Modos de ruptura e padrões de fissuração de vigas pré-moldadas de concreto armado geopolimérico: Estudo de caso

Abstract

RESUMOEsse trabalho apresenta um estudo comparativo do comportamento mecânico de vigas pré-moldadas de concreto armado convencional (CCP), fabricadas por uma empresa local e de concretos geopolimérico de metacaulim (CCG) e geopolimérico com 20% de cinza volante e silicato de cinza de casca de arroz (CCG-20CV-CCA), como matrizes substitucionais. Os resultados mostraram que os concretos geopoliméricos apresentaram comportamento similar ao do CCP, na mesma classe de resistência do concreto, taxa de armadura e disposição das armaduras no elemento estrutural estudado. O uso das cinzas promoveu aumento do módulo de rigidez à flexão e dos limites de deformação das vigas geopoliméricas, em especial para a CCG-20CV-CCA sob a maior taxa de armadura. Os padrões de fissuração e os modos de ruptura encontrados foram similares àqueles mostrados pelo CCP, com a conclusão, neste estudo de caso, de que as vigas pré-moldadas, como fabricadas pela empresa, foram superarmadas ao longo do bordo superior. Embora o dimensionamento da viga não tenha sido objeto deste estudo, foi mostrado que o concreto geopolimérico pode substituir plenamente o CCP, em concreto armado, abrindo oportunidade de uso dos mesmos códigos de dimensionamento desenvolvidos para este material tradicional. Palavras-chave:Geopolímero. Pré-moldado. Concreto armado. ABSTRACTThis work presents a comparative study of the mechanical behavior of precast concrete beams (CCP), manufactured by a local company and geopolymer concrete of metakaolin (CCG) and geopolymer concrete with 20% of fly ash and rice husk ash silicate (CCG-20CV-CCA), as substitutional matrices. The results showed that the geopolymer concretes presented similar behavior to the CCP, in the same class of concrete strength, reinforcement rate and arrangement in the structural element studied. The use of the ashes promoted an increase of the flexural stiffness modulus and the limits of deformation of the geopolymer beams, in particular for the CCG-20CV-CCA under the highest reinforcement rate. The cracking patterns and failure modes found were similar to those shown by CCP, with the conclusion, in this case study, that precast beams, as manufactured by the company were super-reinforced along the top of the beams. Although the dimensioning of the beam has not been the object of this study, it has been shown that the geopolymer concrete can completely replace the CCP in reinforced concrete, opening up the opportunity to use the same structural design codes developed for this traditional material.

Rehabilitation of Reinforced Concrete Beams: Mechanical Performance With Alkali-Activated Repair Mortar

“…The first cracks are formed during Stage II (PIRES et al, 2018). RP.AAM had a slight decrease in the ultimate deflection (10,6% lower) and maximum compressive strength (1,9% lower) when compared to the reference The deflection at the mid-span was measured and plotted against the load (Figure 7).…”

“…In the hardened state, the cracks are originated from design errors (e.g., the misconception of the service load, lack of reinforcement detailing, and errors in designing calculation) or construction defects (e.g., incorrect placement of steel, inadequate concrete cover, incorrectly made construction joints, insufficient compaction, segregation, poor curing conditions, and high water to cement ratio) (JUMAAT et al, 2006). Different factors influence the crack pattern, such as the properties of steel and concrete, and size of the beam (FAYYAD and LESS, 2017;PIRES et al, 2018).…”