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Article
Publication date: 20 February 2020

Daniel Paul Thanaraj, Anand N. and Prince Arulraj

The purpose of this study is to investigate the effect of standard fire on the strength and microstructure properties of concrete with different strength grades.

Abstract

Purpose

The purpose of this study is to investigate the effect of standard fire on the strength and microstructure properties of concrete with different strength grades.

Design/methodology/approach

Different strength grades of concrete used for the investigation are M20, M30, M40 and M50. An electrical bogie hearth furnace was developed to simulate the International Standards Organization 834 standard fire curve.Concrete samples were subjected to high temperatures of 925, 1,029, 1,090 and 1,133°C for the duration of 1, 2, 3 and 4 h, respectively, as per standard fire curve. Compressive strength, tensile strength, thermal crack pattern and spalling of heated concrete specimens were evaluated by experimental investigation. Scanning electron microscopy and thermo-gravimetric analysis were performed to investigate the microstructure properties of heated concrete specimens.

Findings

Test results indicated reduction in the strength and changes in the microstructure properties of concrete exposed to elevated temperature. The degree of weight and the strength loss were found to be higher for concrete with higher grades. An empirical relation is proposed to determine the residual strength of concrete with different strength grade using regression analysis.

Social implications

Results of this research will be useful for the design engineers to understand the behavior of concrete exposed to elevated temperature as per standard fire.

Originality/value

When concrete is exposed to elevated temperature, its internal microstructure changes, thereby strength and durability of concrete deteriorates. The performance of concrete with different strength grade exposed to standard fire is well understood. This research’s findings will be useful for the designers to understand more about fire resistance of concrete. A simple relationship is proposed to determine the residual strength of concrete exposed to various durations of heating.

Details

Journal of Structural Fire Engineering, vol. 11 no. 3
Type: Research Article
ISSN: 2040-2317

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Article
Publication date: 15 May 2019

Daniel Paul Thanaraj, Anand N. and Prince Arulraj

This paper aims to explain the influence of Standard Fire as per ISO 834 on the strength and microstructure properties of concrete specimens with different strength grade.

Abstract

Purpose

This paper aims to explain the influence of Standard Fire as per ISO 834 on the strength and microstructure properties of concrete specimens with different strength grade.

Design/methodology/approach

The strength grades of concrete considered for the experimental investigation were Fck20, Fck30, Fck40 and Fck50. The specimens were heated up to 1, 2, 3 and 4 h as per standard fire curve. Effect of elevated temperature on compressive and flexural behavior of specimens with various strength grades was examined. Effects of age of concrete, weight loss, surface characteristics and thermal crack pattern were also investigated.

Findings

Experimental investigation shows that strength grade, duration of exposure and age of concrete are the key parameters affecting the residual strength of concrete. For the beams exposed to 3 and 4 h of heating, the residual flexural strength was found to be so insignificant that the specimens were not able to even sustain their own weight. The loss in compressive and flexural strength of Fck50 concrete specimens heated up to 1 h were found to be 26.41 and 86.03 per cent of the original unheated concrete, respectively. The weight loss was found to be more for higher grade concrete specimens, and it was about 8.38 per cent for Fck50 concrete. Regression analysis was carried out to establish the empirical relation between residual strength and grade of concrete. Scanning electron microscopy and thermogravimetric analysis were carried out to examine the damage level of fire-affected concrete specimens.

Originality/value

Empirical relationship was developed to determine the residual strength of concrete exposed to elevate temperature, and this will be useful for design applications. This database may be useful for identifying member strength of reinforced beams subjected to various durations of heating so that suitable repair technique can be adopted from the available database. It will be useful to identify the proper grade of concrete with regard to fire endurance, in the case of concrete under compression or flexure.

Details

Journal of Engineering, Design and Technology , vol. 17 no. 5
Type: Research Article
ISSN: 1726-0531

Keywords

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