4 FM quick reads on grounds
1. A Closer Look At Pavement Maintenance
Managers are constantly looking for the right mix of PM and major restoration. The longer problems such as potholes remain unattended, the larger they become, and the deeper into the base they penetrate, resulting in safety issues and costly repairs.
Filling cracks is much less labor-intensive than filling potholes, and filling potholes is far less costly than having to replace major sections of paved surfaces.
As shown in step four above, one key to effective repairs is selecting the most appropriate repair method, which includes specifying the proper material for the surface and for conditions at the repair site.
For example, managers need to select concrete sealants and coatings that are formulated for either wet or dry conditions. Extensive independent testing has shown that epoxies, siloxane/silane materials, and high-molecular-weight methacrylates are the best types of material for controlling the deterioration of concrete where freezing and thawing occur repeatedly and water is present.
Workers should inspect sections of concrete that most often deteriorate from freezing weather. These sections include exposed surfaces, such as posts, handrails, piers, parapets, and the top 2 feet of walls.
Also vulnerable are curbs, sills, ledges, copings, cornices and corners. Surfaces exposed to spray or other frequently changing amounts of water during freezing weather also are likely to require a great deal of attention.
As with any other asset, concrete and asphalt surfaces need periodic inspection and PM to ensure sustainability and lower life-cycle costs. Annual inspections are the most economical way to retain and improve the value of the asset.
The best PM for asphalt is applying a sealant. Workers should reseal new asphalt between 90 days and one year after placement. This practice locks in the binder, keeps the pavement flexible, and prevents cracks and further degradation, which can destroy the surface and the base. Two coats — possibly three in areas with heavy traffic — of a premium-grade, hot, rubberized crack sealer or acrylic cold sealer application will work well if done before cracks, heavy alligatoring or holes become visible.
2. Asphalt Repair Strategies and Tactics
Common asphalt repairs include resealing the surface, sealing cracks, applying cold- and hot-mix patches to potholes, and applying skin patches. A hot patch is more permanent than a cold patch and might be necessary during cold weather to temporarily repair a hole in a road surface.
Workers can make cold-mix patches by sweeping up loose rubble, using compressed air to blow away residual materials, applying a primer, and pouring the cold mix from bags into the hole. The final step is tamping with a hand tamper, air-powered tamper, or gas-powered vibrating tamper. The thicker the patch, the more compaction passes are needed.
Because hot-mix patches are intended to be more permanent than cold-mix patches, they tend to require more preparation work.
First, the worker must dig out the hole with pick and shovel or air-operated pavement breaker to square the sides and bottom to a uniform depth of at least 5 inches. Gravel is replaced to bring the depth to 3 inches and tamped using a hand or power tamper. The hot-mix asphalt fills the top 3 inches. The worker then rakes the patch evenly to 1 inch higher than the adjacent pavement.
The next step is to tamp the asphalt with a hand or powered tamper or roller to a level slightly higher than the adjacent pavement. This allows for further compaction by traffic without creating a depression, which can collect water.
Where alligatoring affects large surface areas or fine cracks cover large areas, one proven remedy is a skin patch. One to three workers can apply a sealer coat to the area after cleaning all loose rubble from the surface. Next, they apply a 1-inch-thick layer of hot-mix asphalt and rake it out evenly with a wide asphalt rake. Next, they tamp the hot-mix surface using a powered roller to ensure good compaction. Skin patches are appropriate only when the base is solid and properly graded for water runoff.
3. Irrigation Issues: Upgrading for Savings
More maintenance and engineering managers nationwide are forced to deal with water restrictions when planning an upgrade of their irrigation systems, but the West Coast has been dealing with such restrictions for many years.
When Sandia National Laboratories in Livermore, Calif., implemented its computerized irrigation system in 2008, part of the motivation behind it was to more effectively comply with such water-reduction requirements.
The organization's science and technology research center, located 45 minutes east of San Francisco, features more than 300,000 square feet of landscapes, 50,000 square feet of hardscape, and 350,000 square feet of plantings over 13 acres of developed area.
Starting in 2007, the laboratory operated under a federal requirement to reduce its water use by 2 percent a year for eight years — a total that required a reduction of 16 percent, says Robert Holland, Sandia's environmental monitoring program lead.
The 2008 system was installed to help minimize unnecessary watering, Holland says. It measures wind and humidity, and when it senses rain, it shuts down within 10 minutes. With the previous system, irrigation could continue for six-eight hours before workers manually turned it off, resulting in hundreds of gallons of water being wasted.
"In 2009, we actually employed the flow-sensing device or option that goes along with the control system," says Gerald Vincent, the team lead for facilities at Sandia. "At that time, we made some additional changes with the master valves. When making the installation, that was a challenge.
"We weren't aware that there were additional equipment devices for the irrigation system that would go along with getting to the point of seeing the water management reduction we were looking for. The evapotranspiration (ET) base, we haven't used to its full capacity. We're bringing that online. There are several challenges there, but we're working through them with the local vendor."
4. Concrete Inspections for Long-Term Performance
Concrete sidewalks, ramps, parking lots and garages around institutional and commercial facilities can perform reliably for years. But they can do so only if maintenance managers implement a comprehensive concrete-maintenance program that identifies small problems early and addresses them before they become larger and more costly.
By developing inspection guidelines focused on common causes of problems, combining them with effective repair procedures, materials and equipment, and specifying coatings to protect surfaces, managers can extend concrete performance life and minimize trip-and-fall hazards.
Managers tackling the challenges of concrete maintenance must accept two contradictory facts: Water is a necessary ingredient in concrete, as well as its single most destructive enemy. Without a vapor retarder to keep water out, concrete coatings on below-grade inside floors or walls soon will fail.
Water expands by 9 percent when it freezes, causing spalling and cracking in exterior concrete walkways, floors, walls, and roofs. Concrete is alkaline and normally protects rebar from rusting, but water mixed with chlorides in de-icing compounds can penetrate to rebar and rust it, causing expansion and cracking. Water also can penetrate structural concrete beams and cause cracking, rusting the rebar and weakening the structure.
The first thing technicians must determine when inspecting concrete is whether the problem is structural or superficial. The start of a structural failure — for example, a deep crack in a structural concrete beam — requires immediate attention and documentation. A concrete engineer using non-destructive evaluation, such as ground-penetrating radar, infrared thermography, and impact-echo technology, can discover hidden problems.
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