How To More Effectively Construct A Concrete Parking Lot
By: John Garcia | Date Posted: June 19, 2022
While concrete parking lots are comparable to other types of pavement, there are significant variances. The majority of existing pavement design techniques are based on moving load cycles. However, parking lots consume half of their space for static vehicle storage; driving load cycles are not the primary design requirement.
Streets and roads are built to handle a wide range of traffic, from residential to heavy industrial. Parking lots are often designed to service a particular sort of traffic, such as all automobiles or all big trucks. In the following post, we’ll look at building a concrete parking lot more effectively.
Parking Lot Design
When compared with other concrete uses, parking lots are generally subjected to greater stresses than floors. Because they are usually stable and slow-moving, leveling and smoothness are less important than they are on streets and roads.
A proper subbase, appropriate surface thickness, as well as traction, are more necessary in a parking lot. So here are some things to know about concrete parking lot design:
Table of Contents
It’s essential to remember that the parking lot is made up of more than simply concrete. Parking lots are made up of slabs, curbs, lighting poles, and drainage systems, all of which must operate together.
Parking lots are usually built simply on top of natural soil as opposed to compacted subgrade. The main thing is to have the subgrade compaction level so that some places don’t sink and break the pavement.
Pavement no thicker than four inches is normally suitable for vehicles and light trucks. The pavement must have a 5 to 6-inch thickness for larger delivery vehicles. This is controlled by the subgrade, how many times a load is applied, and vehicle weight.
Parking lots typically drain to the pavement’s edge or into a gutter. Drainage is often installed within the paved area. To avoid automobiles from dragging, the slope of parking lot entrances should not surpass 8%.
A concrete parking lot’s jointing is the same as it is on any other level surface. Isolation joints should be installed to separate parking lots from building foundations, drainage systems, or light pole foundations. It is recommended that contraction joints are smooth rather than staggered, square rather than rectangular, and placed at intervals. According to ACI 330, the spacing of contraction joints is listed below.
In most cases, reinforcement is not required for a parking lot that is concrete. In the case that contraction joints are placed wider apart than indicated in the infographic for whatever reason, reinforcing may be required to keep cracks together. Likewise, joints with dowels that carry vertical pressures across panels are unneeded unless there are very severe loads such as significant truck traffic.
Tie bars are an alternative to the rule regarding no reinforcements or dowels. During construction, the first piece of pavement joint from the border needs to be tied to the rest of the pavement to protect the initial piece of slab from slipping away from the parking lot. Tie bars must be ½2 inches in diameter, 24 inches long, and 30 inches apart.
If automobiles park near the edge of a parking lot, the edges should be strengthened. It is possible to thicken edges by including curbs or extending the bottom.
The exterior of parking lots can be finished with almost any external aesthetic finish; however, big lots would be prohibitively costly to texture or stamp. Integral color is an excellent choice since it keeps the lot appearing cleaner.
Parking Lot Materials
Materials endurance should be the key priority. The longevity of pavement is dependent on its surface, freezing and thawing resistance, and overall durability. The required compressive strength for a parking lot located in freezing-thawing zones where deicing salts are utilized should be 4000 psi.
Although, the main strength concern is flexural strength instead of compressive strength because pavements must withstand bending and breaking rather than crushing. Note how flexural strength is typically around 15% of compression strength, and how the pavement’s bending strength is proportionately thick. So, in order to acquire the long-lasting concrete we seek for parking lots, keep the following in mind:
It is crucial that air be entrained in concrete to maintain its integrity. The cycle of freeze-thaw will dissolve non-air-entrained concrete in a year, especially if deicing salts are used. Consult the infographic below to determine the air content.
Like any slab, a bigger top size aggregate will result in less shrinkage and hence less cracking, although maintain it less than 1/3 the slab’s thickness. Well-graded mixtures are easier to deal with and shrink less and, therefore, robust pavement.
If the soil contains sulfate, use cement that are sulfate-resistant. Pozzolans and mixed types of cement can also assist in minimizing sulfate impacts.
when it comes to screeded uses, the slump of concrete needs to be 4 inches or 1 inch for slipforming.
Parking Lot Construction
Concrete parking lots can be built in a variety of ways, just like any other slab. Wet screeding the concrete to the appropriate thickness is the easiest but least exact procedure. Another, and certainly the most usual, alternative is to set side forms and use hand screeds, truss screeds, or other vibrating screens.
Slipforming is quick and creates very high-quality pavement, but the equipment is costly, and placing the equipment is problematic unless the lot is very large. Another alternative is to utilize a Laser Screed with a 3-D component that can accurately and quickly pour concrete. Here are some pointers for building a parking lot:
Compact Sub Base
To get a flat surface and homogeneous density, compact the subbase. The subgrade must be within plus ¼ inches or minus ½ inches of the required grade. Because parking lot pavements are often thin, elevated locations might lead to weak parts that crumble. Cracking can be an issue in thick areas.
Backfill for any holes under the parking lot should be compacted in 6-inch lifts. A low-controlled material flowable fill is an excellent choice for this.
In hot or windy weather, dampen the subgrade before pouring concrete.
3-D Laser Screed
If you own a screed and need to get the most out of it, the 3-D Laser Screed is a fantastic method to install concrete parking lots. The screed can modify the slope of the surface to any profile requested by using a robotic Geodimeter. The main issue with this strategy is that it is so rapid.
Curing is required to get a nice, robust surface. Use a spray-on curing chemical to cure the slab.
Parking lot slabs are often finished with screeding, bull-floating, and brooming to get a slip-resistant top. Troweling air-entrained concrete frequently results in surface layer debonding and extremely slippery surfaces when wet.
Joints must be sawed as soon as feasible on the concrete—between 4 and 12 hours for standard saws and 1 to 4 hours for early entry saws. Begin your saw cuts at the corners first to avoid horizontal cracks if there are any re-entrant corners.
Concrete parking lots are a highly profitable market for concrete contractors, as well as a favorable financial investment for property owners. A concrete parking lot is nothing but an outside slab on the ground or slab on grade. Apparently, the sloping pavement for drainage, the capacity to withstand significant automotive loads, and the extreme environmental exposure distinguish it as a parking lot and make it a little unusual to plan and install.
Thank you for reading!