Concreto de alta resistência: influência da incorporação de fibras sintéticas e de agente de cura interna (SAP) em propriedades mecânicas e de durabilidade

Abstract

High-strength concrete (HSC) has become widespread in civil construction due to the need for greater strength and durability of structures. However, its high mechanical performance is also associated with the low w/c ratio, the high consumption of cement and the highly reactive mineral additions, which densify the microstructure and refine the pores, reducing permeability. These factors provide high rates of self-drying, which cause autogenous shrinkage. Early cracking, triggered by the phenomenon of autogenous shrinkage and drying shrinkage, is a limiting factor for the use of HSC, as it directly affects its performance and durability. Early cracking, triggered by the phenomenon of autogenous shrinkage and drying shrinkage, is a limiting factor for the use of HSC, as it directly affects its performance and durability. This phenomenon has been considerably attenuated by internal curing with superabsorbent polymer (SAP), however, its performance in terms of mechanical properties still generates controversy in the scientific environment. Thus, the Barchip macrofiber (0.5% in volume) and the internal curing agent (0.32% in relation to the cement mass) were incorporated into the concrete, totaling four mixtures, with and without fiber, both with and without SAP. The mixtures were compared through tests related to the study of pore structure (absorption and void index and water absorption by capillarity), heat release of hydration, free shrink-age, uniaxial compression, flexural tension and, finally, modulus of static and dynamic elasticity. The results indicate that the addition of SAP as a curing agent significantly contributes to improve cement hydration and reduce the rates of autogenous shrinkage and drying shrinkage. Its disadvantage is related to the increase in porosity, which tends to reduce the mechanical properties, especially the compressive strength.The fiber, in turn, although it does not significantly alter the performance of the matrix, it increased the ductility of the matrix, reinforcing the residual strength. Still, between attraction for the interconnectivity, significantly mitigating the retraction of SAP, reaching to overcome the total retraction. That of materials, in turn, was not efficient for properties as properties. In this way, it is concluded that adding SAP and Barchip fiber in isolation can improve the performance of CAR in terms of shrinkage. Keywords: superabsorbent polymer, shrinkage, Barchip macrofiber, porosity.