Acompanhamento da hidratação de cimento Portland simples com resíduo de bauxita

Abstract

ResumoA substituição parcial de cimento Portland por resíduo de bauxita (RB) resulta em produtos com, no mínimo, propriedades similares às dos produtos fabricados com o ligante puro. No entanto, as interações físico-químicas entre os diferentes tipos de cimento e o RB durante a reação de hidratação ainda é pouco explorada em literatura. A elevada quantidade de sódio e a presença de Al 2 O 3 , SiO 2 e Fe 2 O 3 são fatores que afetam a formação dos produtos hidratados e dependem do tipo de cimento utilizado na mistura. Sendo assim, este trabalho foi realizado com o objetivo de avaliar o impacto da presença do resíduo de bauxita em associação ao cimento Portland simples nas primeiras idades de hidratação. Calorimetria de condução isotérmica, difração de raios X, análise termogravimétrica e espectroscopia de infravermelho foram as técnicas escolhidas para o monitoramento. Os resultados ilustraram que a presença do resíduo coletado na planta da Alcoa (Poços de Caldas) aumenta o tempo de indução, o consumo de portlandita, e as quantidades de etringita e monossulfoaluminato formadas. Ao mesmo tempo, houve formação de silicoaluminato de sódio e bicarbonato de sódio, devido às reações com silicatos, aluminatos e com o carbonato do cimento. Palavras-chave: resíduo de bauxita, cimento, hidratação, termogravimetria, DRX, infravermelho. Abstract The partial substitution of Portland cement by bauxite residue (BR) results in products with

Optimization of the Percentage of Cellulose, Latex and Metakaolin in the Production of Cementitious Composites

“…Some of the main peaks of ettringite, C-S-H, portlandite, calcite and quartz possibly could not be identified due to the small amount present in the composite and/or overlap of the peaks. Similar results were reported by [33,34] In general, a dense matrix was observed, with few pores and well adhered to the fibers. It was not possible to note the detachment of the fibers in the interface region that would be provided by the volume variation due to the high water absorption.…”

Effects of storage temperature and time on false setting behavior of CPI-S Portland cement

“…2) were performed on two CPI-S-32 samples, sample CPI-S-32 130.120, which presented false setting, and CPI-S-32 100.30 sample, which did not show false setting. It was possible to note the presence of the main crystalline compounds in both samples as alite (C 3 S), belite (C 2 S), tricalcium aluminate (C 3 A), tetracalcium ferroaluminate (C4AF), and calcite (CaCO 3 ) [32][33][34][35][36][37][38][39]. In addition to these compounds, the presence of gypsum (CaSO 4 .2H 2 O) was observed in the CPI-S-32 100.30 sample at 11.6° and 20.8° (2θ).…”

Clay Ceramic Waste as Pozzolan Constituent in Cement for Structural Concrete

“…This is apparently a consequence of the chemical composition of a hardenable cement with around 55% of C–S–H and 8–10% of ettringite and other compounds such a calcium mono sulfate aluminate 5% and secondary aluminate and ferrite phases 8%. This composition results in 22–24% of CH in the finally hardened concrete [ 43 , 44 ]. As material by its own definition, in a pozzolanic material only the CH is reactive up to these values.…”

“…All pH modifications are attributed to pozzolanic reactions and correlated to its potential. However, it is known that other factors not necessarily related to these reactions may modify the pH by forming a late ettringite or precipitation of calcium mono sulfate aluminite [ 43 , 44 ]. As such, none of these works listed in Table 1 has directly measured the pozzolanic activity of their respective ceramic waste.…”