Installing concrete is a challenging job, and almost every placement is different. Size, shape, color, finish and depth all have to be considered. Once those are decided, the steps to place concrete are much the same in layout, preparation and placement. Here is what that looks like on a Down Right Concrete job.
Step 1: The Estimate & Contract
After looking at the logistics of the job, we propose a price. Once you decide to go with Down Right Concrete LLC, you receive a written contract that clearly states the work to be completed, expectations for finish, color and texture, the price, and the payment schedule. The contract also explains what to expect from your new concrete and how to maintain it as it ages. Once it is signed (and any pre-payment made), the real work begins.
Step 2: Site Work
Before concrete can be placed, the site has to be prepared. We often use earth-moving equipment to clear the area and speed up this process. Grass, rocks, roots, shrubs and old concrete are removed down to raw earth. A sub-base of at least 4 inches of granular fill or road base is recommended unless the soil is already very compact and stable. The sub-base is placed and compacted over the entire area, with special attention to the edges. Proper sub-base prep helps the concrete cure properly and reduces the chance of heaving from expansive soils and frost.
Step 3: Forming & Rebar
Once the sub-base is ready, forms are set. For most residential projects we use wood forms held with metal or wood stakes, fastened with screws or duplex nails for easy removal. Forms must be straight (not warped), set to the proper slope for drainage (a minimum of 1/8 inch per foot for residential), and meet in clean corners. Stairs get special forms and forming methods. Drains are dug and placed if needed. The last step is rebar. Reinforcement significantly extends the life of a slab and helps keep cracks from widening and separating.
Step 4: Placement
Residential concrete should have a minimum cement content of 470 lb per yard, and more in colder climates to help prevent scaling and spalling (the smooth top wearing away and exposing rough aggregate). Regular 3/4 inch stone is used for broom or smooth finish slabs. The concrete arrives in a ready-mix truck with the drum turning to keep it from setting. If the truck can reach, it pours straight into the forms. Otherwise we use wheelbarrows or a concrete pump. As it is poured we work it with shovels, rakes and come-alongs to eliminate voids and air pockets, and a rod screed helps with leveling.
Step 5: Early Finishing
Once the concrete is in the forms, a straightedge screed is pulled across the top to consolidate it and begin leveling. Next it is floated, using a hand float for edges and detail or a bull float for large areas, to further compact the surface, even out high and low spots, and create a smooth surface. Joints and edges are worked in with special hand tools at the same time.
Step 6: Troweling
If the concrete will be smooth troweled or stamped, it needs a steel-trowel finish. We let the surface begin to set, then steel trowel it for a smooth, hard, uniform surface, using large trowels on poles (fresnos) and getting on knee boards to apply a hand finish.
Step 7: The Finish
With troweling done, the final finish goes on. The most common is a broom finish: a special broom is pulled across the surface for a textured, slip-resistant surface. Other finishes include exposed aggregate, stamped and smooth trowel.
Step 8: Curing
Now the concrete rests and cures (gets hard). Curing takes about 28 days, and the first 48 hours are the most critical. A liquid cure-and-seal compound can be applied right after finishing to help the concrete cure slowly and evenly, which reduces cracking, curling and discoloration. Light foot traffic is usually fine after 3 to 4 days, and you can typically drive and park on it after 5 to 7 days.
Step 9: Maintenance
Concrete that is placed, finished and cured properly should last a lifetime, but a little maintenance goes a long way. A quality sealer is always a good idea: a cure-and-seal on pour day, or a high-quality sealer about a month after placement. Exterior sealers last roughly 1 to 5 years depending on conditions. Occasional cleaning with soap and water keeps it looking its best, and sealing helps prevent staining from oil, leaves and other contaminants.
Driveway Specs We Recommend
- A 4,000 psi mix with a 0.50 water-to-cement ratio for driveways gives better wear and a denser concrete than a typical 2,500 psi mix.
- The sub-grade should be compacted to an even thickness. A standard driveway is 4 inches thick, and you want a consistent 4 inches, not 3 to 4 inches. This matters even more here, where soils expand.
- Rebar reinforcement significantly extends the life of your concrete.
- Control joints should be at least 25% of the slab thickness (1 inch deep in a 4 inch driveway) and spaced 2 to 3 times the thickness in feet, so no more than 8 to 12 feet apart on a 4 inch slab.
- Below 40°F, curing blankets should be used for the first few days. Concrete should not be placed when temperatures will drop below 20°F. The colder it is, the longer it takes to cure.
Frequently Asked Questions
How long before I can drive on new concrete?
Light foot traffic is usually fine after 3 to 4 days. Most driveways can take vehicles after 5 to 7 days, and the concrete continues to gain strength for about 28 days.
How thick should a concrete driveway be?
A standard residential driveway is 4 inches thick, and it should be a consistent 4 inches throughout, over a compacted base of at least 4 inches of crushed rock.
What PSI concrete is best for a driveway?
We recommend a 4,000 psi mix with a 0.50 water-to-cement ratio. It wears better and is denser than a typical 2,500 psi mix.
Should I seal my concrete?
Yes. A cure-and-seal on pour day or a quality sealer about a month later helps prevent staining and surface wear. Exterior sealers typically last 1 to 5 years.