Asphalt binder for porous pavements
View Patent ↗An asphalt binder is provided, comprising 85 to 97.5 parts by weight of a bitumen and 16 to 2.5 parts by weigh of a polymer composition, wherein the polymer composition comprises: (i) from 2 to 8, preferably from 3 to 6 parts by weight of a styrenic block copolymer having at least two blocks of monovinylaromatic hydrocarbon (A) and at least one block of a conjugated diene (B), wherein the block copolymer composition has a vinyl content of at least 25% by weight, preferably from 25 to 40% by weight, based on the total diene content; (ii) from 0 to 5, preferably from 1 to 3 parts by weight of a styrenic diblock copolymer having one block of monovinylaromatic hydrocarbon (A) and one block of a conjugated diene (B); and (iii) from 0.5 to 3, preferably from 1 to 2.5 parts by weight of an ethylene-vinyl acetate copolymer, wherein the weight ratio of (i)+(ii):(iii) is from 2:1 to 6:1, preferably from 3:1 to 4:1. In addition, an asphalt mix is provided comprising 2 to 8 parts by weight of the asphalt binder of the present invention and 98 to 92 parts by weight of gap-graded aggregate or open-graded aggregate material. Furthermore, a porous pavement is claimed, produced from the open or gap-graded mixes, by compacting the asphalt mix mentioned above.
1. An asphalt binder comprising 85 to 97.5 parts by weight of a bitumen and 16 to 2.5 parts by weigh of a polymer composition, wherein the polymer composition comprises:
(i) from 2 to 8 parts by weight of a styrenic block copolymer having at least two blocks of monovinylaromatic hydrocarbon (A) and at least one block of a conjugated diene (B), wherein the block copolymer composition has a vinyl content of at least 25% by weight, by weight, based on the total diene content;
(ii) from 1 to 5 part by weight, of a styrenic diblock copolymer having one block of monovinylaromatic hydrocarbon (A) and one block of a conjugated diene (B); and
(iii) from 0.5 to 3 parts by weight of an ethylene-vinyl acetate copolymer, wherein the weight ratio of (i)+(ii):(iii) is from 2:1 to 6:1.
2. An asphalt binder as claimed in claim 1 , wherein the bitumen has a PEN value below about 300 dmm as measured by ASTM Method D5 (at 25° C.).
3. An asphalt binder as claimed in claim 2 , wherein the bitumen has a PEN value in the range of from 25 to 300 dmm.
4. An asphalt binder as claimed in claim 1 , wherein component (i) is a block copolymer having an apparent molecular weight in the range of from 100 to 500 kg/mol.
5. An asphalt binder as claimed in claim 4 , wherein component (i) has a bound styrene content of within the range of 20 to 40% mass; an apparent molecular weight in the range of 120 to 200 kg/mole, and a vinyl polybutadiene content of at least 35%.
6. An asphalt binder as claimed in claim 1 , wherein component (ii) is a styrenic diblock copolymer, with optionally no more than 30% triblock copolymer contained therein, based on styrene and butadiene and having an apparent molecular weight in the range of from 75 to 225 kg/mole.
7. An asphalt binder as claimed in claim 6 , wherein component (ii) is a clear linear diblock copolymer based on styrene and butadiene, with a bound styrene content of within the range of 30 and 32% mass, and a diblock content of about 78%.
8. An asphalt binder as claimed in claim 1 , wherein Component (iii) is an ethylene-vinyl acetate copolymer having a melt flow index of from 0.3 to 33 g/10 minutes (ASTM D1238), and a vinyl acetate content in the range of from 20 to 50% wt, based on the copolymer.
9. An asphalt binder as claimed in claim 8 , wherein component (iii) has a vinyl acetate content of about 24% wt and a melt index of about 1.8 g/10 minutes (ASTM D1238).
10. An asphalt binder as claimed in claim 1 , wherein the asphalt binder exhibits a PEN value in the range of 10 to 100 dmm (ASTM method D5, at 25° C.).
11. An asphalt mix comprising 2 to 8 parts by weight of the asphalt binder of claims 1 and 98 to 92 parts by weight of gap-graded aggregate or open-graded aggregate material.
12. An asphalt mix according to claim 11 , comprising porphyry aggregate.
13. A porous pavement produced from the asphalt mix of claim 1 , by compacting this asphalt mix.
14. An asphalt binder as claimed in claim 3 , wherein the styrenic block copolymer is from 3 to 6 parts by weight of the composition, the styrenic diblock copolymer is from 1 to 3 parts by weight of the composition, ethylene-vinyl acetate copolymer is from 1 to 2.5 parts by weight of the composition, and the weight ratio of (i)+(ii):(iii) is from 3:1 to 4:1.
15. An asphalt binder as claimed in claim 3 , wherein the bitumen has a PEN value in the range of from 30 to 250 dmm.
16. An asphalt binder as claimed in claim 15 , wherein the bitumen has a PEN value in the range of from 40 to 200 dmm.
17. An asphalt binder as claimed in claim 5 , wherein component (i) has a bound styrene content of within the range of 28.5 to 32.5% mass and an apparent molecular weight in the range of 138 to 162 kg/mole.
18. An asphalt binder as claimed in claim 6 , wherein the styrenic diblock copolymer has an apparent molecular weight in the range of from 100 to 200 kg/mole.
19. An asphalt binder as claimed in claim 10 , wherein the asphalt binder exhibits a PEN value in the range of from 20 to 75 dmm (ASTM method D5, at 25° C.