Abstract
The study examines a methodology based on the assessment of factors which further influence properties of concrete, that is its physical and mechanical characteristics analysis. The methodology is based on the research results obtained in the Samara School of Material Engineering and previously developed by the authors themselves. Its essence is based on the study of concrete destruction processes with account of existing rules of fracture mechanics. The researchers merged the energy conception of A.A. Griffiths with the kinetic theory of S.N. Zhurkova and developed a mathematical apparatus capable of modeling the conditions of external influence on concrete. They also estimated "Rebindera effect" while applying external load from the described types of external influence. They determined three stages in the course of destruction development depending on quantity and quality of initial defects. The first stage of destruction occurs at the micro level, the destruction is negligible. At the second stage cracks begin to fuse and already influence on change of values of concrete stress-strain properties. Finally, the third stage is "direct fracture" when the main cracks are formed dividing the specimen into separate fragments not capable of carrying the external load. The work reveals parameters and divide them into two groups. These parameters have a significant influence on the nature and kinetics of the destruction processes, respectively. The authors introduce a criterion of concrete crack resistance named "the length of the reduced crack". This criterion represents the total length of all surfaces of destruction at a single width of a crack. The proposed method can be applied with the use of non-destructive acoustic methods and destructive mechanical methods. Approbation of this methodology showed sufficient reliability and authenticity of the proposed indicator as a criterion of crack resistance.
Highlights
IntroductionThe researchers of various departments of the Academy of Construction and Architecture of Samara state technical university are engaged in the development of methods for evaluating the physico-mechanical characteristics of various materials [1-5] and the optimal design of structures from various materials [6-28]
The researchers of various departments of the Academy of Construction and Architecture of Samara state technical university are engaged in the development of methods for evaluating the physico-mechanical characteristics of various materials [1-5] and the optimal design of structures from various materials [6-28].Numerous studies carried out in the field of destruction of brittle materials, including concrete, have shown that the latter are destroyed due to the development of cracking processes
Studies of the destruction processes of concrete carried out by the authors for a number of years [29-31] have shown that the nature and kinetics of concrete destruction processes are affected by two types of characteristics: the initial parameters of the concrete structure and the kinetic characteristics of the processes of its destruction
Summary
The researchers of various departments of the Academy of Construction and Architecture of Samara state technical university are engaged in the development of methods for evaluating the physico-mechanical characteristics of various materials [1-5] and the optimal design of structures from various materials [6-28]. In concrete with any structure, there are defects in the form of microcracks and pores that appeared in it in the process of formation. These defects cause the development of cracks and adsorption of a sufficient amount of moisture on their surface. With a further increase in the load, flat cracks of various sizes are formed due to the intergrowth of microcracks in macrocracks. The latter lead to the destruction of the material, the loss of its operational properties and the inability to perceive external impact
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