Guilherme Chagas Cordeiro

Cement replacement by sugar cane bagasse ash: CO2 emissions reduction and potential for carbon credits.

This paper presents a study of cement replacement by sugar cane bagasse ash (SCBA) in industrial scale aiming to reduce the CO(2) emissions into the atmosphere. SCBA is a by-product of the sugar/ethanol agro-industry abundantly available in some regions of the world and has cementitious properties indicating that it can be used together with cement. Recent comprehensive research developed at the Federal University of Rio de Janeiro/Brazil has demonstrated that SCBA maintains, or even improves, the mechanical and durability properties of cement-based materials such as mortars and concretes. Brazil is the worlds largest sugar cane producer and being a developing country can claim carbon credits. A simulation was carried out to estimate the potential of CO(2) emission reductions and the viability to issue certified emission reduction (CER) credits. The simulation was developed within the framework of the methodology established by the United Nations Framework Convention on Climate Change (UNFCCC) for the Clean Development Mechanism (CDM). The State of São Paulo (Brazil) was chosen for this case study because it concentrates about 60% of the national sugar cane and ash production together with an important concentration of cement factories. Since one of the key variables to estimate the CO(2) emissions is the average distance between sugar cane/ethanol factories and the cement plants, a genetic algorithm was developed to solve this optimization problem. The results indicated that SCBA blended cement reduces CO(2) emissions, which qualifies this product for CDM projects.

Use of Ultra-Fine Sugar Cane Bagasse Ash as Mineral Admixture for Concrete

Alcohol factories and sugar boilers generate a combustion byproduct known as sugar cane bagasse ash (SCBA). SCBA is composed mainly of silica and can be used as a concrete mineral admixture. Residual ultra-fine SCBA (9, 10, 15 and 20%) were used to produce conventional and high-performance concretes (CCs and HPCs, respectively) as a cement replacement (in mass) in this investigation. Tests performed for these concretes consisted of adiabatic calorimetric, durability, mechanical, and rheological. That concrete mechanical properties were not significantly changed through SCBA use at all replacement levels was indicated by results. When compared with the reference mixtures, there was superior rapid chloride-ion permeability, water sorption capillary, and rheological test performance by the ultra-fine SCBA concretes. Replacing 15% of cement with ultra-fine SCBA substantially decreased (11%) the maximum CC adiabatic temperature rise.

Ultrafine sugar cane bagasse ash: high potential pozzolanic material for tropical countries

Abstract Resumo This work describes the characterization of sugar cane bagasse ashes produced by controlled burning and ultrafine grinding. Initially, the optimum burning conditions of the bagasse were determined aiming the maximum pozzolanic activity. In sequence, an ultrafine sugar cane bagasse ash was produced in vibratory mill. Finally, the influence of use of ultrafine sugarcane bagasse ash (10, 15 and 20% of cement replace-ment, in mass) in properties of high-performance concretes was studied. Rheology (BTRHEOM rheometer), compressive strength (7, 28, 90, and 180 days) and rapid chloride penetrability were investigated. The results indicated that the addition of sugarcane bagasse ash improved the durability characteristics, and did not change the rheological and mechanical properties.Keywords: sugar cane bagasse ash, pozzolan, concrete, grinding, calcination. Este trabalho descreve a caracterizacao de cinzas do bagaco de cana-de-acucar produzidas a partir de queima controlada e moagem ultrafina. Inicialmente, as condicoes otimas de queima do bagaco foram determinadas com o objetivo de alcancar a maxima atividade pozolânica. Em seguida, uma cinza ultrafina de elevada reatividade foi produzida em moinho vibratorio. Por fim, estudou-se a influencia do emprego de cinza ultrafina do bagaco de cana-de-acucar (10, 15 e 20% de substituicao de cimento, em massa) nas propriedades de concretos de alto desempenho. Foram avaliadas a reologia (reometro BTRHEOM), a resistencia a compressao (7, 28, 90 e 180 dias) e a penetracao acelerada de ions cloro. Os resultados indicaram que a cinza do bagaco nao altera as propriedades reologicas e mecânicas e possibilita a obtencao de concretos mais duraveis.Palavras-chave:

