PAVEMENT DESIGN GUIDELINES FOR CHEMICALLY STABILIZED SUBGRADES

Abstract: Pavement subgrade improvement measures are designed to achieve target performance indicators during the construction phase and throughout the service life. Measures designed for the construction phase are defined as short-term modification techniques that provide sufficient strength of the subsurface layer that allows it to function as a construction platform for heavy equipment (e.g. limiting the deflection under wheel load). Measures designed to act throughout the service life are defined as long-term stabilization techniques that provide adequate strength, uniformity, and durability of the subsurface layer that allows it to function as a foundation without causing excessive maintenance (e.g. reducing susceptibility to frost and high-water table actions, and by adding a stronger, durable and additional structural layer immediately over the in-situ soil.)

Although subgrade stabilization is widely used in many highway agencies, its benefits for pavement design are not considered by most of highway agencies. This paper examines the current state of practice of the inclusion of properties of chemically stabilized subgrade layers in pavement design procedures. The analysis will be conducted using current versions of AASHTO 1993 and Pavement ME methods. In the AASHTO 1993 guide, a layer coefficient for the stabilized layer will be considered. In the Pavement ME method, a sensitivity analysis of geotechnical parameters such as resilient modulus (MR), Liquid Limit (LL), Plasticity Index (PI), hydraulic conductivity (k), and percentage passing #200 sieve (P200) will be performed. This analysis will provide practical recommendations for the use of chemically stabilized layer properties in pavement design.