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Hardscape design and construction
review: tools of the trade

By Brian Burton

As the market for ICPs have grown so has the variety of specialized tools available to the installer and contractor. Many of these specialized tools can improve on-site efficiency and safety, reduce labour intensive procedures, and as a result, increase productivity and profits.

COMPACTION EQUIPMENT

Proper compaction of soils is critical to the performance of ICPs to avoid settlement. Soils vary widely across Canada. As a result, so does their ability to be compacted to the minimum recommended level for pedestrian sidewalks and driveways of 95% (Standard Proctor Density), and to a depth of at least 150 mm for pedestrian areas and 400 mm for areas subject to vehicle traffic. It should also be noted --soils that are continuously wet, very fine, or contain organic matter will not compact to these recommended minimums and may require treatment or replacement.

MACHINE TYPES

The action of compaction equipment is described in terms of frequency and amplitude. Frequency is expressed in vibrations per second or hertz (Hz) and amplitude is expressed as half the distance traveled by the vibrating drum or base plate.

Compaction equipment is generally classified into three machine types, each producing a different kind of compactive effort: rammers, vibratory machines, and static rollers. The manufacturer can provide guidance of which type of machine to use for various soil types.

Rammers (or jumping jacks as they are often referred) are distinguished by their low frequency (800-2,500 blows per minute) and high stroke (40-90 mm), and work well with clay soils. Rammers can also be used for granular material if the soil being compacted is in a confined area such as a trench. The stroke of a rammer is the height the ramming shoe or plate reaches from ground level while operating.

 

Power sweeping saves time and effort on the job. Machines like the one shown also assist in ensuring that joints between pavers are entirely filled with sand.

 

 

A plate-type, self-propelled rammer plate uses eccentric counter-rotating weights to provide both the ramming force and travel speed. A hand-held upright rammer uses a spring mechanism.

Vibratory Machines exert low amplitude and high frequency (2,000-6,000 Hz). Each rotation of the eccentric shaft in the drums forces energy into the ground. This vibration energy sets the soil particles in motion and rearranges them more tightly.

Static Rollers use only their weight and no vibration for compaction. They are used to proof-roll pavers in large-scale industrial applications such as port and airport applications after plate compaction.

To select the right compaction equipment, knowledge of the basic properties and classification of soil is beneficial. For example, when compacting clay soils, a rammer-type machine with an impact that forces out the air and water and rearranges the particles works well. For compacting granular soils, vibratory plates and vibratory rollers are recommended, as well as for compacting aggregate base under pavers. Vibrating plate compactors are also used after the installation of pavers, and used again to compact the pavers after the joints are filled with sand.

SCREEDING EQUIPMENT

Screeding is the process of leveling the bedding sand prior to placing the pavers In the past screeding was typically accomplished using 25-40 mm square pipe or bars set on the compacted base prior to dumping and spreading the sand.

A screed, or strike board, usually 3-4 m long, is pushed and/or pulled along the top of the screed rails to smooth and level the sand. The screed can be wood, although aluminum lasts longer and remains straight

The newer versions of screeding equipment operate by using rollers, which travel over screed rails or curbs.

Powered screeds save time and reduce fatigue because a smaller loader is used to pull them. The screed rails are set on the base and checked with a transit level or string line. The height of each end of the screed can be adjusted to accurately obtain the needed depth of bedding sand. Some screeds extend up to 4 m between rails. A wider area can be screeded by connecting more rails and lengthening the screed. As the screed is pulled, one or two persons spread the pile of sand that accumulates behind it.

CUTTERS AND SAWS

Most jobs with concrete paving stones involve cutting. Pavers are typically cut along the edge of the pavement around planters or drainage inlets or when there is a change of pattern.

There are three basic tools for cutting pavers. The first is a mechanical splinter (also referred to as a paver splitter, stone cutter or guillotine). It is a non-motorized piece of equipment that relies on leverage or hydraulic action to split a paver. The larger models of these cutters can also cut blocks and small retaining wall sections.

Two blades in the jaws of the machine have two hardened pieces of steel that cut by pinching the paver. If the blades are smooth and the paver is dense, a mechanical cutter can produce a cut with a fairly even face.

