Current Research and Challenges in Bitumen Emulsion Manufacturing and Its Properties

Abstract

The global increase of road infrastructure and its impact on the environment requires serious attention to develop sustainable and environmentally friendly road materials. One group of those materials is produced by using bitumen emulsion. However, there are still scientific and technical obstacles standing against its regular application. The bitumen emulsion formulation process and compositional optimization are subjected to a high number of degrees of freedom. Consequently, obtaining the desired product is mostly based on a series of random and tedious trials because of the enormous number of tests that are carried out to meet the required properties, such as emulsion stability, viscosity, droplet size (and distribution), and bitumen emulsion chemistry. Several pre-established formulation procedures have been presented in the literature. Some of them have technical limitations to be utilized for practical industrial application, whereas others are still not understood enough to be applied in bitumen emulsion formulation. Therefore, discussing some important issues in this field could be useful to offer a practical guide for bitumen emulsion manufacturers when trying to formulate a well-defined bitumen emulsion to best fit its use in pavement infrastructure rather than to simply to meet standard specifications. This review paper aims to enable the ultimate potential of bitumen emulsion by further reviewing the research progress of bitumen emulsion manufacturing and discussing the literature available up to now on this topic, in the realm of bitumen emulsion manufacturing and emulsion chemistry.

Keywords: bitumen emulsion; emulsification temperature; formulation.

Figure 13

Conceptual chart of the Krafft point and CMC adapted from [131].

Figure 1

The systematic framework of discussion in this review.

Figure 2

Example of a cationic soap production adapted from [5].

Figure 3

Example of an anionic soap production adapted from [5].

Figure 4

Bitumen emulsion flocculation, coalescence, and sedimentation adapted from [5].

Figure 5

Schema of bitumen emulsion droplet changes adapted from [4].

Figure 6

Surfactant adsorption by ionic change: (A) anionic; (B) cationic adapted from [4].

Figure 7

The interrelationship between manufacturing variables and properties for bitumen emulsion adapted from [103].

Figure 8

Colloid mill cross section adapted from [110].

Figure 9

Schematic of a bitumen emulsion plant adapted from [4].

Figure 10

Schematic of bitumen emulsion manufacturing using the HIPR technique [113].

Figure 11

Unimodal and bimodal bitumen emulsion particle size distribution adapted from [117].

Figure 12

Schematics of micelle formation at concentrations above the CMC and bitumen droplet dispersion by micelle in the aqueous phase.

Figure 14

HLD as a balancing of system conditions [182].

Figure 15

Inputs and outputs of HLD equation.

Figure 16

Determining $\mathrm{K}$ constants as the slope [172].

Figure 17

Classical formulation-composition diagram (HLD-WOR) showing the inversion line and emulsion types and the basic properties (stability, drop size, and viscosity) adapted from [195].