High Temperature Mechanical and Material Properties of Burnt Masonry Bricks

Abstract

Fire hazard is one of the most severe environmental conditions to which buildings and dwellings may be subjected, therefore, the provision of appropriate fire safety measures is an important aspect in-built infrastructure. In recent years there have been an increased research in fire performance of both normal strength concrete (NSC) and high strength concrete (HSC) for structural members in buildings and built infrastructure. On the other hand, brunt bricks are either used partially or as a major portion in structures around the world, however, the studies on fire performance of burnt bricks are scarce. There are also no studies available on comparative fire performance of burnt bricks to that of NSC or HSC. A test program was designed to undertake high temperature tests on burnt bricks commonly used in buildings and domestic construction. Mechanical properties namely compressive strength, tensile strength, elastic modulus, and compressive toughness were investigated at elevated temperatures (hot state) from 20°C to 800°C. These tests were done according to ASTM and RILEM test procedures. Results from high temperature experiments show that burnt bricks lose compressive strength in a manner similar to that of NSC and HSC. The measured tensile strength of burnt bricks is quite low as compared to compressive strength, with a very little gain around 200°C. High temperature properties also exhibit high reduction in stress-strain response of these bricks with increase in temperature. It was also observed that the failure response of bricks under stress changes form very stiff to soft with increasing temperatures and no spalling phenomenon was observed in burnt masonry bricks. Scanning electron microscope and X-ray fluorescence analysis of burnt bricks were also carried out to differentiate the microstructural and mineral changes that take place at elevated temperatures. To provide high temperature material properties of burnt bricks for analytical studies, data generated from mechanical property tests was utilized to develop simplified mathematical expressions as a function of temperature.