BIOCHAR-MODIFIED BITUMEN

FIELD

The present disclosure relates generally to a method of producing a biochar-modified bitumen.

BACKGROUND

Bitumen is a colloidal mixture of different hydrocarbons characterized by the presence of several substance classes each having a different range of molecular weights, including saturates, aromatics, resins, and asphaltenes. Due to the different distillation processes of oils used to produce bitumen, the resulting bitumen may have a wide range of properties and characteristics. Bitumen is widely used in different applications, such as road paving and for roofing.

However, bitumen can be costly, inelastic, and is subject to oxidation and ageing during short-term heating in the hot mixing cycle and during long-term exposure to in-service environmental conditions. Attempts have been made to use various additives and fillers to improve the rheological properties of bitumen. What is needed are new methods to prevent the oxidation and ageing of bitumen and methods for improving its rheological properties.

The compositions and methods disclosed herein address these and other needs.

SUMMARY

As disclosed herein, the inventors have developed novel methods for producing biochar- modified bitumen. By treating the biochar with an oxidizing agent or oxidizing treatment, the biochar is modified in a manner that allows covalent attachment to bitumen. The resulting biochar-modified bitumen has improved rheological properties and improves the stiffness and ageing of the bitumen, and provides improved resistance to rutting.

In some aspects, disclosed herein is a method for producing a modified bitumen, comprising: treating a biochar with an oxidizing agent or oxidizing treatment to produce a chemically -treated biochar; mixing the chemically -treated biochar with bitumen; and allowing the chemically-treated biochar to become covalently linked to the bitumen to produce the modified bitumen.

In some embodiments, the biochar is treated with an oxidizing agent and the oxidizing agent includes a peroxide solution. In some embodiments, the peroxide solution is hydrogen peroxide. In some embodiments, the hydrogen peroxide is present in an amount of 0.03 to 0.06 millimoles per gram of bitumen. In additional embodiments, the method further comprises adding an FeS04 catalyst to the oxidizing agent or oxidizing treatment. In some embodiments, the FeS04 catalyst is in a 1 : 1 molar ratio with the peroxide solution.

In some embodiments, the biochar is treated with the peroxide solution from 65 °C to 85 °C. In some embodiments, the biochar is treated with the peroxide solution and the FeS04 catalyst from 65 °C to 85 °C.

In other embodiments, the biochar is treated with the peroxide solution from 20 minutes to 30 minutes. In some embodiments, the biochar is treated with an oxidizing treatment and the oxidizing treatment is selected from ozone, corona discharge, air plasma treatment, or combinations thereof. In some embodiments, the biochar is covalently linked to the bitumen through a carboxylic linker.

In some embodiments, the method further comprises adding bentonite to the modified bitumen. In some embodiments, the bentonite is present in amount greater than zero wt% to 25 wt%. In some embodiments, the bentonite is present in amount of 1 wt% to 5 wt%.

In further embodiments, the chemically -treated biochar is mixed with bitumen from 165

°C to 185 °C. In some embodiments, the chemically -treated biochar is mixed with bitumen from 170 °C to 180 °C.

In some embodiments, the chemically -treated biochar is mixed with bitumen from 2 hours to 5 hours. In some embodiments, the chemically -treated biochar is mixed with bitumen from 3 hours to 4 hours. In some embodiments, the biochar is produced by pyrolysis of wood or timber. In some embodiments, the biochar is produced by pyrolysis of hard wood chips. In some embodiments, the biochar is present in an amount of 10 - 20 wt% based on the weight of the modified bitumen.

In some embodiments, the modified bitumen has a viscosity from 200 Pa*s to 700 Pa*s at 60 °C. In some embodiments, the modified bitumen has a viscosity from 300 Pa*s to 600

Pa*s at 60 °C. In some embodiments, the modified bitumen has a viscosity from 400 Pa*s to 500 Pa*s at 60 °C.

In some embodiments, disclosed herein is a modified bitumen composition prepared according to methods herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the infrared spectrum of untreated biochar.

FIG. 2 shows the infrared spectrum of biochar treated with hydrogen peroxide.

FIG. 3 shows the infrared spectrum of biochar treated with polyphosphoric acid. FIG. 4 shows the infrared spectra of untreated biochar, biochar treated with hydrogen peroxide, and biochar treated with polyphosphoric acid, aligned in one graph for comparison.

