IE48642B1 - Asphalt composition - Google Patents

Description

This invention relates to an asphalt composition consisting of bitumen and an organic manganese, cobalt and/or copper compound soluble in bitumen and the use thereof in road construction.

Bitumen is obtained as the solid residue during the distillation of crude petroleum and has been used in road construction for many years.

According to the information in US patent 2,342,861 it is possible to improve the adhesion of cutback bitumen or bituminous emulsions to the aggregate by adding a metal compound, in particular a lead salt of oleic acid or naphthenic acid. The resultant asphalt compositions, however, must also contain a flux oil, US patent 2,928,753 reveals bitumen compositions which consist of bitumen and 0.001 to 0.5% of an oil-soluble copper, cobalt or manganese salt of naphthenic or oleic acid. The bitumen composition, however, does not contain any aggregates.

To prevent the formation of cracks in blown or oxidized asphalt surfaces, heavy metals of organic acids with a high molecular weight such as naphthenates and linoleates may be used according to the information in US patent 2,282,703, The heavy metals used for this purpose include cobalt, manganese, iron, lead, vanadium or zinc which are dispersed in the blown asphalt.

According to the information in US patent 1,328,310, the physical properties of an asphalt composition can be improved by adding copper sulfate, Besides copper sulfate, the sulfates or selenates of aluninum, chromium, manganese, iron, indium, gallium as well as the sulfates or selenides of sodium, potassium, rubidium, an>oni'j«i, silver, gold, platinum and thallium may be used. All these compounds, however, are insoluble in bitumen.

According to the information in US patent 1,505,880, the strength and resistance of an asphalt composition is enhanced by admixing it with copper slag and aggregates.

To improve the adhesion of the asphalt composition to mineral aggregates, British patent 533,927 proposes using double lead or iron salts of organic acids or even those of other bi- or polyvalent metals such as aluminum, chromium, copper and mercury.

The abject of the invention was to develop an asphalt composition which can be used in road construction and which provides asphalt surfaces which not only exhibit good adhesion to the aggregates, but also improved physical properties, expecially enhanced strength and improved resistance to fatigue.

It has been found that this object can be accomplished in accordance with the invention with an asphalt composition consisting of bitumen and an organic manganese, cobalt and/or copper compound soluble in bitumen which is characterized in that it contains at least 85¾ by weight of aggregates as well as a manganese, cobalt and/or copper concentration of 0.01 to 0.50% by weight, based on the bitumen.

When the asphalt composition in accordance with the invention is used in road construction, asphalt surfaces are obtained which not only adhere extraordinarily firmly to the substrate, but which also have improved physicial properties, in particular high resistance to pressure, bending and fatigue, elasticity and also self-sealing properties and which permits the use of poor aggregates.

Especially good results are obtained with an asphalt composition of the afore-mentioned composition containing 90 to 98% by weight of aggregates.

In accordance with a preferred embodiment of the invention, a manganese concentration in the asphalt composition of 0.05 to 0.20% by weight ofc a cobalt concentration of 0.001 to 0.20% by weight, in each case based on the bitumen, led to a very decisive improvement in the resistance to pressure, bending and fatigue of the final, hardened road surface produced using the asphalt composition according to the invention.

It has been found that in practice the asphalt composition containing organic manganese, cohalt and/or copper compounds soluble in bitumen can be produced by liquifying the bitumen by heating it to a temperature above the melting or softening point thereof and subsequently admixing the organic metal compound in cited amount. The resultant asphalt composition can then be mixed directly with the desired aggregate in this form in the cited amount. It has also been found that an asphalt composition produced in this manner can be stored in quantity prior to its use in road construction without any appreciable thickening. It is also unimportant whether the organic metal compounds contained in the asphalt composition in accordance with the invention are admixed to the bitumen as finished compounds or are formed in situ from the corresponding inorganic or organic compounds.

The asphalt composition in accordance with the invention generally has a penetration of less than 400, preferably 40 to 300, at 25°C (determined according to the ASTH Standard Procedure D-5). The viscosity of the asphalt composition in accordance with the invention amounts to in excess of 65 poise at 60°C, The organic manganese, cobalt and/or copper compounds contained in the asphalt composition in accordance with the invention are 8 6 4 2 - 4 5 4C soluble in bitumen so that they are distributed equally when worked into the bitumen, thus causing their resistance-improving effect to act uniformly throughout the final product. The organic compounds used in accordance with the invention may contain sulfur or phosphorus, e.g, as organic sulfonates or phosphates.

