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Concrete Restoration

Without proper protection, exposed concrete, can experience weathering conditions that can potentially result in concrete deterioration, spalling, & moisture leaking to surfaces below. Left unprotected, destructive forces such as chemicals (salt), water, and freeze/thaw conditions can result in cracks in the concrete.  Moisture entering these cracks potentially can reach the reinforcing steel causing rust and corrosion which can lead to major deterioration of the entire structure. Under a worst case scenario, moisture & de-icing salt enters the concrete deck and is allowed to reach the concrete reinforcing steel below. Premature deterioration of the concrete of the parking structure will likely occur.  It is important to note that the structural integrity of the concrete itself is not the only concern, but safety & liability issues are also an issue.  The likelihood of delaminating concrete falling & striking a pedestrian or vehicle is a definite possibility. A pedestrian tripping over a deteriorated “pothole” in the concrete floor  is another accident waiting to happen.  As we discussed, simply repairing the concrete spalled areas will not solve the underlying problem of moisture & de-icing salt migration from the deck locations above. Without stopping the cause of the problem the new concrete repairs would likely fail.   An appropriate repair solution must be engineered to: (1) resolve the cause of the problem & (2) result in a long term repair solution.     

General Concrete Repairs & Repair Material Options

 

One of the purposes of this report is to specify proper repair materials for each area of concern.  In addressing these repair areas we will discuss each of them in order.  However, it is important to understand that all of the concrete repair areas should be properly prepared prior to application of the repair mortar.  The following procedure should be followed: square cut all the edges of the repair area (minimum of 3/8 inch); remove all unsound concrete (minimum of ¾ inch around rebar); prime the   cleaned rebar with MBT Zincrich Rebar Primer or MBT P24 Primer; base concrete should have a roughened profile (not smooth); dampen patch area with water (SSD – saturated surface dry); remove all standing water; apply a bond scrub coat; apply repair material; cure. 

Horizontal Concrete Repair Options [Partial or Full Depth]

 

(1) Form & Pour MBT Emaco S66 (minimum 1 inch - maximum 8 inches).

(2) Form & Pour MBT Emaco T430  or 1060 (minimum of 1/2 inch - maximum 1 inch neat. Over 1 inch      add aggregate. Advantage = faster set times than S66.

 

Overhead & Column Concrete Repair Options

 

(1) Hand apply MBT Gelpatch (minimum 1/8 inch maximum lift   2 ½ inches).

(2) Hand apply MBT Emaco S88 (minimum 3/8 inch maximum lift   2 inches).

(3) Form & Pour - apply MBT S77 (minimum of 3/8 inch & maximum of  1 ½ inch).

(4) Form & Pour - apply MBT S66 (Minimum of 1 inch & maximum of 8 inches).

 

Inspection Notes 

 

• Our investigation revealed failed expansion joints (Photo ).
• Photo shows the worn deck coating material which was applied to the lower deck which is  located over occupied space below.
• Photos show exposed & rusted rebar and cracked & delaminated concrete.
• Photo shows an example of cracked concrete located at the ceiling of the parking ramp.

 

Repair Recommendations

 

• Replace failed expansion joints.
• Repair all horizontal & overhead deteriorated concrete with the MBT products described above.
• Repair the cracked structural concrete by pressure injection with a structural epoxy repair material (MBT Concresive Standard LVI).
• Inspect existing concrete for floor cracks. Rout out cracks to a minimum of ¼ by ¼ inch & install NP2  or SL2 sealant. Replace all failed urethane sealant in the horizontal joints with NP2 or SL2 sealant.
• Recoat the worn existing deck coating material with Sonneborn Conipur Plus coating system.
• Apply a good quality Hydrozo water repellent to the concrete surface.

Repair Options

 

Repair Option #1 [The Best] – Install Deck Coating System

 

Polyurethane deck coating systems provide a waterproof coating for vehicular and pedestrian traffic areas.  They act a complete barrier for moisture and salt penetration into the concrete surface.  The slip resistant surface is also an added benefit by increasing a slit resistant safety finish to the coated concrete surface. 

 

During our inspection we discussed the need to complete the deck coating process as quickly as possible & turn it back to service.  The general consensus was that the best deck coating system to achieve this goal would be to apply Sonoguard Base Coat (60 square feet per gallon) followed by  Conipur II top Coat (60 square feet per gallon) with aggregate.  Conipur II Top Coat requires only 24 hour cure time.

 

Sonneborn Conipur II seals the concrete from moisture entry.  It is applied as a two-component liquid material  which quickly cures to form a  waterproof elastomeric polyurethane traffic deck coating system designed for surfaces exposed to vehicular and pedestrian traffic.  Properly applied, the system will provide a continuous, seamless, waterproof, skid resistant protective coating.  It is important to note that Conipur deck coating materials have very low odor.

 

Repair Option #2 [Better] Apply a 100% Solids Water Repellent

Apply Hydrozo 100 which is a clear, breathable, high-performance, 100% silane sealer for all horizontal concrete surfaces in the parking garage.  It penetrates deeply, sealing out water & chloride ions.  It  chemically reacts with concrete to form an extra  long lasting water-repellent surface.  Application of Hydrozo 100 protects concrete from damage caused by chloride intrusion & extends the life of the structure. Coverage rate for Hydrozo 100 normally averages approximately 250 square feet per gallon.  On heavily trafficked parking garages, re-application of 100% solids silane sealers such as Hydrozo 100 normally takes place every 10-11 years on average.

