Effect of Silica Fume and Siliceous Fly Ash Addition on the Fracture Toughness of Plain Concrete in Mode i

Abstract

Nowadays, structural concretes should meet strict requirements such as: strength, durability, and resistance to adverse weather conditions and corrosion. Therefore, research on modifying concrete with mineral additives and chemical admixtures is conducted. Siliceous fly ash (FA) and silica fume (SF) are by-products of industrial processes and their application to the concrete mixtures can improve both parameters of composites, as well as greatly contributing to environmental protection. This paper presents the results of fracture toughness tests, specified at the Mode I fracture (tension at bending; opening mode), based on RILEM Draft Recommendations. The experiments were carried out after 28 days of curing of plain concrete, which consisting the following additives: 10% SF + 0% FA, 10% SF + 10% FA, 10% SF + 20%FA. To assess mechanics parameters compressive strength tests and fracture toughness tests were conducted. Fracture toughness tests were carried out on MTS 809 Axial/Torsional Test System.In our studies, the fracture toughness of the composites based on the experimental results of critical stress intensity factor - . Detailed analysis of the obtained results lead to conclusion that the combined addition of FA and SF clearly changes the fracture toughness according to the Mode I fracture.