FIG. 5 shows the biochar-modified bitumen (BMB) sample (with untreated biochar) after 48 hours at 180°C.

FIG. 6 shows the biochar-modified bitumen (BMB) sample (with treated biochar) after

48 hours at 180°C.

DETAILED DESCRIPTION

The inventors have developed novel methods for producing biochar-modified bitumen. By treating the biochar with an oxidizing agent or oxidizing treatment, the biochar is modified in a manner that allows covalent attachment to bitumen. The resulting biochar-modified bitumen has improved rheological properties and improves the stiffness and ageing of the bitumen, and provides improved resistance to rutting.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. The term "comprising" and variations thereof as used herein is used synonymously with the term "including" and variations thereof and are open, non-limiting terms. Although the terms "comprising" and "including" have been used herein to describe various embodiments, the terms "consisting essentially of and "consisting of can be used in place of "comprising" and "including" to provide for more specific embodiments and are also disclosed. As used in this disclosure and in the appended claims, the singular forms "a", "an", "the", include plural referents unless the context clearly dictates otherwise.

Methods for Producing Biochar-Modified Bitumen

In some aspects, disclosed herein is a method for producing a modified bitumen, comprising:

treating a biochar with an oxidizing agent or oxidizing treatment to produce a chemically-treated biochar;

mixing the chemically -treated biochar with bitumen; and

allowing the chemically -treated biochar to become covalently linked to the bitumen to produce the modified bitumen.

As used herein, the term "biochar" refers to charcoal created by pyrolysis of biomass. The term "pyrolyzing a biomass" as used herein refers to obtaining gaseous or vaporous products by heating a biomass. The yield of products from pyrolysis varies heavily with temperature. The lower the temperature, the more char is created per unit biomass. High temperature pyrolysis is also known as gasification, and produces primarily syngas from the biomass. The two main methods of pyrolysis are "fast" pyrolysis and "slow" pyrolysis. Fast pyrolysis yields about 60% bio-oil, about 20% biochar, and about 20% syngas, and can be done quickly (for example, in seconds). Slow pyrolysis can be optimized to produce substantially more char (about 50%), but can take much longer (for example, hours) to complete.

The term "biomass" as used herein refers to biological material derived from living, or recently living organisms, such as wood, waste, and alcohol fuels. Biomass is commonly plant matter grown to generate electricity or produce heat. For example, forest residues (such as dead trees, branches and tree stumps), yard clippings and wood chips may be used as biomass.

However, biomass also includes plant or animal matter used for production of fibers or chemicals. Biomass may also include biodegradable wastes that can be burnt as fuel. Industrial biomass can be grown from numerous types of plant, including miscanthus, switchgrass, hemp, com, poplar, willow, sorghum, sugarcane, and a variety of tree species, ranging from eucalyptus to oil palm (palm oil). The particular plant used is usually not important to the end products, but it does affect the processing of the raw material.

Biochar is produced from the pyrolysis of a biomass at high temperatures in the absence of oxygen. The high carbon content of the biochar has a twofold impact on the properties of bitumen. First, it acts as an antioxidant thus retarding the ageing properties of bitumen and secondly it stiffens the bitumen by increasing its rheological (flow) properties.

In some embodiments, the methods disclosed herein provide carboxylic sites on the biochar surface that can then be attached to bitumen. In some embodiments, the carboxylic sites are obtained by treating the biochar with a peroxide solution. In some embodiments, the peroxide solution is hydrogen peroxide. The hydrogen peroxide creates carbonium ions on the surface of biochar particles, then converts these ions to carboxylic sites. The newly created carboxylic sites on the biochar can then interact with functional groups from bitumen to produce a biochar- modified bitumen. The biochar-modified bitumen (BMB) then comprises the desired rheological properties.

The term "bitumen" as used in this application is meant to refer not only to the product from oil by direct distillation or from distillation of oil at reduced pressures, but also to the product coming from the extraction of tar and bituminous sands, the product of oxidation and/or fluxation of such bituminous materials, as well as to blown or semi-blown bitumens, and synthetic bitumens. Hence, the terms tar, resin and pitch, as well as other bituminous substances, are regarded as falling within the term "bitumen" as used herein.