 

Application of Hydrozo 100 to the concrete deck surfaces would be an excellent choice for the Cedar River Tower Parking Ramp. Advantages would include the following:

 

• Additional  Silane protection against chloride intrusion - resulting in life extension of the structure.
• Longer lasting protection – re-application after 10-11 years not 5-6 years.  Material and labor cost savings are the direct result.  In addition, the parking garage would not have to be shut down at the 5-6 year interval.
• Higher coverage rate than the 40% silane sealers.

 

Repair Option #3 [Good] Apply a 40% Solids Water Repellent

In order to provide for a low cost protection to the concrete surfaces of the concrete garage, application of a water repellent would be an excellent choice.  Apply Hydrozo Enviroseal 40 (a patented, clear, breathable, water-based, low odor, VOC-compliant, silane penetrating sealer) to all horizontal concrete surfaces in the parking garage. It penetrates deeply and chemically reacts with concrete to form a long lasting water-repellent surface.  Application of Enviroseal 40 protects concrete from damage caused by

chloride intrusion & extends the life of the structure. Coverage rate for Envioseal 40 normally averages approximately 125 to 150 square feet per gallon. On heavily trafficked parking garages, re-application of 40% solids silane sealers such as Enviroseal 40 normally is recommended every 5-6 years on average.

 

 

Repair Options - Application of a Corrosion Inhibitor

The corrosion process in steel reinforced concrete is spontaneous and similar to the process in a galvanic cell or battery.  In the corrosion process, the formulation of ferrous oxide (rust) takes up more volume than the original steel and causes stress on the concrete.  These stresses manifest themselves as cracks, spalls, and delaminations in the concrete structure. But the main consequence of concrete corrosion is the loss of steel cross-section and the resulting loss of structural capacity.  The three main factors affecting the corrosion rate are the concentration of chloride ions (de-icing salts), moisture, and oxygen.  Application of Masterseal CP inhibits the corrosion of the rebar.

Masterseal CP works on the molecular level to effectively inhibit the electrochemical interaction of the corrosion process. It is a surface-applied clear liquid that penetrates concrete and inhibits the corrosion process between the rebar and the chloride ions, oxygen and moisture in the concrete.  This advanced inhibiting action makes Masterseal CP the best choice for difficult applications.  An effective repair and/or maintenance option would be to apply Masterseal CP to all exposed concrete patch areas in the Cedar River Tower parking ramp to limit future corrosion of the reinforcing steel (rebar) in the concrete.

Repair Options – Application of a Light Reflective Coating

In order to: (1)  improve safety; (2) improve the Parking Ramp image; and (3) mask the concrete repairs, application of a light reflective coating (Sonneborn Parkcoat) to all the ceilings of the parking garage areas would be an excellent choice.  Sonneborn Parkcoat is a one-coat water-based, VOC compliant acrylic coating an 88% light reflective rating.   A mock up test section would be an excellent way to evaluate the effectiveness of this reflective coating.

Warranties

Utilizing all repair materials listed above, manufactured by BASF Building Systems, results in the fact that a single source warranty  is available for the Cedar River Tower parking ramp.

Maintenance - Periodic Inspections

Thorough inspections of the parking ramp should be done semi-annually (Spring & Fall).  Locations of damage should be identified & corrective repairs undertaken as soon as possible.  Common areas of concern include: (1) Failed sealant joints, (2) Failed concrete repair patches, (3)  Areas that may experience high abrasion in turn lanes, & entrance/exit, locations, & (4) Excessive sand, small rock, dirt, & debris located on deck surface causing abrasion damage, (7) Snow Plow damage. 

Maintenance - Cleaning

                                                                                        

Thorough cleaning of the parking lot should be done at a minimum of semi-annually (Spring & Fall), however more frequent cleaning may be required if: (1) Excessive sand, salt, small rock, dirt, & debris located on concrete surface is causing abrasion damage to the concrete surface & sealants. & (2) Aesthetic issues are a concern (example / entrance & exit areas).

 

Snow Removal

 

Snow and/or ice presents a combination of potential problems. When snow removal is required, one must if possible avoid the use of metal blades.  Blades of snowplows or buckets should  be fitted with rubber blades, or rubber sections attached to the bottom of the plow or bucket in order to protect the sealant joints, expansion joints,  & concrete surface.  The plows or buckets should also be provided with "runners or shoes" to carry the weight of the plow. 

 

In order to protect the horizontal concrete surfaces of the , good maintenance practice would suggest that all repairs listed above should be completed.  As we discussed, each project may have  special repair conditions to be considered such as: (1) available down time for repairs & (2) financial limitations for repairs. Each repair option should be considered thoroughly and a decision made as if all the repairs options could be accomplished or if certain repair options could be scheduled into an ongoing maintenance program.  

 

Application of a deck coating membrane or a good quality water repellent will protect the concrete surface from deterioration caused by salt, water, and freeze/thaw conditions which may lead to: (1) continued spalling of the concrete surface; and (2) corrosion of the reinforcing steel in the concrete.  It is understood that all BASF Building System’s products be applied  as per their technical data sheets.  It is important to note: If a more in depth analysis of these parking structures is required, it may be appropriate to consult with a local structural engineer.   

 

Technical Specialty Systems is an industry leader in the concrete restoration market with products ranging from high-performance adhesives & sealants, wall & floor coatings, waterproofing membranes, concrete repair products & expansion joints – everything you need to get the job done right.  Technical Specialty Systems has a multi-faceted problem solving approach in creating products for the construction market, combining state-of-the-art processes, superior research, and the expertise of its specialists in polyurethane  coatings, concrete, and silane technologies – designed to offer the very best.

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