalt pavements. Following the installation of the base, bedding sand is placed to a uniform thickness, typically 1 to 1-1/2 inches (25-50mm) by a process of hand or mechanical screening (See Figure 4). The paver units are then placed either by hand or mechanically. Depending on the type of edge restraint used, it is installed either before the installation of the bedding sand or after. The pavers are then placed and vibrated into place with a high frequency plate vibrator with a minimum force of 22 kilo-newton to facilitate compaction of the bedding sand and migration into the bottom of the joints of the pavers . Joint sand is then swept into the joints by hand or mechanically. The units are compacted again to ensure complete filling of the joints and the necessary interlock for performance of the pavement
Conclusion
Interlocking concrete pavers are proving to be a viable design option for municipal applications. Proven design tools are available to designers and new methods of construction offer fast and efficient installation for immediate serviceability of the pavement. In Srilanka the use of concrete pavers for these applications is increasing dramatically. International research and development continues to improve the analytical tools. The summation of global work takes place every three years at the international conferences on concrete block paving. Each conference produces proceedings that have provided much of the technical basis for design, specification, construction and maintenance in Srilanka. The next international conference will be in Sun