Effect of Elevated Temperature on Mechanical Properties of Limestone, Quartzite and Granite Concrete

Muhammad Tufail,Khan Shahzada,Bora Gencturk,Jianqiang Wei

doi:10.1007/s40069-016-0175-2

Abstract

Although concrete is a noncombustible material, high temperatures such as those experienced during a fire have a negative effect on the mechanical properties. This paper studies the effect of elevated temperatures on the mechanical properties of limestone, quartzite and granite concrete. Samples from three different concrete mixes with limestone, quartzite and granite coarse aggregates were prepared. The test samples were subjected to temperatures ranging from 25 to 650 °C for a duration of 2 h. Mechanical properties of concrete including the compressive and tensile strength, modulus of elasticity, and ultimate strain in compression were obtained. Effects of temperature on resistance to degradation, thermal expansion and phase compositions of the aggregates were investigated. The results indicated that the mechanical properties of concrete are largely affected from elevated temperatures and the type of coarse aggregate used. The compressive and split tensile strength, and modulus of elasticity decreased with increasing temperature, while the ultimate strain in compression increased. Concrete made of granite coarse aggregate showed higher mechanical properties at all temperatures, followed by quartzite and limestone concretes. In addition to decomposition of cement paste, the imparity in thermal expansion behavior between cement paste and aggregates, and degradation and phase decomposition (and/or transition) of aggregates under high temperature were considered as main factors impacting the mechanical properties of concrete. The novelty of this research stems from the fact that three different aggregate types are comparatively evaluated, mechanisms are systemically analyzed, and empirical relationships are established to predict the residual compressive and tensile strength, elastic modulus, and ultimate compressive strain for concretes subjected to high temperatures.

Highlights

Concrete is the most widely used construction material in the world because of its durability, strength, and resistance to fire
The line fits indicate that the tensile strength of limestone, quartzite and granite concrete decrease by 0.29, 0.34 and 0.36 MPa, respectively, for every 100 °C increase in temperature. These results indicate that limestone concrete performs slightly better in terms of retaining its absolute strength with temperature compared to quartzite and granite concrete which showed very similar results
The effect of different coarse aggregates; namely, limestone, quartzite and granite, on the mechanical properties of concretes subjected to elevated temperatures from 95 to 650 °C were studied

Summary

Introduction

Concrete is the most widely used construction material in the world because of its durability, strength, and resistance to fire. In general, has a high resistance to fire, its mechanical properties such as strength and elastic modulus decrease when subjected to high temperatures. At a temperature of 105 °C, the free water starts evaporating rapidly. When the temperature reaches to 300 °C, the chemically bound water starts to evaporate, which in turn decreases the compressive strength of concrete. When temperature increases beyond 400 °C, the concrete strength decreases more rapidly due to the degradation of calcium–silica–hydrate (C–S–H). Second phase of the C–S–H decomposes in the temperature range from 600 to 800 °C forming b-C2S (Hager 2013). The critical temperature for concrete ranges from approximately 400 to 900 °C.

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