How To Calculate Asphalt Tonnage? [2024]

How To Calculate Asphalt Tonnage? Asphalt is a commonly used paving material for roads, parking lots, driveways, and more. It is composed of aggregate (stone, sand, gravel) glued together with bitumen (a petroleum byproduct). When paving a surface with asphalt, it is important to calculate the exact quantity needed to complete the job.

An accurate tonnage calculation helps minimize wastage and ensures you order the correct amount from an asphalt plant. This saves time and money in the long run.

Calculating tonnage seems complicated but is actually quite straightforward with some basic information. This article provides a step-by-step guide to calculating asphalt tonnage for your paving project.

Things You Need to Calculate Asphalt Tonnage

Before starting the tonnage calculation, you need to determine some key details about your project:

• Area to be paved (square feet or square yards)
• Thickness of the asphalt layer (inches)
• Density of compacted asphalt (pounds per cubic foot or cubic yard)

The area and thickness will determine the total volume, while the density allows you to convert from volume to weight/tonnage. Most asphalt plants specify the density of their mix designs. Common ranges are:

• Hot Mix Asphalt: 140-150 lbs/cubic ft
• Warm Mix Asphalt: 130-140 lbs/cubic ft

Step 1: Calculate Volume

The first step is determining the volume of asphalt needed, using the area to be paved and the planned asphalt thickness.

• Area: Measure and calculate the total area to be paved in square feet or square yards. Include irregular shapes.

• Thickness: Decide how thick the asphalt layer should be, in inches. Common depths are:

• Driveways: 2-3 inches
• Parking lots: 3-4 inches
• Roads: 4-6 inches

Volume formula:

[Area (sq ft) x Thickness (ft)] / 27 = Volume (cubic yards)

Or

[Area (sq yd) x Thickness (ft)] = Volume (cubic yards)

Example:

Paving a driveway that is 12 ft x 50 ft with a 3 inch (0.25 ft) layer of asphalt.

Area: 12 x 50 = 600 sq ft
Volume: (600 sq ft x 0.25 ft) / 27 = 55.6 cubic yards

Step 2: Choose Density Rate

Contact your asphalt supplier or check typical densities for the mix type you will use. For our example, let’s assume a hot mix asphalt with density = 145 lbs/cubic ft.

Step 3: Convert Volume to Tons

Now that you have the volume in cubic yards and density in pounds per cubic foot, you can calculate the weight in tons:

Volume (cubic yards) x Density (lbs/cubic ft) / 2000 = Tons required

Continuing our example:

55.6 cubic yards x 145 lbs/cubic ft = 8,062 lbs
8,062 lbs / 2000 = 4.03 tons

So, 4.03 tons of hot mix asphalt are needed for this 600 sq ft driveway paved to 3 inches thick, assuming a density of 145 lbs/cubic ft.

Step 4: Add Overage Percentage

Once you’ve calculated the estimated asphalt tons required, add 5-10% as an overage percentage. This accounts for natural settling and compaction in the paving process.

In our example, add 10%:
4.03 tons x 1.1 = 4.43 tons

Therefore, round up and order 5 tons of asphalt.

That’s it! By following these key steps – area, thickness, volume, density, overage – you can accurately determine asphalt tonnage for any paving project.

Metric Conversions

If using metric units instead of imperial, the same process applies:

• Area: Measure in square meters
• Thickness: Specified in millimeters or meters
• Volume: Cubic meters (m3)
• Density: Kilograms per cubic meter (kg/m3)

And 1 metric tonne = 1000 kg = 2204.6 lbs

Estimating Charts

Some aggregate and asphalt suppliers provide tonnage estimate tables or charts to simplify the calculation. By looking up the required depth and area, you can directly determine the asphalt tons without conversions.

However, these charts make general assumptions for density and overage – best practice is still to calculate tonnage separately whenever possible for maximum accuracy.

