Three samples of bituminous material with different softening temperatures of 321, 332, and 356.4 K were obtained by the method of chemical modification of tar with formaldehyde using sulfuric acid as a catalyst. The determination of the group hydrocarbon composition was carried out for the raw materials of the modification process (tar) and the resulting bitumens. An FTIR study of the obtained groups of hydrocarbons (oil, resins, and as-phaltenes) was also carried out. The structural transformations were investigated and a possible chemistry of the tar modification process with formaldehyde was proposed.

Nowadays, the most common ways to dispose of acid tars and paper production waste are
burial or incineration, but it is ecologically and economically expedient to use such waste in building
materials. A new variant of filler aggregate—wastepaper sludge ash (paper production waste) and a
chemical activator for filler aggregates—acid tar (oil-refining industry waste) is proposed. Elemental
and mineralogical compositions of wastepaper sludge ash for comparison with commodity limestone
mineral powder are established. Chemical activation of wastepaper sludge ash and limestone mineral
powder was carried out and the wetting properties of the obtained materials were investigated
by means of primary and neutralized acid tar. The physical and mechanical properties of stone
mastic asphalt samples with different filler aggregate variants were studied. The possible chemical
transformations in stone mastic asphalt using limestone mineral powder and wastepaper sludge ash
activated by acid tar are shown. The possibility of replacing traditional limestone mineral powder
with industrial wastepaper sludge ash has been proven, and the effectiveness of activating filler
aggregates by acid tar has been confirmed. It was established that acid tar as an activator for filler
aggregates does not require neutralization because stone mastic asphalt, in this case, demonstrates
better properties compared to acid tar neutralization. As a result of our research, the application
of wastepaper sludge ash is possible as a filler aggregate for stone mastic asphalt. And to obtain
improved stone mastic asphalt characteristics, wastepaper sludge ash is required to activate 5 wt.%
acid tar.

A literature review of the five main theories describing the interaction mechanisms in the bitumen/aggregate system was conducted: theory of weak boundary layers, mechanical theory, electrostatic theory, chemical bonding theory, and thermodynamic theory (adsorption theory). The adhesion assessment methods in the bitumen/aggregate system are described, which can be divided into three main groups: determination of adhesion forces for bitumen with different materials, determination of bitumen resistance to the exfoliating action of water with different materials, and determination of adhesion as a fundamental value (contact angle measurements, interfacial fracture energy, adsorption capacity and others). It is proposed to evaluate the quality of adhesive interaction in the bitumen/aggregate system in two stages. The authors recommend using the adhesion determination methods for these two stages from the second group of methods the determination of bitumen resistance to the exfoliating action of water with different materials. In the first stage, the adhesion in the bitumen/aggregate system is determined by an accelerated technique in which the used bitumen binder and mineral material are considered as test materials. After the first stage, there are positive results in the second tests on compacted mixtures (indirect tensile strength test, Modified Lottman indirect tension test, immersion-compression test, and Hamburg wheel tracking test).

Phenolformaldehyde resins were obtained by polycondensation of concentrated phenols with formaldehyde in the presence of hydrochloric acid. Concentration of phenols is carried out by treating the phenolic fraction of coal tar with an aqueous solution of sodium hydroxide followed by neutralization of water-soluble phenolates with hydrochloric acid. The kinetic dependences of resin yield and softening temperature on the duration of the process at 333, 353, and 373 K were obtained. The order of the reaction was determined and the effective activation energy of this process was determined by a graphical method. In the interval 333-373 K for polycondensation reactions, the equation of the dependence of the resin yield on the temperature and duration of the process was obtained.