Preliminary High-Temperature Tests of Textile Reinforced Concrete (TRC) (original) (raw)
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Journal of Composites Science, 2021
Textile-reinforced concrete (TRC) is a promising composite material with enormous potential in structural applications because it offers the possibility to construct slender, lightweight, and robust elements. However, despite the good heat resistance of the inorganic matrices and the well-established knowledge on the high-temperature performance of the commonly used fibrous reinforcements, their application in TRC elements with very small thicknesses makes their effectiveness against thermal loads questionable. This paper presents a state-of-the-art review on the thermomechanical behavior of TRC, focusing on its mechanical performance both during and after exposure to high temperatures. The available knowledge from experimental investigations where TRC has been tested in thermomechanical conditions as a standalone material is compiled, and the results are compared. This comparative study identifies the key parameters that determine the mechanical response of TRC to increased tempera...
2012
This Research Committee, for three years from 2009 to 2011, conducted research on the latest experimental findings and analytical methods with regard to relations between concrete properties and load resistance/deformation properties of structures on fire, as well as literature research concerning fire resistance test methods, and inspections/diagnosis/measures of structures damaged by fire, and then summarized the present technical status of the design/construction/maintenance management of refractory concrete structures (including concrete products). In addition, the Committee made proposals such as "tentative proposal on diagnosis and repair/reinforcement plan for fire-damaged concrete structures", and identified future issues.
Thermomechanical Behavior of Textile Reinforced Cementitious Composites Subjected to Fire
Applied Sciences
The mechanical behavior of textile reinforced cementitious composites (TRC) has been a topic of wide investigation during the past 30 years. However, most of the investigation is focused on the behavior under ambient temperatures, while only a few studies about the behavior under high temperatures have been conducted thus far. This paper focused on the thermomechanical behavior of TRC after exposure to fire and the residual capacity was examined. The parameters that were considered were the fiber material, the thickness of the concrete cover, the moisture content and the temperature of exposure. The specimens were exposed to fire only from one side and the residual strength was measured by means of flexural capacity. The results showed that the critical factor that affects the residual strength was the coating of the textiles and the law of the coating mass loss with respect to temperature. The effect of the other parameters was not quantified. The degradation of the compressive str...
BEHAVIOUR OF CONCRETE WHEN EXPOSED TO FIRE AND RETROFITTING
Behaviour of concrete structures in fire relies upon several elements. These consist of change of material property because of fire, temperature distribution in the elements of the buildings, details of reinforcement, severity of exposure and duration. This document discusses the outcomes of increased temperatures on a some of the steel and concrete. The goal of this is to provide a top level view of results at improved temperature of the behaviour of concrete elements and systems. The main goal of this research work is to summarize the properties of concrete at rising temperature. The properties of conventional concrete and the properties of high strength concrete subjected to elevated temperature are compared. Fire reaction of concrete structural participants is depending on the thermal, mechanical, and deformation properties of concrete. These properties vary drastically with temperature and additionally rely on the composition and characteristics of concrete batch mix in addition to heating rate and different environmental situations. The variation of thermal, mechanical, deformation, and spalling residences with temperature are defined.
Textile Reinforced Mortar at High Temperatures
Applied Mechanics and Materials, 2011
Textile reinforced mortar (TRM) is a composite made by fine grained matrix and glass fabric reinforcement. The main advantages of such a material are the orientation of the reinforcement in the direction of tensile forces, no concrete cover requirement against corrosion and the capability to produce thin and light weight elements. Special attention was given by researchers to the time dependent loss in strength of AR-glass reinforcement embedded in a cement based matrix. Some research has shown durability models to calculate the amount to the strength loss related to material, humidity and temperature. Nevertheless, the behaviour of TRM when exposed to high temperature requires further investigations. A suitable experimental programme was planned to investigate the behaviour of TRM when exposed to high temperatures. Uniaxial tensile tests were performed after thermal cycle on 400 mm x 70 mm specimens 6 mm thick, reinforced with 2 layer of AR-glass fabric. Several thermal thresholds (20, 200, 400 and 600°C) were considered for the mechanical characterization in fire condition. Thermal cycles were performed in an oven considering a heating rate of 30°C/h up to the maximum temperature and by a cooling branch at 15°C/h after a stabilization phase at maximum temperature.
Concrete is a construction material composed of cement as well as other cementatious materials such as fly ash and slag content, aggregate (generally a coarse aggregate such as gravel, limestone, or granite, plus a fine aggregate such as river sand), water, and chemical admixtures. Apart from its excellent properties, concrete shows a rather low performance when subjected to tensile stress. Another rather recent development is steel fiber reinforced concrete (SFRC). The concept of using fibers as reinforcement is not new. Fibers have been used as reinforcement since ancient times. As fiber reinforced concrete (FRC) represents a complex material composed of various components with different response to high temperature, to determine its behavior and mechanical properties in fire is a demanding task. Namely, the information on steel fiber reinforced concrete (SFRC), synthetic fiber reinforced concrete and hybrid (steel + synthetic) fiber reinforced concrete have been gathered from various contributions published up to date. The mechanical properties including the melting point and ignition point of fibers affect significantly the properties of concrete composites with addition of fibers.
