Investigation of the mechanical and physical properties of bio-modified cold asphalt emulsion mixtures by microbial carbonate precipitation

Abstract

The effects of Microbial Carbonate Precipitation -MCP- on physical and mechanical properties of Cold<br>Asphalt Emulsion Mixtures -CAEMs- have been investigated. MCP method was performed on CAEMs by<br>two scenarios: -I- Bio-deposition treatment of aggregates and, -II- using a medium culture containing<br>bacteria and urea-CaCl2nutrient solution as a replacement for optimum water content. Additionally, in<br>the second scenario, the effect of different curing durations -7, 14, 28 and 56 days- on the mixtures’<br>properties has been examined. X-Ray Diffraction, Fourier-Transform Infrared Spectroscopy, Atomic<br>Force Microscopy and FE-SEM technique tests were employed to evaluate the formation of CaCO3<br>precipitation, micro-roughness of aggregates’ surface and the structure of bio-modified CAEMs. The<br>physical properties, and mechanical properties including ultrasonic pulse velocity, dynamic modulus,<br>indirect tensile strength, fracture energy and resistance to crack propagation -semi-circular bending<br>test- were measured. Results indicated the formation of CaCO3 precipitations and increase of<br>roughness on the surface of treated aggregates. Significant improvements -p-value &lt; 0.05- were<br>observed in the mechanical properties of CAEMs of first and second scenarios, however, these<br>improvements are higher in the CAEMs of first scenario -p-value &lt; 0.05-. Findings revealed that MCP<br>method can significantly improve the mechanical properties of CAEMs. But, it doesn’t significantly<br>affect their physical properties.