The organic metal compounds used in accordance with the invention may also be added to the bitumen in the form of a solution in an organic solvent to facilitate dispersion and mixing. The volatile solvent evaporates at the temperature used for mixing so that it cannot adversely affect the adhesion properties.

Suitable anions for the organic metal compounds are those derived from carboxylic acids, alcohols, phenols and ketones. Especially goods results are obtained with manganese acetyl acetonate. Preferable anions are those derived from carboxylic acids with as many as 30 carbon atoms ir· the chain such as acetates, linoleates, caprylates, naphthengtes, oleates, caprinates, stearates, laurates and mixtures ttereof. It has been found that the anions derived from caprylates, naphthenates and acetates are by far the most effective of the compounds examined, since they are the best soluble in the asphalt composition. In addition, anions derived from other carboxylic acids, e.g. anions derived from tertiary carboxylic acids, may also be used.

Considerable improvements in the physical properties of the asphalt composition are attained by adding comparatively small quantities of the organic metal compounds. A manganese concentration of 0.01% by weight based on the bitumen, for instance, results in an asphalt composition with an enhanced load compression strength. Optimum properties can be obtained when the asphalt composition contains 0.05 to 0.50% by weight of manganese. Still higher manganese concentrations, i.e. those of about 1% by weight, cause only very minor improvements. Due to economic reasons, therefore, the optimum range lies between 0,05 and 0.20% by weight based on the weight of the bitumen.

The asphalt composition in accordance with the invention has a viscosity comparable to that of commercial asphalt compositions in the l’guid state at elevated temperatures when used for road construction, A road surface produced using the asphalt composition in accordance uith the invention, however, has a much greater strength after hardening than a road surface produced using a commercial asphalt composition.

The aggregates used in accordance with the. invention are generally the ones normally used in road construction as well. They may be fine-grained, e.g. sand, or coarse like broken stone, gravel or slag.

The addition of manganese, cotalt and/or copper compounds causes an appreciable improvement in the strength and temperature sensitivity of the road surfaces produced from the asphalt composition in accordance with the invention. The cited metals may be used either alone or in combination with one another, the use of manganese yielding by rar the best results. The use of cobalt in addition to the use of manganese results in a synergistic im50 i - 5 prouement in the strength of a road surface produced with the asphalt composition in accordance with the invention.

One essential advantage of the asphalt composition in accordance with the invention is that it allows high-strength road surfaces to be made from a comparatively soft aslphalt composition (e.g. one with a penetration of 350 to 400) which is obviously due to the presence of the afore-mentioned metal ions. An increase in the number of pockets in the asphalt composition according to the invention causes an increase in the hardening rate. If an asphalt composition has pockets amounting to 20% and contains sand as the aggregate, considerable hardening can be achieved within a week. An conventional road surface generally has pockets amounting from 5 to 10% and this is sufficient to utilize the advantages in accordance with the invention, The invention will now be explained in detail on the basis of the following examples.

Example 1 Comparison tests were carried out using various heavy transition metals as aggregates in the asphalt composition.

A dune sand having such a grain size distribution such that 51% passes through a sieve with a mesh width of 0.425mm and not more than 10% passes through a sieve with a mesh width of 0.075mm was mixed in a ratio of 100:4 with a standard bitumen having a viscosity of 8000 poise at 60°C, The individual organic metal compounds listed in Table I were then added in such an amount that the metal content of the asphalt composition amounted to 0.2% by weight based on the bitumen. The metal soap which existed in liquid form was then mixed with the liquid bitumen at a temperature of 100 to 120°C, The mixture was then stirred by hand to thoroughly disperse the metal by dissolving it in the bitumen.

The bitumen together with the metal and sand contained therein was shaped at 154 to 158°C into small short cores with a diameter of 3.33cm and compressed at the cited temperatures. These cores were then hardened for seven days at 50°C, The cores were tested both at 22° and 50°C to determine the compression strength.