Influence of initial CaO/SiO2 ratio on the hydration of rice husk ash-Ca(OH)2 and sugar cane bagasse ash-Ca(OH)2 pastes

This work presents the results of a study on the hydration of pastes containing calcium hydroxide and either rice husk ash (RHA) or sugar cane bagasse ash (SCBA) in various initial CaO/SiO2 molar ratios. The products of the reactions were characterized by thermal analyses X-ray diffraction, and scanning electron microscopy. In the case of the RHA pastes, the product was composed of CaO-SiO2-H2O (type I C-S-H) or CaO-SiO2-H2O (type II C-S-H) according to the CaO/SiO2 ratio of the mixture. In contrast, in the case of the SBCA pastes, the product was composed primarily of CaO-SiO2-H2O that differed from both the previous types; the product also contained inclusions of calcium aluminate hydrates.

PRODUCTION OF SILICA GEL FROM RESIDUAL RICE HUSK ASH

This paper presents a study on the production of silica gel in hydrothermal process using residual rice husk ash. Measurements of the chemical composition, X-ray diffraction, infrared spectroscopy, particle size distribution, and pozzolanic activity were carried out in order to characterize the obtained material, and the optimal silica gel was selected for use as a mineral additive in cement pastes. The compressive strengths were determined for cement pastes containing silica gel (0.0, 2.5 or 5% by mass) in different times. The results indicate that the mixtures containing silica gel showed improved mechanical behavior over all time periods evaluated.

Influência de resíduos de corte de rochas e de blocos cerâmicos moídos na hidratação e no empacotamento de pastas cimentícias

The present work aims to study the replacement of Portland cement (PC) by stone cutting waste (SW) and ground waste clay brick (BW) in binary and ternary pastes. Thermogravimetry and differential thermal analysis tests were carried out at various ages in order to investigate the development of the cement hydration reactions in the presence of those wastes. The packing density was calculated in accordance with the Compressible Packing Model to understand the physical effect of those wastes. Compressive strength tests were also performed and the results were related to hydration and packing. Considering the substitution levels studied, the results indicated that the use of SW in the binary mixture accelerated the hydration reactions, and the particles packing density and compressive strength were maintained. The use of BW in the binary mixture caused a small acceleration in the hydration reactions and there was an indication of pozzolanic activity, although the compressive strength was reduced in comparison with the reference paste. In the ternary mixture, the combined effect of both wastes resulted in the maintenance of compressive strength for cement replacement content of 30%.

Effect of the Sodium and Potassium Chloride on the Mechanical and Plastic Properties on the Oil Well Cement Slurries

In recent times, a large reserve of oil and gas in a Pre-Salt zone has been identified in Brazil. In this reserve it is necessary to drill and cement a layer of approximately 2.000 meters of salt rock. In salt rocks, the contact of cement with the rock during the cementing operation can cause the dissolution of the rock and salt can migrate to the cement slurry. Cementitious systems containing salt in their composition have been proposed to minimize the transport of rock salt to the slurry. Considering that the presence of salt can cause changes in the properties of the slurry and compromises the cementing quality. Studies are necessary to understand how the type and concentration of salt can affect the short and long term behavior of the slurry. In this work, the effect of the amount of sodium chloride (NaCl) and potassium chloride (KCl) on the properties of the oil well cement slurry was studied. For this, slurries containing 5%, 10%, 12.5%, 15%, 17.5%, 20% and 36% NaCl by the weight of water (BWOW), and 1%, 3%, 5%, 7%, 10% and 34% KCl (BWOW) were designed. The effect of salt type and content on the rheology, free-fluid and mechanical properties such as compression strength, Young’s modulus, Poisson’s rate and splitting tension strength was investigated. The mechanical properties were evaluated at an age of 8 hours of curing in water at 38°C (100° F) and 60° C (140° F) and 7 days of curing in water at 60° C. The addition of NaCl and KCl resulted in similar behavior in almost all the properties studied. The properties of freshly and early-age, as free-fluid and compression strength, of saline slurry differed in two different mechanisms depending by the salt concentration. For other side, in most cases, the rheological and long-age properties were reduced with an increase in salt content.© 2012 ASME

