Size matters-Importance of particle size in the design of effective nano modified emulsion(NME) stabilising agents for naturally available granular road materials

Abstract

The successful application of a Nano Modified Emulsion (NME) stabilising agent for Naturally Available Granular Materials (NAGM) for use in the load-bearing layers of a road pavement structure is mainly dependent on the mineralogy of the granular material determining the properties of the modifying agent to achieve strong chemical bonds and the particle sizes of all the different materials comprising the stabilised mix, i.e., the granular materials (grading), the modifying agent, e.g. nano-silane and the binder (bitumen emulsion or equivalent polymer). The importance of the mineralogy of granular materials for infrastructure has been covered in several publications since the 1800s. In addition to the mineralogy, the particle sizes of the NAGM, as well as that of the nano silane modifier and the binder, are crucial inputs to the design of an effective NME stabilising agent to optimise the potential of any NAGM through the use thereof. The chemical composition of the nano silane modifier is mainly a function of the available broken chemical bonds within an NAGM. The finer fractions of the NGAM determine the required particle sizes and the volume of the modifying agent and the binder to optimise the potential use of an NAGM. It follows that no single NME stabilising agent will be suitable for all available NAGMs. Each NAGM with different characteristics will require adjustments in the design of a Material Compatible (MC) NME stabilising agent (MC-NME). This paper discusses the importance of the particle sizes of all components comprising an NME-stabilised road pavement layer. The influence of the particle sizes of the material mix on the engineering properties (tensile strength and compressive strength) measured is demonstrated through the test results of materials tested in South Africa. Due to the scientific approach developed, the materials design method is universally applicable.