Air-entrainment as an alternative to polypropylene fibers and its effect on the compressive strength of concrete at high temperatures

Holan, Jakub; Novák, Josef; Štefan, Radek

doi:10.1088/1757-899x/596/1/012032

Cited by 4 publications

(3 citation statements)

References 14 publications

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“…Several researchers have studied the effects of air entrainment on the properties of concrete at ambient and elevated temperatures [ 115 , 116 , 117 ]. As shown in the previous sections, the permeability of concrete samples greatly affects the performance of concrete spalling.…”

Section: Influencing/mitigating Factorsmentioning

confidence: 99%

Heat-Induced Spalling of Concrete: A Review of the Influencing Factors and Their Importance to the Phenomenon

et al. 2022

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Heat-induced spalling in concrete is a problem that has been the subject of intense debate. The research community has, despite all the effort invested in this problem, few certain and definitive answers regarding the causes of and the way in which spalling happens. A major reason for this difficulty is the lack of a unified method for testing, which makes comparing data from various studies against each other a difficult task. Many studies have been performed that show the positive effects of using synthetic micro-fibres, such as polypropylene (PP). The mechanism with which PP fibres improve heat-induced spalling resistance in concrete, however, remains a subject of debate. This paper, therefore, looks at the work that has been performed in the field of spalling (particularly spalling of self-compacting concrete (SCC)). Influencing factors are identified and their links to each other (as reported) are discussed. A particular emphasis is put on discussing the role of PP fibres and how they improve the behaviour of high-performance concrete (HPC) at elevated temperatures. A brief summary of the reviewed papers are provided for each of the influencing factors to help the reader navigate with ease through the references. An introduction to heat-induced spalling and the common causes (as reported in the literature) is also included to highlight the wide range of theories trying to explain the spalling phenomenon.

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Section: Influencing/mitigating Factorsmentioning

confidence: 99%

Heat-Induced Spalling of Concrete: A Review of the Influencing Factors and Their Importance to the Phenomenon

et al. 2022

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“…A similar problem during vibration can occur in the case of concrete, which requires a higher amount of air in fresh concrete with respect to the final required properties, whether it is freeze thaw resistance or resistance to high temperatures or spalling of concrete [1].…”

Section: Introductionmentioning

confidence: 95%

The Analysis of the Intensity and Vibration Time on the Mechanical Properties of Hardened Concrete

Trtík

Chylík

Fládr

et al. 2021

SSP

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In order to achieve optimal physical and mechanical properties of hardened concrete, it is necessary to determine the right intensity and vibration time of fresh concrete during casting. Since concrete is considered as a polydisperse substance and various aggregate grains move randomly during vibration, it is very difficult to describe this stochastic phenomenon using exact physical equations and it is more advantageous to apply an experimental approach to verify the effects of vibration on fresh concrete. The effect of vibrations on fresh concrete increases the speed gradient of individual grains and thus reduces the viscosity of the cement paste. The intensity of vibration is determined mainly by the frequency, amplitude and centrifugal force of the eccentric of the vibrating machine. The optimal vibration time is generally considered to be the "minimum required". Insufficient vibration caused by an unsuitable vibrating machine or a short vibration time can result in insufficient compaction of the aggregate grains, non-release of accumulated air from the fresh concrete mixture, formation of cavities or poor-quality casting of parts of the structure with a higher degree of reinforcement. Vibration with excessive intensity or time can also be considered dangerous. The over-compaction of concrete is most often demonstrated by segregation of aggregates. The presented research deals with the determination of the optimal time and intensity of vibration of fresh concrete mixture to achieve the required physical properties of concrete, i.e. high compressive strength and modulus of elasticity of hardened concrete while reducing the negative effects of vibration, especially segregation of aggregates.

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“…The rate of the strength development of concrete was affected by the W/C ratio as well as the cement type and temperature [14,15]. The mechanical properties of air-entrained concrete at elevated temperatures were studied [16]. The air entrainment had an adverse effect on the compressive strength of concrete at elevated temperatures.…”

Section: Introductionmentioning

confidence: 99%

Temperature Effect on the Compressive Behavior and Constitutive Model of Plain Hardened Concrete

El‐Zohairy

Hammontree

et al. 2020

Materials

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Concrete is one of the most common and versatile construction materials and has been used under a wide range of environmental conditions. Temperature is one of them, which significantly affects the performance of concrete, and therefore, a careful evaluation of the effect of temperature on concrete cannot be overemphasized. In this study, an overview of the temperature effect on the compressive behavior of plain hardened concrete is experimentally provided. Concrete cylinders were prepared, cured, and stored under different temperature conditions to be tested under compression. The stress–strain curve, mode of failure, compressive strength, ultimate strain, and modulus of elasticity of concrete were evaluated between the ages of 7 and 90 days. The experimental results were used to propose constitutive models to predict the mechanical properties of concrete under the effect of temperature. Moreover, previous constitutive models were examined to capture the stress–strain relationships of concrete under the effect of temperature. Based on the experimental data and the proposed models, concrete lost 10–20% of its original compressive strength when heated to 100 °C and 30–40% at 260 °C. The previous constitutive models for stress–strain relationships of concrete at normal temperatures can be used to capture these relationships under the effect of temperature by using the compressive strength, ultimate strain, and modulus of elasticity affected by temperature. The effect of temperature on the modulus of elasticity of concrete was considered in the ACI 318-14 equation by using the compressive strength affected by temperature and the results showed good agreement with the experimental data.

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Air-entrainment as an alternative to polypropylene fibers and its effect on the compressive strength of concrete at high temperatures

Cited by 4 publications

References 14 publications

Heat-Induced Spalling of Concrete: A Review of the Influencing Factors and Their Importance to the Phenomenon

Heat-Induced Spalling of Concrete: A Review of the Influencing Factors and Their Importance to the Phenomenon

The Analysis of the Intensity and Vibration Time on the Mechanical Properties of Hardened Concrete

Temperature Effect on the Compressive Behavior and Constitutive Model of Plain Hardened Concrete

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