Factors That Affect Asphalt Density

The density or unit weight of asphalt can vary depending on:

1. Aggregate: Limestone vs granite aggregates have different densities. Specific gravity tests can determine exact aggregate density if required.
2. Compaction: Better compaction produces denser asphalt. Assumed densities account for average compaction level.
3. Mix Components: Higher percentages of stone or aggregates increase density.
4. Temperature: Hot mix asphalt is denser than warm mix when measured soon after paving. Density equalizes over time.

Because of these variables, published asphalt densities are always approximate values. The tons required formula already accounts for reasonable variance by including a 5-10% overage percentage.

Tracking Actual Quantities

During the paving process, keep a tally of actual tons delivered and used each day. Compare this to the calculated estimate:

• If actual tons exceed the estimate, the area, depth or density calculation may have been inaccurate.
• If actual tons fall far short of estimate, the paving depth may not meet specifications or compaction is not sufficient.

Tracking real quantities can help improve accuracy of estimates for future projects.

Other Paving Materials

The process of calculating tons required is similar for other paving materials like concrete, gravel, etc. The same principles apply:

1. Measure area
2. Choose depth
3. Calculate volume
4. Find density
5. Convert to tons
6. Add overage percentage

Only the standard density rates differ because each material has a different specific gravity.

Including Base Material

Most asphalt paving projects also require an aggregate base layer beneath the asphalt – commonly crushed stone or gravel.

This base depth must also be included when determining the total tons of materials needed. Calculate separate volumes and densities for the asphalt layer vs base layer.

Then add both tonnage estimates together to order the total quantity.

Waste Factor for Irregular Areas

For unusual paving shapes or areas with numerous curves and edges, a further 5-10% can be added to the tonnage estimate to account for higher waste.

Contractors may cut and discard more asphalt pieces to achieve a clean paving edge. Using this extra waste factor helps ensure you don’t run short on material due to irregular sections.

Ordering Asphalt for Future Maintenance

When paving roads, parking lots or other large surfaces, it’s smart to order 5-10% extra asphalt during the initial paving project, even on top of the overage allowance already added.

This provides spare hot mix on-site for future maintenance needs – pothole repairs, patch jobs, section replacement, etc. Without leftover hot mix, maintenance crews must request a special small batch from the plant when issues arise later. Having extra material on hand ensures you can quickly maintain the integrity of the paving.

The Complete Asphalt Order Estimate

Bringing all the steps together, here is an overview of each factor contributing to a complete asphalt order estimate for a paving contractor:

1. Square area to be paved
2. Planned asphalt depth
3. Density of the hot/warm mix used
4. Conversion of volume (area x depth) to tons
5. + 5-10% overage margin
6. + Extra for irregular shapes and waste
7. + 5-10% spare asphalt for future repairs/maintenance
8. = Final asphalt tons to purchase

Following this methodology helps guarantee you have the exact quantity needed to complete any asphalt paving project from start to finish. An accurate estimate means avoiding unexpected shortages or costly overages – saving time, money and frustration all around.

Conclusion

Estimating the exact tons of asphalt required for a paving project is an essential step to ensure successful execution. Though the process requires measuring areas, volumes, and densities, it is straightforward to determine an accurate quantity with some basic information about your site and materials.

By following the step-by-step tonnage calculation process outlined here, you can dial in the precise asphalt order amount needed for any driveway, parking lot, road, or other surface – avoiding both wasteful overages and job-halting shortages. Applying small overage allowances as a buffer is wise to account for real-world variation during paving.

In closing, remember these key takeaways when estimating asphalt tonnage:

• Measure detailed area dimensions
• Confirm thickness and density with your contractor
• Convert area x depth to volume and then to weight
• Buffer with 5-10% overages as needed
• Order spare extra hot mix for future maintenance

With an organized, methodical approach you can accurately hit the asphalt tons required for successful, cost-effective paving projects time after time. Consistently applying these volume and density calculations will ensure you purchase the precise quantities from start to finish.

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