Evaluation of Aging of Reinforced Concrete Structures by Laser-Induced Breakdown Spectroscopy of Reinforcement Corrosion
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Journal of Applied Spectroscopy, Vol. 87, No. 5, November, 2020 (Russian Original Vol. 87, No. 5, September–October, 2020)
EVALUATION OF AGING OF REINFORCED CONCRETE STRUCTURES BY LASER-INDUCED BREAKDOWN SPECTROSCOPY OF REINFORCEMENT CORROSION PRODUCTS A. S. Bryukhova,a A. A. Kuznetsov,a I. V. Seliverstova,b A. M. Popov,b T. A. Labutin,b* and N. B. Zorovb
UDC 543.42:621.375.826
Laser-induced breakdown spectroscopy (LIBS) is considered as a method for elemental analysis of concrete in situ. However, the content of chlorine responsible for corrosion of the iron reinforcement may be lower than the LIBS sensitivity needed to detect corrosion in the initial stage. This is especially true for portable LIBS systems without gating and signal amplification. The use of analytical signals of elements in reinforcement corrosion products (Fe, Mn, Cr) when they emerge on the concrete surface is proposed to detect corrosion. It was found that signals of Fe, Mn, and especially Cr could be reliably registered using LIBZ-200 only on surface areas painted with corrosion products. Keywords: laser-induced breakdown spectroscopy, corrosion, concrete structures. Introduction. The trolley network (TN) is the most important part of the system of interrelated devices of an electric railroad. It operates under severe climatic and operating conditions. Corrosion of the steel reinforcement is the main reason for the loss of strength of reinforced concrete. The reinforcement is subjected to the action of various aggressive media and factors (chlorides, sulfates, nitrates, and other salts), significant environmental temperature drops, precipitation, spills, cable heating, etc. [1]. Strict requirements are applied to the reliability of the network because it has no backup. One of the main components of the network is the pole that suspends and holds the network devices. The movement of trains is disrupted if a pole falls and breaks the network cables [2]. The total number of TN poles on all Russian railroads as of 2017 was 1.738 million, of which 91.5% were reinforced concrete poles (1.59 million). Therefore, attention must be paid to diagnosing the condition of the TN poles. Methods for diagnosing the condition of TN reinforced concrete poles have several deficiencies [3]. An inductive method is limited by excavation of the pole, external electromagnetic field effects, the inability to diagnose through the reinforcing framework, the thickness of the protective layer, attachment firmness of the sensor, and determination of corrosion from indirect parameters. Acoustic and electrochemical methods determine the presence of corrosion using indirect parameters. A vibration method does not determine the presence and degree of corrosion. Chloride ions are hazardous for corrosion of reinforcing rods in concrete because they destroy the passive film of the reinforcement and lead to the development of corrosion. Accumulation of NaCl in concrete pores causes destruction because the NaCl forms a crystal dihydrate that occupies 2–3 times more volume than t
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