Concrete Repairs 101
DEAR TIM: A two foot long by approximately 4 inch thick chunk of concrete detached from one of my outdoor steps. The remainder of the steps are in good condition. Is it possible to restore the broken step? What can I do to insure that the patch will not separate? What are your suggestions as to mixing concrete? Do you feel I can tackle this project? My boyfriend is betting that I will fail miserably. E. R.
DEAR E. R.: Do you have some scrap wood? How about a concrete block or two? Can you rent or borrow a hammer drill? Is there a masonry supply house near your home? Great! Tell your boyfriend, we will take the bet. I'll split the winnings with you!
Repairing a broken concrete step or a cracked corner of a driveway or sidewalk is not a problem. The trick to a successful patch job depends on pinning the new concrete patch to the old concrete.
You need to get the following things: one bag of Portland cement, three 4 inch long pieces and one 20 inch long piece of one half inch steel rebar, a bucket of coarse sand, and a bucket of clean gravel. Pick up the hammer drill from the tool rental shop with a 6 inch long, 1/2 inch bit.
Begin your repair by removing all loose concrete from the broken step area. Use a one half inch cold chisel with a hammer to remove partially loose stones. Wear safety glasses! Drill three holes approximately 2 inches deep into the old step area. These holes should be spaced equally in the area to be patched. Drive the 4 inch long pins into these holes. Take a broom or old paint brush and sweep away all the dust.
Using your scrap lumber, cut and size a board which will act as your vertical form. This form will be held in place with the concrete blocks. You may need to put shims between the board and the concrete block to achieve the correct angle.
Take some pure Portland cement and put it in a bucket. Add water and stir until you achieve the consistency of a thick bodied paint. Slightly dampen the area to be patched with some water. Apply the cement paint to the old concrete and the pins. Mix 3 measures of gravel, 2 of sand, and 1 and a half of Portland cement to make your concrete. Add enough water so the mixture will pour from your mixing basin. Don't add too much water, as it will weaken the concrete.
Pour the concrete into the form. Insert the 20 inch piece of steel into the middle of the fresh concrete. Using a scrap piece of wood, strike off any excess concrete using a back and forth motion as you scrape. At this time take a bricklaying trowel and slide it up and down between the vertical form board and the concrete. This will minimize the presence of stones on the face of the patch.
Within two - three hours, the concrete should begin to stiffen. Gently remove the vertical form. Rub the face of the concrete with a small block of wood to achieve a sandy finish. Do the same with the top of the step. When you are satisfied with the texture, replace the form carefully. Cover the patch with plastic. Don't remove the form or plastic for three days. Also, be sure to get our money!
