Papers by Keyword: High Performance Concrete (HPC)

Abstract: Permeability of concrete is a good indicator of the risk of explosive spalling, concrete with low permeability is more prone to explosive spalling. To study explosive spalling of concrete, experimental tests on the concrete permeability have been carried out at ETH. The influences from temperature and moisture content have been investigated. The permeability of concrete is found to increase with the temperature and to decrease with moisture content. Based on the test results, a permeability model has been proposed. The explosive spalling has been predicted and an engineering boundary permeability for the liability to spalling is recommended to be 2 × 10^-17 m² for a concrete slab heated according to ISO fire curve. The boundary permeability is influenced by moisture content, tensile strength and heating rate.

Abstract: Nanotechnology proved to be a useful tool that can significantly improve the mechanical properties of ultra-high performance concrete. This paper presents the results of a long-term research which is focused on the influence of SiO₂ nanoparticles on the mechanical properties of high performance concrete. Three types of HPC specimens with a weight content of 0%, 1% and respectively 3% silica nanoparticle were prepared for flexural and compressive tests. SEM analysis was done in order to understand the effect of silica nanoparticle dispersion inside the cement matrix. The aim of this paper was to investigate the nanoparticles dispersion and how it affects concrete’s mechanical properties.

Abstract: Fire resistance of concrete structures could be improved by add of polypropylene fibres in to the concrete mixture in butch from 1 to 2 kg per 1 m³ of fresh concrete. This method is effective, but it is not possible to use it for existing concrete and existing reinforced concrete structures. The new method which has good potential for fire protection of existing structures is based on creation of capillary pore and micro cracks system, which allowed water vapour evaporate from concrete. This study deals with determination of appropriate temperature in which is created adequate network of capillary pores and micro cracks which has no influence on strength and durability of the concrete. The formation of macro cracks and bigger pores could cause rapid reduction of compressive and tensile strength, decrease of resistance to aggressive substances and decrease of the frost resistance. The high performance concrete (HPC) has very low porosity, which can cause explosive spalling while the water vapour tries to evaporate from concrete structure during the fire. The HPC concrete has high compressive strength and high density. The HPC samples were exposed to temperatures 150, 250, 350 a 450°C, and after cooling down to normal ambient were carried out tests to define changes in porosity by mercury porosimetry, mass looses and compressive strength changes. The heated HPC concrete is regaining humidity into its structure from surrounding atmosphere, which can cause rehydratation of some chemical compounds. [1] For verification of these hypotheses the HPC samples were kept in water storage for 4 weeks and then tested.

Abstract: In civil engineering, steel reinforced concrete is currently still the most widely used composite material. For broad spectrum of utilization is the most important combination of a high compressive and tensile strength [1]. The increasing demand for subtle concrete elements gave impetus to the development of the new materials for the reinforcement of concrete which are non-corrodible and thus do not need such a thick coating layer-technical textiles. These composite materials are known under the title Textile Reinforced Concrete – TRC. The current research reported the use of AR glass fibers reinforced material for HPC and comparison with other reinforced materials.