With proper installation and maintenance, ready-mix concrete driveways can withstand heavy traffic and inclement weather and last for decades.
Six Steps to Achieve Quality Exterior Concrete
- Proper Subgrade Preparation – Prior to pouring, ensure the subgrade slopes away from structures by ¼” per linear foot for adequate drainage. Subgrade that is ready for pouring is thawed, dry, and uniformly compacted. Never pour concrete on frozen or muddy subgrade.
- Proper Slab Design – All slabs should have 4-inch depth with control joints placed directly after the pour, at a minimum of 1/4th the overall depth and spaced 2 to 2½ the depth of the slab converted to feet. For example, a four-inch slab should have a joint placed every 10 feet (4” x 2½ = 10 ft.). When concrete touches an existing structure, isolation joints should be installed the full depth of the slab.
- Proper Concrete Mix Design – The mix must contain a minimum water/cementitious ratio of .45 entrained concrete (4500 psi) to meet the following requirements:
- 6 percent air content when placed (plus or minus 1 percent)
- 4 inches slump (plus or minus 1 inch)
- Wisconsin Department of Transportation-specified course and fine aggregate
- Proper Placing and Finishing – Once concrete is placed in the truck, it should be poured within 90 minutes. Shorter placement times are required in hot weather. Finishing options include screeding or strike-off, bull floating prior to appearance of bleed water, edging and jointing, and broom texturizing. Protect finished concrete while it strengthens and cures.
- Proper Curing – As concrete cures, its surface strengthens and enhances its resistance to freeze/thaw cycles and deicer salts. Moisture content and temperature must be maintained during this process. The most common curing method is using applying a spray-on compound per the manufacturer’s suggestion. During transitional seasons, when the temperature is below 50 degrees, use cold weather practices and allow the concrete to cure for at least seven days.
- Consumer Sealing and Aftercare – Allow freshly placed concrete to cure for at least seven days before driving on it. Once the concrete has air dried, a process that normally takes 30 days, it may be sealed to protect against moisture and contaminates. High-traffic areas can be resealed every few years to maintain appearance. Water can damage new concrete in other ways. Avoid cracking by using down spouts to redirect water flow from the slab’s base. Additionally, prevent snow and ice accumulation during the concrete’s first winter. Warning: never use deicers with fertilizer ingredients, such as ammonium sulfate, ammonium nitrate, calcium chloride, and magnesium chloride. These chemicals can cause deterioration.
Use County Materials’ Ready-Mix for your next project by contacting our Central Ready-Mix Dispatch Team at (715) 845-2100.
The Wisconsin Ready Mixed Concrete Association offers valuable technical resources for designers and contractors who provide ready-mix solutions for customers. For more information, refer to the WRMCA’s publication titled, “Six Steps to Quality Exterior Concrete”.