Bitumen is the heaviest portion from the oil distillation process and, as such, the residue left over from petroleum distillation. Due to the different origins and distillation processes of such oils, the resulting bitumen may have a wide range of properties and characteristics.

Typically, bitumen is characterized by the presence of four substance classes each having a different range of molecular weights: saturates, aromatics, resins, and asphaltenes.

Bitumen is widely used in different applications, such as aggregate blends for road paving, fiber reinforced membranes for roofing and bitumen-water emulsions in surface treating both for paving and roofing. In such mixtures, the bitumen acts as a binder material which is mixed with aggregates that can be of different size, shape and chemical nature.

Bitumen comprises different hydrocarbons and contains varying amounts of paraffinic, naphthenic, and aromatic hydrocarbons. Bitumen also has properties which make it useful in a number of applications including its use as a component in road surfaces, its use as a sealing compound, its use as a coating material, its use in the preparation of tar paper and the like. It can also be used to protect building structures, and as a caulking or waterproofing material or the like, to protect against ground water. These mixtures are particularly used for construction or maintenance of sidewalks, roads, highways, parking lots or airport runways and service roads and any other rolling surfaces.

Bitumen generally has little or no elasticity. Because of its inherent properties, coatings or pavement layers comprised of bitumen are brittle at low temperatures and soft at higher temperatures.

The biochar-modified bitumen disclosed herein can be used to substitute for bitumen. In some embodiments, the biochar can comprise from 1 to 50% of the biochar-modified bitumen composition. In some embodiments, the biochar can comprise from 5 to 40% of the biochar- modified bitumen composition. In some embodiments, the biochar can comprise from 10 to 30% of the biochar-modified bitumen composition. In some embodiments, the biochar can comprise from 20 to 30% of the biochar-modified bitumen composition. In some embodiments, the biochar can comprise at least 1% of the biochar-modified bitumen composition (for example, at least 1%, at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 45%). In some embodiments, the biochar can comprise 5% of the biochar-modified bitumen composition. In some embodiments, the biochar can comprise 15% of the biochar- modified bitumen composition. In some embodiments, the biochar can comprise 25% of the biochar-modified bitumen composition.

In some embodiments, the method further comprises adding a nanoclay to the modified bitumen. Nanoclay s are nanoparticles of layered mineral silicates. An example of a nanoclay includes bentonite. In some embodiments, the method further comprises adding bentonite to the modified bitumen. In some embodiments, the bentonite is present in amount greater than zero wt% to 25 wt%. In some embodiments, the bentonite is present in amount of 1 wt% to 5 wt%. In some embodiments, the bentonite is present in amount greater than 1 wt% (for example, greater than 1 wt%, greater than 2 wt%, greater than 3 wt%, greater than 4 wt%, greater than 5 wt%, greater than 10 wt%, greater than 15 wt%, greater than 20 wt%).

In some embodiments, the chemically -treated biochar is mixed with bitumen from 165 °C to 185 °C. In some embodiments, the chemically -treated biochar is mixed with bitumen from 170 °C to 180 °C. In some embodiments, the chemically -treated biochar is mixed with bitumen at a temperature greater than 150 °C (for example, greater than 150 °C, greater than 155 °C, greater than 160 °C, greater than 165 °C, greater than 170 °C, greater than 175 °C, greater than 180 °C).

In some embodiments, the chemically -treated biochar is mixed with bitumen from 2 hours to 5 hours. In some embodiments, the chemically -treated biochar is mixed with bitumen from 3 hours to 4 hours. In some embodiments, the chemically -treated biochar is mixed with bitumen for at least 1 hour (for example, at least 1 hour, at least 1.5 hours, at least 2 hours, at least 2.5 hours, at least 3 hours, at least 3.5 hours, at least 4 hours, at least 4.5 hours, at least 5 hours).

In some embodiments, the biochar is produced by pyrolysis of hard wood chips.

In some embodiments, the biochar is present in an amount of 10 - 20 wt% based on the weight of the modified bitumen. In some embodiments, the biochar is present in an amount of 5 - 25 wt% based on the weight of the modified bitumen. In some embodiments, the biochar is present in an amount of at least 5 wt% (for example, at least 5 wt%, at least 10 wt%, at least 15 wt%, at least 20 wt%, at least 25 wt%) based on the weight of the modified bitumen.

