Abstract: The invention relates to bituminous binder compositions containing in the proportion of 0.5 to 2% by weight of the bitumen used, a mixture of polynitrogenous compounds such as those obtained by reacting polyalkylene polyamines having the general structure: R -- NH (CH.sub.2 -- CH.sub.2 -- CH.sub.2 -- NH).sub.n -- H with formic acid while removing the reaction water. The main component consists of a tetrahydropyrimidine substituted on nitrogen by means of a long linear chain comprising one or a plurality of amine groups having the general structure: ##STR1## wherein R is a saturated or unsaturated linear hydrocarbon comprising 8 to 22 carbon atoms, n is an integer from 2 to 5 and p another integer equal to (n - 1), that is from 1 to 4.