Estudo de compósitos cimentícios do tipo SHCC com o uso da metacaulinita e a sua avaliação quando utilizado no encamisamento de concretos

Abstract

In this research, an experimental study was performed aiming to develop and characterize a Strain Hardening Cementitious Composite (SHCC), reinforced with short PVA fibres and high metakaolinite content, with the purpose of using them to rehabilitate concrete structures. The SHCC is an innovative material with enormous potential in the field of structural rehabilitate due to its high ductility and strain hardening and deflection hardening behaviour. However, this composite is fabricated with an elevated cement content, around two to three times more than conventional concrete. To overcome the economic impact, and improve its mechanical properties, fly ash is normally used as a supplementary material in its manufacture. However, in this work another alternative supplementary material was studied. The SHCC composite with an elevated metakaolinite content was developed in this study, given the high pozzolanic activity of this addition and its abundance of resources in Brazil. In this study, the parameters, metakaolinite, water and sand content and the PVA fiber length were studied. The SHCC with a partial replacement of 50% cement by metakaolinite showed the best mechanical performance and economy ratio, taking into account the high replacement content of cement with metakaolinite, with compressive strength of approximately 59 MPa, tensile strength of 4 MPa and strain capacity of 1,3%. One polymeric additive to increase the adhesion of cementitious materials was also tested in this experiment. Concrete specimens with 100 mm diameter and 200 mm height, and with two compressive strengths (19 MPa and 28 MPa) were prepared and tested to 50% and 80% of the load-carrying capacity under compression loads. The damaged and non-damaged specimens were repaired using the SHCC, by using 1,7 cm and 2,2 cm SHCC thickness. The effectiveness of the repairing schemes was evaluated by comparing load-carrying capacities under compressive loads at 7 and 28 days. In all the cases studied, confinement with SHCC was able to increase the compressive strength of the specimens and reduce the modulus of elasticity, showing a confinement effectiveness in the range of 1.19-1.27 and proving to be an excellent material for reinforcing concrete structures.