Repair of heat-damaged reinforced concrete slabs using fibrous composite materials

Sixteen under-reinforced high strength concrete one-way slabs were cast, heated at 600 °C for 2 h, repaired, and then tested under four-point loading to investigate the coupling effect of water recuring and repairing with advance composite materials on increasing the flexural capacity of heat-damaged slabs. The composites used included high strength fiber reinforced concrete layers; and carbon and glass fiber reinforced polymer (CFRP and GFRP) sheets. Upon heating then cooling, the reinforced concrete (RC) slabs experienced extensive map cracking, and upward cambering without spalling. Recuring the heat-damaged slabs for 28 days allowed recovering the original stiffness without achieving the original load carrying capacity. Other slabs, recured then repaired with steel fiber reinforced concrete (SFRC) layers, regained from 79% to 84% of the original load capacity with a corresponding increase in stiffness from 382% to 503%, whereas those recured then repaired with CFRP and GFRP sheets, regained up to 158% and 125% of the original load capacity with a corresponding increase in stiffness of up to 319% and 197%, respectively. Control, heat-damaged, and water recured slabs showed a typical flexural failure mode with very fine and well distributed hairline cracks, propagated from the repair layers to concrete compression zone. RC slabs repaired with SFRC layers failed in flexural through a single crack, propagated throughout the compression zone, whereas those repaired with CFRP and GFRP experience yielding failure of steel prior to the composites failure.