Asphalt Rice Number: A Simple Contractor’s Guide for 2025

The asphalt Rice number directly impacts every paving job you complete. 

This theoretical maximum specific gravity value determines whether your crew hits target compaction percentages and passes DOT inspections. 

For example, a typical Rice value of 2.500 multiplied by 62.4 PCF equals 156.0 PCF maximum unit weight, the baseline for all density calculations. In this post, we’ll explain the role of the asphalt Rice number for contractors and why it matters. 

What Is the Asphalt Rice Number?

The asphalt Rice number is the theoretical maximum specific gravity (Gmm) of your HMA mixture, excluding all air voids. This value can be multiplied by the density of water to obtain the theoretical maximum density (TMD) or "Rice" density, named after James Rice, who developed the test procedure. 

The Rice number serves as the reference point for compaction testing, allowing you to calculate percent air voids in your compacted mix.

Typical Rice numbers range from 2.400 to 2.700, depending on your aggregate specific gravity and asphalt binder content. Labs determine this value by weighing loose HMA samples and calculating their volume through water displacement testing.

Why Does the Rice Number Matter?

Your asphalt Rice number matters because it affects every aspect of quality control and project acceptance.

Compaction testing 

Compaction tests compare your in-place density directly to the Rice number to determine if you've achieved target percentages. 

For example, if your mix has a Rice value of 2.485 (155.1 PCF) and your nuclear gauge reads 147.8 PCF, you've achieved 95.3% compaction; a passing result for most DOT specs. Without the correct Rice number, that same 147.8 PCF reading becomes meaningless data.

Air void calculations 

Percent air voids equals 100% minus your compaction percentage; if you hit 93% Rice, you have 7% air voids. This relationship is critical because air voids directly affect pavement longevity. 

Research from the Transportation Research Board shows that each 1% increase in air voids results in about a 10% loss in pavement life; so a parking lot with 12% air voids (88% compaction) will crack and deteriorate within 5–7 years, whereas the same mix at 4% air voids (96% compaction) can last 15–20 years. 

Insurance companies and warranty providers often require proof of proper compaction percentages based on Rice values.

Spec compliance 

Quality control reports, DOT forms, and specification requirements all reference the Rice number as the standard. On a typical DOT project, you'll submit daily compaction reports showing Rice values, target percentages, and actual field results. 

Failing to meet Rice-based targets can trigger stop-work orders, material rejection, or requirements to remove and replace entire sections at your expense.

Crew performance 

When roller crews don't hit target compaction percentages, they're measured against the Rice number to determine if more passes are needed. A crew achieving only 91% of Rice (2.460) could need three extra breakdown roller passes, whereas achieving 94% might only require one finishing pass. This directly impacts your production rates and fuel costs; extra roller passes can add 15–30 minutes per lane-mile.

How do Rice values impact operations?

Rice values impact operations by determining your crew's productivity, material acceptance, and project profitability on every job. 

When Rice values are accurate and communicated properly, your crews know exactly what density targets to hit. When they're wrong or outdated, you face delays, rework, and potential material rejection.

• Production scheduling effects: Incorrect Rice values create false density failures that halt paving operations. Say, if your crew is using last week's Rice value of 2.520, but this week's mix tests at 2.485, your compaction percentages will be artificially high. 
  
  Field technicians might report 97% compaction when you're actually only achieving 94%, potentially failing spec without knowing it until cores are tested later.

• Material costs and waste: Using outdated Rice values can lead to over-rolling, which breaks down aggregate and creates tender spots that require removal and replacement. 
  
  Based on current market data showing asphalt costs of $75–125 per ton, replacing even 2% of placed material on a 10,000-ton highway project costs $15,000–25,000 in materials alone, not including equipment and labor.

• Quality control workflow: Every density test your crew performs relies on the current Rice value for accurate percentage calculations. If your QC technician uses an incorrect Rice number, you may approve material that doesn't meet specs or reject good material that passes. 
  
  This creates documentation problems during final project acceptance and can impact your prequalification status with DOT agencies.

• Daily operation decisions: Rice values help define rolling patterns, gear selection, and placement temperatures. A mix with a Rice value of 2.440 might require different compaction methods than the same aggregate blend with a Rice value of 2.510 due to differences in asphalt content or aggregate absorption. 
  
  Your roller operators need current Rice data to adjust their patterns and achieve consistent results across the mat width.

What's a passing compaction percentage?

A passing compaction percentage typically ranges from 92 to 98% of the Rice number, depending on your project specifications. 

Many DOT specs require 95% compaction as the minimum acceptable standard. For instance, with a Rice value of 2.500 (156.0 PCF), 95% compaction means achieving at least 148.2 PCF in-place density.

Where Does the Rice Number Show Up in Your Work?

The Rice number shows up throughout your project documentation whenever density testing occurs. When density tests fail, the first thing inspectors check is whether the correct rice value was used in calculations.

You'll see Rice number references in:

• Core reports: Laboratory analysis of pavement cores uses the Rice number to calculate actual compaction percentages achieved.
• Daily compaction logs: Field technicians record density readings as percentages of the current Rice value for your mix.
• Inspector feedback: QA inspectors reference Rice numbers when discussing compaction issues or approval status.
• Mix delivery tickets: Especially for DOT jobs, asphalt thickness requirements and compaction targets tie directly to asphalt Rice test results.

