Concrete Driveway Strength & Design

Concrete Driveway Strength

The majority of concrete used in residential pavements and driveways is ‘Normal’ class concrete with a minimum strength of 20MPa (i.e. N20 concrete) in accordance with AS13791 . A higher strength may be required in certain situations,for example: Heavier Loads. If the pavement is being used by vehicles between 3 ton and 10 ton gross mass, and infrequently by heavier vehicles that do not exceed the statutory limits for tyre, wheel and axle loads, anN25 concrete is recommended. Pavements for heavier vehicles than this will require more detailed design by a qualified engineer.

Concrete Abrasion Resistance.

This is the ability of the concrete surface to resist wear. It is directly related to the strength of concrete and the quality of the surface finish. An N20 concrete is satisfactory for most residential paving applications, including typical driveways. For use by heavier pneumatic-tyred vehicles up to 3 ton, an N25 concrete is recommended, and for pneumatic-tyred vehicles over 3 ton, an N32 concrete will be required (AS36002 ). 

Freezing and Thawing

An S32 concrete should be used if the pavement is subjected to occasional exposure to freezing, and an S40 concrete where more than 25 freezing cycles occur each year. Also, an air entraining agent should be used in the concrete mix to achieve air content between 4% and 8%. (See AS3600 2 ).

Concrete Driveway Thickness

Pavements for foot traffic only (e.g. paths and patios) should have a minimum thickness of 75 mm. Pavements for vehicles less than 3 tonne gross mass should have a minimum thickness of 100 mm. Pavements for vehicles between 3 tonne and 10 tonne gross mass and infrequent use by heavier vehicles that do not exceed the statutory limits for tyre, wheel and axle loads, should have a minimum thickness of 150 mm. Pavements for heavier vehicles than this will require more detailed design by a qualified engineer.

Reinforcement

The use of steel reinforcement or mesh does not increase the load capacity of the pavement, or affect its thickness. Its function is mainly to hold tightly closed any cracks that may form. In general, the amount of reinforcement required to provide the appropriate degree of crack control will depend on the thickness of the slab and the joint spacing. A guide to the minimum reinforcement used in slabs for different conditions is provided in AS36002 sections relating to “Crack control for shrinkage and temperature effects”. These requirements on common slab formats are given in Table 1.