Anti-stripping agents in asphalts

Anti-stripping agents are also used in the production of hot or warm asphalts (bituminous mixtures) in order to improve the adhesion between bitumen and hydrophilic aggregates in the presence of water. The addition of anti-stripping agent not only preserves the cohesion, stability and stiffness of the asphalts when wet but also prevents ravelling. 

Asphalts treated with anti-stripping agent, apart from increasing their retained stability, showed better behaviour in bitumen ageing (Anderson et al. 1982 Christensen and Anderson 1985). Furthermore, some anti-stripping agents decrease the susceptibility of the bitumen to temperature variations (Anderson et al. 1982). 

The determination of susceptibility to stripping in the presence of water or affinity between aggregate and bitumen and thus the necessity of anti-stripping agent usage is carried out by various laboratory tests. In fact, by carrying out these tests, the hydrophilia of the aggregate 

The tests may be conducted on loose or on compacted bituminous mixture. In the first case, the affinity between aggregates and bitumen or aggregate s hydrophilia is determined directly. In the second case, the moisture susceptibility of the compacted bituminous mixture (specimen) is specified and the susceptibility to stripping or aggregate/bitumen affinity or aggregate s hydrophilia is determined indirectly. 

The tests that belong to the first category are (a) the rolling bottle method, (b) the static method and (c) the boiling water stripping method. These tests are described in EN 12697-11 (2012). 

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