In some embodiments, the modified bitumen has a viscosity from 200 Pa*s to 700 Pa*s at 60 °C. In some embodiments, the modified bitumen has a viscosity from 300 Pa*s to 600 Pa*s at 60 °C. In some embodiments, the modified bitumen has a viscosity from 400 Pa*s to 500 Pa*s at 60 °C. In some embodiments, the modified bitumen has a viscosity of at least 200 Pa*s (for example, at least 200 Pa*s, at least 250 Pa*s, at least 300 Pa*s, at least 350 Pa*s, at least 400 Pa*s, at least 450 Pa*s, at least 500 Pa*s, at least 550 Pa*s, at least 600 Pa*s, at least 650 Pa*s) at 60 °C.

In some embodiments, disclosed herein is a modified bitumen composition prepared according to methods herein.

The bitumen compositions disclosed herein can be used for many applications, including paving and roofing. When such bitumen composition for paving is applied on a surface, the paving results with improved properties as mentioned herein. Improved properties include better ageing, increased stiffness, and/or improved resistance to rutting. The compositions and method, however, are not limited to use in paving roads and in roofing applications, but can be used anywhere oxidation prevention is needed. Oxidizing Agents and Oxidizing Treatments

In the methods disclosed herein, the biochar is treated with an oxidizing agent or oxidizing treatment, thus allowing for covalent linkage to bitumen to form a biochar-modified bitumen. In some embodiments, the oxidizing agent or oxidizing treatment is selected from a peroxide solution, ozone treatment, corona discharge, air plasma treatment, or combinations thereof.

Peroxide Solutions

In some embodiments, the biochar is treated with an oxidizing agent and the oxidizing agent includes a peroxide solution. In some embodiments, the peroxide solution is hydrogen peroxide. In some embodiments, the hydrogen peroxide is present in an amount of 0.03 to 0.06 millimoles per gram of bitumen.

The term "peroxide" as used herein refers to any compound containing a bivalent O— O group, i.e., the oxygen atoms are univalent. The peroxy O— O group can be found in both inorganic and organic compounds. Examples of peroxides suitable for use with the presently disclosed subject matter can include (but are not limited to) hydrogen peroxide (H2O2, the simplest and most stable peroxide), sodium peroxide (Na2C ), lithium peroxide (L12O2), calcium peroxide (CaC ), and percarbamide (i.e., urea peroxide). Per-acids are also included as peroxides. Examples of per-acids can include (but are not limited to) peracetic acid, performic acid, and persulfuric acid.

In some embodiments, the method further comprises adding an FeS04 catalyst to the oxidizing agent or oxidizing treatment. In some embodiments, the FeS04 catalyst is in a 1 : 1 molar ratio with the peroxide solution. In some embodiments, the FeS04 catalyst is present between a 1 :2 and a 2: 1 molar ratio with the peroxide solution.

In some embodiments, the biochar is treated with the peroxide solution from 65 °C to 85

°C. In some embodiments, the biochar is treated with the peroxide solution at a temperature greater than 65 °C (for example, greater than 65 °C, greater than 70 °C, greater than 75 °C, greater than 80 °C).

In some embodiments, the biochar is treated with the peroxide solution and the FeS04 catalyst from 65 °C to 85 °C. In some embodiments, the biochar is treated with the peroxide solution and the FeS04 catalyst at a temperature greater than 65 °C (for example, greater than 65 °C, greater than 70 °C, greater than 75 °C, greater than 80 °C).

In some embodiments, the biochar is treated with the peroxide solution from 20 minutes to 30 minutes. In some embodiments, the biochar is treated with the peroxide solution for at least 10 minutes (for example, at least 10 minutes, at least 15 minutes, at least 20 minutes, at least 25 minutes).

In some embodiments, the biochar is treated with an oxidizing treatment and the oxidizing treatment is selected from ozone, corona discharge, air plasma treatment, or combinations thereof. In some embodiments, the biochar is covalently linked to the bitumen through a carboxylic linker.

