Prediction of the Tensile Strength of Normal and Steel Fiber Reinforced Concrete Exposed to High Temperatures

Mehrdad Abdi Moghadam,Ramezan Ali Izadifard

doi:10.1186/s40069-021-00485-6

Abstract

The tensile strength of concrete has a great impact on the performance of concrete structures, especially for members exposed to high temperatures. The inclusion of steel fibers in concrete is one of the measures to retrieve the loss of tensile strength. The previous equations for the prediction of the tensile strength, are valid for conventional concrete and can predict the tensile strength after high-temperature exposure. Therefore, they are unsatisfactory for forecasting the tensile strength of plain and steel fiber reinforced concrete under high-temperature exposure. To establish a model that can effectively simulate the tensile strength of plain concrete, specimens with compressive strengths of 20–80 MPa are tested. Then by performing tensile strength tests on the specimens containing various content of steel fiber, an equation for prediction of the tensile strength at the ambient temperature is proposed. Meanwhile, the tensile strength tests are conducted at temperatures of 100–800 °C to develop a model for high-temperature exposure. The results indicate that an increase of compressive strength from 20 to 84 improves the tensile strength by 169.4%, and the incorporation of 0.25 and 0.5% of steel fibers can improve the tensile strength of normal concrete by 58.48 and 80.29% on average at the tested temperatures, respectively. Moreover, the proposed model is able to predict the tensile strength of normal and steel fiber reinforced concrete exposed to high temperatures accurately. This equation would help a wider application of the steel fibers in the construction industry with the risk of a fire accident.

Highlights

One of the widely used construction materials is concrete which enjoys a higher compressive strength in comparison with tensile strength
4 Conclusions This study focused on the effects of high temperatures on the tensile strength of normal and steel fiber reinforced concrete
A review of the previous experimental results illustrated this loss did not occur for specimens that were tested after exposure to high temperatures. 200 °C onward, they recover their strength because of the hydration of un-hydrated cement owing to autoclave curing condition

Summary

Introduction

One of the widely used construction materials is concrete which enjoys a higher compressive strength in comparison with tensile strength. The tensile strength of concrete after high-temperature exposure, which illustrates the residual tensile strength of concrete was investigated in previous studies (Khaliq & Waheed, 2017; Uysal et al, 2012). The experimental test on the tensile strength of the normal, high strength, and pozzolanic concrete during exposure to high temperatures showed severe damage at temperatures below 200 °C (Izadifard et al, 2021a, b; Mehrdad Abdi Moghadam, 2019). Ali et al incorporated a range of 0.05–2% of steel fibers to investigate the compressive and tensile strength of concrete at ambient temperature. They showed that the optimum content for compressive strength was 0.25% (Ali et al, 2020)

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Conclusion