Just the other day, as I was walking down the street (singing do-wah-didydiddy-dum-diddy-do. You'd be amazed, my spell checker just said that I'm nuts and the grammatical checker said that I just flunked English; thank you very much!) What I meant to say was, that as I was... oh, never mind. CIinics - that's what I wanted to talk about, OK!?
Have you ever noticed how many clinics there are nowadays? There are financial clinics, health clinics, and I would assume, even clinic clinics! But we are going to have a concrete and masonry clinic, where we will talk about common questions and problems. Here is a typical question that we shall be dealing with:
Question: The concrete slab where we park our cars is getting ugly because of the accumulation of oil stains. Is there an effective way to remove these stains?
Answer: I have yet to see a product work as well as it claims to do so in cleaning this type of problem. There are many good cleaners on the market today. I like to first try using Dawn Liquid Detergent, applying it to the surface and letting it soak in. Then using a brush, agitate it and then rinse. You will have to repeat this several times to remove the oil. This will not clean 100% of the stains, and you will be lucky to get even 80% of the stains removed. This is because the oil has actually entered into the surface of the aggregates that make up your concrete, and to remove it from that depth is very rarely successful.
Now the National Ready Mix Concrete Association found these solutions to be effective:
1. A solution of 5% sodium hydroxide to be used with ground limestone. Using either pellets or flakes, mix up one-half pound of sodium hydroxide to ten pounds of water, or 6.5 ounces per gallon. Mix with enough ground limestone to make a stiff paste, and then spread the paste over the stain and allow to dry. This will take at least 24 hours. Remove the dried paste with a putty knife.
2. Granular TSP, or trisodium phosphate and hot water. The TSP crystals are sprinkled over the stain area, until the stain is completely hidden. Hot water is added and then the area is scrubbed with a stiff brush. Rinse after 30 minutes.
3. Any de-greaser or driveway cleaner that contains sodium metasilicate and petroleum distillate. Use as instructed.
Question: How about removing roofing tar from concrete?
Answer: Yeah, right!
Question: Seriously, how do I remove roofing tar from concrete?
Answer: Call a roofing company to see what products they have available. You will need to look at water blasting. Don't sandblast, as it will cause serious damage to your concrete slab. A slow but somewhat effective method is dry ice and scrapers.
Question: Can I waterproof my masonry wall now or should I wait until spring?
Answer: It is too cold and wet to allow most products to dry, bond and cure effectively. The best thing to do is to protect your wall with tarps or plastic and wait until spring before waterproofing your wall. If absolutely necessary to seal a wall, tarp the wall, but leave a space where you can walk through it, like a tent, and purchase or rent some heaters. Apply your product to the wall, and allow the maximum amount of time for it to dry, cure and bond before removing your cover.
Question: I went to a store the other day and saw that there are several different types of cements. What are they and what do those numbers mean?
Answer: Type 1-2 means that it is good for common building requirements or general use. Also it can be used when moderate sulfate resistance or moderate heat of hydration is needed. Type 3 means high early strength-usually a special order product. Plastic cement has plasticizers included in it for increased adhesion and body. This does not mean that it has increased waterproofing capability.
Again, since we will be having our own little clinic like this for a while, please feel free to call or write in any questions you might have. Until next week, see ya'! .
Originally published in the Daily Courier January 27, 2000