Additional Oxidizing Agents

In some embodiments, the biochar is treated with an oxidizing agent and the oxidizing agent includes polyphosphoric acid (PPA).

Ozone Treatment

In some embodiments, the biochar is treated with an oxidizing treatment and the oxidizing treatment comprises ozone treatment.

The term "ozone" as used herein refers not only to ozone in the form of gaseous O3, but also ozone combined with other gases required for generating ozone, such as oxygen, nitrogen or carbon dioxide; ozone as dissolved in a strong inorganic acid such as sulfuric acid; as well as the highly oxidative radicals formed by reaction of ozone with the inorganic acid.

In some embodiments, the biochar is treated with ozone. In some embodiments, the biochar is treated with ozone in combination with a peroxide or other chemical oxidant.

Ozone is highly reactive and with a very fine and porous material can modify the surface surprisingly quickly. Advantages can include faster processing through a simple mixing or flow through process, no addition of moisture and no need for the cost and time for drying (as dry mat is critical for bitumen), and a more complete surface modification as the gas penetrates porosity more readily.

Description of methods of using ozone for oxidation (for example, ozonation of fly ash carbon) are further described in US6521037 and US6890507, each of which are incorporated by reference herein.

Corona Discharge

In some embodiments, the biochar is treated with an oxidizing treatment and the oxidizing treatment comprises corona discharge treatment.

The term "corona discharge" as used herein is intended to cover a range of discharge phenomena including a streamer type of irregular pulse discharge, a steadier glow type discharge, and a breakdown discharge or spark discharge which may be a complete slot discharge.

Employing corona discharge generators can require dry air or dry oxygen, which can add an additional expense when using this method. Corona discharge techniques are widely used in industry on account of their effectiveness (Martinez-Garcia, A., Sanchez-Reche, A., Gisbert- Soler, S., Cepeda- Jimenez, C. M., Torregrosa-Macia, R, Martin-Martinez, J. M. (2003) Treatment of EVA with corona discharge to improve its adhesion to polychloroprene adhesive, Journal of Adhesion Science and Technology, 17 (1): 47; Strobel, M., Lyons, C. S. (2003).

Corona discharge is further discussed in the following: Martinez-Garcia, A., Sanchez- Reche, A., Gisbert-Soler, S., Cepeda- Jimenez, CM., Torregrosa-Macia, R., Martin-Martinez, J.M. (2003). Treatment of EVA with corona discharge to improve its adhesion to

polychloroprene adhesive, Journal of Adhesion Science and Technology, 17 (1): 47; and US20170036983, each of which are incorporated by reference herein. Air Plasma Treatment

In some embodiments, the biochar is treated with an oxidizing treatment and the oxidizing treatment comprises air plasma treatment.

"Air plasma treatment" as used herein refers to a stream of air charged with a large amount of energy. Air plasma behaves like a gas and it emits light and contains free ions and electrons. In addition, the molecules and ions are highly energized. In some embodiments, the stream is a homogeneous, zero voltage, flame like plasma beam. When air plasma is directed at the surface of an object at high speed the plasma reacts with the surface to clean it and to activate the surface. In some embodiments, the surface is activated by breaking polymer chains and creating polar groups and active radicals. The oxygen in the energized plasma also reacts with contaminants, such as hydrocarbons on the surface of substrates. An example device for applying the air plasma is a Flume Plasma System available from Plasmatreat® North America Inc., Mississauga, Ontario, Canada. The Flume Plasma System is applied in an open-air environment under atmospheric conditions including atmospheric pressure. The plasma is generated by a controlled electrical discharge inside a jet. Air flow of standard air through the jet projects the plasma outside of the jet onto a substrate surface. In some embodiment, the air feed is oil and water free compressed air.

In some embodiments, the hydrogen peroxide is used in combination with air plasma treatment. See Johansson, B.L., Larsson, A., Ocklind, A., Ohrlund, A. (2002). Characterization of air plasma-treated polymer surfaces by ESCA and contact angle measurements for optimization of surface stability and cell growth, Journal of Applied Polymer Science, 86 (10): 2618.

Air plasma treatment for plasma oxidation of biochar is further described, for example, in US8398738 and US8709122, each of which are incorporated by reference herein.

