The effects of reed fly ash modified bitumen on the volumetric and mechanical properties of open grade friction course mixtures

Abstract

Abstract The global use of open grade friction course (OGFC) asphalt pavements began in 1950, though this practice has gained further interest over time, especially for high-speed high-volume roads, due to the material’s excellent characteristics in terms of skid resistance, drainage control, and noise reduction. Unfortunately, the porous structure of this type of mixture results in other problems related to mechanical and durability properties, despite extensive studies being conducted to overcome such problems using virgin modifiers such as polymers or fibres. Recently, the concept of using recycled and by-product materials as stabilising additives for asphalt binders and mixtures has became more popular, both in order to reduce the construction costs and to increase pavement service life, as well as preserving natural resources and reducing the environmental impact of construction. This study investigates the effect of using one such by-product material, reed fly ash (RFA), as a modifier for asphalt binder and to examine the performance of the resulting OGFC asphalt mixture. The effect of RFA on the OGFC mixture performance is examined in terms of volumetric (bulk density, air voids, porosity and permeability) and mechanical (indirect tensile strength (ITS), skid resistance, and Cantabro abrasion loss (CL)) properties. The results indicate that adding RFA to asphalt binder has a positive influence on mixture performance. In terms of volumetric measures, it leads to increases in air voids, porosity, and permeability of about 17%, 37%, and 102%, respectively at 18% RFA, while the bulk density is reduced as RFA dosage increases. Simultaneously, mechanical properties are increased, with ITS and skid resistance increased by about 10% and >25%; respectively at 18% RFA. However, the resistance to abrasion was enhanced only at lower dosages of RFA (6% RFA), by about 36%. Nevertheless, the use of RFA at optimal percentages appears to offer a sustainable approach to stabilising asphalt binder for OGFC mixtures.