Things You'll Need
Strike hammer and chisel, or jackhammer
2 by 4s
3-inch wood screws
Concrete can be used to build any number of different kinds of ramps. Among the uses for ramps are handicapped access, boat launches, skateboarding and loading. The specifications for each ramp are unique, so there are no one-size-fits-all plans. There are, however, certain basic steps that apply to building most concrete ramps. There is one unique consideration for building the ramp on an existing concrete slab.
Research the regulations. There are specific regulations that apply to handicapped access, loading ramps and boat ramps. There are also local building codes and permits that you must understand and with which you must comply.
Mark your ramp's footprint on the slab. Chisel or jackhammer the surface inside the footprint to ensure stronger adhesion once the ramp is poured. The weight of the ramp will guarantee the adhesion to some extent, but a roughed-up surface will prevent slipping and ensure a stronger bond.
Determine the side dimensions of the ramp. Determine the rear (wall side) dimensions. Mark those dimensions on ½-inch plywood. Use one sheet for each side and one for the wall. Cut out the plywood forms.
Screw 2 by 4 braces along the outside vertical edges of the side-forms. Fit the wall side form to the side-forms. The surface of the wall form must be flush with the edges of the side forms. Place 2 by 4 braces over the two vertical edge surfaces of the wall form, overlapping onto the vertical braces of the side forms. Screw the new braces into both the surface of the wall form and the side form braces. Your whole form will now stand along on three sides.
Screw 2 by 4 struts into the upper edges of the side forms, joining the sides so they can't spread, but not inside the pouring area of the forms. Place the whole form onto the footprint you've prepared on the slab. Sandbag the bottoms of the side forms.
Calculate how much Quickrete you will need. Mix the Quickrete one bag at a time. Mix the Quickrete until it is approximately the consistency of cooked oatmeal. If it is too thin, it will not trowel easily up the ramp slope. If it is too thick, it will cake and fail to pour. Fill the form from the high side toward the down slope, placing your cut rebar in crisscross patterns every 8 to 12 inches, and ensuring no rebar will be exposed when the concrete is finished.
Smooth the surface of the concrete with a trowel as it fills to the edges of the form. Check the level frequently along the entire surface. When the concrete surface has dried enough to "crumble" when it is scratched, you can remove the struts one at a time and trowel the surface under them.
Cover the work with a tarp if there is any danger of rain. Allow at least four dry days of drying before removing the forms. Remove the forms by unscrewing the braces.
Quantities and sizes of materials vary with each ramp plan.