The influence of high temperature on the bond in reinforced concrete

Flexural response of corroded reinforced concrete beams at elevated temperatures

“…respectively, this water is released (Haddad and Shannis, 2004;Morley and Royles, 1979). Additional water is expelled from the pores of the concrete at a temperature of 500°C (Haddad and Shannis, 2004).…”

“…Additional water is expelled from the pores of the concrete at a temperature of 500°C (Haddad and Shannis, 2004). This dehydration causes the concrete matrix to become more porous and also causes shrinkage in the cement paste (Haddad and Shannis, 2004;Morley and Royles, 1979). Normal weight concrete has a density between 2200 kg/m 3 to 2300 kg/m 3 (Buchanan, 2002).…”

“…In general the aggregates are composed of either siliceous materials or carbonic materials which begin to degrade at temperatures of 500 °C and 1200 °C, respectively (Haddad and Shannis, 2004). The net result of these expansion and contraction forces is the introduction of large thermally induced stresses which can cause excessive cracking, increased porosity and spalling of the concrete (Haddad and Shannis, 2004;Morley and Royles, 1979). These physical changes are reflected in reduced mechanical properties and reduced bonding strength between the reinforcing and the main concrete matrix (Haddad and Shannis, 2004).…”

“…When considering the actual structural application of steel embedded into concrete, the importance of the bond interaction becomes clear. The frictional and mechanical interlocking forces that transfers the tensile loads from the concrete to the steel (particularly in flexural members) is critical, and can be affected by high temperatures (Morley and Royles, 1979;Bingol, 2009). This bond is affected mainly by changes in the confining concrete as it is heated due to cracks that will develop.…”

“…This is one of the reasons that reinforcing is typically protected with a specific thickness of concrete known as 'cover'. While the apparent yield strength of hot rolled steel tends to increase as its temperature increases up to approximately 250 °C, its actual yield strength will quickly drop off as the temperature continues to increase (Morley and Royles, 1979). At ~600°C hot rolled steel is said to be at 50% of its actual yield strength (Morley and Royles, 1979).…”