Effects of elevated temperatures on properties of concrete (original) (raw)

The Effect of Elevated Temperatures on the Behavior of Concrete Material

International Journal for Research in Applied Science & Engineering Technology (IJRASET), 2023

The purpose of this study was to provide an overview of the effect of elevated temperature on the behavior of concrete materials. The effects of elevated temperatures on the properties of common portland cement concretes and manufacturing materials are summarized. The effect of elevated temperature on conventional concrete, GGBS concrete and BFS concrete is considered and the performance is compared with the strength of conventional concrete. Concrete in case of an unexpected fire, the properties of the concrete will change after the fire. The building must be designed to withstand high temperatures and also mainly fire. When exposed to high temperatures, such as during a fire, the mechanical properties of concrete such as strength, modulus of elasticity and volume stability are significantly reduced. Concrete structure is exposed to high temperatures, it degrades in many different ways, such as color, compressive strength, elasticity, and high temperature affects concrete density and surface appearance. Keywords: High Strength concrete, Self compacting Concrete, Quartz powder, Quartz sand , Crushed basalt, Split tensile strength etc. I. INTRODUCTION The behavior of concrete at high temperatures is influenced by several factors, such as the speed of temperature rise and the type and stability of the aggregate. Sudden changes in temperature can cause spalling and cracking due to thermal shock, and aggregate expansion can also damage concrete [1]. High temperatures also affect the compressive strength of concrete. Above 212ºF, the cement paste begins to dry out (lose chemically bound water of hydration), which gradually weakens the bond between the paste and the paste material. The temperature that concrete often reaches can be determined by observing the color changes in the aggregate. For example, limestone materials turn pink when their temperature reaches about 570º F, which can cause a significant reduction in compressive strength [2]. The thermal properties of concrete are more complex than most materials, because the performance of portland cement-based materials at high temperatures is very difficult, and it is difficult to characterize concrete as a composite material with different properties in its composition, but its properties. also depends on. to ensure moisture and porosity. Exposure of concrete to high temperatures affects its mechanical and physical properties. The changes in properties are due to three processes that occur at high temperatures [3]: phase transformation (eg, loss of free water at approximately 100 ˚C, decomposition of calcium hydroxide at approximately 50 ˚C, and quartz crystal transformation at 573 ˚C. ˚C from C temperature-to form), pores structure development (eg, pore volume and surfaces increase to the temperature of an accidental fire, etc.) causes severe damage and undergoes a series of changes and reactions, thus causing a gradual degradation of the cement gel structure, reduced durability, increased tendency to drying and shrinkage, structural cracks and associated overall discoloration [4]. Fire safety measures of structural parts are measured by fire resistance, which is the time during which a structural part lasts in terms of structural integrity, stability and temperature permeability. Concrete generally offers the best fire resistance properties of all building materials. This superior fire resistance is due to the constituents of concrete (ie, cement and aggregates) which, when chemically combined, form an essentially inert material with low thermal conductivity, high heat capacity, and slower loss of strength with temperature. It is this slow rate of heat transfer and loss of strength that allows concrete to act as an effective fire protection not only between adjacent rooms, but also to protect itself against fire damage [5]. The behavior of a concrete structural part exposed to fire depends partly on the thermal, mechanical and deformation properties of the concrete from which it is composed. As with other materials, the thermophysical, mechanical and deformation properties of concrete change significantly in the temperature range associated with construction fires. These properties vary with temperature and depend on the composition and properties of the concrete. The strength of concrete significantly affects its properties both at room and high temperatures. The properties of high strength concrete (HSC) vary with temperature unlike normal strength concrete (NSC). This variation is more pronounced in the mechanical properties, which are affected by strength, humidity, density, heating rate, amount of silica fume and porosity [6].