The asphalt compaction test process relies on having accurate Rice numbers from your current mix design. Labs should test Rice values regularly during production because asphalt binder content and aggregate properties change over time.

Regular Rice testing ensures your compaction calculations reflect the actual material being placed, not outdated lab values from initial mix approval.

What Else Affects Compaction?

The asphalt Rice number sets your baseline, but several field factors determine whether you actually hit target density. You need to understand these variables to troubleshoot compaction problems when Rice values look correct, but density tests keep failing.

Mix temperature and delivery time

Mix temperature directly affects how much time you have for compaction. For example, a mix placed at 300°F takes longer to cool to the cutoff temperature of 175°F than the same mix placed at 250°F. 

Higher initial mat temperatures require more time to cool down to cessation temperature, increasing the time available for compaction. Delays in delivery can cost you critical compaction time; every minute counts when your mix is cooling from optimal rolling temperatures.

Roller pattern and coverage

Poor roller patterns create density variations across your mat width. The fifth pass overlaps the pavement surfaces compacted during the first four passes but gives only a single pass over the middle 18 inches of the panel, resulting in weak spots. 

The correct rolling pattern gets a uniform density. Your breakdown roller should operate in echelon (side by side) to compact the full mat width while the asphalt is hottest.

Mat thickness effects

Thicker lifts retain heat longer and compact more easily than thin lifts. Minimum lift thickness should be at least 3 times the nominal maximum aggregate size to ensure the aggregate can align itself during compaction to achieve the required density.

For example, a mix containing 1/2-inch NMS stone should be placed at a compacted depth of at least 1.5 to 2 inches. If a 1/2-inch top-size mix is placed at 1 inch compacted depth, the mat may pull and tear, and the stones may be broken by the rollers. 

Asphalt thickness charts help contractors avoid these compaction problems by matching lift depth to aggregate size.

Subgrade moisture issues

Wet subgrade conditions create unstable support for your asphalt layer. If the subgrade is too wet, the material will displace and rut. 

The base temperature affects heat transfer from your mat; hotter bases slow cooling, whereas cold, wet bases pull heat away faster and reduce compaction time.

Weather and wind speed

Wind velocity greatly impacts mat cooling rates. A strong wind can cause the surface to cool so rapidly that a crust will form. 

This crust must be broken down by the rollers before the compaction process can be completed. Lower wind speeds will decrease mat heat loss by convection, which will increase the time available for compaction.

Outdated Rice test problems

Using old Rice values from different production runs causes major compaction calculation errors.

During production, the theoretical maximum specific gravity should be determined at regular intervals because it may change over time as the asphalt binder content and properties, as well as aggregate properties, vary over time. 

Remember: When field density tests fail, inspectors first verify you're using the current Rice number, not last week's value.

OneCrew Helps Contractors Stay Ahead

Tracking Rice numbers is one piece of quality control. Running a successful paving operation requires managing everything from estimates to final invoicing across multiple crews and complex projects.

That's where OneCrew comes in.

Most platforms are built for plumbers or electricians. OneCrew is designed specifically for paving contractors who handle complex asphalt and concrete projects. Here's what sets OneCrew apart:

• Estimates built for paving work: Use plan-based takeoffs and aerial mapping, then apply cost templates for fast, accurate bids that factor in your actual compaction requirements and asphalt thickness specifications.
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• Project scheduling that works: Coordinate crews and job phases in one view. Keep your roller operators and QC teams aligned without juggling spreadsheets or losing track of compaction windows.
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• Real-time job costing: Track actual margins as projects progress. Know where you're making money and where costs are running over before the job wraps up.
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• Everything in one platform: From proposals to payment collection, OneCrew replaces the patchwork of disconnected tools most paving companies rely on.

Whether you're laying residential driveways, building commercial parking lots, or managing multi-crew highway work, OneCrew gives you the visibility and control to grow your business.

Ready to make your operations run smoother? Join top paving teams across North America using OneCrew to close deals faster and run better jobs. Book your free OneCrew demo today.

FAQs

1. What does Gmm mean in the asphalt industry?

Gmm means theoretical maximum specific gravity, which is the same as the Rice number. It represents the specific gravity your HMA mixture would have if all air voids were removed. This value serves as the baseline for calculating compaction percentages and air void content.

2. Who runs the Rice test: Contractors or labs?

Labs typically run the Rice test, including asphalt producers, state DOT labs, and independent testing facilities. The test requires specialized equipment like vacuum pycnometers and mechanical agitators that most contractors don't have on-site. Labs then provide results to contractors for use in compaction calculations.

3. Can poor compaction be caused by the mix?

Yes, poor compaction can definitely be caused by the mix design or production issues. Mixes that are too rich in asphalt, have aggregate that's too rounded, or contain asphalt cement that's too soft can create “tender” mixes that shove under rollers. Temperature problems during production also affect compactibility.

4. What’s the connection between Rice number and thickness?

The connection is that the Rice number doesn't directly determine pavement thickness, but it's crucial for verifying that your specified thickness reaches the target density. Thicker lifts are easier to compact and retain heat longer, giving you more time to reach the percentage of Rice number required by specifications. Your asphalt thickness must allow adequate compaction to hit the target Rice percentages.

5. Do I need to know the Rice value as a contractor?

Yes, contractors need to know the current Rice value for accurate compaction testing and quality control. Your field density readings are meaningless without the correct Rice number to calculate percentages against. Always verify you're using the most recent Rice value from the current production run, not outdated lab results.