Influencia de aditivo aireante combinado con macrofibras de polipropileno en hormigones de alta resistencia frente al spalling

Abstract

This experimental study analyzes the influence of an air-entraining admixture (AEA) combined with polypropylene macrofibers on the behavior of high-strength concrete subjected to spalling under high temperatures. Seven mix designs (D1–D7) were developed with different air-entraining contents (0.03% and 0.07%) and fiber dosages (1 and 3 kg/m³), producing a total of 105 specimens exposed to temperatures of 20°C, 100°C, 300°C, 700°C, and 1200°C for 3 hours. The results showed that mass loss increases with temperature, reaching values of 20.2% in the control mix at 1200°C, while modified mixtures reduced this value to 11.2%, demonstrating improved thermal stability. Regarding compressive strength, an initial increase was observed at 100°C (up to 136%), followed by a proportional decrease at 300°C, and a significant reduction at 700°C, with values ranging between 21% and 32%. At 1200°C, mixes without fiber exhibited complete failure (0.00 MPa), whereas those incorporating fibers retained residual strength of up to 6.69 MPa. Additionally, spalling was more severe in conventional concrete, while mixtures with AEA and fibers showed reduced disintegration and cracking. It is concluded that their combination helps reduce internal vapor pressure, improve structural integrity, and enhance the residual strength of concrete under extreme thermal conditions.E