Catching Problems Early, Making Repairs is Key to Concrete Parking Garage Maintenance
Facility managers are often tasked with maintenance of parking garages. Made of concrete and steel, these multi-level hubs provide visitors and their vehicles with shelter from the elements and often provide access to housing or office space. However, protecting the structure itself from the constant onslaught of environmental stressors and wear-and-tear comes with its own set of challenges.
Vehicles regularly entering parking garages leave water, oil and muck behind. Not to mention salt and de-icers tracked in during the winter months that can corrode the structure's concrete and steel support system.
When temperatures turn colder in the fall and winter, freeze and thaw cycles can cause big problems with concrete parking garages. When water infiltrates concrete, it can freeze, causing the water to occupy 9 percent more volume than in its liquid state. This expansion can cause distress on the concrete, which can lead to fractures that will continue to grow exponentially as saturation of the material increases.
Essentially, the goal of parking garage maintenance is to keep water and corrosives away from the garage's reinforcing steel. The damaging and compounding cycle of water infiltration never gets better on its own, and the longer that warning signs are ignored, the more serious and costly the repairs can become.
The signs of deterioration can be seen on all types of parking structures. The three most common types are double tee precast, conventional and post-tensioned.
Here are the five key indicators that a parking garage is in need of preventative maintenance:
· Water Leakage: Leaking water is a clear sign that a parking garage is in need of repairs. The longer the condition is left unattended, the more expensive the consequences can become. Three indicators that water leakage is occurring are: exposed metals rusting, rust stains along the walls and efflorescence.
· Ponding Water: Water and parking garages do not mix well, so standing water is obviously an issue. A simple drain installation or protective waterproof membrane will prevent future, larger problems.
· Expansion Joint Failure: Failed expansion joints provide another avenue for water to penetrate and reach the reinforcing steel and T-to-T connector plates. Repairing expansion joints is much simpler than resolving issues created by corroded reinforcing steel and connector plates. Detecting expansion joint problems and reacting quickly to make repairs will be beneficial in the long run. Wear at the T-to-T joints, expansion joint failure and flange connection deterioration are commonly found in double tee precast structures.
· Delaminated, Spalled, Horizontally Cracked and Vertically Cracked Concrete: Concrete is bound to crack at some locations. Delaminated or spalled concrete is when a piece of concrete detaches from the structure. Along with delaminating and spalling, vertical and horizontal cracks in the concrete also represent threatening areas of weakness. These issues are problematic as they can lead to structural damage because they allow water to reach the garage's reinforcing steel. This type of damage is commonly seen on post-tensioned and conventional cast-in-place concrete parking garages.
· Exposed Rebar (Reinforcing Steel): If rebar can be seen, there is a problem that deserves swift attention. When rebar is introduced to water, it corrodes and expands up to eight times its original size. This condition usually is the result of a crack in the concrete that allows water to travel through and reach the rebar. The force of the expanding rebar causes more damage to the concrete around it, which creates greater access for water and more corrosion. It is imperative to stop this compounding cycle as soon as possible.
Recent strides in technology have provided new and effective ways to extend the life of parking structures. These advances consist of conventional means, including better coatings and sealants, as well as all new methods of handling challenging concrete repairs.
Parking structure restoration services that may be utilized include:
· Concrete repair and replacement
· Structural repairs
· Expansion joint installation/replacement
· Clear sealer application
· Deck coating installation
· Post tension repair (strand and button-head systems)
· Epoxy injection
· Chemical grout injection
· FRP (Fiber Reinforced Polymer Systems)
· Cathodic protection
· Shotcrete (spray applied concrete)
· Sacrificial galvanic anodes
Always choose a specialty contractor with experience in parking structure repair and restoration to identify specific problem areas and hazards and recommend a repair plan and maintenance schedule. Performing routine maintenance on parking structures will delay or avoid costly restoration, decrease liabilities, retain ideal parking volume and rates, adhere to local permitting guidelines and maintain the property's value.