EXAMPLES

The following examples are set forth below to illustrate the compositions, methods, and results according to the disclosed subject matter. These examples are not intended to be inclusive of all aspects of the subject matter disclosed herein, but rather to illustrate representative methods and results. These examples are not intended to exclude equivalents and variations of the present invention which are apparent to one skilled in the art.

Example 1. Methods for production of biochar-modified bitumen

Biochar produced by pyrolysis of hard wood chips from Boral Timber is chemically treated by mixing with hydrogen peroxide at a temperature of about 65-85°C while stirring for about 20 to 30 minutes to produce a freely flowing powder. The freely flowing powder is then sprinkled on the surface of softer bitumen (Class 170 - the viscosity at 60°C is around 170 Pa*s) at a temperature of about 180°C under continuous stirring for about 3-4 hours while maintaining the temperature. For C I 70 base bitumen supplied by Puma, the amount of hydrogen peroxide was 6% per gram of bitumen. The amount was experimentally determined to produce the best results. The amount of additive is a function of the polar compounds and the functional groups in bitumen.

The properties of the biochar were examined after treatment with peroxide or with polyphosphoric acid. Figure 1 shows the infrared spectrum of the untreated biochar. As shown in Figure 2, treatment of the biochar with peroxide yields the oxygenate groups on the biochar. As shown in Figure 3, treatment of the biochar with polyphosphoric acid (PPA) yields the oxygenate groups on the biochar. Figures 1, 2, and 3 are aligned in one graph for ease of comparison (Figure 4). Fourier transform infrared spectrometer (Brukner) in the range of 4000- 400 crrT ¹ was used for characterization of functional groups on the surface of all samples (untreated or chemically treated biochar). The samples were prepared as pellets using KBr. The peak seen at around 2900 c f ¹ corresponds to C-H groups. The weak peak on chemically treated biochar (PPA or peroxide treated) at around 1744 crrT ¹ indicates the formation of carbonyl containing groups. The peak at 1400 crrT ¹ can be attributed to oxygen containing functional groups for example C=0 and C-0 of carboxylic groups or in-plane vibration of O-H of carboxylic group. According to AS 2008, the classification of Australia base bitumen is based on the following properties before and after ageing:

A. Before ageing

- Viscosity at 60°C - measured using the capillary tubes as AS 2341.12 (based on this value the bitumen is named class CI 70, C240, C320, AR 450 and C600);

- Viscosity at 135°C - measured by Brookfield viscometer;

- Penetration at 25°C;

B. After ageing, using Roll Thin Film Oven (RTFO):

- Viscosity at 60°C

- Viscosity of RTFO residue as % of original;

- Penetration at 25°C.

Also presented herein is the softening point and G*/sin5, the complex shear modulus elastic portion. These two properties are not in the Australian specification. G*/sin5 is measured before and after ageing at 60°C (See Tables 2 and 3). The measurement at 60°C is correlated to the rut depth of asphalt tested in the lab.

The properties of bitumen change rapidly during mixing in the asphalt plant and during compaction. The binder characteristics also change during pavement lifetime due to oxidation. Roll thin film oven test (or RTFO) stimulates aging after asphalt production and paving. The RTFO procedure takes imaged bitumen samples in cylindrical glass bottles and places these bottles in a rotating carriage within an oven. The carriage rotates within the oven for 85 minutes at the 163°C to mimic the binder aging that occurs in the hot mix plant. After RTFO aging is completed, the rheology properties of aged bitumen at 60°C is measured by capillary tubes (viscosities at 60°C) and Dynamic Shear Rheometer (the complex modulus G* and phase angle d). The viscosity of aged bitumen at 60°C is reported as the percent of original viscosity at 60°C after RTFO. The Roll Thin Film Oven test was performed according ASTM D 2872. The viscosity of aged bitumen at 60°C was measured in accordance to AS 2341.2 using Asphalt Institute vacuum capillary viscometer.

Complex shear modulus can be considered the sample's total resistance to deformation when repeatedly sheared while phase angle is the delay between applied shear stress and the resulting strain. Relation G*/sin(d) is found to correlate well with rutting resistance at high temperature, while the relation G*sin(d) is found to correlate well with fatigue resistance. The complex shear modulus and phase angle were tested with the round plate (diameter, 25 mm) using the oscillatory mode. The larger the phase angle is, the more viscous the bitumen is. Early in pavement life, rutting is the main concern; while later in pavement life, fatigue cracking becomes the major concern. The test is performed on both original and aged binder. The testing was performed in accordance to ASTM D7175.

