Field investigation of a deep recycled base course layer containing dedicated three component hydraulic and bituminous binder

Abstract

This paper provides an analysis and validation test of a recycled mix containing a three-component binder consisting of CEM I 32.5R (40 %), hydrated lime (20 %) and cement by-pass dust (40 %). A monitoring system based on fibre optic sensors was used to verify the strain state of the recycled layer and the effectiveness of the solution. The strain state simulation relied on the information from additional monitoring of environmental factors, such as temperature and moisture content in the cross-section of the recycled layer. The temperature effect was included in the numerical model based on the Fourier-Kirchhoff model. In addition, the generalized Maxwell model was employed to account for the load application time to describe the pavement layers' stiffness modulus. The strain state findings from the monitoring system were found in good agreement with the laboratory numerical simulation results. The numerical simulation used the results of the Leutner test to quantify the bond between the SMA and the FB-RCM/EB-RCM recycled layer. The analysis presented here was supplemented by nondestructive testing with the Falling Weight Deflectometer (FWD). The results confirmed the convergence between the recycled base course stiffness moduli obtained in the laboratory and the results of FWD identification. The comparative field tests of the strain state and standard properties (Sm, Va and ITSdry) validated the assumed aim of this study: obtaining a recycled layer made with a three-component road binder, which exhibited reduced stiffness and increased indirect tensile strength. Compared to the bitumen emulsion (EB-RCM), foamed bitumen in the recycled mix (FB-RCM) provided more favorable physical and mechanical properties and tensile strain reduction at the bottom of the recycled layer.