# Nonlinear Characteristics of Tensile and Compressive Mechanical Parameters for Typical Pavement Materials

## TL;DR

This study examines how pavement materials behave under tension and compression, finding that their mechanical properties change nonlinearly with factors like gradation and loading rate.

## Contribution

A multi-factor model is developed to quantify the nonlinear mechanical behavior of pavement materials under tension and compression.

## Key findings

- Tensile and compressive stress–strain behavior of CSM and AM showed bilinear characteristics consistent with bi-modulus theory.
- Mechanical parameters like strength and modulus increased with loading rate, stabilizing beyond 0.1 MPa/s.
- Gradation type had the most significant impact on mechanical parameters, especially the elastic modulus.

## Abstract

The reliability of the mechanical property values adopted for current pavement structural design remains low. Therefore, this study investigated the nonlinear characteristics for the tensile and compressive properties of cement-stabilized macadam (CSM) and an asphalt mixture (AM) under different gradation types and loading rates. And a multi-factor value model was developed for both. The results show that the tensile and compressive stress–strain behavior of both CSM and AM exhibited bilinear characteristics consistent with the bi-modulus theory (elasticity with different moduli in tension and compression). The strength, elastic modulus, and Poisson’s ratio followed a power function relationship with increasing loading rates, stabilizing at values beyond 0.1 MPa/s. The skeleton-dense gradation demonstrates the most favorable mechanical performance. For semi-open-graded AM with a void ratio of 8~16%, the mechanical parameters exhibit relatively high rates of change. Among the influencing factors, gradation type had the most significant impact on the mechanical parameters, especially on the elastic modulus. In general, tensile mechanical parameters were more sensitive to changes than compressive ones. Rc/Rt was most strongly affected by gradation type. Accordingly, a quantitative value model was established to describe the variation in tensile and compressive mechanical parameters of typical asphalt pavement materials, which vary with air void ratio, loading rate, binder content, and temperature. The findings provide a reference for the prediction of pavement structure design parameters considering the difference in compression and tension.