The behavior of members during fire, as part of a structure, is different from that exhibited by small unrestrained samples. Full scale fire tests are costly and, because fire cannot be controlled, data is sometimes lost during testing. In this investigation 1/5 scale model frames were prepared from normal strength, high strength, fiber reinforced, latex modified and lightweight aggregate concrete. After heating to 800 °C, with either a superimposed load or without any loading, the frames were assessed using Schmidt hammer and ultrasonic pulse velocity. The effect of fire on compressive strength was studied on companion cubes made from the same concrete types. It was found that the deterioration suffered by a member depends not only on the type of concrete, from which the frame was made of, but also on the type of member and stress state. The Schmidt hammer test is not suitable for assessing concrete after a fire, mainly because fire reduces the rebound number greatly and this in turn makes readings obtained using the conventional hammer invalid. Pulse velocity measurements reflected the internal damage suffered by members, but the results need to be interpreted in light of materials properties, restraint, visual examination and stress states of members within structures. Pulse velocity-compressive strength relationship was profoundly affected by fire. For example, a UPV reading of 3 km/sec would indicate a compressive strength of either 382 or 82 kg/cm 2 , depending on whether the concrete has been or has not been subject to elevated temperature, respectively. This needs to be taken into account in recommended procedures for assessing structures after fire. INTRODUCTION Deterioration of concrete during exposure to elevated temperature, like that encountered during a fire, is the result of many complex factors including: a) The thermo-mechanical process. The temperature gradients induce gradients of thermal dilation, which in turn generate tensile stresses perpendicular to the heated surface. Local strain incompatibilities occur between the cement paste and aggregate. The aggregate dilate until they are chemically degraded, whilst the paste shrinks due to drying. b) The thermo-hydral process. This is associated with the transfer of mass (water in liquid or vapor phases and air). The partial evaporation of water due to temperature increases the vapor pressure in concrete pores. This pressure leads to mass transfer towards both the heated surface and the cooler center of the elements. The center of the sample may become with time saturated with condensed vapor and pressure is generated [1]. c) Phase transformations. Free moisture evaporates at 100 °C. At 350 °C calcium hydroxide is decomposed into lime and water vapor. At 500 °C, quartz aggregate is transformed accompanied by 1% increase in volume. At 600 to 700 °C cement paste starts to decompose and finally at 800 °C limestone aggregates calcine, leading to expansion and loss of carbon dioxide [2].
Behaviour of concrete structures in fire
2007
This paper provides a" state-of-the-art" review of research into the effects of high temperature on concrete and concrete structures, extending to a range of forms of construction, including novel developments. The nature of concrete-based structures means that they generally perform very well in fire. However, concrete is fundamentally a complex material and its properties can change dramatically when exposed to high temperatures.
Strength Studies on Different Grades of Concrete Considering Fire Exposure
American Journal of Civil Engineering
Concrete is generally strong in compression and weak in tension also it resist against fire. Cement concrete is a complex mixture of different materials, for which the properties may alter in different environmental conditions. The behavior of concrete is depends on difference in temperatures and its mix proportions. The principle effects in the concrete due to elevated temperatures are loss in compressive strength, loss in weight or mass, change in color and spalling of concrete. The objective of this research attempt was to prove experimentally the effects on the behavior of concrete under elevated temperatures of different grades (M20, M40 and M60) of concrete. The compressive strength was determined at different temperatures, thus providing scope of determining loss in strength. In addition, effects on strength under cooling for different grades of concrete were studied. The specimens were kept in oven at certain temperatures (200°C, 400°C, 600°C, and 800°C) for 1 hour at constant temperatures. Non-destructive testing (NDT) methods, i.e. Rebound hammer test was adopted to study the changes in surface hardness of concrete specimens subjected to elevated temperatures.
Concrete under Fire: Damage Mechanisms and Residual Properties
The paper firstly presents the basic damage mechanisms of concrete under fire attacks, and then the experimental study of the residual compressive strength and durability properties of normal and high strength concretes made of materials available in Hong Kong after exposure to high temperatures up to 800°C. The effects of post-fire-curing on the strength and durability recovery of fire-damaged concrete were also investigated. It was found that concretes containing fly ash and blast furnace slag gave the best performance particularly at temperatures below 600°C as compared to the pure cement concretes. Explosive spalling occurred in most high strength concretes containing silica fume. The high-strength pozzolanic concretes showed a severe loss permeability-related durability than the compressive strength loss. The post-fire-curing resulted in substantial strength and durability recovery and its extent depended upon the types of concrete, exposure temperature, method and the duration of recuring.