The Brookfield DV-II plus viscometer was used to test the viscosity of base bitumen and biochar modified bitumen at 135°C.

The resistance of asphalt to deformation at high temperature was tested using Cooper wheel tracking equipment. The wheel tracking device consisted of a loaded wheel that bears on a sample held on a moving table. A load of 700 N is applied to the asphalt sample at a testing temperature of 60°C.

The fatigue resistance of asphalt mix is its ability to withstand repeated loading without fracture. Fatigue in asphalt pavements appears as cracking at the surface of the pavement.

Fatigue life of asphalt samples were tested according to AG:PT/T233 four-point loading using IPC equipment. A closed pneumatic testing machine capable of applying both continuous harvesine displacement loading and continuous sine displacement loading at frequencies up to 10Hz.

The resilient modulus of asphalt is a value that is used to describe material behaviour and to predict pavement performance in many pavement design procedures. The IPC testing machine is capable of applying an approximately harvesine load pulse with a rise time in the range of 0.025 s to 0.1 s with an accuracy of ±0.005 s. The machine is applying load pulses with a load of 3.9kN with an accuracy of ±0.05kN for at least 10 cycles for each sample.

The bitumen in Table 4 shows the specification values for each class of base bitumen and the value obtained for CI 70, C450 and biochar-modified bitumen (BMB) measured in the laboratory experiments.

The properties of bitumen after ageing using Roll Thin Film Oven describe the bitumen from asphalt in the plant (which is laid down on the field). As can be seen for the biochar- modified bitumen (BMB) sample obtained using 25% biochar in C170, this sample has a lower viscosity after ageing then the AR 450 specification. The value range between 850 - 1300 Pa*s was chosen to obtain lower rut depth value. Biochar in base bitumen reduces the ageing and therefore the life of asphalt is longer than the asphalt with bitumen without biochar. The biochar from BMB improves the resistance to rut depth and the resilient modulus of asphalt but has a negative effect on fatigue.

The amount of hydrogen peroxide used is a function of the polar compound and functional groups from bitumen. In this example, the amount of peroxide solution requires is within the range of 0.03 to 0.06 millimoles per gram of bitumen. Hydrogen peroxide treatment is also significantly improved when FeSCn catalyst is used. Thus, the biochar activation was carried out in two methods:

1. Using hydrogen peroxide at 0.03 mmol/gram of bitumen.

The surface activation was the creation of carboxylic sites on the surface of biochar particles that are latter added to bitumen. The H2O2 first creates carbonium ions on the surface of the biochar particles, then converts these ions to carboxylic sites. The functional groups in asphalt and the carboxylic sites on the biochar particles interact with each other.

2. Using hydrogen peroxide at 0.03 mmol/gram of bitumen, with FeSCk

The second activation method was similar to the previous method (0.03 mmol/gram of bitumen), but FeS04 (where the molar ratio of FeS04 to peroxide was 1 : 1) was used as a catalyst for increasing the amount of carboxylic groups on the surface of biochar. The process is highly reactive and the hydroxyl radicals in the presence of the catalyst reacts with hydrogen peroxide.

The bitumen and asphalt results are shown below in Tables 1 to 4. As bitumens are seen as viscoelastic materials, dynamic mechanical properties such as complex shear modulus (G*) and phase angle (d) are considered the most crucial rheological indicators of bituminous binder. G* is a measure of the total resistance of the bitumen to deformation when repeatedly sheared while cf is the lag between the applied shear stress and the resulting shear strain.

The samples (imaged or aged) were measured in accordance with ASTM D7175 by dynamic shear rheometer (DSR) at an angular frequency of 10 rad/s which simulates the shearing action corresponding to a traffic speed of about 90 km/h (50 mph). For rutting resistance, a higher value of G*/sin(d) makes a suffer binder and leading to higher rutting resistance which is in good agreement with the rut depth results presented in Table 4.