The cores were tested again under the same conditions after two weeks of storage. In the second test, the cores had a slightly larger diameter so that the results must be adjusted by multiplying them approximately by a factor of 0.97. The results of these tests are compiled in Table I below. 8 6 4 2 - 6 Table I Results Metal catalyst Load 22°C open (kg) after 1 week at 50°C Load 20°C open (kg) cl. after 2 weeks at 50°C cl. 50°C open closed 50°C open closed Mcngcnese 476 441 166 140 539 539 133 132 ncphthencte Copper 291 291 60 47 423 443 70 66 ncphthenctA Cobalt 373 379 54 40 413 434 40 33 ncphthere le Iron 212 194 10 8 281 204 8 8 ncphthe^ct^ Zirconium 102 100 3 2.3 124 131 1.8 0.9 ccprylote Nickel 78 73 2.7 2.3 182 179 3.6 3 ncph’bercte CalcLuat 69 53 0.9 0.9 133 115 1.8 1.8 ncphthencte Zinc 56 58 1.4 0.9 124 115 1.8 0.9 ncphthencte Le«J 53 50 0.9 0.5 110 117 0 0 nophthencte The expression closed (cl.) used in the right columns indicates that the composition «as hardened in containers to reduce, but not entirely eliminate oxygen contact. The compression strength of the samples which were hardened in a partially closed or completely open state are comparable, i.e, partial exclusion of oxygen to the cores during hardening had no effect.

Table I reveals that of the organometallic compounds examined, manganese is the highly preferable metal. Compared to the other metals examined, however, the use of copper and cobalt also produce extraordinary improvements in structural strength.

Example 2 A series of additional tests was carried out using the asphalt composition of Example 1, except using manganese caprylate in an amount of 0.2S based on the bitumen. The same amount of bitumen and aggregate was used. The results are compiled in Table II below. All samples were hardened in air for one week at 50° C, Similar results were also achieved using lower ambient temperatures (e.g. 22°C), although with prolongation of the hardening times . Table II Non-mod i fied bitumen Modified bitumen Compression test: Strength at 22°C, kg/cm’ Strength at 50°C, kg/cm’ 8.4 0.5 65.2 20.5 - 7 Marshall stability test: Stability (kg) Flow value, 0.0254 cm 113.4 14 816.5 12 5 Static flexure test: Modulus of elasticity kg/cm’ 780 5175 Modulus of rupture Final load (xl0-i*) 3.4 17.3 152 Dynamic fatigue test: Modulus of elasticity kg/cm* Fatigue limit, e x 10” _ -* 60,000 10 80 *These values were unable to be determined for non-modified bitumen.

It was found that complete hardening was achieved for the test temperature of 22°C in about four weeks, whereas a longer time was required at a test temperature of 50°C to achieve complete hardening (ASTM Standard Test Procedure D 1074-76).

Plastic fractures occurred. The unsat is factory samples were able to be tested several times within a relatively short period (e.g. within 1 or 2 days), nevertheless retaining the same strength.

The Marshall stability test revealed increased stability at a 2C lower hardening rate after more than one month.

The static flexure tests were carried out using shaped-compressed samples with a length of 25 cm and a cross section of 2 cm x 3 cm. The samples were hardened for one month at 22°C and then subjected to a static flexure test with load support sites at three points and a free span of 22 cm. The load rate amounted to 0.127 cm/min and the test temperature amounted to 22°C. The results are compiled in Table II above. The final flexure load of the non-modified bitumen-sand samples could not be ascertained, since these were deformed continuously during the duration of the test. The final strength of the modified bitumen 3C samples was approximated by adding the elastic load near the final load point to the plastic load by one rupture point.

Samples of the afore-described type were also tested in a dynamic fatigue device in which they were clamped into position with a free span of 22 cm and then repeatedly subjected to a load in the center. A steal leaf was disposed transversely beneath the samples and designed to push them back into their original position after the load test. The load rate amounted to three load repetitions per minute and the test temperature was 22°C.

Good results were not obtained for the non-modified bitumen samples in this fatigue test, since the samples were deformed both vertically and laterally even at a relatively low load level.

The results of the fatigue test were plotted on a double logarithmic scale to obtain an equation in the standard form 8 6 4 2 - 8 where indicates the number of load repetitions until fracture, e the corresponding flexure load and K and c the regression constants. The values of K and c were determined to be 1.82 x 101 and 3.29, e being expressed in microunits.

It was determined that the modulus of dynamic elasticity of the sand-bitumen samples amounted to approximately 59,755 kg/cm’.

This means that the modified bitumen-sand product has been improved at this modulus value relative to the durability up to the level of asphalt concrete.

Example 3 Bitumen and dune sand from Saudi Arabia, the dune sand amounting to 96.15¾ by weight, were mixed with 0.05K, 0.10¾ and 0.20Si manganese. Standard Marshall cores of the asphalt composition with a content of 4% bitumen were shaped and compressed. Half of the cores with the respective manganese contents were introduced into a furnace heated to 50°C. The remaining half was left on the bench.

