Materials with the ability to restore their own functionality are a promising type of smart materials for road construction. The use of encapsulated functional modifiers is a common solution aimed at implementing self-healing technology. The paper presents general trends in the development of self-healing technology in the field of road materials. A mathematical interpretation of the destruction model of self-healing materials is proposed. The direction of technology development is proposed for the formulation of general requirements and quality indicators of self-healing materials for construction, characterizing the degree of their effectiveness depending on the conditions of use.

The comparative analysis of quality indicators of asphalt concrete and methods of their control is discussed in the present article. Classifications of modifiers for improving the quality of asphalt concrete are given. Novel nanoscale modifier for the improvement the resistance to climatic influences on asphalt is developed. The nanomodifier is based on sols of iron hydroxide and silicic acid. Nanomodification consists in processing of the mineral component by nanomodifier; such processing leads to the formation of nanoscale layer on the surface of the mineral carrier. As a mineral carrier we propose a highly porous mineral diatomite powder. The influence of the nanomodifier on the weathering resistance of asphalt concrete is investigated. Resistance to climatic influences was estimated by loss of strength after one nominal year of exposure. To simulate environmental impacts, an environmental chamber was used. The specimens were held in conditions that correspond to combination of summer and winter climate. One nominal year of exposure included 10 cycles of variable water saturation-drying at a temperature of 20 °C and 10 cycles of freezing-thawing (freezing was performed at –20 °C, thawing – at 20 °C). Saturation-drying and freezing-thawing duration was four hours. It was shown that by means of nanomodification the weathering resistance can be increased by 36 %.

New requirements for the operational reliability of roads make the utilization of polymer-modified bitumen (PMB) more common in road construction. The application of polymer-modified bitumen based on traditional technology for the production of asphalt mixtures is associated with technological and economic difficulties and does not provide proper adhesion to the mixture’s mineral components. In addition, the method of producing a binder over a long time at high process temperatures leads to increased aging, which significantly reduces the service life of the material in the pavement. This paper presents the results of studies on the effect of polymer–bitumen concentrate (PBC) consisting of styrene–butadiene–styrene, plasticizer, and surfactant on the bitumen characteristics. It has been established that the use of PBC in the bitumen binder leads to an increase in the temperature range of plasticity, softening temperature, elasticity, and cohesive strength with a decrease in the viscosity of the modified bitumen. With a complex modifier rational content of 8% by weight of bitumen, the temperature range of plasticity is 79 °C, and elasticity is 82%, which exceeds the parameters of the factory PMB-60 based on SBS polymer. Tests of binders using the Superpave method allow classifying the modified binder to the PG 64-28, which shows an increase in the temperature range of viscoelastic properties by 6 °C compared with the binder produced by traditional methods. Thus, the expediency of using a complex additive containing a polymer and surface-active substances (surfactants) that can be distributed in bitumen without the use of a colloid agitator and plasticizer has been proven to improve the quality of an organic binder.

The present study aims at experimentally and numerically investigating the effect an encapsulated healing agent on the mechanical characteristics of a stone mastic asphalt (SMA). As a healing agent a thiol-containing urethane AR-polymer is used in this study. In order to gain a numerical insight into mechanical behavior of the capsules in SMA, a micromechanical finite element modeling is employed. The developed model allows capturing the stresses induced in the capsules at different load cases applied to the SMA on macro-scale. Particular attention is paid presently to the numerical evaluation of the local stress state that arises around capsules during compaction, operation, and also during crack initiation. SMA mixtures with various volumetric contents of healing capsules were manufactured and the capsules survival during mixture production was evaluated based on X-Ray Computed Tomography measurements. The effect of capsules on the self-healing properties of asphalt mixtures has furthermore been examined with repeated compressive strength tests. The obtained experimental results indicate that the absolute majority of capsules survive mixture production, and that their addition increases the SMA strength recovery during the healing period. The experimental and numerical results concerning capsules breakage are found to be in reasonable agreement. The developed micromechanical model may thus potentially provide a useful tool for optimization of capsules mechanical properties in order to improve their survival during mixture production as well as their timely activation.

The effect of the formulation factors of calcium-alginate suspension preparation on the properties of calcium-alginate microcapsules was studied. The maximum useful volume of the reducing agent is set it was established, up to 93.8% of the total volume, in microcapsules, from the beating, to retain 2.31% sodium alginate and 10.5% reducing agent. The proposed mechanism for the formation of calcium-alginate capsules, which occurs due to shrinkage during the drying of a single drop of suspension, breaking the emulsion and forming an integral shell with a nucleus from the reducing agent.

The possibility of using an active polymer component as a reducing agent for the implementation of the self-healing of asphalt concrete technology is considered in the paper. It was found that the thiol-containing urethane AR-polymer is an effective reducing agent capable of replacing traditional reducing agents based on hydrocarbon oils. AR-polymer is a reducing agent that can be encapsulated using alginate technology. The volume of the reducing agent in the capsule is limited to a maximum allowable value of 83±1%, which can be achieved using the alginate technology. It has been proven that the type and properties of the reducing agent does not affect the change in the mechanical properties of the capsules. The strength of the capsules decreases by 2…6% for different ratios of RA/A when the content of sodium alginate decreases from 3.33% to 2.08%. The greatest efficiency of capsules with the maximum content of AR-polymer as a reducing agent and higher strength is achieved when using emulsions containing 2.50% sodium alginate at RA/A = 5.0 ± 0.2.