Degradation of mechanical properties and durability of reinforced concrete structures occur when they are subjected to fire situations, depending on the characteristics of the material, fire duration and the ways of fire extinguishing. Mechanical properties such as compressive strength, tensile strength and elasticity modulus are some examples of typically altered characteristics in concrete during high temperature exposure. Nevertheless, little is known about the advance of the carbonation front on fire-damaged concrete, which is a characteristic directly related to the durability of the structural system. For this purpose, the carbonation front was evaluated in specimens with characteristic strengths of 20 MPa and 35 MPa, subjected to high temperatures (200 °C, 500 ºC and 700 ºC) and different types of cooling (fast and slow). It was observed that the concrete durability is harmed by exposure to high temperatures and fast cooling. However, advance of the carbonation front was not verified in slow cooling situations.
ResumoEste trabalho propõe avaliar a atuação do polietileno tereftalato (PET) como um agregado substituto na fabricação de concreto para pavers, pavimento intertravado com peças de concreto, a fim de minimizar os efeitos colaterais da construção civil. PET triturado substituiu o agregado natural, pó de pedra, nas porcentagens de 10%, 15% e 20% em massa. Os testes mecânicos de resistência à compressão realizado aos 28 dias mostraram que os corpos de prova moldados a partir dos traços substituídos apresentaram significativa melhora da resistência à compressão, que a substituição parcial de 10% em massa de PET atende ao recomendado pela NBR 9781 (2013) para concreto para pavimentação e que todos os concretos produzidos atendem a resistência mínima a compressão de 20 MPa, recomendado pela NBR 6118 (2003) para concreto estrutural. Palavras-chave:PET; Pavers; Resistência à compressão; Construção civil. STUDY OF PARTIAL REPLACEMENT OF STONE POWDER FOR PET TO PAVERS MANUFACTURE AbstractThis work proposes the performance evaluation of polyethylene terephthalate (PET) as an aggregate replacement in the concrete manufacturing for interlocking concrete pavements, in order to minimize the side effects of the construction industry. Crushed PET replaced the natural aggregate, stone dust, in percentages of 10%, 15% and 20% by mass. The compressive strength test performed after 28 days showed that the specimens molded from the replaced mix showed significant improvement in compared to specimens molded by the reference mix PET in percentages of 10% by mass meets the minimum strength of 35 MPa recommended by NBR 9781 (2013) for pavers and all concretes produced meets the minimum strength of 20 MPa recommended by NBR 6118 (2003) for structural concrete.
ResumoO presente trabalho tem como objetivo estudar a influência da adição do rejeito de pó de balão nas propriedades mecânicas do concreto destinado à fabricação de pavers, visto que a indústria da construção civil é a maior responsável pela geração de resíduos, sendo responsável pelo consumo de aproximadamente 40% dos recursos naturais extraídos. Sendo assim, o rejeito foi analisado granulometricamente por peneiramento e foram feitos dois traços, um denominado traço referência e o outro denominado traço substituído, sendo este último com adição de 4% em massa do pó de balão. A partir dos traços calculados foram moldados corpos de prova e avaliados a resistência à compressão destes. Os corpos de prova moldados a partir do traço substituído exibiram maior resistência à compressão tanto na idade de 7 dias quanto na idade de 28 dias, quando comparados aos corpos moldados a partir do traço referência. Esse incremento na resistência mecânica é justificado pela distribuição granulométrica do pó de balão, que por ser constituído em sua maior parte por finos inferiores a 0,15mm atua preenchendo vazios, reduzindo zonas de transição interfacial e formando uma microestrutura mais refinada. Palavras-chave: Pó de balão; Pavers; Resistência à compressão; Construção civil. STUDY OF THE PARTIAL REPLACEMENT OF STONE DUST BY BALLON POWDER IN PRECAST CONCRETE BLOCKS AbstractThe presente work aims to study the influence of the addition of balloon powder waste on the mechanical properties of concrete used to manufacture pavers, since the construction industry is the main responsible for the generation of waste, being responsible for the consumption of approximately 40% of all mined natural resources.Therefore, the waste was granulometrically analysed by sieving and two diferente concrete dosages were made. The first one was called reference dosage and the second one was named substituted dosage, being the latter with addition of 4% in mass of balloon powder. Using the concrete dosages calculated, concrete samples were made and their compressive strenght was evaluated. The concrete samples made from the substituted dosage showed higher compressive strenght in the age of 7 days as well as in the age of 28 days, when compared to the reference dosage. This higher compressive strenght is justified by the particle size distribution of the balloon powder, which consist mostly of thin particles below 0.15mm, that act filling empty spaces, reducing interfacial transition zones and forming a more refined microstructure.
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