Lay out the path of your concrete wheelchair ramp as it is detailed on your design plans, using wood stakes. Your architect may have chosen an L-shape or a U-shaped path to best incorporate the ramp on the site while taking into account the specific requirements of the Americans with Disabilities Act (ADA) for span and rise. Transfer the measurements from your plan to the ground, using wood stakes to mark the path every 6'. It is easiest to begin by locating the point where your plans connect the ramp to the structure and then work "backwards" to place the measurements all the way to the beginning of the ramp.
On each wood stake, place a mark where the height of the finished ramp will be. These measurements (from the ground to the top of the ramp) will be on your drawing, with notes on how they change every 6'; transfer the measurements to the stakes and run a string line so it passes over each of your marks so you can see the rise of the ramp.
Double-check that the measurements for the rise of the ramp match ADA requirements when laid out on the site. A simple rule of thumb is that for every 12" of ramp the slope cannot be more than 1". So if your ramp is 10' long, the highest end of it can be no more than 10" higher than the height at the ramp's lowest end. If any changes need to be made, contact your architect or structural engineer who drew your designs to gain written approval of the change, for liability reasons.
Set concrete forms for the sides of your concrete wheelchair ramp. Your plans will detail the width of these side walls. (The ramp itself is poured later.) Use rebar stakes to hold the wall forms in place; you should set the wall forms so that the concrete poured in between them will create the exact width of wall required. Make sure that the height of your walls does not go beyond the string you set up to show the height of the ramp. Double-check that the side wall extends underneath where the ramp will be, not outside of it.
Create a "step" at the top of each wall if your design requires it. These "steps" are created so the ramp will sit on top of the walls but also have 6" of wall coming up to the ramp's full height on the outside edges of the ramp, to help hold the ramp in place. To create this, cut the inside form of each wall down to the height of the bottom of the slab. Make two L-shaped forms, with the bottom of each "L" covering the width of the wall that will be directly under the ramp, and the vertical leg creating a new small side wall for the narrow top outer section of the wall. Attach the L-shaped forms to the tops of the wall forms. A good way to picture this is to imagine you are making a box (the ground and side walls) with a sliding lid (the ramp); when the lid is in place the box is smooth across the top and you do not see the steps, but the steps support the lid.
Pour your concrete walls by pouring the bottom 12" first, to provide weight in the forms. Then begin to fill the forms to the height desired, from the lowest point first, working your way to the highest. You can use a small scrap of 2x4 to rough float the finish on the top of the wall so that the concrete of the slab can form a "lock" with it to prevent the slab from sliding; you do not want a smooth finish, or the two pours will not adhere.
Strip the wall forms from the cured concrete. You should now have two sloping walls that follow the path of your ramp and have a space between. The ramp is not poured solid with the walls because the expense of the concrete would be too great. You now need to fill that space between the walls with fill dirt, so that when you pour the ramp it will match the height of the wall but will be only be 6" thick. Make sure that you tamp your fill as you go, and when it is at the height of the bottom of the proposed concrete slab for your ramp, perform whatever required compaction test is called for by your code.
Hold 2x6 wood to the outside of each wall and nail it in place using concrete nails. This will become the outer form of your slab pour. If your plan called for "steps" to be created, you do not have to do this, those "steps" becomes the outer edges of the ramp. Cut the metal mesh to fit between the two sides formed by the wood but maintaining at least 1" of clearance from both pieces. Using 2x2 concrete brick, raise the mesh so it rests near the bottom center of your ramp.
Begin pouring your concrete slowly, starting at the bottom of the ramp and working your way up. As you go, level off the concrete with a 2x4, and then as it begins to set, smooth-finish it with a concrete float and follow with a broom finish to provide traction on the cured ramp.
Strip the 2x6 forms off the cured ramp (if you used them). Lay out the stanchion positions for your railing system and use a hammer drill to create the bolt holes. Position your railings, inject epoxy into the holes and bolt the railings down to the concrete ramp.