Kaolinitic calcined clays – Portland cement system: Hydration and properties

Pozzolanicity of the material obtained in the simultaneous calcination of biomass and kaolinitic clay

“…A gas furnace with two atmospheric premix burners with liquefied petroleum gas fuel was used. The mix proportion for the thermal treatment of the materials was 91% kaolinitic clay and 9% rice husk; since the density of the former ð1:05 g cm 3 Þ is almost seven times the density of the latter ð0:16 g cm 3 Þ, a given amount of mass of rice husk occupies almost seven times the volume occupied by the kaolinitic clay and given the fact that, the typical ash content of rice husk is only about 16% [18] and the corresponding value for kaolinitic clay is about 86% [19], kaolinitic clay was chosen to be the major component of the mix; in this proportion more than half the volume (60%) of the containers used is occupied by the kaolinitic clay and after each calcination, more than 80% of the mass initially loaded into the furnace is available to test as a potential pozzolan. The containers used were selected to allow a better supply of oxygen for the material, especially for an effective combustion of the rice husk, which during the calcination needs to be rid of the most possible carbonaceous content.…”

Alternative binders for concrete: opportunities and challenges

“…To create a more significant ecological effect, a push toward high-volume SCMs is inevitable [15], and involves development of binders based on SCMs with small amount of cement used as an activator [16]. To meet a growing demand for cement and concrete, and considering limited supplies of high-quality SCMs, research is focussed on alternative SCMs such as red mud [17], [18], biomass ash [18][19][20], copper slag, calcined clays [21], limestone [22], and their engineering combinations [23]. The main challenge is to find materials that are available in significant quantities and that have favourable chemical and physical properties (such as particle size distribution presented in Figure 2) for use as mineral addition to cement.…”

“…Limestone is normally used as filler in cement industry; however, in recent years, it started to be used as a partial replacement for ordinary Portland cement [25]. One of the methods of activating reactivity of limestone is by adding reactive and silica-rich and alumina-rich materials, such as calcined clays [21], [26], [27]. In countries with an established ceramic industry substantial reserves of suitable clays are currently stockpiled as waste [28].…”

Efeito do teor de gipsita na resistência à compressão do cimento LC3

“…Em um estudo utilizando argilas cauliníticas -pobres‖ (44% de caulinita), calcinadas a 750 o C em combinação com fíler calcário, idem [18] demonstraram que as fases hidratadas encontradas correspondem à reação pozolânica (contribuição da argila calcinada) e à estabilização de fases (contribuição do fíler), modificando a estrutura porosa e desenvolvendo interessantes propriedades mecânicas com larga redução de consumo de energia e emissões de CO 2 . Os autores concluíram que os cimentos compostos com argila calcinada e fíler calcário demonstram resistência mecânica similar à da referência aos 28 dias (ainda que a argila calcinada tenha um baixo grau de pureza) devido à interação entre esses dois componentes.. A adição de argila calcinada e fíler aumenta o volume de poros com menor diâmetro [18].…”