The Marshall stability tests were conducted after a seven day hardening period. The results of these tests are compiled in the following Table III. Table III Hardening and Test % Manganese content in bitumen 0.05 0.10 0.20 Hardening at 22°C, Marshall stability (kg) 168 467 517 Hardening at 50°C, Marshall stability (hg) 584 1220 1461 It was found that the maximum stability effect per unit amount of manganese ranged between 0.08¾ and 0.12¾. Although higher manganese contents rfaulted in greater stability, they produce a lower stability per unit amount of manganese.

Example 4 Various tests were performed to verify the considerable improvement in the strength of cores in which a small amount of cobalt was admixed with the bitumen in addition to the manganese. Furthermore, the relative strengths obtained using manganese, cobalt, copper and iron were compared with one another.

The following organoaeta11ic compounds were used; manganese naphthe.nate (6% manganese) cobalt naphtheate (65 cobalt) copper naphthenate (8¾ copper) and iron naphthenate (6% iron).

A mixture of commercial bitumen (with a penetration of 8.0 10.0 nn) and dune sand from Saudi Arabia, said sand amounting - 9 10 to 96.15% by weight, was heated to 100°C and the afore-mentioned metal compounds were added and uniformly dissolved in the mixture. The process cited in Example 1 was subsequently used to shape and compress short miniature cores. All cores were hardened at 45°C until testing, Each core was tested at 45°C for its compression strength, then maintained at a temperature of 45°C for at least one hour, then cooled to room temperature for at least 1.5 hours and then retested at this temperature. The results of these tests are compiled in the following Table IV.

Table IV Test Metal ion Compression strength (kg/cm’) Temp.°C 3 days 7 days 14 days 28 days 45 Mn(0.2%)+Co(0.227%) 8.02 -9.68 12.21 12.68 45 Mn(0.2%)+Co(0.038%) - 7.00 6.66* 7.55 45 Mn(0.2%)+Co(0.006%) - 5.54 6.07 7.57 45 Mn(0.2%)+Co(0.001%) 3.85 4.31 4.99 8.04 45 Mn(0.2%) 4.10 4.62 5.23 6.28 45 Co(0.2%) 3.64 3.24 2.61 3.30 45 Cu(0.2%) 2.42 2.32 1.81 2.30 45 Fe(O.ZS) 0.71 0.64 0.67 1.22 22 Mn(0.2%)+Co(0.227%) 13.99 15.91 19.81 21.24 22 Mn(0.2%)+Co(0.38%) 14.28 16.43* 15.95 22 Mn(0.2%)+Co(0.006%) - 12.43 14.22 14.96 22 Mn(0.2%)+Co(0.001%) 9.15 11.62 - 15.88 22 Mn(0.2%) 10.47 10.97 15.22 16.20 22 Co(0.2%) 10.38 10.99 10.38 10.04 22 Cu(0.2%) 6.12 7.34 8.15 8.76 22 Fe(0.2%) 3.76 4.07 4.73 7.21 ♦Tested after 15 days, not 14 days Table IV above reveals that the use of small amounts of cobalt results in a substantial increase in the strength of the composition at the elevated temperature of 45°C, This constitutes an important test, since the asphlt is weakest at elevated temperatures. After a period of 28 days, the composition which contains 0.2!» manganese and 0.001% cobalt attained a strength of 8.04 compared with a strength of 6.23 when only manganese is used. A total increase in the metal ion concentration of merely 0.5% results in an increase in strength of almost 30%.

Moreover, Table IV above also reveals that the use of manganese produces much better results in the test at 45°C after 28 days than the other metal ions.

Example 5 Another comparison test was carried out to illustrate the importance of the use of manganese in the form of a soluble organometallic compound compared to an inorganic, insoluble form such as manganese sulfate. For this purpose, manganese naphthenate uas compared to manganese sulfate. - 10 The manganese (in the form of naphthenate and sulfate) was added to the bitumen (with a viscosity of 4000 poise at 60°C) and mixed as in the examples above. Cores were then produced using 5.2% of such a modified bitumen and desert sand from Iraq, the desert sand amounting to 95.1% by weight of the mixture. The cores were hardened for 8 days at 45°C and then tested in a pressure test at 22°C and 45°C. The results are compiled in Table V below.

