Production of a highly pozzolanic sugarcane bagasse ash via densimetric fractionation and ultrafine grinding  <span class="so-article-trans-title" dir="auto"> Translated title: Produção de uma cinza do bagaço da cana-de-açúcar de elevada pozolanicidade via fracionamento densimétrico e moagem ultrafina </span>

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Abstract

Abstract Sugarcane bagasse ash is a by-product produced by the energy cogeneration from biomass burning. Different processes can be applied to this material to adapt its chemical and physical characteristics to its use as pozzolan. This work aims to evaluate the effectiveness of the densimetric fractionation process in production of sugarcane bagasse ash with high pozzolanicity. Initially, a quartz-rich ash was collected in an industrial boiler and subjected to densimetric fractionation to remove the quartz particles through decantation. Then, the potentially pozzolanic ash portion was subjected to ultrafine grinding. The results showed high amorphous content (94.8%) in the ash after fractionation. Electrical conductivity and performance index tests confirmed the adequate pozzolanicity of the processed ashes. In addition, cement-based pastes with 20% cement replacement by bagasse ash (in mass) showed a reduction in the heat of hydration. Thus, the densimetric fractionation was efficient in producing a material with high reactivity compared to the original ash due to the reduction of contaminants and, consequently, the increase in the amorphous silica concentration.

Translated abstract

Resumo A cinza do bagaço da cana-de-açúcar é um resíduo produzido pela cogeração de energia a partir da queima de biomassa. Diferentes processos podem ser aplicados a esse material para adequar suas caracteríscitcas químicas e físicas ao emprego como pozolana. Este trabalho visa avaliar a efetividade do processo de fracionamento densimétrico na produção de uma cinza do bagaço da cana-de-açúcar de elevada pozolanicidade. Inicialmente, uma cinza rica em quartzo foi coletada em caldeira industrial e submetida ao fracionamento densimétrico para remoção das partículas de quartzo por meio de decantação. Em seguida, a parcela de cinza potencialmente pozolânica foi submetida à moagem ultrafina. Os resultados mostraram elevado teor de amorfos (94,8%) na cinza após fracionamento. Ensaios de condutividade elétrica e índice de desempenho confirmaram a adequada pozolanicidade das cinzas processadas. Além disso, pastas com 20% de substituição por cinzas do bagaço (em massa) mostraram redução do calor de hidratação. Portanto, o fracionamento densimétrico foi eficiente na produção de um material de elevada reatividade em comparação com a cinza original devido à redução de contaminantes e, consequentemente, pelo aumento da concentração de sílica amorfa.

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Use of Brazilian sugarcane bagasse ash in concrete as sand replacement.

Almir Sales, Sofia Lima (2010)

Sugarcane today plays a major role in the worldwide economy, and Brazil is the leading producer of sugar and alcohol, which are important international commodities. The production process generates bagasse as a waste, which is used as fuel to stoke boilers that produce steam for electricity cogeneration. The final product of this burning is residual sugarcane bagasse ash (SBA), which is normally used as fertilizer in sugarcane plantations. Ash stands out among agroindustrial wastes because it results from energy generating processes. Many types of ash do not have hydraulic or pozzolanic reactivity, but can be used in civil construction as inert materials. The present study used ash collected from four sugar mills in the region of São Carlos, SP, Brazil, which is one of the world's largest producers of sugarcane. The ash samples were subjected to chemical characterization, sieve analysis, determination of specific gravity, X-ray diffraction, scanning electron microscopy, and solubilization and leaching tests. Mortars and concretes with SBA as sand replacement were produced and tests were carried out: compressive strength, tensile strength and elastic modulus. The results indicated that the SBA samples presented physical properties similar to those of natural sand. Several heavy metals were found in the SBA samples, indicating the need to restrict its use as a fertilizer. The mortars produced with SBA in place of sand showed better mechanical results than the reference samples. SBA can be used as a partial substitute of sand in concretes made with cement slag-modified Portland cement.