Experimental investigation of mechanical properties and physical characteristics of concrete under standard fire exposure

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.

Post-fire damage assessment and capacity based modeling of concrete exposed to elevated temperature

“…This higher weight loss is observed beyond 120 min (1029 C) duration of heating and explosive spalling also occurred in the same duration. Larger crack width and more number of cracks were observed for concrete with lower w/c ratio (Daniel et al, 2019) and these specimens exhibited explosive spalling.…”

Flexural behavior of fire damaged self-compacting concrete beams strengthened with fiber reinforced polymer (FRP) wrapping

“…The stiffness values were found to be 50 N/mm, 19 N/mm and 16 N/mm for HCFRB-50AC, HBFRB-50AC, and HGFRB-50AC beams, respectively. In the Specimens exposed to high temperatures exhibited significant reductions in flexural strength due to micro-cracks triggered by thermal shocks and the development of weak microstructures (Aydin and Baradan, 2007;Thanaraj et al, 2019Thanaraj et al, , 2020. The prevailing investigation shows that CFRP wrapped beams had the highest ultimate load compared to BFRP and GFRP-wrapped specimens.…”

Influence of Various Design Parameters on Compressive Strength of Geopolymer Concrete: A Parametric study by Taguchi Method

“…The sides and top of the furnace were lined with electrical heating coils embedded in refractory bricks. The specimens were heated uniformly on three sides [28]. Heat curing of specimens is shown in Figure 1A.…”