By Dennis Von Ruden
As our infrastructure continues to deteriorate, it would seem there is a never-ending supply of pavement cracks that continue to challenge society’s mobility.
By Dennis Von Ruden
As our infrastructure continues to deteriorate, it would seem there is a never-ending supply of pavement cracks that continue to challenge society’s mobility. Cracks seem to be everywhere you go. In fact, there’s no such thing as a totally crack-free pavement surface. Whether it’s avoiding them on the sidewalk in front of your home or suffering their misery while cruising in your car, negotiating pavement cracks and their lasting effects continues to plague our efforts to move around.
|The often-neglected step in pavement repair, crack sawing is absolutely essential to quality repairs that stand the test of time. Note the operator pulls the saw toward himself as he walks backward.|
Proper crack-filling procedures can dramatically increase the useful service life of virtually any pavement surface. Surfaces do not normally wear out because of their inability to support pedestrians or vehicular traffic. On the contrary, their useful service life is usually limited by improper base compaction or because of environmental effects.
Causes of Cracks
We’ve all seen pavement surfaces that have literally broken down as a result of improper compaction techniques used during construction or because the base simply failed over time as a direct result of environmental effects. Think of a pavement surface as a dynamic system that is subject to constant shrinkage and expansion caused by both applied loads and the environment. Environmental effects can be the result of seasonal temperature differences, including the intense, radiant heat energy of the sun as well as long-term effects of freezing. Next, factor in the damaging effects of precipitation.
The shrinkage and expansion of the pavement material is usually what creates initial cracking. Over time, repeated material expansion and contraction can increase the crack size and eventually lead to the vertical displacements that wreak havoc on your auto’s suspension system or, even worse, become the cause of many trip-and-fall pedestrian accidents. Left unchecked, cracks of this magnitude will allow precipitation to eventually destroy the base compaction. When that happens, cracks begin to expand in size while sinking at the same time. The result is the creation of massive secondary cracking problems. That’s when pavement repair gets really expensive because now the crack area needs to be excavated and the base properly compacted.
Proper crack-filling technique is probably one of the most misunderstood maintenance activities related to construction. It’s far more complicated than what you see being done in the parking lot at your favourite neighbourhood big-box store. So many times there is only a half effort to dabble some type of rubberized compound over the crack, just to have it reappear a few days later. Obviously, this is not money well spent.
A proper crack-filling procedure is a well-defined process that has historically provided a justifiable ROI relative to the cost. The basic rule is, if a pavement crack is as wide as a credit card, it must be sawed or chased. This process allows the filler material to first properly bond with the pavement and then form a closed, tight seal to exclude further precipitation damage. The material used to fill the crack needs to be extremely flexible to expand and contract with temperature changes while maintaining the integrity of the bond to the parent pavement material.
With filler materials, you get what you pay for. Materials that deliver the proper results will be heated to a liquid state and then directly pumped into the crack with the use of a wand. What you can easily purchase in the gallon jug from a local big-box store and directly apply cold does not work. This type of filler material does not expand or contract sufficiently to maintain seal integrity. End of story.
Sawing versus chasing
Two processes are used in the industry to produce the smooth-sided edges for bonding the filler material: sawing and chasing. The sawing process usually involves using an eight-inch-diameter diamond blade to dry cut either asphalt or concrete pavements. If you are asking yourself if a round blade will actually follow a typical crack, the answer is yes. And, it does so very well.
A crack chaser will use tungsten-carbide-tipped tools rotating at a high speed to route the crack. By the very nature of its design, the chasing process is really limited to asphalt. The conventional tungsten-carbide routing process in concrete does not provide the productivity rates or the desired finish. The inherent ability to cut both asphalt and concrete pavements makes the extra versatility of a random crack saw appeal to a wider cross-section of pavement-maintenance contractors and their job applications.
How it works
All crack saws function on the same principle. The majority use an eight-inch diameter blade in various widths. The major differences are in blade positioning relative to the rear wheels. Some manufacturers position the blade on the side of the crack saw. General Equipment Company, however, positions the blade in the middle, inline with the rear wheels to make operation more intuitive. The resulting cutting action is also smoother and increases productivity rates. Another benefit of a centre-mounted blade configuration is that the learning curve is substantially reduced.
