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Q. we had a bad experience with a crew that poured a walkway and driveway for us. The surface is very rough, to the point it hurts to walk on with barefeet! Is there anything we can do (without blasting it out) to help smooth the surface? THanks!! |
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-Kelley,
Collierville,
TN
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A. Fear not there is help out there. What you need is concrete grinding and possibly some polishing. If you absolutely must do it yourself then you can purchase sanding/grinding disks for angle grinders and power drills usually available at your local hardware store. This is a very dirty and time consuming job and you will need to use protective gear (eye goggles and dust mask at the least) and appropriate clothing (jean pants and preferably long sleeved shirt). But as usual I recommend hiring a professional as any mistakes could prove to be costly to have repaired.
If you would like assistance in finding a local contractor we can help. Please call 888-326-0653 opt #1.
Thank you,
T. Tizon
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Q. Is there a minimun hydrogen to concrete ratio the must exist in a concrete mixture in order for it to be a viable mixture? If so, what is that ratio and how is it defined or calculated?
Thanks,
J. Blair Briggs |
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-J. Blair Briggs,
Idaho Falls,
Idaho
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A. Yes, there is a hydrogen to concrete ratio that needs to be maintained. Unfortunately it is a varied ratio depending on many different factors including climate and reason for concrete (i.e basement, foundation, sidewalk...etc.). The best course of action would be to contact a local concrete company to see what is the best mix ratio for your area. If you have a concrete project that you would like to get resolved we would be happy to assist you in finding a concrete professional in your area. Please call 888-326-0653 option #1.
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Q. What is the purpose of fly ash? How much calcium should be used in cold weather pouring? |
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-slade,
locust grove,
oklahoma
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A. From our Expert, Daniel Herzner of
DecoCrete Depot.
Fly ash is a byproduct of burning coal. It is commonly used as an admixture to make the concrete stronger, more durable and easier to work with. It is also a “green” building material and a terrific way to get the most from natural coal resources. Additionally, there are a tremendous number of major building projects taking place around the globe which tend to put a real strain on global supplies of cement (the “glue” of concrete). So, fly ash also provides a great way to extend naturally mined cement resources.
Calcium is frequently used as a low cost set accelerator (it helps the concrete set up more quickly and promotes early strength). Its relatively low cost may be its only advantage. NEVER use calcium chloride in integrally colored concrete. It tends to attack the pigments, causing blotchiness and color fading. It also has a tendency to cause efflorescence. In order to side step any potential issues that calcium can cause, it is recommended to use a non-chloride accelerator. If these issues are not a concern (because perhaps the finished slab will not be visible once the work is completed) your local concrete ready mix company can make recommendations on how much to put in. Finally, hot water can be used when mixing the concrete and will dry much more quickly than using cold water.
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Q. What grade of concrete is required for columns if number of floors will be five? |
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-Baz Mohammad,
Jalalabad,
Afghanistan
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A. Dear Baz,
The answer to your question will depend on several factors, including the quality and slope of the ground on which you are building and the requirements of your city or township. My recommendation is to speak with several commercial builders as well as your local building authority before proceeding.
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Q. We had concrete pool deck constructed and finished in stamped concrete technique in August of 2005 by a local contractor. After first winter (in central Illinois)the surface of the deck started chipping and flaking. After close inspection we found that in some areas decorative surface chipped as deep as ¼ to ½ of inch deep, exposing aggregate. We immediately contacted the contractor; the contractor suggested that this problem is not his fault, but possibly concrete supplier’s problem. He suggested the concrete mix could have been mixed improperly, and he stated that concrete is a an unpredictable material so it cannot be controlled. I would like to hear opinions on that matter … is it the truth that I have made a mistake that cost me over 20 thousand dollars? |
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-Tatiana Dycus,
Litchfield,
IL
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A. From our Expert, Daniel Herzner of
DecoCrete Depot.
The condition of your top layer of concrete flaking off is known as spalling. Spalling is more common in cold weather areas and can occur when water seeps into the concrete surface pours and freezes. Concrete is a volatile material and difficult to fully control. However, some measures could have been taken upfront to help mitigate the possibility of spalling, although it is impossible to say that these measures would have necessarily eliminated the problem. So, it’s difficult really to blame your contractor or the folks who delivered the concrete. First, always ensure that your contractor will finish the job with a high quality, penetrating sealer to help prevent water from seeping into the surface. Second, air entrainment admixtures can be used which create tiny air bubbles within the slab to help give expanding water in the concrete somewhere to go. At this point, to correct the problem you can look into having your pool deck resurfaced. If you have any further questions regarding this situation feel free to call us at (914) 285-9274.
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Q. I have several questions. When does a crack change from cosmetic to structural? How many cracks are acceptable per 1000 square feet? |
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-thomas,
riviera beach,
fl
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A. Hi Thomas,
Concrete cracks as it changes in volume.
According to the Portland Cement Association (PCA): "Concrete, like all other materials, will slightly change in volume when it dries out. In typical concrete this change amounts to about 500 millionths. Translated into dimensions-this is about 1/16 of an inch in 10 feet (.4 cm in 3 meters). The reason that contractors put joints in concrete pavements and floors is to allow the concrete to crack in a neat, straight line at the joint when the volume of the concrete changes due to shrinkage." If the cracks to which you refer are in your home's foundation, you may want to look into liquid urethane injection. This method of repairing cracks in concrete actually fills the cracks and prevents water seepage.
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Q. The edges on my concrete porch are breaking off. How can it be repaired -- or should it be replaced? |
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-Joe,
Buffalo,
NY
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A. Hi Joe,
You can definitely repair the edges of your concrete porch! The first step will be to clean out the entire area that is chipped or broken. A diamond blade will be most effective in achieving this (you can rent a diamond blade and cutter from your local tool rental company). NOTE: this process can get mighty dusty, so be sure to close/tape all the doors and windows near the porch, and invest about $10 in the proper mask (check the back of the mask's packaging for "cement dust"). Next, mix a concrete compound with acrylic fortifier, which will help secure the bond to your porch. If your porch is raised, you'll need to build out a small mold to hold the replacement mix -- you can use scrap wood for this and cover it with WD-40 so that the concrete does not stick to it. Use a metal trowel to smooth the surface of the new cement, then cover with plastic for two days. Once the patched edges have hardened, you may wish to seal the entire porch to even out the coloring between the new and original concrete. Please remember to wear protective gloves during the entire process.
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Q. I have 6000 square feet of new cement floor that we need to cover. What do you recommend? |
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-ahmed orra,
Maumee,
Ohio
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A. Hello Ahmed, How exciting! Have you thought about decorative concrete? Your cement flooring can be transformed into a showcase! You can choose from almost endless looks with concrete staining: create the look of a marble floor, a terrazzo floor... you can even replicate the look of tile or slate for a fraction of the cost. Today's sealants resist staining and water damage, leaving you with a floor to enjoy for years to come.
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Q. Twenty years ago a foundation with partial basement was laid for a house plan. They stopped building because there wasn't enough water for the well. I want to build a modular home on this foundation but the original house plan's foundation is too small. Can a foundation with basement be extended to accommodate a larger house plan? Please help us. My brother gave me the house site and we would like to build there. Thank you. |
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-Darla Miller,
Neosho,
MO
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A. Hello Darla,
I would suggest first checking with your local building authority in terms of what is allowed by state and town regulations. From there, two elements to consider are soil quality and the grade of your land. Finally, you may wish to think about extending only the foundation without extending the basement: this approach will be less expensive and more expedient.
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