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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.

Open-graded friction course (OGFC) asphalt mixture, usually used to construct porous pavements, represents one of the materials supporting low-impact development (LID) philosophy due to its use of coarse aggregate gradation. Using such mixtures brings several benefits related to safety, environment and economy. Alas, coarse, open-graded skeleton of OGFC mixtures is prone to failure, particularly raveling and stripping. Continuous traffic loading and the environmental impacts give hand in hand to further increase the potential for failure, hence higher pavement maintenance and rehabilitation costs. Application of different types of modifiers has proved effective in mitigating failure potential. The most common modifiers are polymers, fibers and anti-stripping agents. Aiming at minimizing the costs and maximizing the lifespan while considering sustainability, the study was to investigate the effect of using a recycled stabilizing material as an asphalt modifier on the performance of OGFC asphalt mixtures. Recycled Low-Density Polyethylene (R-LDP) was adopted in this investigation. Changes in mixture air void, porosity, draindown, permeability, rut depth, moisture damage and abrasion loss were observed to evaluate the effect. Compared with unmodified asphalt samples, R-LDP modification increased mixture air void, porosity and permeability by 15%, 10% and at least 40%, respectively. Also, it noticeably contributed to reducing rut depth, moisture damage and abrasion loss (both unaged and aged) by 31%, 20% and at least 40%, respectively. More significantly, it almost eliminated the draindown problem. Incorporating R-LDP proved effective in upgrading OGFC mixture properties to an acceptable level required by most specifications.

The main concept of using waste and recycled materials as modifiers for construction materials, is to improve their performance, keep the resources, and conserve the environment from pollution problems. This investigation is tended to evaluate the effect of using two different types of modifiers on the physical properties of asphalt binder. The modifiers are Recycled-Low-Density-Polyethylene (R-LDPE) polymer and waste-Paper Fiber (w-PF), they were mixed individually and collectively with neat asphalt binder. The first set of modified binders comprised neat binder with 3% R-LDPE alone, the second is comprised 0.3%, 0.5% and 0.7% of w-PF alone, while the third comprised collective modifiers of 3% R-LDPE and 0.3%, 0.5% and 0.7% w-PF. The influence of these modifiers on neat asphalt binder was evaluated in terms of penetration (Pen.), softening point (SP), penetration index (PI), ductility, rotational viscosity (RV), penetration aging index (PAI) and softening point index (SPI). The obtained results indicate that the utilization of modifiers helps in improving the physical properties of asphalt binders by different levels. the modification by collective modifiers leads to an increase SP, RV, PI, PAI, and SPI to 65%, 2 times, 1.044, 0.93, 2.5 respectively compared to neat bitumen. As well, leads to a decrease in both Pen. and ductility to the levels 45% and 79% respectively. This indicates that the use of waste and recycled modifiers especially in the combined form encourage the production of comparative modified asphalt binder.

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