Abstract

Encapsulated rejuvenators based on sunflower oil and alginate biopolymer have recently gained attention to promote self-healing in asphalt mixtures. However, the complex interaction between these millimetre-size capsules and the asphalt mortar and the potential early release of the rejuvenator from the capsules could compromise the mechanical performance of the asphalt composite. This study evaluates the effect of an optimised alginate capsule design with sunflower oil on the rheological properties of short-term aged (STA) and long-term aged (LTA) asphalt mortars. A total of 15 capsule designs were synthesised by the vibrating jet technique and based on five oil-in-water (O/W) emulsions varying their biopolymer:oil (B:O) mass ratio (1:1, 1:3, 1:5, 1:7, and 1:9) and three CaCl2 solutions (2%wt., 5%wt., and 8%wt. of deionised water). Morphological, physical, thermal, and mechanical properties of each capsule were statistically evaluated to select the optimal design. The selected capsule was incorporated to STA and LTA cylindrical asphalt mortars to evaluate their rheological properties, through the dynamic shear modulus, using the Dynamic Mechanical Analysis (DMA) test and their susceptibility to permanent deformation using a modified Multi-Stress Creep Recovery (MSCR) test. The main results showed that the capsules had sizes between 1.12 and 1.64 mm with regular spherical morphology. The optimum capsule design was that with a B:O ratio of 1:7 and 5%wt. of CaCl2, which presented a size of 1.54 mm, high encapsulation efficiency and thermal/mechanical stability. The addition of the optimised capsule design to STA and LTA mortars resulted in i) a softening effect, significatively reducing the dynamic shear modulus at lower temperatures, and ii) no significant impact on the susceptibility to permanent deformations. © 2024 Elsevier B.V.