Investigation of Integral and Differential Characteristics of Variatropic Structure Heavy Concretes by Ultrasonic Methods

Abstract

The article develops methods and methodology for experimental studies of centrifuged and vibro-centrifuged concrete products of annular cross-section. They assess the real variatropy of the structure and confirm the correctness of the accepted research. An original technique for experimental studies of the variatropy of the cross-sections of vibrated, centrifuged and vibro-centrifuged concretes is proposed to determine their integral (common) and differential (differing in layers) strength and strain characteristics and deformation diagrams. It has been proved that with vibro-centrifugation it becomes possible to obtain concretes with improved structure and higher characteristics compared with centrifugation and vibration techniques. Experimental studies of the differential characteristics of centrifuged and vibro-centrifuged concretes under compression and tension revealed that the outer layer of concrete had the best characteristics after centrifugation and vibro-centrifugation, and the inner layer had the worst ones. The three-layer model of the variatropic structure for centrifuged and vibro-centrifuged concrete has been experimentally confirmed. The concrete of the outer layers had the highest strength and modulus of elasticity and the least deformability; the concrete of the inner layers had the lowest strength and modulus of elasticity and the highest deformability; and the concrete of the middle layers had average characteristics. The deformation diagrams of centrifuged and vibro-centrifuged concretes were also differentiated by layers, confirming the variatropy of the structure of such concretes. The deformation diagrams for the outer concrete layer demonstrated the highest strength; the diagrams for the inner concrete layer showed the lowest strength; and the diagrams for the middle concrete layer corresponded to mean characteristics.

Influence of Mechanochemical Activation of Concrete Components on the Properties of Vibro-Centrifugated Heavy Concrete

“…For the manufacture of vibro-centrifuged samples, an experimental laboratory vibrocentrifuge was used, a schematic diagram of this installation and a detailed description are presented in [37]. In addition, in [13,32,37] the mode of molding of prototypes of vibro-centrifuged concretes is described.…”

“…The technique for manufacturing prototypes of vibrated, centrifuged and vibrocentrifuged concretes is presented in [37].…”

“…For the manufacture of vibro-centrifuged samples of annular section, heavy concrete of class B30 was designed in accordance with previously developed recommendations [13,32,37].…”

Optimization of Composition and Technological Factors for the Lightweight Fiber-Reinforced Concrete Production on a Combined Aggregate with an Increased Coefficient of Structural Quality

“…The main aim of the research presented in this article was to develop a dispersedreinforced lightweight concrete [24][25][26][27][28] that includes both heavy and light aggregate [29]. Thus, a part of the traditional heavy aggregate from dense rocks was replaced by an analogue of lightweight porous filler with equal volume but that was significantly lighter in weight.…”

“…Additionally, the aim of this work is to identify and develop proposals for a rational formulation and technology for new materials with an increased coefficient of constructive quality (CCQ). In the scientific and technical literature, CCQ means the ratio of the strength and density characteristics [24][25][26][27][28].…”