Evaluation of partial clinker replacement by sugar cane bagasse ash: CO2 emission reductions and potential for carbon credits

Este trabalho apresenta um estudo sobre a viabilidade de possiveis cenarios de reducao de emissao de CO2 na fabricacao de cimento atraves da implementacao de projetos de Mecanismo de Desenvolvimento Limpo (MDL) associados a substituicao parcial de cimento por cinza do bagaco de cana de acucar (CBCA). Estudos sobre o comportamento termico, quimico e mecânico de concretos com 5 a 20% de cinza indicaram que existe melhora no desempenho de todas as propriedades analisadas e que a cinza pode ser usada como aditivo na fabricacao de cimento. As emissoes de CO2 de dois cenarios hipoteticos de implementacao de projeto de MDL atraves desta tecnologia no estado de Sao Paulo, com base na metodologia oficial aplicavel, foram avaliadas. Os resultados demonstram que existem reducoes de emissoes em ambos os cenarios, inclusive para o mais desfavoravel, evidenciando a possibilidade de obtencao de creditos de carbono negociaveis.

Study on the pozzolanic activity of sugar cane straw ash produced using different pretreatments

This work systematically describes a laboratory study on different pretreatments of sugar cane straw to produce pozzolanic ash. Two procedures were used to accelerate the hydrolysis of celluloses and hemicelluloses and remove metallic impurities present in significant levels in sugar cane straw: hot water washing and acid leaching. Proximate analysis by thermogravimetry was carried out to cover volatile matter, fixed carbon, and ash content of the different straws. Detailed measurements of X-ray diffraction, oxide percentages, loss on ignition, and BET specific surface area were performed to compare hot water washed, acid leached, and nonpretreated ashes, after controlled processes of burning and grinding. The pozzolanic activity of the ashes was evaluated from the modified Chapelle and electrical conductivity methods. The results revealed that ashes with a high content of amorphous silica were produced, in spite of the straw pretreatments. However, both straw pretreatments induced a significant increase in pozzolanic activity, mainly associated with the removal of impurities, especially CaO, SO3, K2O, and carbon compounds. The effect of the hot water washing treatment was relatively small in relation to the acid leaching, but the hot washed ash was significantly more pozzolanic than non-treated ash.

Avaliação do desempenho estrutural em serviço de lajes treliçadas pré-moldadas de concretos com agregados leves

O concreto com agregado leve tem sido cada vez mais empregado em razao da reduzida massa especifica, do elevado isolamento termico e acustico e da melhoria na resistencia estrutural a carregamentos ciclicos. Neste trabalho foram estudados concretos com agregados leves com resistencia a compressao em torno de 20 MPa e seu desempenho estrutural em lajes trelicadas pre-moldadas. Utilizaram-se tres diferentes concretos com valores de massa especifica entre 1.200 e 1.600 kg/m3. Os concretos foram avaliados com relacao a resistencia a compressao (aos 3, 7 e 28 dias) e a absorcao total de agua (aos 28 dias). Com os tres tipos de concreto foram produzidas e ensaiadas a flexao lajes pre-moldadas (duas lajes para cada tipo de concreto), com a avaliacao de seu comportamento no estado limite de servico (ELS) para cargas de curta duracao, ou seja, sem considerar efeitos ao longo do tempo. Os resultados mostraram o potencial do uso de concretos com agregados leves nesse tipo de laje estrutural.