Technical Committee on Concrete Properties under High Temperature and Fire Resistance of Concrete Structures (original) (raw)
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DURABILITY PERFORMANCE OF CONCRETE STRUCTURES EXPOSED TO FIRE
The present work looks into the developments related to understanding the impact of extreme heat on concrete and concrete-based forms of different nature. Being made of this material implies that any building should naturally resist fire; yet, concrete is, in eessence, is very complicated complex and likely to shift in terms of features when experiencing extreme heat. Fire, basically, reduces compressive strength, as well as spalling in concrete-the latter being described as forced removal of substances from the surface of any piece of fabrication. Despite vast amounts of data on these two effects, better structured investigations are to be carried out. The way buildings react to such fires in actual scenarios, in itself, is a different issue because of the interactions occuring among various components, effect of complicated small-scale events in theri entirety, and also the spatial and temporal changes in heat such as the cooling stage after the fire recedes. There have been advancements in the field of simulating thermo-mechanical patterns; however, how to handle intricate behaviours like hygral effects and spalling remains a question. On top of all this a major shortage exists in the amount of infoirmation related to actual structures for the purpose of validation, while precious other data can be obtained if we focus on behavior of concrete formations in such actual fire events.
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.
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.
THE BEHAVIOUR OF CONCRETE STRUCTURES IN FIRE
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. The principal effects of fire on concrete are loss of compressive strength, and spalling – the forcible ejection of material from the surface of a member. Though a lot of information has been gathered on both phenomena, there remains a need for more systematic studies of the effects of thermal exposures. The response to realistic fires of whole concrete structures presents yet greater challenges due to the interactions of structural elements, the impact of complex small-scale phenomena at full scale, and the spatial and temporal variations in exposures, including the cooling phase of the fire. Progress has been made on modelling the thermomechanical behaviour but the treatment of detailed behaviours, including hygral effects and spalling, remains a challenge. Furthermore, there is still a severe lack of data from real structures for validation, though some valuable insights may also be gained from study of the performance of concrete structures in real fires.
2015
Concrete is a composite construction material consisting basically of a binder, aggregates, water and with or without admixture to modify either or both its physical and chemical properties. The rate at which concrete structures especially buildings are gutted by fire hazards is on the increase and this has adverse effect on the strength, hence, the need to assess the post fire structural strengths of Normal Strength Concrete(NSC). NSC of grade 50 was produced and cast into specimens of sizes 150mm cubes and 100mm x 100mm x 500mm reinforced concrete beams. The concrete cubes and beams were subjected to elevated cyclic thermal loadings after 7, 14 and 28 days of curing, while the rate of heating was maintained at 1 o C/min until the target temperature of (100, 130, 160, 200 and 250) o C where attained and this was maintained for one hour and then allowed to cool at 1 o C/min to room temperature of 32 o C. Unstressed Residual Uniaxial Compressive Test (URUCT and Flexural Stre...
The Effect of Fire on the Strength of Concrete Material
2021
Structural members exposed to fire may damage considerably, lose their durability, and even collapse due to the failure of the members. This work presents the results of an experimental investigation of the effect of fire on the strength of concrete. Cylindrical and beam specimens were prepared and burnt in the fire for one hour. In both cases, two systems were followed for cooling the samples, (i) natural cooling in the air (ii) forced cooling in the water. Afterwards, the compressive and flexural strength of the specimens were determined. The result shows that the strength of concrete was considerably reduced due to burning in fire. The compressive strength of cylindrical specimens was decreased by 44% and 60%, respectively, for the natural and forced cooling of the specimens. In the case of beam samples, the flexural strength was decreased60% and 69%, respectively, for the natural and forced cooled specimens. This research also reveals that the specimen cooled in air showed bette...