Q: I have a concrete driveway about 24 by 60 feet that was poured one year ago on a dry day in about 60 degrees. About three weeks after installation, the surface appeared "dusty" and wet leaves made spots on the driveway. What causes this problem and what can be done to correct this?
A: According to my concrete expert, dusting usually occurs when the water to cement ratio on the surface is too high or bad finishing techniques were used. It could have been a very weak mix of cement, not enough cement on the surface and too much water.
We recommend having it tested for strength. (A properly mixed one-year-old driveway should achieve 2800 psi.) This test involves drilling a six inch diameter piece core from the floor (which will then be replaced) and having a concrete laboratory test the strength of the concrete.
I do not know the warranty laws in your state. If licensed contractors are required to warrantee their work longer than a year, contact the contractor who originally installed your driveway and ask him to have the floor tested. If they don't know who to contact, have him or her ask a structural engineer for a referral to a good concrete lab in your area. If they are unwilling to do so, paying for it yourself will give you the information you need to determine if the driveway should be replaced.
Wet leaves left on a driveway will have a tendency to stain but can be cleaned up with a pressure washer or hot water mixed with tri sodium phosphate (1 pound per gallon).
To contact some reliable concrete contractors to evaluate your driveway, visit Home Advisor and be matched with the ideal service professional in your area.
by Kathy Maynard, reprinted courtesy of HomeAdvisor.com