Mix Design: Power 45 Curve

The document provides an overview of Power 45 gradation analysis, maximum density line determination, differences between lab and plant production, gradation limits, and the use of Tx2MixSolver for mix design optimization.

Power 45 Basics and Gradation Analysis

• The Power 45 method uses cumulative percentage passing and sieve size raised to the 0.45 power for straight-line density plotting.
• Gradation limits are defined by Superpave specifications, including upper and lower master limits and reference zones.
• Proper gradation ensures optimal mixture density and prevents over-sanding or excessive fines.

Maximum Density Line Explanation

• The maximum density line is a straight line from the maximum aggregate size to the origin.
• It helps in designing gradations that achieve maximum density with less VMA.
• Closer gradations to this line tend to have less VMA and may require less asphalt content.

Lab Design Versus Plant Production

• Gradations can fining up during production, affecting asphalt content and mixture properties.
• Laboratory and plant gradations may differ due to aggregate breakdown and process variations.
• Adjustments are necessary to maintain target specifications during production.

Gradation Limits and Specification Zones

• Superpave gradation limits include restricted zones, max density lines, and control points.
• These limits help control mixture quality and prevent undesirable gradation shifts.
• Different gradation standards (Item 344, SS3077) specify specific sieve limits.

Tx2MixSolver Tool for Mix Design

• The Tx2MixSolver is an Excel-based macro tool for optimizing gradations.
• Users input stockpile gradations, and the solver suggests modifications to meet specifications.
• The tool does not optimize lime recycle or SAC but calculates total SAC A.
• The process involves inputting data, running the solver, and reviewing proposed gradations.