Restoring Millennium Lakeside Garage
The Western Specialty Contractors Chicago, Illinois, Branch completed a mammoth project in 2015 to restore and waterproof a 750,000-square-foot concrete parking garage (equivalent to 12 football fields) located underneath the newly designated, 20-acre Maggie Daley Park in Downtown Chicago. Western served as the prime contractor on the garage project.
Formerly known as Daley Bicentennial Plaza, Maggie Daley Park is part of a larger network of adjacent parks including Millennium Park to the west and Grant Park to the south. It is bordered on the east by Lake Michigan and Lake Shore Drive. Together these interconnected garages comprise the largest parking facility in the country.
The $60 million project was divided into three phases: removal of the existing park by James McHugh Construction Company; waterproofing and repairs to the concrete parking structure by Western Specialty Contractors and American Hydrotech Inc.; and re-installation of the park and construction of its new features by Walsh Construction.
Restructuring the Garage
The concrete parking structure, originally constructed and waterproofed in the 1970s, had become compromised from years of wear and tear and ground water infiltration. Essentially a giant green roof, ensuring proper waterproofing of the large parking structure was key to maintaining the structural integrity of the garage beneath the park. The scope of the parking garage project included structural repairs to the existing concrete roof slab, full removal and re-installation of a new waterproofing system and major drainage improvements. The project was full of challenges along the way related to logistics, coordination with other contractors, a tight schedule, public relations, location of the project, and the sheer size of the job-site. In order to help with job-site logistics, security and contractor coordination, high definition cameras installed high above the park were used on a daily basis to coordinate daily activities, work locations, material staging locations, as well as job site safety and security.
The project began with Desman Associates, a Chicago-based engineering firm, researching solutions to resolve the parking garage's major drainage issues. While the parking garage sloped naturally from north to south, pooling water had become a problem in specific areas due to the lack of drains throughout the massive garage roof. This problem was solved by the installation of numerous new drains and a composite drainage mat system.
After the existing park (Daley Bicentennial Plaza) was completely demolished and removed from the site, work began on preparing the 750,000-square-foot surface for application of the new waterproofing system. The entire surface of the concrete roof was power washed and then shot-blasted to achieve the proper surface profile required by the waterproofing manufacturer. Next, installation of the waterproofing system began.
Installing the Waterproofing System
The waterproofing system, manufactured by American Hydrotech, consisted of seven layers, which all serve an important function in the overall operation of the system. The initial step of applying the system included spraying the concrete deck with primer. The next phase required melting 40-pound, rubberized asphalt bricks to a liquid state by heating them to 400 degrees in a kettle. The rubberized asphalt would then be poured out onto the concrete, while it was still hot and in its liquid state. Workers then spread the rubberized asphalt out to evenly coat the area. In total, this project required over 1.3 million pounds of rubberized asphalt applied by multiple crews consisting of 40 workers per day.
Constant measurements were taken during the process to confirm that the material was not being spread too heavy or too thin along the deck. After the first layer of rubberized asphalt was spread out, workers rolled reinforcing felt fabric onto the layer of melted rubber, while still in its liquid state. Another layer of melted rubber would then be poured and spread out over the area. The next step required workers to roll out sheets of heavy-duty, rubberized asphalt protection board, which was specially made to prevent tree roots from puncturing the waterproofing.
The final layers of the system included a drainage mat, filter fabric and approximately 400,000 cubic feet of gravel overburden. In order to help speed up the project, Western worked directly with the manufacturer to have special, extra large rolls of drainage mat made for the project. Standard rolls of drainage mat are 300 square feet, but American Hydrotech manufactured job-specific rolls that were 1,050 square feet. This helped to keep the project on schedule. Walsh completed installing the layer of gravel overburden, although a large amount of coordination was required between Walsh and Western to accomplish the task.
At the same time that waterproofing work was being completed on the topside of the garage roof, structural repairs were being performed on the underside of the roof slab. Coordination between crews on the topside and underside of the slab was a daily challenge for the management team. Use of cell phones was not an option due to very limited reception inside the garage. In order to overcome this obstacle, Western's management team was headquartered inside the garage for the duration of the work.
