Performance Improvement of Cold Recycled Bitumen Emulsion Mixture with Multicomponent Filler

Abstract

In order to solve the problem of poor mixture performance of cold recycled bitumen emulsion mixtures (CRBEM) during service, the improvement effects of air voids, 15°C indirect tensile strength (ITS), and immersion ITS of CRBEM were evaluated under the synergistic action of functional admixtures such as silica fume, microbeads, and water-reducing admixture based on orthogonal testing. The optimal mixing scheme was selected by verifying the mixture performance of CRBEM with functional admixtures. The micromorphology of cold recycled bitumen emulsion mortar under the optimal mixing scheme of multicomponent filler was observed by scanning electron microscopy (SEM). The mortar morphology was analyzed and labeled. The results show that the maximum decrease of air voids of CRBEM with functional admixtures can reach 23.6%. The maximum increase of ITS and immersion ITS can reach 115% and 104%, respectively. When the stress ratio is 0.3, the fatigue life times of Groups 4 and 5 reach 49,495 and 48,772, respectively, which are 9.91 and 9.77 times higher than those of Group 1. Silica fume plays a leading role in multicomponent fillers. The synergistic effect of multiple admixtures in CRBEM is significantly better than that of single or double admixtures. The morphology of bitumen emulsion composite mortar under the optimal mixing scheme of a multicomponent filler is a three-dimensional dense skeleton structure. The multicomponent filler can effectively improve the size and length of the mortar crystal. The multicomponent filler adding method is recommended to improve the performance of CRBEM. The optimal mixing scheme of the multicomponent filler is 1.5% cement, 2.4% external water, 1.5% silica fume, 2.0% microbeads, and 0.5% water-reducing admixture.