Table V T reatment Pressure strength 45°C kg/cm 22°C untreated 1.05 7.78 0.2% manganese naphthenate 14.70 24.89 0.2% manganese sulfate 2.37 13.64 It is obvious that the core, which was produced using bitumen treated with manganese naphthenate, has six times the strength at 45°C than the sample produced using bitumen treated with manganese sulfate, and that it has 14 times the strength compared to the core produced using untreated bitumen. This table explains the importance of the measure that the manganese must be added to the bitumen in soluble form.

Example 6 Materials used: Iraqi desert sand (95.1% by weight, based on sand and bitumen) bitumen (as in Example 5) manganese acetate manganese acetyl acetonate, Mn-fAcAc^ manganese acetyl acetonate, Mn-(AcAc)t manganese benzoate manganese-p-tolaene sulfonate manganese naphthenate manganese caprylate The manganese compounds were added to the bitumen in such an amount that 0.2% manganese was formed. The compound was stirred at 110aC. The solids did not dissolve immediately when acetyl acetonate, benzoate and toluene sulfonate were used. The samples were heated further and stirred at 135°C before being mixed with the sand. Microscopic examination revealed.the presence of different amojnts of particulate solids in the bitumen.

The sand and the bitumen were mixed at 135 to 140°C and compressed to form short miniature cores. These were hardened at 45°C. Two cores were examined one week later to determine the pressure strength, The remaining four were examined two weeks later. - 11 Table VI Bitumen content: 5.2%, based on the weight of the sand T reatment Mn content Hardening Strength in kg/cm in bitumen duration at 45°C at 22°C % days none 0.00 8 1.05 7.78 Mn naphthenate 0.2 7 14.70 22.75 Mn naphthenate 0.2 14 16,08 24.89 Mn acetate 0.2 7 9.80 29.95 Mn acetate 0.2 14 17.05 33.74 Mn-(AcAc)_ 0.2 7 1.04 9.72 Mn-(AcAc), 0.2 14 1.70 14.69 Mn-(AcAcK 0.2 7 19.76 35.59 Mn-(AcAc)j 0.2 14 20.92 38.24 Table VII 8itumen content: 4.8%, based on the weight of the sand Treatment Mn content Hardening Strength in kg/cm in bitumen duration at 45°C at 22°C Of Λ days none 0.00 7 0.63 7.62 Mn naphthenate 0.10 7 11.25 21.94 Mn naphthenate 0,10 14 16.09 23.94 Mn caprylate 0,10 7 8.79 24.51 Mn caprylate 0.10 14 14.15 23.69 Mn benzoate 0,10 7 0.87 9.45 Mn benzoate 0.10 14 1.89 13.78 Mn-p-toluene sulfonate 0,10 7 1.80 11.20 Mn-p-toluene sulfonate 0.10 14 2.33 15.03 The acetyl acetonate (Mn+*>) and the acetate (Mn+^) proved to be extremely effective in increasing the strength. These studies confirmed the conclusion that various oxidation values of manganese (at least the +2 and +3 values) are effective, provided that the manganese compound is soluble and can be dissolved (or ionised) in bitumen.

Example 7 Materials used: local aggregate with a limestone content Australian bitumen (penetration: 8.0-10.0 mm) manganese naphthenate (6% Mn) manganese caprylate* (12% Mn) manganese caprylate and cobalt naphthenate ♦Commercial product with low amounts of other acid residues (e.g. 180 g bitumen (treated or untreated) were added to 3300 g aggregate. This was followed by mixing after which cores were produced (three at a time), shaped and compressed at 140°C, - 12 The bitumen was treated with 0.025 manganese, whereby manganese naphthenate was used. Using manganese caprylate, the bitumen was treated with 0.050 and 0.075 manganese. The bitumen which was treated with 0.103 metal was treated with a mixture of man5 ganese caprylate (9 manganese) and cobalt naphthenate (6 Co), This material contained 0,098 manganese and 0.0097% cobalt.

All cores were hardened at 45°C until tested for their Marshall stability.

