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MASONRY MAINTENANCE

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Using SET-45 for Masonry Repairs

The following is the manufacturers recommended procedure for using this product. As with all materials used, always follow the manufacturers recommended instructions unless you have specific procedures on the use of the product.

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Surface Preparation

A sound base is essential for good repairs. Remove all oil, grease, dirt, and loose, disintegrated, or unsound concrete from the areas to be patched.

Saw a cut 1/2 inch deep or more to form the perimeter of each patch. A bond breaker is required at all joints. Featheredge patching is not recommended.

Where the bond between reinforcing steel and concrete is destroyed, remove the adjacent concrete to a depth that will provide a minimum of inch of new concrete over all cleaned concrete surfaces and all exposed reinforcing steel. Remove rust from rebar by wire brushing or sandblasting. Do not use a bonding agent on the steel or on the prepared concrete surface.

Flush the area thoroughly with clean water to remove dust, and then airblast to remove all water before placing the Set-45. (Note: Set-45 bonds better to a dry surface interface.)

Equipment

Have the proper measuring containers and tools on the job. Be certain the labor force is adequate to handle the rapid-setting Set-45.

Use a mortar-type mixer, as the shearing action of the blades yields optimum blending. For large jobs, the mixer should be capable for mixing up to 500 lb of material. A continuous-type mixer may be used. For smaller quantities, an electric drill with a jiffler-type mixer may also be used.

Addition of Aggregate

  • Under 1-inch depth--Use neat material for shallow patches. Set-45 should not be used for patches less than 1/2-inch.
  • Deep patches --A 50-lb bag of Set-45 may be extended by adding up to 30 lbs of thoroughly washed, dried, uniform-size, sound 1/4- to 1/2-inch round aggregate. When using angular aggregate, reduce the amount added to obtain proper workability. (Note: Do not add any sand, aggregate fines, or Portland cement to Set-45.)

Mixing

Locate the mixer as close as possible to the repair area. Allow no more than 10 minutes to mix, place, and finish Set-45 in normal temperatures of 72F (22C).

NOTE:

Water content is critical. Use 1/2 gal of water per 50-lb bag of Set-45. In certain conditions, the water content may vary between 3-1/2 and 4 pints, but in normal situations, do not deviate from the recommended water content or mixing instructions.

IMPORTANT: Always follow this mixing order:

  • Pour clean water into mixer at the rate of 1/2 gal per 50-lb bag of Set-45.
  • Add aggregate, if necessary, for deep patches. If damp aggregate is used, reduce the water content accordingly.
  • Add Set-45. Mix the Set-45 for approximately 1 to 1-1/2 minutes.

Placing

After mixing, immediately place the Set-45, working from side to side. Do not place Set-45 in lifts. Work the material firmly into the bottom and sides of the patch to ensure a good bond. Do not use a bonding agent.

Level the Set-45 and screed to the elevation of the surrounding concrete. When properly screed, Set-45 will self-level and yield a skid-resistant finish. Seal the edges and all saw cuts with light hand floating. Minimal finishing is required. Do not retemper Set-45. Clean tools and the mixer frequently with water to prevent any buildup.

Special Considerations: The setting speed of Set-45 is dependent upon both the temperature of the mixture and the area to be repaired.

Cold Weather, below 50F/10C

Heat the concrete surface until it is warm to the touch. Use warm material and warm the water to 90F (32C) to increase the hardening speed. Keep the patch warm by tenting or insulating. This will aid in obtaining a more rapid strength development in cold weather. Do not use anti-freeze or accelerators.

Hot Weather, over 85F/ 29C

The Set-45 Hot Weather formula is recommended. Keep the material cool. The use of ice water for mixing is recommended to extend the working time. (Caution: Placing Set-45 on a hot concrete surface may affect the bond. When the sun has heated the surface excessively, delay placement until additional dampening of the area has lowered the slab temperature. Be certain to remove all standing water immediately prior to application of Set-45.)

Curing

Set-45 should be allowed to air dry for a proper cure. Do not use a curing compound or wet-curing process. In normal temperatures, Set-45 patches will take traffic approximately 45 minutes to 1 hour after placing. If Set-45 is not being used, the following are general procedures for masonry repairs.

Hairline Cracks

  1. Clean out any loose material and wet the crack for several hours.
  2. Make a grout using Portland cement and water mixed to the consistency of a thick paste.
  3. The crack should be moist, but it should not have freestanding water.
  4. Force the cement into the crack using a putty knife or pointing tool.
  5. Smooth the repair. Let it dry for a couple of hours, and then cover it with a plastic sheet.
  6. Keep the crack moist for at least 5 days.

Larger Cracks in Sidewalks

Cracks that are larger than a hairline crack must be enlarged using a cold

chisel

and

hammer

The enlarged area must be undercut so that the top of the crack is smaller than the bottom (Figure 1). The undercut area must be to a depth of at least 1 inch.


Figure 1: Repairing Large Crack in Sidewalk

  1. Clean out the crack and remove all loose material.
  2. There are at least two methods of repairing the crack; one method uses a concrete adhesive, and the other uses a method similar to that above.
    • If a concrete adhesive is not used, prepare the crack as above by wetting the crack for several hours.
  3. For small patches, ready-mix concrete is suitable. Just add water and use it.
  4. For larger patches, a mixture of 1 part Portland cement and 2 parts fine sand should be used.
  5. For heavier patches, use a mixture of 1 part cement, 2 parts sand, and 3 parts gravel.
  6. Fill the crack in completely and let it set for a while.
  7. When it starts to set, smooth it with a metal trowel or wooden float, depending on the surface smoothness desired.
  8. After smoothing, let it set for two hours, then cover it with wooden sheets or plastic.
  9. Keep it covered and moistened for at least 5 days.

Cracks in Driveways

Due to the heavier traffic that driveways are subjected to, the patch will be larger and deeper than that of a sidewalk repair and will use the heavier concrete mixture of 1 part cement, 2 parts sand, and 3 parts gravel. The repair is basically as above, except larger and deeper.

Cracks and Holes in Walls

Preparation and application of cement is similar to preparing a crack in a sidewalk. The more difficult task is matching the finish of the new cement patch with that of the existing wall.

This may be done by trial and error as the concrete is setting up, using combinations of different trowels and brushes to match the finish (Figure 2).


Figure 2: Repairing Crack in Concrete Wall

Repair Hole in Wall

Safety Precautions:

  • Safety glasses
  • Work gloves

Tools Required:

  • Cold chisel
  • Small sledge hammer
  • Mixing trowel
  • Mixing container
  • Water
  • Brush for cleaning out the hole

Steps to repairing a hole in the wall:

  • Repair a hole in a wall.

Broken Corners on Concrete

The broken corner should be cleaned and moistened prior to applying the mixture. The repair is made using epoxy cement. The mixture is built up ? inch at a time for small repairs. For larger repairs, a form should be built around the corner to hold the epoxy mixture until it dries (Figure 3).

Figure 3: Repairing Broken Concrete Corner