Marcos Alyssandro Soares dos Anjos

Evaluation of hydration of cement pastes containing high volume of mineral additions

Abstract The use of mineral additions is a common practice in the production of cementitious materials. Recently proposed usage of high amounts of cement replaced by mineral additions requires the study of the chemical interaction of these additions with the cement. This study intends to evaluate, by means of TG/DTG techniques, XRD and compressive strength, the effect of high volume of mineral additions in the hydration of cementitious pastes. Pastes with 50–70% of cement replaced by mineral addition and with different combinations of fly ash and metakaolin were evaluated, two pastes without mineral addition and two other pastes with lime addition. Results showed TG/DTG and XRD techniques are more suitable for evaluating kinetics of reactions of hydration, making it possible to quantify the substantial reduction in the levels of portlandite in hydrated pastes containing high volumes of mineral additions. These techniques allowed to find important differences in the evaluation of calcium hydroxide, because its morphology can change in the presence of additions. Also showed that it is possible to achieve, enhanced or even high compressive strength (50–80 MPa) in concretes containing reduced cement contents. As well as more resistance against harmful agents and carbonation attack.

INFLUENCIA DO USO DE CINZA DE BIOMASSA DA CANA-DE-AÇÚCAR NO COMPORTAMENTO CONCRETOS AUTO-ADENSÁVEIS

O presente trabalho apresenta um estudo feito com concreto auto-adensavel, com o objetivo de avaliar a influencia da incorporacao de cinza de biomassa da cana-de-acucar no comportamento no estado fluido do concreto auto-adensavel. A avaliacao foi feita atraves da producao de tres tracos: traco de referencia (TR), sem adicao; traco com a substituicao parcial de 20% do cimento por cinza (T1) e traco (T2) com a substituicao de 20% de areia por cinza. A avaliacao do comportamento no estado fluido foi feita atraves de ensaios de slump test, espalhamento – T500 (slump flow) e tempo de escoamento no funil “V”, Verificou-se que a adicao de cinza de biomassa melhorou o comportamento do concreto no estado fluido, tornando o concreto mais coeso, e que os tracos analisados atendem aos requisitos para concretos auto-adensaveis. PALAVRAS-CHAVE: Concreto auto-adensavel, cinza de biomassa da cana-de-acucar, comportamento no estado fluido.