The growth of the world population has increased the production of wastes. These are generally incinerated or deposited in outdoor landfills, which impacts the environment and affects human health. A technique that allows to reuse of wastes and diminishes adverse effects on the environment is pyrolysis. Through this technique, a material known as Biochar (BC) is produced, which has proven to have interesting physical-chemical properties for it to be used as an asphalt modifier, and simultaneously, helps to mitigate negative impacts on the environment. The foregoing article presents a bibliographical review on the use of BC as a modifier for asphalt binders and asphalt mixes. This has the purpose of becoming a starting point for future research efforts. In the reviewed literature, there was no review found on this topic. In general terms, BC increases the performance of asphalt binders in high-temperature climates, and tends to reduce its performance in low-temperature ones. Few studies have evaluated the performance of BC on asphalt mixes and the long-term properties associated with durability. Based on the reviewed literature, at the end of the article, recommendations are provided for future study topics.

A recently used material that shows environmental and technical advantages for use as an asphalt binder modifier is biochar (BC). Different biomasses can be converted into BC by pyrolysis. One agro-industrial biomass that is abundant in copious quantities is oil palm mesocarp fiber (OPMF) obtained from African palm cultivation. In the present study, the use of a BC obtained from OPMF (BC-OPMF) as a modifier of asphalt binder (AC type) to produce a hot mix asphalt (HMA) was evaluated. This type of BC has not been investigated or reported in the reference literature as a binder and/or asphalt mix modifier. Initially, AC was modified with BC in three ratios (BC/AC = 5, 10, and 15%, with respect to mass) to perform penetration, softening point, and rotational viscosity tests; rheological characterization at high and intermediate temperatures; and scanning electron microscope (SEM) visualization. Based on this experimental phase, BC/AC = 10% was chosen to manufacture the modified HMA. Resistance parameters under monotonic loading (stability—S, flow—F, S/F ratio of the Marshall test, and indirect tensile strength in dry—ITSD and wet—ITSC conditions) and cyclic loading (resilient modulus, permanent deformation, and fatigue resistance under stress-controlled conditions) were evaluated on the control HMA (AC unmodified) and the modified HMA. Additionally, the tensile strength ratio (TSR) was calculated to evaluate the resistance to moisture damage. Abrasion and raveling resistance were evaluated by performing Cantabro tests. BC-OPMF is shown to be a sustainable and promising material for modifying asphalt binders for those seeking to increase stiffness and rutting resistance in high-temperature climates, resistance to moisture damage, raveling, and fatigue without increasing the optimum asphalt binder content (OAC), changing the volumetric composition of the HMA or increasing the manufacturing and construction temperatures.

Replacing natural aggregates (NA) for blast furnace slag (BFS) is seen as a technique that is beneficial for the environment. Additionally, in high temperature climates, rigidizing the asphalt by employing gilsonites (G) could be an alternative in order to increase rutting resistance. This study substituted in volume, part of the coarse fraction of NA for BFS in a hot mix asphalt (HMA) that employed asphalt modified with G in wet process. Physical properties of BFS are presented, as well as its chemical and mineral compositions. Additionally, physical properties of asphalt modifi ed are shown. In regards to HMAs, their resistance under monotonic load (Marshall test and indirect tensile strength test), cyclic (resilient modulus, permanent deformation and fatigue) and moisture damage (tensile strength ratio – TSR) was evaluated. All HMAs were manufactured employing the same asphalt content from the control mix. An ANOVA variance analysis was conducted. Based on ANOVA, when the NA volume is substituted with BFS, Marshall stability/ /flow relation significantly drops. However, when such substitution is carried out using G-modified asphalt, resistance under monotonic load, stiffness under cyclic load, resistance to permanent deformation and moisture damage notably increase. Fatigue resistance also increases but such increase is not statistically significant.

Diverse types of waste are generated during the sawmilling process. One of them is pine wood shavings (PWSs). This waste can be transformed by pyrolysis into biochar (BC) to produce a sustainable material that can serve as an asphalt binder modifier. In this study, a BC produced with PWS as biomass (BC-PWS) was used to modify the properties of an asphalt cement (AC). This type of BC has not been investigated as a modifier of ACs and asphalt mixtures. Three BC-PWS contents were used for this purpose (BC/AC = 5, 10, and 15% by weight). Conventional characterization tests such as penetration, softening point, and rotational viscosity were performed on the unmodified and modified ACs. Rheological properties were also evaluated at high and intermediate temperatures, and observations were made with a scanning electron microscope (SEM). The modified BC/AC = 10% binder was chosen to manufacture a hot-mix asphalt (HMA). Marshall, indirect tensile strength—ITS, Cantabro, resilient modulus (RM), permanent deformation, and fatigue resistance (under stress-controlled mode) tests were performed on the HMA. The Tensile Strength Ratio (TSR) parameter was determined from ITS tests. BC-PWS is a promising material as an AC modifier from the technical-environmental point of view, which tends to enhance the evaluated properties of AC and HMA (monotonic load, rutting, fatigue, moisture damage, and raveling resistance), without resorting to increases in asphalt content or increases in mixing and compaction temperatures.

Los pavimentos muestran cambios reológicos y químicos durante su ciclo de vida, principalmente a causa del envejecimiento a largo plazo (LTA), además de este fenómeno, pueden verse afectados por la influencia de los componentes de las mezclas asfálticas, presentando fallos como grietas, ahuellamiento, huecos, baches, entre otros; debido generalmente a variables externas (radiación solar, temperatura, humedad) e internas (materiales, aglomerantes, aditivos). Este artículo de revisión sistemática busca compilar investigaciones publicadas en los últimos 5 años, que tienen como objetivo analizar múltiples condiciones de envejecimiento y determinar las variables más estudiadas por parte de los autores. El propósito del documento es ser un punto de inicio como parte del estado del arte para futuros proyectos de tipo experimental, a partir de los hallazgos que se han sintetizado. Pavements show rheological and chemical changes during their life cycle, mainly due to long-term aging (LTA), in addition to this phenomenon they can be affected by the influence of the components of the asphalt mixtures, presenting failures such as cracks, rutting, holes, potholes, among others, generally due to external (solar radiation, temperature, humidity) and internal (materials, binders, additives) variables. This systematic review article seeks to compile research published in the last 5 years that aims to analyze multiple aging conditions and determine the variables most studied by the authors. The purpose of the document is to be a starting point as part of the state of the art for future experimental projects, based on the findings that have been synthesized.