Another obstacle Western encountered during this work was poor ventilation. Using high-powered vacuum fans to circulate air throughout the work locations solved this problem. Since a large portion of the garage was closed during this work, every day represented a loss of possible revenue to the owner. Therefore, there was no room for extensions in the schedule. Twenty four-seven monitoring of the garages was also required during this work due to high volumes of pedestrian traffic in the area.
The work inside the garage consisted of 3,000 square feet of overhead concrete replacement, and the detachment of two pedestrian access tunnels from the garage. Due to the excessive loads placed on the roof slab by the park above, the concrete slab was poured with additional reinforcing steel. This made removal of delaminated concrete more difficult. All 3,000 square feet of the concrete was removed using hand-held jackhammers. After removal, all exposed rebar was sandblasted and coated. When prep work was complete, concrete was re-applied using a dry-mix, shotcrete method.
To ensure that there were no breaches in the waterproofing system after it had been installed, International Leak Detection (ILD) was hired to use its sophisticated Electric Field Vector Mapping (EFVM) technology to locate even the smallest leak in the roofing membrane.
The garage restoration work took a total of 33,554 hours to complete, with about 45 workers on the job per day.
Repairing the Multi-Level Nalley Ford Parking Garage
Crews with the Western Specialty Contractors Atlanta, Georgia, Branch recently completed a one-month project to repair, restore and protect a three-level, concrete parking garage used by Nalley Ford of Sandy Springs, Georgia, to store new car inventory.
Western crews surveyed each parking deck individually to determine specific damage for each, then provided the owner with a detailed outline of recommended work needed to restore each level. The dealer worked to sell down inventory and rotate his vehicles to make room in the garage for Western's crews to begin work.
Western crews began restoration of the top level, which is most exposed to the elements, by cleaning all concrete surfaces using a high-pressure water blaster (3,000 psi). Once the pressure washing was complete, Western crews heavily saturated the concrete surfaces with an Enviroseal 20 clear penetrating sealer. Approximately 5,580 lineal feet of existing cracks and control joints were routed, then sealed with a urethane sealant. Western crews went on to remove approximately 318 lineal feet of existing sealant around the perimeter joint, then lightly grinded the joint edges to remove any loose residual sealant. A new urethane sealant was then applied.
A total of 1,300 square feet of new pour strips were installed to allow for expansion/contraction of the concrete intersections. Slab areas, perimeter column caps and exterior wall weld plate embeds where deteriorated/cracked concrete was detected were saw cut and chiseled out and replaced with new concrete.
At the exterior wall joints, approximately 550 lineal feet of existing sealant was removed, grinded down and replaced with a new urethane sealant. Oxidation at the exterior wall weld plates was removed and an epoxy chromate primer and urethane topcoat applied.
To complete the top level restoration, Western crews applied two coats of Thorolastic elastomeric coating to approximately 8,160 square feet of wall substrate and applied an Auto-Gard FC traffic-deck coating system manufactured by Neogard to the deck. Auto-Gard FC is a two-component, fast cure, low odor urethane system for fast turnaround and/or odor sensitive applications.
Western crews cleaned all concrete surfaces using a high-pressure water blaster, routed approximately 5,580 lineal feet of existing cracks and control joints, then sealed them with a urethane sealant. Approximately 540 lineal feet of existing sealant around the perimeter joints was removed and replaced with a urethane sealant. Oxidation on corbel bearing plates and double tee bearing plates was removed and refinished with an aliphatic urethane topcoat. The precast wall perimeter was also re-sealed and repairs were made to damaged columns, which were resealed with two coats of an anti-corrosion bond inhibitor. Damaged concrete on the slab floor was saw cut and chipped out and replaced with new concrete.
On the lower level, Western crews removed oxidation on the gusseted steel corbels, spanning plates and double tee bearing plates, then applied an aliphatic urethane top coat. Deteriorated concrete around the beams was removed, any damaged steel replaced and the beams patched with new concrete. On areas where steel web was showing as a result of deteriorating concrete, the surrounding concrete was removed, the damaged steel was replaced and the area patched with new concrete.