Drahomír Novák; David Lehký; Radomír Pukl
Abstract
Methods and software tools used to identify the material parameters of high-performance cementitious composites are presented. The aim is to provide techniques for the advanced assessment of the mechanical fracture properties of these materials, and the subsequent numerical simulation of components/structures ...
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Methods and software tools used to identify the material parameters of high-performance cementitious composites are presented. The aim is to provide techniques for the advanced assessment of the mechanical fracture properties of these materials, and the subsequent numerical simulation of components/structures made from them. The paper describes the development of computational and material models utilized for efficient material parameter determination with regards to a studied composite. This determination is performed with the help of experimental data from four-point bending tests. The data is used in inverse analysis based on artificial neural networks. Sensitivity analysis plays an important role in the process. It is a part of a complex methodology for the statistical and reliability analysis of structures made of high-performance cementitious composites. The procedure also utilizes statistical simulation of the Monte Carlo type for the preparation of a training set for the artificial neural network utilized in the material parameter identification process. In the case of fiber-reinforced concrete, the simulation mainly includes tensile strength, modulus of elasticity and the parameters of the tensile softening model.
Ivan Janotka; Michal Bačuvčík; Lukáš Húlek; Peter Paulík
Abstract
During the research study focused on 100 years, old concrete bridges in Slovakia an unexpected observation was made. Two bridges were found with a very low carbonation depth under an ordinary cement-based render coat used at the time of its construction for aesthetic reasons. The average measured value ...
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During the research study focused on 100 years, old concrete bridges in Slovakia an unexpected observation was made. Two bridges were found with a very low carbonation depth under an ordinary cement-based render coat used at the time of its construction for aesthetic reasons. The average measured value by phenolphthalein test was less than 2 mm after more than 100 years of service life in exposure class XC3 of EN 206. The remaining investigated bridges, from this period of construction, exposed to the same environment and made of concrete of comparable quality, showed significantly higher carbonation depths. Low carbonation depth, can be explained by the presence of a thin (2-4 mm) layer of the protective render coat (PRC) applied to concrete surface around 100 years ago. The place, where the PRC was of good quality was almost impermeable and the carbonation of the concrete underneath was even 0 mm. A narrow free space filled with the carbonates can cause increased non-permeability of the thin PRC creating thus the best condition for the built limestone-based (anti-carbonation) barrier with the ability to dramatically reduce CO2 penetration into the beneath concrete over time. This article is focused on the probable explanation of this phenomenon.
Rajiv Gupta; Ayub Ahmed; Sasidhar Kumar Reddy Ithepalli
Abstract
Large quantities of ash are generated every year by the various manufacturing industries as a waste by-product. This study aims to utilize waste by-product in concrete and to reduce its cost by replacing cement in parts with bottom ash. This research presents the results of the experimental investigations ...
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Large quantities of ash are generated every year by the various manufacturing industries as a waste by-product. This study aims to utilize waste by-product in concrete and to reduce its cost by replacing cement in parts with bottom ash. This research presents the results of the experimental investigations to study the use of bottom ash as partial replacement for cement in concrete and masonry units. Bottom ash is the coarser material, which falls into furnace bottom and constitutes about 20% of total ash content. The strength development for various percentage replacements (5-15%) of cement with bottom ash has been compared to control specimens of concrete and masonry.
Aldo G. P
Abstract
The effect of gamma-irradiated SiO2 nanoparticles on microstructure and mechanical properties of concrete was studied. SiO2 nanoparticles were irradiated at different irradiation doses (10, 50, 100 and 150 kGy) and then analyzed by transmission electron microscopy, Fourier-transform infrared and Raman ...
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The effect of gamma-irradiated SiO2 nanoparticles on microstructure and mechanical properties of concrete was studied. SiO2 nanoparticles were irradiated at different irradiation doses (10, 50, 100 and 150 kGy) and then analyzed by transmission electron microscopy, Fourier-transform infrared and Raman spectroscopies. Such ionizing treatment allowed improving the physical interactions between the nanoparticles and the cementitious matrix. Compressive strength and dynamical modulus of elasticity on concrete samples were determined. The results show significant improvements on these mechanical features when irradiated SiO2 nanoparticles were added; having up to 127 % of improvement for compressive strength and a 24 % for elasticity modulus when comparing to non-irradiated nanoparticles-reinforced concrete. Such improvements are related to the microstructural changes of concrete analyzed by Infrared spectroscopy and observed by scanning electron microscopy. Research shows important advances in the development and understanding of microstructure for nanoreinforced concrete with irradiated SiO2 nanoparticles.
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