Effect of Elevated Temperature on Mechanical Properties of Limestone, Quartzite and Granite Concrete (original) (raw)
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Fire and Materials, 2015
This paper presents the results of an experimental study on the behaviour of high-performance concretes after high temperature exposure. The high temperature exposure is related to the potential risk of fire, and mechanical properties analysis is needed afterwards to assess the residual strength of the material. The results presented in the paper show the properties evolution of four concretes made with four different aggregate types: basalt, granite, dolomite and riverbed gravel. The mix compositions allow comparisons, because the cement paste and mortar compositions and their volumes remain the same for all the four concretes. Moreover, the aggregate particle size distribution was chosen to be quasi identical so that this factor does not affect the concrete behaviour. The decrease of tensile strength value with the increase of temperature is more pronounced than compressive strength reduction thus, the exponential and power function equations were proposed to describe f tT -f cT relationship. The change of modulus of elasticity in relative values is similar, although the initial values of modulus are different and correspond to the aggregate type.
Influence of the nature of aggregates on the behaviour of concrete subjected to elevated temperature
An experimental study is carried out on concretes composed of three different types of aggregates: semi crushed silico-calcareous, crushed calcareous and rolled siliceous. For each aggregate type, two water/cement ratios (W/C), 0.6 and 0.3 are studied. Aggregates and concrete specimens were subjected to 300, 600 and 750 °C heating–cooling cycles. We analyse the evolution of thermal, physical and mechanical properties of concrete in terms of behaviour and physical characteristic evolutions of aggregates with temperature. The study of thermal behaviour of aggregates showed the importance of initial moisture state for the flints. The crystallisation and microstructure of quartz play an important role in the thermal stability of siliceous aggregates. The residual mechanical behaviour of concrete varies depending on the aggregate and the influence of aggregates is also dependent on paste composition. This study allowed to better understand the influence of chemical and mineralogical characteristics of aggregates on the thermomechanical behaviour of concrete.
Effect of elevated temperature on physico-mechanical properties of blended cement concrete
Construction and Building Materials, 2011
This study aims to investigate the effect of thermally treated temperatures up to 800 °C on the physical properties, microstructure and phase composition of pozzoloanic cement pastes. Pozzolanic cement was prepared from three different pozzolans, namely silica fume (SF), ground granulated blast-furnace slag (WCS) and ground clay bricks (GCB). The samples were subjected to heat treatment at the rate of 10 o C/min, and then kept for 3 hours from 200 up to 800 o C, then cooled to the room temperature in the furnace switched off. It was concluded that the cement paste M.10 (70 % OPC + 10 % WCS + 10 % GCB + 10 % SF) is the optimum mix which gives a higher compressive strength up to 600 °C. It was also found that M.10 has more hydration products than other mixes. The microstructure shows a massive dense closed texture, with the lower number of voids and pore size, with the formation of inner fibers and crystalline needle like CSH hydrated which is responsible for the increase in compressive strength up to 500 °C. 158 thereby causing progressive breakdown of cement gel structure, reduced durability, increased tendency of drying shrinkage, structural cracking and associated aggregate colour changes [1].
Effects of elevated temperatures on properties of concrete
Concrete material in structures is likely exposed to high temperatures during fire. The relative properties of concrete after such an exposure are of great importance in terms of the serviceability of buildings. This paper presents the effects of elevated temperatures on the physical and mechanical properties of various concrete mixtures prepared by ordinary Portland cement, crushed limestone, and river gravel. Test samples were subjected to elevated temperatures ranging from 200 to 1200 1C. After exposure, weight losses were determined and then compressive strength test was conducted. Test results indicated that weight of the specimen significantly reduced with an increase in temperature. This reduction was very sharp beyond 800 1C. The effects of water/cement (w/c) ratio and type of aggregate on losses in weight were not found to be significant. The results also revealed that the relative strength of concrete decreased as the exposure temperature increased. The effect of high temperatures on the strength of concrete was more pronounced for concrete mixtures produced by river gravel aggregate. The results of the physical and mechanical tests were also combined with those obtained from differential thermal analysis, and colour image analysis.
2017
Concrete is a building material commonly used in the construction structures. There are many reasons why concrete is preferred. One of these reasons is fire resistance of concrete. Concrete is not a combustible material, but it behaves differently under high temperature. Aggregates constitute an important part of concrete volume. Differences in aggregate properties significantly affect the performance of the concrete during heating. Differences in these properties also cause cracks and breakages in parts of the concrete and significant losses in adherence. When we look at these effects, we have seen that high temperature creates a threatening environment for concrete. Therefore, it is necessary to investigate the behavior of the concrete caused by the high temperature. In this study, we investigated the effect of high temperature on the compressive strength of concrete specimens prepared using different aggregate types. For this purpose, 10 × 10 × 10 cm and 15 × 15 × 15 cm cube samp...
Effect of aggregate and water to cement ratio on concrete properties at elevated temperature
Fire and Materials, 2016
Properties of concrete during and after fire exposure are of significant importance for serviceability and rehabilitation of buildings. This article presents an experimental investigation on the effects of elevated temperature on physical and mechanical properties of concrete made using two types of locally available coarse aggregates (crushed and wadi aggregates) and water-to-cement (w/c) ratios of 0.50 and 0.70. Temperature range from 200°C to 1000°C was used with intervals of 200°C. Test results indicate that the weight of concrete reduced with increase in temperature. This reduction was quite sharp beyond 800°C. Minor spalling was observed in concrete with Wadi aggregates at temperatures beyond 800°C. The results also reveal that relative strength of concrete decreased as exposure temperature increased. The effect of high temperatures on the strength of concrete was more pronounced in concrete with Wadi aggregates. w/c ratio had insignificant effect on weight loss after exposure to elevated temperatures, but it increased the rate of strength degradation irrespective of aggregate type used. Comparison of results with Eurocode (EC-2) and American Concrete Institute (ACI) standards indicate that the concrete with both aggregate types can satisfy the limits of siliceous aggregates set by ACI, but concrete made with Wadi aggregates with w/c ratio of 0.50 failed to satisfy limits of EC-2.
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].
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...
2019
In this study, the effects of the elevated temperature on concrete specimens prepared with different aggregate types were investigated. For this purpose, 4 different series were prepared by using CEM I 42,5 (N) type Portland Cement and four different types of aggregates (basaltic crushed aggregate, stream aggregate, limestone and pumice as lightweight aggregate). 100 mm and 150 mm cube concrete samples were prepared for each series. When reached the specified curing age, prepared each concrete specimen was taken from the curing pool and exposed to high temperatures of 300 ºC, 600 ºC and 900 ºC respectively. Control specimens of each series were stored at room temperature. The compressive strengths, ultrasonic pulse velocity and the adherence strength of the concrete samples exposed to these temperatures were examined. At the end of this study, the compressive strengths of the series exposed to high temperature are compared. It is observed that the series which is produced with basaltic crushed aggregate is least affected and the series which is produced with lightweight aggregate is the most affected from the elevated temperature. Pull-out tests were carried out to the all prepared series and it was found that the adherence strength between the concrete and the reinforcement decreased as the temperature increased.