Determination of Mechanical Properties for Cement-Treated Aggregate Base

About the report:

The Virginia Department of Transportation (VDOT) currently follows pavement design procedures for all new and rehabilitated pavements based on the 1993 AASHTO Guide for Design of Pavement Structures. VDOT’s Materials Division is in the process of implementing the Mechanistic-Empirical Pavement Design Guide (MEPDG) procedure via AASHTOWare Pavement ME Design software. The MEPDG uses mechanical properties of pavement materials for pavement structural design. The mechanistic-empirical design process presents a major change in pavement design from the 1993 AASHTO design guide. It calculates pavement responses through mechanistic analysis based on inputs such as traffic, climate, and materials properties to predict the pavement damage or distress over time for both asphalt and concrete pavements. The purpose of this study was to evaluate the mechanical properties of cement-treated aggregate (CTA) and recommend values for use in AASHTOWare Pavement ME Design software.

The field construction of CTA was monitored, and samples were collected for laboratory determination of the compressive strength, modulus of elasticity, and modulus of rupture. Tests with the falling weight deflectometer were conducted to back-calculate the CTA modulus of elasticity, and field cores were collected for testing compressive strength and modulus of elasticity. CTA gained strength with increases in cement content, and the increase in strength and the strength level depended on the aggregate properties, such as the resilient modulus of unbound aggregate. All measured properties were highly variable.

VDOT would need to implement a strength-based CTA design to be able to use the required mechanical properties of CTA in the MEPDG system. The study recommends using a target design 7-day compressive strength of 600 to 800 psi. Such strength corresponds well with VDOT’s current pavement design practice in accordance with the 1993 AASHTO design guide. CTA mechanical properties were suggested based on this target strength. Most of the default values presented in the MEPDG are considered reasonable. In addition, the values recommended for use in the MEPDG are 1.5 million psi for modulus of elasticity and 200 psi for modulus of rupture.

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