The only option offered by General Equipment Company is a water kit that allows wet sawing, just like a standard slab-type saw. While cutting wet does not create dust, it does create a slurry mixture that usually needs to be properly disposed of. If the dust created with dry cutting can become an issue, then it would be wise to make an investment in a high-quality vacuum system.
For normal crack sawing operations, the blade cutting depth will not typically exceed 1-1/2 inches deep. Sometimes, the cutting depth can be as little as ½ inch deep. Because of the shallow cutting depth, the machine can be manoeuvred to follow random crack configurations.
General Equipment Company’s random crack saws use standard double-row ball bearings that can be externally greased. The fines (dust) that are created by the sawing process are extremely abrasive and are known to quickly destroy bearing seals. The solution is to grease the bearings in short intervals. This purges the old, contaminated grease from the balls and cages to form a dam that helps minimize contamination of the fines. Proper lubrication will substantially increase the service life of the bearings.
CHOOSE YOUR WEAPON
Most random crack saws will use a gasoline or diesel engine in the 11-to-13-horsepower range. Because of the nature of the cutting process, a credible manufacturer will always provide the maximum horsepower allowable for any given diamond blade configuration. As with anything dealing with cutting asphalt or concrete, you can never have too much horsepower. Any high-quality engine brand is suitable just as long as it has the best air intake filter system available to help reduce and minimize the amount of damaging dust than can destroy it in a matter of minutes.
When looking at crack saw ergonomics, the most important issue to consider is operator control. Does the machine design actually aid the operator in cutting, or is it something that they are always fighting? How easy is it to manoeuvre on the slab surface? The geometry of a crack saw is much different than that of an ordinary slab saw. That’s because slab saws normally cut in a straight line, while crack saws are intended to follow random crack configurations, which requires additional skill sets, body strength and common sense.
A half-inch diamond blade will require additional skill and human strength to manoeuvre over that of a quarter-inch-wide blade. Productivity rates can also be reduced with a wider blade, depending upon the specific crack configuration.
You also get what you pay for in diamond blades. All sorts of blades are available over the Internet — each of questionable diamond content and matrix configuration. Manufacturers generally recommended using a high-quality, laser-welded, diamond blade purchased from a known vendor. It is important that the diamond segments be laser-welded rather than just furnace-brazed. The crack cutting process creates high temperatures that can actually melt the welding braze and allow the segment to be thrown.
Where rental centres fit in
With no shortage of pavement cracks, why are there so few random crack saws in the equipment rental industry? Or, simply restated, with all these apparent opportunities, should the crystal ball reveal a random crack saw in your future equipment fleet? Both are good questions that deserve further investigation.
|Crack sawing does not require deep penetration of the blade into the pavement surface. A sawing depth between 1/2 and 1 1/2 inches will achieve the desired effect and allow the operator to manoeuvre effectively.|
Large-scale pavement repair work is usually performed by specialized contractors who have invested in the necessary equipment and employee training to deliver a quality procedure that can be guaranteed to the property owner. It’s not uncommon to see these contractors repairing privately owned parking lots, parking decks and roads with their own equipment. These contractors are probably not high-priority customers for the equipment rental dealer.
The niche for the rental industry is developing the demand from small contractors who channel their focus toward those pavement repair jobs that are going to be unprofitable for larger, specialized contractors. This new opportunity is being created because of the size and resulting profitability of smaller-sized crack-filling jobs. The evolving rental customer is typically the same person who performs a wide range of landscaping, pavement sweeping and general floor maintenance projects. There’s a growing trend for these same contractors to expand their services to include crack filling and seal coating.
Depending upon pavement size and configuration, these smaller contractors can offer very cost-effective maintenance solutions to targeted property owners — the same property owners who historically do not address proper maintenance procedures because of a perception of inherent high cost. Because equipment utilization rates will not always support an outright purchase, this emerging customer can be found searching for dealers where random crack saws can be rented.
Safety is always a top concern while operating any type of powered equipment. Obviously, proper operator apparel is key, including safety glasses and good, sturdy gloves, along with suitable hearing protection. Wearing leather-type shoes with non-slip soles is equally important. And, since most crack saws are pulled toward the operator while in normal use, it’s always a good idea to know exactly what’s behind you.
In this age of market specialization, you can fully expect to see a further diversification of contractors developing niche capabilities and the resulting demand for their services. Small-scale crack repair could be a golden opportunity for everybody to make money.
CRACK SAW MANUFACTURERS
The following manufacturers distribute crack saws to the Canadian rental market: