SURFACING FIELD OF THE INVENTION

This invention relates to a binder and method for improving the strength and quality of a conventional road, more particularly an improved, durable, cost effective binder and method of road construction and surfacing.

BACKGROUND TO THE INVENTION

Asphalt concrete principles and methods of road construction are well known in the art. The quality of roads is dependent on the material/principles and methods of construction employed, more particularly in the case of asphalt concrete road construction - roads that are typically built in urban areas, for example highways. In asphalt concrete road construction, bituminous binders such as bitumen are commonly used as a binder through a mixing process with aggregates to create asphalt concrete.

For purposes of this specification, it shall be appreciated that the term bituminous binder shall refer to but not limited to is a sticky, black, and highly viscous liquid or semi-solid form of petroleum. The term bituminous binder may be construed to refer to naturally occurring materials, i.e. naturally occurring asphalt, or as refined products, i.e. bitumen is manufactured from crude oil or as processed (‘synthetic’) materials, i.e. vegetable-based binders to produce materials for construction and/or public works CA2463174A1 as patented by Colas SA in France in 2004.

Bituminous binders are well known in the prior art. Most bituminous binders available on the market are composed of mixtures of different organic materials and mostly produced through vacuum distillation of petroleum. Bituminous wearing surfaces provide a resilient, waterproof medium that protects a road base from water and traffic. Properly designed bituminous wearing surfaces, when compared with concrete wearing surfaces are less affected by temperature strains. Bituminous surfaces resist wear, weathering, and however, it is important to note that bituminous wearing surfaces lack appreciable bearing action to carry wheel loads over weak spots along the wearing surface. For this reason, a sub-base of the bituminous surface must have an adequate, uniform bearing strength and a base must have adequate thickness, bearing capacity, and cohesion.

The invention is concerned with the technical problem of developing a binder that may achieve levels of performance comparable to those of bituminous binders insitu, i.e. a binder with good cohesive and elastic properties, high resistance to rutting and fatigue, good resistance to hydrocarbons/fuel and lower mixing temperatures as compared to conventional bitumen. Such a binder and method of road construction may have significant cost and environmental advantages over the use of bituminous binders. Furthermore, the use and development of binders constituted from natural and renewable ingredients is desirous. These binders provide alternatives to bitumen-based binders and therefore reduce the carbon footprint of the road construction process.

It is an object of the invention to provide for an improved, durable, cost effective binder and method of constructing and surfacing of high-quality roads.

SUMMARY OF THE INVENTION According to one aspect of the invention, there is provided a binder for road construction, in use which binder comprises:

20 to 30% by mass water;

10 to 20% by mass mineral acid;

15 to 25% by mass gelatine;8 to 12% by mass resin; 17 to 27% by mass polyol; and

7 to 12% by mass at least one eight-valent non-metallic promoter. It shall be appreciated that the term binder in this specification shall refer to but not limited to a substance that sets and hardens and can bind materials together and accelerate a curing process within a road construction context. The binder may include water with a total concentration of between 22 to 26% by mass of the total mass of the binder, preferably between 23 to 25% by mass.

The binder may include a mineral acid selected from a group consisting of sulfuric acid, hydrochloric acid, nitric acid or combinations thereof.

The binder may include sulphuric acid with a total concentration of between 10 to 16% by mass of the total mass of the binder, preferably between 11 to 13% by mass. The binder may include gelatine with a total concentration of between

19 to 24% by mass of the total mass of the binder, preferably between 21 to 23% by mass. The eight-valent non-metallic promoter may be selected from a group of sulphur, selenium, tellurium or combinations thereof.

The binder may include sulphur with a total concentration of between 8 to 12% by mass of the total mass of the binder, preferably between 10 to 11% by mass.

The polyol may be selected from a group as consisting of glycerine, pentaerythritol, ethylene glycol or combinations thereof.

The binder may include glycerine with a total concentration of between 19 to 24% by mass of the total mass of the binder, preferably between 21 to 23% by mass. The binder may include a resin selected from a group consisting of polyester, polyurethane, polyurea, urea-formaldehyde or combinations thereof.

The binder may include urea-formaldehyde with a total concentration of between 7 to 11% by mass of the total mass of the binder and most preferably between 8 to 10% by mass.

The binder may include polychloroprene.

According to a second aspect of the invention, there is provided a method of manufacture of a binder for road construction, which method includes the following steps: admixing gelatine, sulphuric acid, sulphur and water to form a gelatinous-inorganic salt emulsion; heating the gelatinous-inorganic emulsion; adding glycerine to the heated gelatinous-inorganic emulsion; and adding resin to the glycerine/gelatinous-inorganic emulsion to thereby form the binder.

The gelatinous-inorganic emulsion heating step may at between 55 to 65 degrees Celsius, more preferably between 58 to 62 degrees Celsius.

According to a third aspect of the invention, there is provided a method of road construction, which method includes the following steps: layering a sub-base of calcined clay; heating the sub-base such that the calcined layer undergoes an irreversible rheological change; boring the sub-base to form a surface for a complementary mating condition with a primary aggregate base; heating the primary aggregate base in the mating condition with the sub-base to a determinable temperature via a heat source; pouring the binder onto the primary aggregate base; layering an impervious material over the primary aggregate base; and sealing the impervious material with a mixture of binder and secondary aggregate layer.

It shall be further appreciated that the term road construction shall be used broadly to describe any construction methodology applied to the construction of roads and not limited to rock, broken rock, gravel (whether pebble, granule, or other size or mixture).

The sub-base may be configured with a cross-sectional thickness of between 50 to 70mm, more preferably between 58 to 62mm.

The primary aggregate layer may be configured with a cross-sectional thickness of between 20 to 30mm, more preferably between 22 to 26mm.

The heat source may be in the form of a light amplification by stimulated emission of radiation (LASER). The heating may be performed at a temperature of between 35 to 55 degrees Celsius more preferably between 38 to 42 degrees Celsius.

The impervious material may be in the form of a layer of raw leather with an average thickness of between 1.5 to 3.0mm, more preferably between 2.0 to 2.5mm.

The secondary aggregate layer may be in the form of stones with an average diameter of between 5 to 7mm more preferably between 6.3 to 6.9 mm in diameter. BRIEF DESCRIPTION OF THE DRAWINGS

The invention is now described, by way of non-limiting example, with reference to the accompanying drawings wherein: Figure 1 shows, a cross-sectional view of a method and principle of construction for improved roads in accordance with the invention; and Figure 2 is an exploded view of Figure 1.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the accompanying drawings, a method and principle of construction for improved roads thereof in accordance with the invention is generally indicated by reference numeral 10. The road 10 includes a sub-base of calcined clay 12, a primary aggregate base 14, an impervious material in the form of a leather layer 16 and a secondary aggregate surface layer 18. A binder (not shown) is used to bind the sub-base 12, primary aggregate layer 14, leather 16 and secondary surface layer 18 to each other. Clay soil is compacted by a compacting means to form the sub-base of calcined clay 12. The clay 12 heated at high temperatures a proprietary light amplification by stimulated emission of radiation (LASER) heat source thus enabling the clay structure of the clay to undergo a rheological change whereby particles in one layer of the clay soil conjoin to particles in adjacent clay layers thus forming hard the calcined clay sub-base 12. This heating process allows clay particles to move into an equilibrium position to thereby enable the calcined clay to be resistant to compaction or tension.

The sub-base is then cored with boring holes 20 for interlocking complementary formations 22 on the primary aggregate base 14 with the sub base 12. The primary aggregate layer 14 is heated stones to 40°C will be placed on the sub-base and compacted using long metal barriers (not shown) along the edges of the road thus preventing any dislodgement of the aggregate base 14. The binder is then poured on top of the aggregate base 14 and levelled using hot metal rods. This allows the binder (not shown) to penetrate coat the aggregate layer 14. Full grain leather (cheapest leather not treated leather) is then layered onto the aggregate layer 14 with an additional coat of binder being applied thinly applied on top of the leather 14 and 6.7mm stones (slightly dipped into the binder) will be placed on top of the leather layer for roughness, the International Roughness Index (IRI) for roads is <2.1%.

For purposes of this specification, it shall be further appreciated that the International Roughness Index (IRI) shall be construed as per the World Bank definition. IRI is used to define a characteristic of the longitudinal profile of a travelled wheel track and constitutes a standardized roughness measurement. The commonly recommended units are meters per kilometre (m/km) or millimetres per meter (mm/m). The IRI is based on the average rectified slope (ARS), which is a filtered ratio of a standard vehicle’s accumulated suspension motion (in mm, inches, etc.) divided by the distance travelled by the vehicle during the measurement (km, mi, etc.). IRI is then equal to ARS multiplied by 1,000.

SPECIFIC EMBODIMENTS OF THE INVENTION

1.0 Example 1 - Binder manufacturing steps

Step 1 - Mix technical gelatine - Grade T20 (175.6g) with sublimated sulphur (90g) to sulphuric acid (100ml). Add water (200ml) to the mixture. Stir until water is absorbed by the technical gelatine.

Step 2 - Take the semi-solid mix into the oven and heat at 60°Celsius The mixture becomes liquid when heated.

Step 3 - Add glycerine (180.7g) (do not heat it) after 15 minutes - this is for flexibility of the binder (technical gelatine) and stir mixture.

Step 4 - After 30 minutes take out the binder out of the oven Add (80g of Urea Formaldehyde (UF Resin) to the mixture binder, the UF Resin helps with thermosetting of the binder and making it resistant to high temperatures. Step 5 - The binder is now ready for application onto a road surface.

Step 6 - Heat the stones (aggregates) at 40°Celsius. The binder this then poured on the heated and compacted stones. A concrete poker to compact and drive trapped air out, polychloroprene adhesive may be added to the to the binder. This is followed by re-compaction of the road surface using concrete poker. Waste leather material is placed on granite aggregates in addition to the binder for aiding in skid resistance.

The binder was then subjected to standard methods of testing road construction materials, namely: Hamburg Wheel Tracking Test (AASHTO T324), Indirect Tensile Strength ITS (TMH1 C12T), Unconfined Compressive Strength UCS (SANS 3001 - GR53), Repeated Shear Strain Test (RSST (AASHTO T320)) and 4pt Beam Fatigue test (AASHTO T321).

AASHTO T 324, 2019 Edition, 2019 - Standard Method of Test for Hamburg Wheel- Track Testing of Compacted Asphalt Mixtures

This test method describes a procedure for testing the rutting and moisture- susceptibility of asphalt mixture pavement samples in the Hamburg Wheel-Tracking Device.

The method describes the testing of a submerged, compacted asphalt mixture in a reciprocating rolling-wheel device. This test provides information about the rate of permanent deformation from a moving, concentrated load. A laboratory compactor has been designed to prepare slab specimens. Also, the Superpave Gyratory Compactor (SGC) has been designed to compact specimens in the laboratory. Alternatively, field cores having a diameter of 150 mm (6 in.), 250 mm (10 in.), or 300 mm (12 in.), or saw-cut slab specimens may be tested.

The test method is used to determine the premature failure susceptibility of asphalt mixture due to weakness in the aggregate structure, inadequate binder stiffness, or moisture damage. This test method measures the rut depth and number of passes to failure. This test method measures the potential for moisture damage effects because the specimens are submerged in temperature-controlled water during loading. 1.1.1 Indirect Tensile Strength (ITS) @ 25°C (TMH1 C12T)

The Indirect Tensile Strength (ITS) test provides a measure of a mixture’s resistance to fatigue cracking and has therefore been selected to investigate the influence of aggregate temperature on the mix properties. This test is extensively used for cold- mix and hot-mix asphalt laboratory design procedures in South Africa. The prepared samples were conditioned at 25°Celsius for two hours. The results are given in Table 1 below:

Table 1: ITS results

1.1.2 Unconfined Compressive Strength (UCS) (SANS 3001 - GR53)

Unconfined compressive strength is carried out as part of the mix design procedure to establish an appropriate stabilizing agent, as well as for quality control purposes during construction. The strengths determined by this test identify the expected C- class that the material will achieve with different stabilizer contents. The working time for unconfined compressive strength is defined as the time measured from the commencement of the addition of the stabilizing agent to the compaction of the stabilized material, which corresponds to 80% of the mean value of three determinations of UCS, for samples compacted one hour after incorporation of the stabilizing agent.” The specified temperature is 25°C.The working time for maximum dry density is defined as “the time measured from the commencement of the addition of the stabilizing agent to the compaction of the stabilized material, which corresponds to 97% of the mean value of three determinations of maximum dry density, for samples compacted one hour after incorporation of the stabilizing agent. All samples shall be cured in a loose condition in airtight containers at 23 ± 2 °C. Three specimens were prepared for UCS testing at 25° Celsius. The test results are given in the Table 2 below.

Table 2: UCS results

1.1.3 Fatigue crack testing

The fatigue crack tests were performed using an IPC 4-PBB test setup according to AASHTO T 321 (2014) test method. The fatigue failure criterion was defined as the number of load cycles to reach a 50% reduction in the initial stiffness (Nso%). The four-point bending beam fatigue test was conducted on two specimens under a controlled-strain loading condition of 400 microstrain levels at a frequency of 10 Hz and temperatures of 5°Celsius and 10°Celsius. Both beams reached 6 000 000 cycles without failing. Table 3 shows the specimen's dimensions and Table 4 summarizes the beam fatigue test results.

Table 3: Specimen dimensions

Table 4: Fatigue results 1.1.4 Hamburg Wheel Tracking Test

Two 150mm cylindrical specimens were produced using the gyratory mould. The samples were tested for rutting and moisture susceptibility using the Hamburg Wheel Tracking test. The test was conducted at the test temperature of 50°Celsius for up to 20 000-wheel passes. Figure 1 summarizes the Hamburg Wheel Tracking test results.

1.1.5 Permanent Shear Strain

A gyratory mould was used to produce 150mm cylindrical specimen. The sample was tested for permanent shear strain using the Repeated Simple Shear Test at Constant Height (RSST-CH). The test was conducted at the test temperature of 55°C with a horizontal shear force of 69kPa. The sample failed at 1 000 cycles with a shear strain of 0.077. Figure 2 summarizes the shear strain test result.

Figure 1: Hamburg Wheel Tracking Test

Figure 2: Shear deformation curve for Specimen 1 at 55°C

Example 2 - Application phase (binder)

Since the binder (cured technical gelatine mixture) is liquid, it will penetrate the gaps between the compacted stones. After 10 seconds, the binder will start to become semi-rubbery and wrap around each stone. Example 3 - Curing phase binder

From the semi-rubbery state (binder) becomes solid (after 5 seconds) with stones inside. Example 4 - Viscoelastic phase

The binder hardens completely (after 6 seconds), allowing any load to be applied on it. At this stage it expands when loaded and retains back its original shape when the load is removed. Additionally, the coating of stones by the binder prevents the stones from moving into the preferred orientation when under load as such the stones can only move slightly inside the binder.

Example 5 - Road Construction 1. Sub-base (secondary-load spreading layer) - 60 mm thick;

2. Base (main-load spreading layer) - 22 mm thick; stones - 10 to 14mm;

3. Biscuit layer (surfacing and waterproofing) - Leather: 2 mm thick; and

4. Small stones - 6.7mm (Roughness)

Although only certain embodiments of the invention have been described herein, it will be understood by any person skilled in the art that other modifications, variations, and possibilities of the invention are possible. Such modifications, variations and possibilities are therefore to be considered as falling within the spirit and scope of the invention and hence forming part of the invention as herein described and/or exemplified. It shall further be understood that the examples are provided for illustrating the invention further and to assist a person skilled in the art with understanding the invention and is not meant to be construed as unduly limiting the reasonable scope of the invention.