Table VIII Treatment Metal Har lening Marshall Flow Increase material in % duration stability value in SS months in kg 0.0254 cm __ 0.000 0.5 948 12.3 0.0 -- 0.000 3.4 1329 11.4 0.0 Mn naphtnenate 0.025 0.5 1275 16.4 35 Mn naphthenate 0.025 1.0 1276 12.8 26 Mn naphthenate 0.025 3.0 1367 11.3 71 Mn caprylate 0.050 0.5 1281 35 Mn caprylate 0.050 1.0 1094 11.9 8 Mn caprylate 0.050 3.0 1328 12.7 4 Mn caprylate 0.075 0.5 1301 11.6 37 Mn caprylate 0.075 1.0 1217 20 Mn caprylate 0.075 3.0 1567 13.4 23 Mn caprylate + Co naphthenate (10:1) 0.108 1.0 1881 15.9 99 tin caprylate + Co naphthenate (10:1) 0.108 2,0 2092 16.1 83 Example 8 Materials used: Iraqi desert said (95.6% by weight based on sand + bitumen) or sand (as in Example 1)(95.1% by weight, based on sarid + bitumen) bitumen (as in Example 5) bitumen (as in Example 7) manganese naphthenate (6% Mn) manganese benzoate (crystalline) manganese-p-toluene sulfonate (crystalline) manganese caprylate (6 Mn) manganese neoieranoate The bitumen was weighed in small amounts at 110°C. The manganese compound was added and the manganese content listed in Table IX was obtained in the bitumen.

The mixture was reheated and stirred until a solution had formed.

The samples were then heated to 14Q-144°C and weighed together with the preheated sand. The bitumen percentage contents listed in Table IX were obtained. 8 6 4 2 - 13 Finally, short miniature cores were shaped and compressed at 140-144°C and then hardened at 45°C. The hardening times are listed in Table VII, Half of the cores were then subjected to a pressure test at 45°C and the other half at 22®C. The cores which contained caprinate were hardened at 50°C, Table IX Bitumen Bitumen content in ϋ Treatment Metal content % based Hardening time at 45°C in days Strength kg/cnv at 45°C at 22« Bitumen 1* 4.6 14 0.68 7.62 Bitumen 1 5.2 14 1.05 7.78 Bitumen 1 4.6 Mn naphthenate 0,10 7 11.25 21.94 Bitumen 1 4.6 Mn naphthenate 0.10 14 16.08 23.34 Bitumen 1 5.2 Mn naphthenate 0.20 8 14.70 24.89 Bitumen 1 4.6 Mn benzoate 0.10 7 0.80 7.69 Bitumen 1 4.6 Mn benzoate 0.10 14 1.89 13.78 Bitumen 1 4.6 Mn tol. sulf. 0.10 7 1.87 13.87 Bitumen 1 4.6 Mn tol. sulf. 0.10 14 2.33 15.03 Bitumen 1 4.6 Mn caprylate 0.10 7 8.79 24.51 Bitumen 1 4.6 Mn caprylate 0.10 14 14.15 23.69 The results obtained were all determined using short miniature cores of sand-bitumen produced using Iraqi sand, The following results were obtained using the sand described in Example 1: Bitumen Bitumen content in “ Treatment Metal content £ based Hardening time at 45°C in days Strength kg/cm’ at 45°C at 22°C Bitumen 2* ♦ 5.0 7 (50°C) 0.17 2.81 Bitumen 2 * Bitumen ** Bitumen 5.0 according according Mn caprinate to Example 5 to Example 7 0.20 7 (50°C) 4.22 11.72 Table IX reveals that the use of all of the various manganese salts results in improved strength, in particular at elevated temperatures. The differences in effectivity are probably due to the different solubilities of the various salts.

Claims (10)

1. An asphalt composition consisting of bitumen and an organic manganese, cobalt and/or copper compound soluble in bitumen, characterized by a content of at least 85% by 5 weight of aggregates as well as a manganese, cobalt and/or copper concentration of 0.01 to 0.50% by weight, based on the bitumen.

2. An asphalt composition according to claim 1, which contains 90 to 98% by weight of aggregates. 10

3. An asphalt composition according to claim 1 or 2, which contains 0.05 to 0.20% by weight of manganese.

4. An asphalt composition according to claim 1 or 2, which contains 0.001 to 0.20% by weight of cobalt.

5. An asphalt composition according to claim 1 or 2 which 15 contains manganese and cobalt.

6. An asphalt composition according to claim 1, which has a penetration (determined according to the ASTM standard procedure D-5) of less than 400 at 25°C.

7. An asphalt composition according to claim 6, which has 20 a penetration between 40 and 300 at 25°C.

8. The asphalt composition according to claim 1 for use in road construction.

9. An asphalt composition according to claim 1, substantially as hereinbefore described with particular 25 reference to the accompanying Examples.

10. An asphalt composition according to claim 1, for use χ- Ιί in road construction, substantially as hereinbefore described.