WE CLAIM:
1. Bitumen/polymer composition comprising:
- bitumen,
- at least one elastomer, and
- at least one olefinic polymer adjuvant functionalized by at least glycidyl functional groups,
characterized in that:
• the elastomer is selected from thermally crosslinkable block copolymers of formula S-B1-B2, in which S represents a monovinylaromatic hydrocarbon block having a peak molecular weight of from 10 000 to 25 000, B1 is a polybutadiene block having a vinyl content of less than or equal to 15 mole percent, B2 is a polybutadiene block having a vinyl content of greater than or equal to 25 mole percent, the B1/B2 weight ratio is greater than or equal to 1:1, and in which the S-B1-B2 block copolymer has a peak molecular weight of from 40 000 to 200 000;
• the elastomer may also comprise at least one thermally crosslinkable block copolymer corresponding to the formula (S-B1-B2)nX in which each S represents a monovinylaromatic hydrocarbon block having a peak molecular weight of from 10 000 to 25 000, each B1 represents a polybutadiene block having a vinyl content of less than or equal to 15 mole percent, each B2 represents a polybutadiene block having a vinyl content of greater than or equal to 25 mole percent, n is an integer ranging from 2 to 6, and X is the residue of a coupling agent, in which the B1/B2 weight ratio is greater than or equal to 1:1, and the (S-B1-B2)nX block copolymer has a peak molecular weight which is from 1.5 to 6.0 times the peak molecular weight of the S-B1-B2 block copolymer;
and the elastomer/adjuvant weight ratio in the composition ranges from 15/1 to 2/1.
2. Composition according to Claim 1, in which the
S-B1 -B2/(S-B1 -B2)nX
weight ratio is greater than or equal to 1:1, preferably from 1:1 to 10:1, and better still from 1:1 to 4:1.
3. Composition according to Claim 1 or Claim 2, in which S represents styrene.
4. Composition according to any one of the preceding claims, which comprises from 0.5% to 20% by weight of elastomer relative to the total weight of the composition, preferably from 0.5% to 15%.

5. Composition according to any one of the preceding claims, which comprises from 0.05% to 2.5% by weight of olefinic polymer adjuvant relative to the total weight of the composition, preferably from 0.15% to 2%.
6. Composition according to any one of the preceding claims, in which the olefinic polymer adjuvant is selected from the group consisting of:
(a) random or block copolymers of ethylene and of a monomer selected from
glycidyl acrylate and glycidyl methacrylate, comprising from 50% to 99.7% by weight
of ethylene;
(b) random or block terpolymers of ethylene, of a monomer A selected from vinyl acetate and C1 to C6 alkyl acrylates or methacrylates and of a monomer B selected from glycidyl acrylate and glycidyl methacrylate, comprising from 0.5% to 40% by weight of units resulting from the monomer A and from 0.5% to 15% by weight of units resulting from the monomer B, the remainder being formed of units resulting from the ethylene; and
(c) copolymers resulting from the grafting of a monomer B, selected from glycidyl acrylate and glycidyl methacrylate, to a substrate consisting of a polymer selected from polyethylenes, polypropylenes, random or block copolymers of ethylene and of vinyl acetate and random or block copolymers of ethylene and of C1 to C6 alkyl acrylate or methacrylate, comprising from 40% to 99.7% by weight of ethylene, said grafted copolymers comprising from 0.5% to 15% by weight of grafted units resulting from the monomer B,
(d) mixtures of at least two compounds (a), (b) and (c).

7. Composition according to Claim 6, in which the olefinic polymer adjuvant is selected from random or block terpolymers of ethylene, of a monomer A selected from vinyl acetate and C1 to C6 alkyl acrylates or methacrylates and of a monomer B selected from glycidyl acrylate and glycidyl methacrylate, comprising from 0.5% to 40% by weight of units resulting from the monomer A and from 0.5% to 15% by weight of units resulting from the monomer B, the remainder being formed of units resulting from the ethylene.
8. Composition according to Claim 7, in which the olefinic polymer adjuvant is selected from random terpolymers of ethylene, of a monomer A selected from C1 to C6 alkyl acrylates or methacrylates and of a monomer B selected from glycidyl acrylate and glycidyl methacrylate, comprising from 0.5% to 40% by weight of units resulting from the monomer A and from 0.5% to 15% by weight of units resulting from the monomer B, the remainder being formed of units resulting from the ethylene.

9. Process for preparing a bitumen/polymer composition according to any one of
Claims 1 to 8, characterized in that the following are brought into contact, the
Operation being carried out at temperatures between 100°C and 200°C and with
stirring for a period of at least 10 minutes:
- bitumen,
- from 0.5% to 20% by weight of at least one elastomer,
- from 0.05% to 2.5% by weight of at least one olefinic polymer adjuvant,
- optionally additives.

10. Asphalt, characterized in that it comprises at least one bitumen/polymer composition according to any one of Claims 1 to 8, and mineral and/or synthetic fillers.
11. Bituminous mix, characterized in that it comprises at least one bitumen/polymer composition according to any one of Claims 1 to 8, aggregates, and optionally mineral and/or synthetic fillers.
12. Use of at least one bitumen/polymer composition as claimed in any one of Claims 1 to 8, for preparing a surface dressing, a hot bituminous mix, a warm bituminous mix, a cold bituminous mix, a cold-poured bituminous mix, an emulsion gravel, said binder being combined with aggregates and/or recycled milled products.
13. Use of at least one bitumen/polymer composition as claimed in any one of Claims 1 to 8, for preparing a waterproof coating, a membrane or a seal coat.