Problem Clinics | From the 1970s

1970s

• Removing Acrylic Seal Coat From Tilt-Up Walls

  The finisher applied too much seal coat to some of the tilt-up panels for a post office building. Most of the panels with normal amounts of seal coat look fine, but where it has been applied thickly it has yellowed. It is reputed to be an acrylic. We have

   

• Dry shakes good or bad?

  I am responding to your April 1979 special issue on concrete finishing. The author of the articles often referred to applying a dry shake when the concrete has started to set but before the water sheen has disappeared. I always thought that the dry shake was a bad concrete practice and highly...

   

• Concreting on a slope

  In June 1965 you published an article "Concreting Inclined Planes" (page 205). We would appreciate additional information relating to concreting on inclined planes.

   

• Electric Cable for Snow Melting Systems

  I need information about electrical systems embedded in a slab to remove snow and ice during the winter.

   

• Progressive disintegration

  When about 25 years old our garage floor began to disintegrate, but only from the front edge. Thin, parallel cracks would form, then enlarge, and pieces would then break off. This continued for about 10 years, by which time the edge of the slab had retreated about a foot from the door. Last year...

   

• Skin burns from concrete

  Why will concrete severely burn the skin? Years ago I ended up with third degree burns on my legs, though prior to that I had concrete on my legs many times and never was burned. I know that there are several concrete burn cases a year at most hospitals, but it is still not a common occurrence in...

   

• Tying concrete walls and stairs to foundations

  An inside stairway and wall are to be built some time later than the foundation walls of a house. Their footings will be built at the same time as the footings for the foundation walls. Will these inside footings be enough to keep the stairway and internal wall from settling independently?

   

• Relative effectiveness of rebar patterns

  I see rebars with several different shapes of deformations on them. Is there any record showing which deformation patterns develop the best bond?

   

• Removing ink stains

  How can we remove ink stains from the floor of an office supply area? The stains vary from small spatters to big spills 10 inches in diameter.

   

• Little Construction Potential for Carbide Lime

  I have access to a supply of byproduct hydrate of lime. Could you provide any information as to how this material could be used in road or holding basin construction or in general concrete work? The lime hydrate is a byproduct of acetylene manufacture fro

   

• Dispensers for Truck Mixers

  Would you please help me find some information on dispensing devices for truck mixers for introducing superplasticizers into concrete? One was shown in your article "Flowing Concrete," in the January 1979 issue.

   

• Heat Buildup in Massive Sea Wall

  We have a problem concerning a sea wall which forms a cutoff to a large underground parking garage we are forming in an old dry dock.

   

• Repair at High Temperature

  We desire to refinish overhead exposed concrete spans in concrete which is at a temperature of 220 degrees F and cannot be cooled. Spalls vary in diameter from roughly 1 inch to 1 foot and resemble ordinary popouts.

   

• Preventing Lumps in Bagged Cement

  We generally keep a supply of bagged cement on hand in our storage shed, and sometimes we hold some of this on the jobsite for extended periods of time. Although the bags are usually covered with a tarpaulin or plastic sheet, even when we store them indoors, we frequently find that after a few...

   

• Aid to Estimating Rebar Requirements

  Where can I get some guidance on estimating reinforcing steel? Sometimes the design details don't make it clear exactly what is required.

   

• Shotcrete Repair in Sea Water in Cold Climate

  We are considering shotcrete for repair of a badly deteriorated dock face exposed to salt tidal waters in a cold climate where freeze-thaw is a major consideration.

   

• Removing asphalt from a wall

  A 10-foot by 60-foot wall that was formerly an exterior basement wall is now the interior wall in an addition and it is desirable to paint it. The trouble is that it has an asphalt coating. How can we get the asphalt off?

   

• Pumping Lightweight Aggregate Concrete

  When we had trouble pumping an expanded shale aggregate concrete we got some relief by increasing the air content (which had been 4 percent) up to 8 percent, and by replacing some of the sand with fly ash.

   

• Equipment for pumping lightweight mixes

  We know that structural lightweight concrete mixes for pumping should be proportioned with pumping in mind. But assuming we have obtained a good mix design, shouldn't we be concerned about the choice of pump and pipelines?

   

• Shotcreting in the Wind

  Is there any admixture that will keep cement and sand from being blown out of the jet stream of nozzle-mixed shotcrete when work is being done in windy weather?