A key to using a mechanical splitter is to place the unit between the blades at a slight angle. When cut, this position will produce an angled face or "under cut" which allows the paver to slip easily into its designated opening in the pavement.

Paver splitters can be very useful on smaller jobs or minor repair projects where setting up masonry saws may be time consuming.

Another cutting tool is the masonry saw with a diamond blade that produces a smooth, precise cut. Masonry saws are gasoline or electric powered and most can run either wet or dry. When water is used it provides lubrication and reduces wear on the blade. Masonry saws can also be mounted on a wheeled cart for easy movement around the site.

A by-product of cutting with a wet masonry saw is residue-filled water which can stain pavers. As a result it is important to wash and remove the water from the pavers before it dries.

A third cutting tool is the hand-held, gasoline powered "quick saws," with engines similar to those used on chain saws. Quick saws are completely portable and can be used to cut pavers in place on the bedding sand. Their air filters must be changed according to manufacturer's recommendations in order to prolong the life of the saw engine. Ear protection and safety glasses are required when cutting with powered masonry or quick saws. Always wear a dust mask when cutting as well.

MATERIAL HANDLING TOOLS

(Power lifting machines like the one pictured here expedite the placement of concrete units, using vacuum power to hit up to 200 kg.)

Efficient movement of materials on-site is important to avoid delays and increase profitability. Here are a few tools, which can help. The paver buggy or paver cart eliminates damage to pavers and delays, which result from the use of wheelbarrows. These lightweight and useful carts designed to handle pavers also allow speedy transfer and stacking of pavers close to the laying face of the installation. Hand held paver clamps also expedite movement of pavers.

SPECIAL TOOLS

Like any professional trade, having the right tool for the job makes a difference in your "bottom line." In addition to saving time and money, using the proper tools reduces the risk of injury.

Many special tools developed in Europe are now available in Canada. Examples include paver hammers and paver alignment bars with rubberized ends tot in-situ adjustments. Angle guides which allow precise 45 degree or 90 degree pavement angles to be achieved also reduce the labour involved with staking and marking.

Also now available and extremely handy is a paver "extractor" which effectively "grabs" an installed unit and enables removal of individual pavers, which may require replacement.

MECHANIZED INSTALLATION

Without a doubt, the ultimate power tool is the mechanized concrete paver-laying machine. These machines, developed in Germany, can lift and install 300 kg of pavers at one time. With one operation and one assistant these machines, which are often used for airports or port installations can install 100 m2 per hour.

The machine operator activates a clamp which grabs and lifts a "cluster" or "layer" of pavers from "cubes" of pavers, turns the machine, lowers the clamp and then releases the pavers. A video which demonstrates the machines in operation is available from the ICPI, as well as technical information on job planning and paving with mechanical equipment.

Interlocking Concrete Pavement Institute

About the Author- Brian Burton is with the Interlocking Concrete Pavement lnstitute and is a Member of the Standing Committee of Technical Evaluations for the Canadian Construction Materials Commission(CCMC). Mr. Burton was also recently appointed to the position of Marketing Director of Communities in Bloom.


A glossary of terms

The installation of interlocking concrete pavement (ICPs) involves a broad range of terms, many of which are unique to CP design and construction.

General terms:

Concrete Paver: Canadian standards define pavers as pre-cast concrete units having a maximum size of 165 x 240 x 240 mm thick. (Minimum thickness is 60 mm.) In general terms, this describes a unit that can be lifted and placed with one hand.

Interlock: The term "interlock" when used in reference to CP systems, refers to establishing and maintaining structural integrity of installed pavers. It has been defined as the "resistance of an individual paver to move (in any direction) independently of surrounding units under loading".

Pavement Structure: Refers to total pavement construction including all courses of selected materials: base soils, sub-base, base, edge restraints, joint sand and pavement surfacing materials.

Monolithic Pavements: Pavements constructed of a single continuous trafficking surface. Generic examples include rigid concrete and flexible bituminous pavements (asphalt).

Elemental or Segmental Pavements: Small elemental pavement systems utilize small units to construct a traffic surface. In the past, roadways have been constructed in this manner using stone setts (cobblestones), wooden blocks and fired brick. Since the 1950's, the most common materials used are concrete pavers.