As can be seen in Tables 1, 2, and 3 the viscosity of any modified binder was

significantly increased which led to a higher rutting resistance. As the biochar content goes higher, the stiffening effect grows more significant. This observation can be explained by the further development of the particle interaction reinforcement, as the rigid modifier particles increase to a certain amount and come into contact, consequently forming a skeletal framework. Complex viscosity (rr*) of all the samples measured at 60°C after short aging (RTFO aging) were reported in order to analyse the effect of aging on bio-char modified bitumen. It was observed that the addition of all the additives increased the viscosity of the asphalt binder to a certain degree before aging and after short term aging. The biochar slowed down the oxidation of bitumen components (as seen in Tables 1 , 2, and 3 by the viscosity of RTFO residue as % of original, which is observed going down for biochar modified bitumen). This can be attributed to the chemical interaction between fine biochar particles and the low molecule components from oxidation. The fine particles can reduce the oxidation due to the high surface areas that promoted the chemical reaction during the aging process. Samples with high content modifier showed negative effect on binder's fatigue cracking resistance, but the resilient modulus is

approximately double that of the asphalt prepared using fresh bitumen.

Results of segregation tests are shown in Figures 5 and 6. Polymer modified binder (PMB) is tested to determine the propensity of a polymer within a PMB to segregate during prolonged storage at high temperatures. This involves placing a sample of PMB into an oven at an elevated temperature (180°C) and, after a prescribed time (48 hours), measuring softening points for the top and bottom halves of the sample. The test is conducted using an empty aluminum can or tube that is filled up with the modified binder. The top and bottom of can are halved after testing and the softening points for the samples are measured. The biochar-modified bitumen and the base bitumen (with untreated biochar) were tested against segregation and the photographs were obtained to show the difference between the samples. Figure 5 shows the biochar-modified bitumen (BMB) sample (with untreated biochar) after 48 hours at 180°C. Figure 6 shows the biochar-modified bitumen (BMB) sample (with treated biochar) after 48 hours at 180°C. According to the AG:PT/T108 - Segregation Test, the sample made using untreated biochar has shown that the segregation occurred (biochar is settled on the bottom after 48 hours at 180°C) (Figure 5), while the BMB sample prepared using the chemically- treated biochar does not show the segregation (Figure 6). The methods of the appended claims are not limited in scope by the methods described herein, which are intended as illustrations of a few aspects of the claims and any methods that are functionally equivalent are intended to fall within the scope of the claims. Various modifications of the methods in addition to those shown and described herein are intended to fall within the scope of the appended claims. Further, while only certain method steps disclosed herein are specifically described, other combinations of method steps also are intended to fall within the scope of the appended claims, even if not specifically recited. Thus, a combination of steps, elements, components, or constituents may be explicitly mentioned herein; however, other combinations of steps, elements, components, and constituents are included, even though not explicitly stated. T _gggy a _B e _f o _r e A _ii A _ft e _r A _i n _{b R} T _F Oble 1. Analysis of ageing by roll thin film oven using untreated biochar-modified bitumen

Australian Specification Experiment

Class Biochar**

Property Test Methods UM C170 C240 C320 AR450 C600 C170 5 10 12.5 15

Viscosity 190 - 260 - 500 -

AS2341.2 Pa*s 140 - 200 Report 166 260 322 360 580 at 60°C 280 380 700

0.32

Viscosity 0.4 - 0.80 0.6 -

AS2341.3 Pa*s 0.25 - 0.45 0.32 0.433 0.511 0.59 0.82 at 135°C 0.65 max 0.85

0.55

era Softening

AS2341.18 °C N/A N/A N/A N/A N/A 49 51.5 53 55 56 Point

Viscosity

of RTFO

ASTM D2872 340 340 340

residue % 340 max Report 191 150 124.22 118.05 116.37 and AS2341.2 max max max

as % of

original

Viscosity

at 60°C 850 -

AS2341.2 Pa*s 337 388 400 425 675 after 1300

RTFO

Mass

± 0.6

Change ASTM D2872 % 0.078 0.15 0.1 0.035 0.012 max

Table 2. Analy ageing by roll thin film oven using biochar-modified bitumen using peroxide treatment

Table 3. Analysis of ageing by roll thin film oven using peroxide treatment with iron sulphate

Table 4. Analysis of C170, C450, and biochar-modified bitumen