Parking Lot Area Construction Using Concrete

Concrete Parking Area Construction

Suggested Specifications

General
Concrete parking lot pavements should be plain un-reinforced concrete built in accordance with the specifications.

Pavement Thickness
Slab depth for parking lots should be as shown on the plans.

Recommended parking area slab depths, based on use, are as follows:

* Light Use: 4" concrete - Parking for passenger cars, light trucks and occasional use by heavier trucks.
* Medium Use: 5" concrete - Driveways and parking areas for light to medium trucks plus occasional use by heavier trucks.
* Heavy Use: 6" or thicker concrete - Driveways and parking areas for heavier commercial and industrial trucks. (Pavements for heavy industrial trucks should be designed on an individual basis.)

Concrete Quality
In general, concrete should be mixed and delivered according to the requirements of ASTM C94, "Standard Specifications for Ready Mixed Concrete". Concrete specifications are as follows:

* Minimum compressive strength of 4000 psi at 28 days.
* Air content of 6½ ± 1½%
* Maximum five (5) inch slump. When mixes containing high range water reducers (superplasticizers) or combination of type A and type E admixtures (flowing concrete) are used, the slump as placed should not exceed eight (8) inches.
* Aggregates meeting ASTM C33 for severe exposure conditions.

Subgrade Preparation
The subgrade under all pavement should be brought to the required lines and grades and compacted to a uniform density. Any pockets of soft material that cannot be compacted should be removed and replaced with suitable material. Ready mixed concrete trucks and other equipment can operate on the prepared subgrade providing the subgrade is kept smooth and compacted prior to placing concrete. At the time of concrete placement, the subgrade should be in a moist, but not muddy condition. Adding granular sub-base material is not required. More information on subgrade preparation.

Concrete Placing, Finishing and Texturing
A uniform thickness of concrete (according to the design) should be placed on the prepared subgrade, adequately consolidated, and struck off to the proper elevation. All concrete should be placed continuously to prevent the formation of "cold joints". Wherever placement operations stop, a bulkhead will be installed to form a straight joint. Concrete should not be placed on a frozen subgrade. The sequence of finishing operations should be as follows: strike off and consolidation, floating (if necessary), edging, and texturing.
No finishing operations should be performed when there is excess moisture or bleed water on the surface. In general, adding water to the surface of the concrete to assist in finishing operations is not recommended.
Check the pavement surface with a ten foot straight edge.
A uniformly textured surface should be provided.

Curbs
Curbs should be constructed at the location shown on the plans. Curb and gutter can be constructed separately from the slab, or the curb may be cast integrally with the slab. The curbs should be textured to match the pavements.

Curing
Immediately after texturing, cover the surface with a white pigmented curing compound complying with ASTM Specification C309 (at the rate of one gallon per 200 square feet) or by 7-day coverage with white polyethylene or waterproof paper.
Mid-April to mid-September: Use a sprayed on curing compound applied according to the manufacturers recommendations. Mid-September to mid-April: Use waterproof covers and maintain curing for at least 7 days at temperatures above 40°F. If concrete sealers are to be used, allow a 30 day air drying period before applying the sealer.

Joints
The pavement should be jointed to control cracking. The joint lay out, compatible with the contractors paving method and equipment, must be submitted to the architect or engineer for approval prior to construction.
Longitudinal and transverse spacing should be at regular intervals. Individual spacing may vary slightly to meet catch basin and manhole castings. (The suggested transverse joint spacing is: 10 feet for 4" slabs, 12 feet for 5" slabs, and 15 feet for slabs 6". The suggested longitudinal joint spacing is 12 feet.)
Contraction joints may be made by sawing, tooling, or installing an approved insert to a minimum depth of 25% of the slab thickness. Sawed joints shall be cut as soon as possible without ravelling the concrete.
Joints should be continuous across the slab and must extend completely through the curb.
Install full depth expansion (isolation) joints, ½" thick, to isolate fixed objects abutting or within the paved area. These fixed objects include existing pavements, sidewalks, castings and structures.
Joints do not require sealing.

Opening to Traffic
Pavement under construction should be protected with barricades and all traffic (with the exception of joint sawing equipment) for seven (7) days.

Pavement Protection
The contractor is responsible for concrete placed during rain or cold weather and any concrete damaged by rain or low temperature should be removed and replaced at the contractor's expense.
When concrete is placed late in the year the contractor should submit a plan of his procedures for protection to the architect or engineer for approval prior to construction.

This information used by permission of the Michigan Concrete Association www.miconcrete.org