Concrete Driveway Structural Design
Strength
The strength of concrete is measured in psi (pounds per square inch) upon a compression test. The mix design for concrete driveways in Minnesota should be at least 4000 psi. AR Masonry will only use a concrete that is rated at 4000 psi or greater for the concrete driveways we install in Minnesota.
Freeze/Thaw resistant
Because of the winters in Minnesota, an essential additive must be in all exterior concrete. The additive is air entrainment. Without air entrainment concrete will begin to flake and deteriorate after the first winter.
Concrete Thickness
The necessary thickness of a concrete driveway is determined by the weight of the vehicles that the driveway will be subjected to. Four inches of concrete is ideal for cars, suv’s, trucks, and 2 axel box trucks. Six inches of concrete is required for dump trucks and semi-trucks.
Reinforcement
Rebar
All concrete driveways must be reinforced with rebar. During the winter the sub-grade (ground) will freeze and move. Rebar keeps the concrete tightly held together throughout the freeze thaw cycle. Rebar prevents the control joints from opening up wide and keeps the slab sections level with each other. AR Masonry's standard rebar lay-out is every two feet each way in a grid fashion.
- Fibers
Fiber mesh is synthetic fiber strands distributed evenly throughout the thickness of the concrete slab. Fiber mesh is considered a secondary reinforcement (rebar is primary) and is not necessary in all concrete driveway designs.
Cure & Sealer
Curing Concrete Driveways
Once concrete is poured and after final finishing, a concrete curing agent is then applied to promote uniform curing. Basically, we do not want the surface to dry faster than the bottom. Concrete that is not properly cured has a tendency to develop surface defects. The curing agent is applied when the temperature is above 70 degrees F and/or on windy days.
Sealer
Ar Masonry seals all concrete driveways with a chemical called siloxane. Siloxane is a penetrating sealer that “soaks” into the concrete pores and creates a water tight surface unlike traditional sealers that form a surface membrane. Siloxane can only be applied once the concrete reaches its designed psi strength which is 28 days after placement.
Control Joints
Control joints are installed using two different methods of which will be determined on a per job basis. AR Masonry most commonly saws the control joints in the next day after placement. On some occasions control joints are tooled in when the concrete is plastic before final finishing. Control joints are installed at intervals no larger than 8 feet each way (except when cosmetically unappealing.)
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