Performance of Different Concrete Types Exposed to Elevated Temperatures: A Review

Materials

Concrete is a heterogeneous material that consists of cement, aggregates, and water as basic constituents. Several cementitious materials and additives are added with different volumetric ratios to improve the strength and durability requirements of concrete. Consequently, performance of concrete when exposed to elevated temperature is greatly affected by the concrete type. Moreover, post-fire properties of concrete are influenced by the constituents of each concrete type. Heating rate, days of curing, type of curing, cooling method, and constituents of the mix are some of the factors that impact the post-fire behavior of concrete structures. In this paper, an extensive review was conducted and focused on the effect of concrete constituents on the overall behavior of concrete when exposed to elevated temperature. It was evident that utilizing fibers can improve the tensile capacity of concrete after exposure to higher temperatures. However, there is an increased risk of spalling due...

Behaviour of Concrete Subjectecd to Defferrents Elevated Temperatures

2021

In this research, the influence of aggregates sizes, cover to reinforcement, Concrete age, and exposure period on the mechanical properties of normal concrete (NC) subjected to different elevated temperatures will be investigated. The total number test specimens of 100 standard 150mm cubes including control specimens were used to evaluate the residual compressive strength of concrete under different elevated temperatures and exposure time. The cubes specimens was cured for one, three, seven, fourteen and twenty eight days, respectively (1, 3, 7, 14, 28 days). The cubes were subjected to the following varying temperature: 100oc, and 300oc. For each of the temperature above, the cubes were subjected to that temperature for the duration of 30mins. The results generally, show that, combined aggregates concrete has better fire performance than the concrete made using single aggregates size. In the case of concrete made using single size aggregates. M2 perform better than M4, which show t...

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.

An Experimental Investigation on Effect of Elevated Temperatures on M35 grade Concrete

In the event of sudden fire break out, the concrete elements such as columns, beams etc. are subjected to extreme temperatures. The assessment of their performance after fire becomes necessary to decide upon its fitness and required repair measures. Hence, it is important to understand the changes in the concrete properties due to its exposure to extreme temperatures. It is important to know the effect of elevated temperature on the properties of concrete. In this project thesis work experimental investigation is carried out to study the effects of elevated temperatures on the compressive strength of normal concrete and on concrete by partial replacement of cement with various percentages of fly ash. In the present study a concrete mix M35 and is taken. In the normal concrete, cement is replaced with (0, 5, 10, 15, 20 and 25%) fly ash.The compressive strength of concrete with various percentages of fly ash (0%to 25%) are subjected to temperatures (400 to 6000C), for different time periods (30 and 60min) which were tested for 28 days and 56 days of curing. The samples are cured in water and later exposed to various temperatures with various time periods. After heating the samples in electrical furnace to the desired temperatures .They are allowed to cool to the room temperatures and tested under compression. The average of the readings obtained is recorded and presented in various tables. This study shows that the compressive strength of fly ash (0%to 10%) concrete is more than the normal concrete at room temperatures and elevated temperatures and also compared to compressive strength of fly ash (15%to 25%) concrete.

Impact of High Temperatures on Multiblended Concretes

2015

Concrete gets affected either by the service environment to which it was exposed or physical – chemical causes due to the reasons residing within. The reduction in engineering properties of concrete such as strength, elastic modulus, and durability occur due to variety of chemical and physical causes such as corrosion of reinforcements, sulphate and sea water attack, carbonation, freezing and thawing, thermal effects, abrasion, and nature of materials (e.g., type of aggregate and cement blend). In case of accidental fire, concrete subject to high temperature which leads to severe deterioration and it undergoes a number of transformations and reactions, thereby causing progressive breakdown of cement gel structure and consequent loss in its load-bearing capacity, reduced durability, increased tendency of drying shrinkage, structural cracking, and associated aggregate colour changes. The behaviour of concrete in fire depends on its mix proportions and constituents and is determined by...

Effect of High Temperature on Compressive Strength of Concrete

This work was carried out to assess the effect of high temperatures on compressive strength of concrete. Effect of fire on concrete is a relatively less explored area because of the lesser use of RCC structures in Europe/USA as compared to steel structures. Ninety concrete cubes of 150 mm size, divided equally over three different grades of design mix concrete viz. M: 30, M: 25 & M: 20 were cast. After 28 days' curing & 24 hours' air drying, the cubes were subjected to different temperatures in the range of 200°C to 800°C, for two different exposure times viz. 1 hour & 2 hours in an electric furnace. The heated cubes were cooled at room temperature for 24 hours & then subjected to cube compressive strength test. Results revealed fairly robust performance up to 500°C, with strength coming down only slightly. Up to this stage, the fire affected structural members remain serviceable although the factor of safety would come down. Affected structure/ structural members would require minor repairs & patchwork to recuperate. At or @ 650°C, the fall in concrete strength would be a cause for concern. Major retrofitting might be required. At or beyond 650°C, concrete stood completely decimated.

