The Characteristics Of Concrete Cylinder At Elevated Temperature

Lately, many high rise reinforced concrete buildings were put on fire. Retrofitting was one of many solutions available. To investigate the characterisc of the structure, a basic research on the behavior of concrete cylinders after fire is needed. A fire test was conducted on sixteen groups of specimens where half of those were showered with water soon they were extracted from fire. At the time of the test, the strength of the control specimen was 34.81 MPa. The specimens were cast on mold and were immediately cured in water for 28 days and subsequently cured in a room temperature until the age of concrete cylinders were about 35 days. The temperatures of the test were 200, 400, 500, 600, 700, 800, 900, and 1000oC. Explosive spalling was observed in concrete cylinders elevated at 750oC. The compressive strength of concrete cylinders elevated at 200, 500, and 1000oC were respectively 115%, 54 % and 20% than that of control concrete. Instant water cooling could have improved the strength of the concrete cylinders of 114% than that air-cooling when incinerated below 500oC. Rate of temperature of incineration influenced the type of deterioration of concrete. The higher the rate of temperature of incineration the more the possibility of the concrete to spall. Loss of weight of concrete was 1.35%, 4.46%, 10.23% after being incinerated at 200, 500, and 10000C respectively. The velocity of ultrasonic test decreased as the temperature of incineration was increased, those velocities were respectively of 8.93 km/second, 7.38 km/second, and 3.45 km/second at room temperature, at 5000C and at 10000C. Keywords: fire tests, compressive, crack, splitting, bonding, flexure, ultra pulse velocit