Abstract
This paper presents an experimental investigation of the behavior of six reinforced concrete columns under elevated temperatures. A lightweight expanded clay aggregate (LECA) was used in three reinforced concrete columns, in the remaining three columns natural aggregate was used. All reinforced concrete (RC) columns have similar square cross-sectional dimensions of 150mm×150 mm and 1250mm total length. The columns were designed according to ACI Committee 318-2014 and exposed to different elevated temperatures of 400 ºC and 500 ºC. After exposure to elevated temperature, the columns were axially loaded by compression force using an eccentricity ratio (e/h) equal to 0.5. The experimental results demonstrated a remarkable decrease in the ultimate carrying capacity of the columns when subjected to elevated temperature. The experimental test results have also revealed that the lightweight reinforced concrete columns have more fire resistance than the normal-weight reinforced concrete columns under the same elevated temperature. The ultimate load capacity of lightweight reinforced concrete (LWRC) columns decreases by about 6.5 % and 14.3 %, at elevated temperatures of 400 ºC and 500 ºC respectively, compared with the control column at ambient temperature. However, the ultimate load capacity of normal-weight reinforced concrete (NWRC) columns decreases by about 14.15 % and 28.6 %, at elevated temperatures of 400 ºC and 500 ºC, respectively, compared with the control column at ambient temperature. This reduction in the load resistance of the columns might be due to degradations in all properties of concrete and reinforcing steel bars when exposed to high temperatures. In addition, one of the possible reasons for the reduction in the load resistance may be due to a decrease in bond strength between concrete and steel, when subjected to heat.