Mechanical and Postfire Structural Performances of Concrete under Elevated Temperatures

Civil Engineering Journal

This article investigates the mechanical and postfire structural performances of concrete under elevated temperatures (200°C, 400°C, 600°C, and 800°C) after 7 and 28 days of concrete curing. The main objective of this study is to evaluate the post-fire behavior of concrete structures and how their modulus of elasticity values influence their structural parameters. Mechanical studies, namely, the compressive strength, splitting tensile strength, and flexural strength, were performed on cubes, cylinders, and prism beams under normal and elevated temperatures. Non-destructive tests, like rebound hammer and ultrasonic pulse velocity, were also conducted on concrete cubes to obtain the strength of concrete before and after heating the specimens. Microstructural studies, in particular, scanning electron microscope and energy dispersive x-ray spectroscopy, were done to analyze the changes in the chemical composition of concrete under the effect of the temperatures. The weight loss of the c...

An experimental study on the performance of M100 concrete at elevated temperature

Journal of Structural Engineering, 2016

the higher strength in concrete could be achieved by using one of the following methods or a combination of some or many of the following: • Higher cement content • Reducing water cement ratio • Better workability and hence better compaction "High-Performance Concrete" has been introduced into the construction industry. the american concrete Institute (ACI) defines high-performance concrete as concrete meeting special combinations of performance and uniformity requirements that cannot always be achieved routinely when using conventional constituents and normal mixing, placing and curing practices. The specification of high-strength concrete generally results in a true performance specification in which the performance is specified for the intended application, and the performance can be measured using a well-accepted standard test procedure. Exposed to elevated temperature causes physical changes including large volume changes due to thermal dilations, thermal shrinkage and creep related to water loss. the volume changes can result in large internal stresses and lead to micro-cracking and fracture. Elevated temperatures also cause chemical and micro-structural changes such as water migration, increased dehydration, interfacial thermal incompatibility and the chemical decomposition of hardened cement past and aggregate. in general, all these changes decrease the stiffness of concrete and increase the irrecoverable deformation. Various investigations indicate that the strength and stiffness of concrete decrease with increasing temperature, exposure time and thermal cycles. fire is one of the most severe conditions when the structures are exposed for it. Mechanical properties such as compressive, split tensile and flexural strengths are considerably reduced during exposure, potentially resulting in undesirable structural failures. therefore, the residual properties of concrete are still important in determining the load carrying capacity and the further use of fire damaged structures. Previous investigations have shown that concrete type, concrete strength, aggregate types, test types, maximum exposure temperature, exposure time, type and amount of mineral admixtures and type and amount of fibres affect the residual properties of concrete after exposure to high temperatures. When the concrete is subjected to elevated temperature, the incompatibility of thermal deformations within the constituents of concrete initiates cracking. Based on the limited amount of experimental data available to date, it has been found that the effects of elevated temperatures on the mechanical properties of high strength concrete vary with a number of factors including the test methods, permeability of concrete, the types of aggregate used and moisture content. Objectives

www.ijsrp.org Behaviour of Concrete Subjected To High Temperature

2015

Abstract- With the mode toward urbanization, rate of construction and hazards related to it has increased to high extend. One such major source is Fire accidents. Structure can undergo fire accident, but because of this the structure cannot be denied neither abandoned. To make a structure functionally viable after the damage due to fire has become a challenge for the civil engineering community. The problem is where to start and how to proceed. The root for such problem lies in the strength parametric study of component material that are use in construction industry. One such major item is concrete, which have very distinct chemical and physical properties because of its elemental components. The study done in this paper is basically for normal M20 grade of concrete subjected to various temperature and thus the changes in properties are marked and highlighted. This paper aims to show the behavior of concrete at various temperature and changes in its compressive strength and physical...