Non-destructive monitoring methods and continuous monitoring systems based on them are crucial elements of modern systems for the management and maintenance of assets which include reinforced concrete structures. The purpose of our study was to summarise the data on the most common sensors and systems for the non-destructive monitoring of reinforced concrete structures developed over the past 20 years. We considered systems based on electrochemical (potentiometry, methods related to polarisation) and physical (electromagnetic and ultrasonic waves, piezoelectric effect, thermography) examination methods. Special focus is devoted to the existing sensors and the results obtained using these sensors, as well as the advantages and disadvantages of their setups or other equipment used. The review considers earlier approaches and available commercial products, as well as relatively new sensors which are currently being tested.

The reference polymers and polymers with molecular imprints of carboxylic acids (MIPs-CA) — propionic (MlP-Propionic) and butyric (MIP-Butyric) acids — were synthesized on the surface of piezoelectric sensors using aromatic compounds by the non-covalent imprinting method. Molecularly imprinted polymer (MIP) is a polymer produced through molecular imprinting, which leaves cavities in the polymer matrix with affinity to a chosen "template" target molecule. The values of the imprinting factor and selectivity coefficients were calculated to assess the ability of MIPs-CA to recognize the target molecules. It is shown that the sensors modified by the molecularly imprinted polymers exhibit high selectivity for the acid that was a template during their synthesis. The detection limits for propionic and buty ric acids are 7.40 x 10~6 and 8.81 x 10-6 g/dm3, respectively. Correctness of the carboxylic acid determination in model solutions was verified in the spike/recovery tests. The relative standard deviation is less than 10%. The modified piezoelectric sensors were tested in analysis of the intermediate products of edible ethanol production (distillate of fermentation mixture, epyurat, bottom liquids of columns). The correctness of the determination of carboxylic acids in liquids was evaluated using an Agilent Technological 7890B GC Systems. The difference in the results of acid determination between both methods (piezoelectric sensor and chromatography-mass spectrometry) does not exceed 6%. The modified piezosensors expand the potential of rapid determination of carboxylic acids in the intermediate products of ethyl alcohol production.

Molecularly imprinted polymers were synthesized as selective coatings of piezoelectric sensors for determination of carboxylic acids in the intermediate fractions of rectified ethanol. Molecularly imprinted polymers were obtained by reorganizing and imidizing polyamic acid chains in N,N-dimethylformamide in the presence of a template by the non-covalent imprinting method. The ability of molecularly imprinted polymers to recognize the target templates was evaluated by studying their sorption properties in comparison with non-imprinted polymers using direct conductometry in static mode. The equilibrium time of polyimide and molecularly imprinted polymers for acetic, propionic, butyric acids is in the range of 40 - 80 min. The type of sorption isotherm of acetic acid is characteristic of polymeric materials with micropores. During the sorption of acetic acid at low concentrations, the solvent-ethanol strongly competes with the adsorbed substance due to the close molecular sizes and the presence of group -OH. The type of sorption isotherms of propionic and butyric acids refers to the monomolecular adsorption. The sorption of carboxylic acids by molecularly imprinted polyimide is carried out mainly due to the formation of hydrogen bonds between carboxyl groups of adsorbent and adsorbate. According to the sorption data, the degrees of extraction, distribution coefficients, and imprinting factor values were calculated (IF = 3.0-15.1). It is shown that the molecularly imprinted polymers for carboxylic acids have better sorption ability to acid molecules than their non-imprinted polymers. At the same time, the molecularly imprinted polymer for butyric acid has the highest sorption capacity. Thus, the possibility of using molecularly imprinted polymers for carboxylic acids based on polyimide as selective coatings of piezosensors has been established.

ПРИМЕНЕНИЕ ПОЛИМЕРА С МОЛЕКУЛЯРНЫМИ ОТПЕЧАТКАМИ НА ОСНОВЕ ПОЛИИМИДА В КАЧЕСТВЕ СЕЛЕКТИВНОГО ПОКРЫТИЯ ПЬЕЗОСЕНСОРА ДЛЯ ОПРЕДЕЛЕНИЯ ОЛЕИНОВОЙ КИСЛОТЫ В МАСЛАХ

The marine environment is highly corrosive for mild and low alloy steels. This study aimed to enhance the corrosion resistance of the AH36 steel in a saline medium by coating it with a copper particles reinforced polyaniline (PANI) layer. PANI and Cu particles were grown on the steel surface by electrodepositing methods. Firstly, PANI was electropolymerized in the presence of oxalic acid, followed by the electrodeposition of Cu particles at different deposition times. The coating showed a well-distribution of Cu particles in the polymer matrix and excellent adhesion. Furthermore, the Cu particles and PANI-coated steels exhibited corrosion resistance significantly in the saline medium compared to the bare substrate and pristine PANI-coated samples. The improved corrosion protection of a Cu@PANI coating on the AH36 steel could contribute to forming a physical barrier by filling Cu particles on the PANI pores.