Activación de arcillas de bajo grado a altas temperaturas

Abstract

ResumenSe presenta una propuesta de producción de puzolanas artificiales a partir de activar arcillas de baja pureza, como alternativa de producción de Metacaolín.Se trabajó básicamente con tierra rica en minerales arcillosos, principalmente caolín. Este material fue sedimentado y luego calcinado a 900 grados Celsius.Igual proceso se realizó al material original sin sedimentar. Producto de la calcinación disminuyó considerablemente la superficie específica, y por ende la actividad puzolánica, que fue evaluada monitoreando el consumo de HC en pastas a varias edades, y la resistencia a compresión en morteros. El material calcinado, aparentemente inerte, fue molido hasta una alta finura. Se introdujo una serie experimental con ceniza de paja de caña, como referencia de puzolana anteriormente estudiada. Las arcillas calcinadas molidas incrementaron cuantiosamente su actividad puzolánica, caracterizado por un mayor consumo de HC en pastas, y una mayor resistencia a compresión en morteros. Aparentemente este cambio se debe al efecto del molido sobre la reactividad de los suelos arcillosos calcinados. Los mejores resultados se obtuvieron para las muestras sedimentadas antes de calcinar. La resistencia a compresión de morteros, sustituyendo un 30% del peso de cemento por dicho material, es similar al control (100% cemento) a 7 días, y mayor a 28 y 60 días. Aunque dicha sustitución no disminuye la porosidad total, se disminuye la sorptividad, principalmente en muestras producidas con material sedimentado calcinado y molido. Posiblemente este fenómeno ocurra por un proceso de refinación de poros capilares inducido por la precipitación de productos de la reacción puzolánica.Palabras Clave: Puzolanas, arcillas calcinadas, microestructura, porosidad, sorptividad Abstract This paper introduces a proposal to produce artificial pozzolans by means of activation of low grade clays, as an alternative to metakaolin production.Basically the work considered clay mineral enriched soils, mainly kaolin. Such material was sediment and later calcined at 900 Celsius degrees. The same process was conducted with non-sediment material. Due to calcinations, the specific surface decreased significantly, and therefore, its pozzolanic activity, which was assessed by monitoring the CH consumption in cement pastes of several ages, as well as compressive strength in cement mortars. Calcined material, apparently inert, was ground until achieving high finesse. An experimental series made of sugar cane straw ash was introduced, as a reference to the pozzolans previously studied. Ground calcined clays increased its pozzolanic activity at a huge extent, which is characterized by a higher consumption of CH in cement pastes and by a higher compressive strength in cement mortars. Apparently this change takes place due to grinding effect on the reactivity of calcined clayey soils. The best results were obtained from sediment samples before their calcinations. The compressive strength of cement mortars, replacing a 30% the cement weight by such material, is s...

The Influence of Thermo-Mechanical Activation of Bentonite on the Mechanical and Durability Performance of Concrete

“…It can be heating of the pozzolan or the high temperature curing of the specimens made with pozzolans. It was reported that thermal treat of clays produce a metastable state due to structural disorder and an amorphous reactive structure is formed [41,42]. Different clays have different calcination effects on their pozzolanic reactivities.…”

Synthesis of Modified River Clay Catalyst for Valuable BTE Production via Catalytic Pyrolysis of Hazardous Plastic Waste

“…Furthermore, the structure of river harvested clay calcined at 900 °C became very dense due to the pore blockage because of the sintering phenomenon. [46] The structure of river clay calcined at 800 °C (Figure 2d) was more flaky and porous in nature as compared to other river harvested clay catalysts. The elemental composition determined by EDX analysis of river harvested clay catalysts i. e., RHC, RHC-600, RHC-700, RHC-800 and RHC-900 are given in Table 1 and corresponding EDX figures are also given in Figure S4 (a-e).…”

Cement production with pozzolans from residual tropical soils formed from paragneiss with a high silicon oxide content

“…Kaolinite content in the samples was below 40% which is unusual in these kinds of studies because high kaolinite content has been associated with good pozzolanic activity [10][11][12]. For example, in studies such as that carried out by Castillo et al, clays with low kaolinite content were used for thermal activation and the kaolinite was decanted in order to increase its concentration [13]. However, this process is not relevant to the focus of this study.…”