Abstract
The paper presents the results of tests on the effect of the low calcium fly ash (LCFA) addition, in the amounts of: 0% (LCFA-00), 20% (LCFA-20) and 30% (LCFA-30) by weight of cement, on fracture processes in structural concretes. In the course of the experiments, compressive strength of concrete and fracture toughness for: I (tensile), II (in-plane shear) and III (anti-plane shear) models of cracking were measured. The tests determined the effect of age of concretes modified with LCFA on the analyzed parameters. The experiments were carried out after: 3, 7, 28, 90, 180 and 365 days of curing. Fracture toughness of concretes was determined in terms of the critical stress intensity factors: , , and then a generalized fracture toughness was specified. The obtained results are significant for the analysis of concrete structures subjected to complex loading. The properties of composites with the additive of LCFA depend on the age of the concrete tested. Mature concretes exhibit high fracture toughness at 20% additive of LCFA, while the additive of LCFA in the amount of 30% weight of cement has a beneficial effect on the parameters of concrete only after half a year of curing.
Highlights
The principles of sustained development and ecology are essential in the design of concrete compositions
On the basis of the comprehensive fracture toughness tests, in which a portion of the binder was replaced with active pozzolanic low calcium fly ash, it can be concluded that: 1
The low calcium fly ash additive in the amount of 20 and 30% of mass of cement significantly affects the change of generalized fracture toughness in tension, shear and torsion
Summary
The principles of sustained development and ecology are essential in the design of concrete compositions. It is connected with the fact that for many years the cement industry has been trying to follow the sustainable development strategy, whose main purpose is the reduction of environmental pollutions, primarily the reduction of CO2 emission as well as the usage of waste materials from other industries. Along with technical and legal means, economic instruments are crucial components in the field of utilizing waste as substitutes of primary materials In this regard, for over several dozen years, the development of a new generation of concrete composites, i.e., environmentally friendly concrete composites, was followed by a significant increase of the production of concrete mixtures containing supplementary cementitious materials (SCMs), of different classes and types [15], often having pozzolanic properties, e.g., [16]. As the concretes with these additives are frequently used as a traditional or modern useful building materials, they require a thorough examination
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