Advances in Natural Fiber Cement Composites: A Material for the Sustainable Construction Industry

The need for economical, sustainable, safe, and secure shelter is an inherent global problem and numerous challenges remain in order to produce environmentally friendly construction products which are structurally safe and durable. The use of sisal, a natural fiber with enhanced mechanical performance, as reinforcement in a cement based matrix has shown to be a promising opportunity. This work addresses the development and advances of strain hardening cement composites using sisal fiber as reinforcement. Sisal fibers were used as a fabric to reinforce a multi-layer cementitious composite with a low content of Portland cement. Monotonic direct tensile tests were performed in the composites. The crack spacing during tension was measured by image analysis and correlated to strain. Local and global deformation was addressed. To demonstrate the high performance of the developed composite in long term applications, its resistance to tensile fatigue cycles was investigated. The composites were subjected to tensile fatigue load with maximum stresses ranging from 4 to 9.6 MPa at a frequency of 2 Hz. The composites did not fatigue below a maximum fatigue level of 6 MPa up to 106 cycles. Monotonic tensile testing was performed for composites that survived 106 cycles to determine its residual strength

Effect of plain and carboxylated styrene-butadiene rubber on the rheological behavior of silica fume-class G Portland cement slurries

The incorpation of a high pozzolan content in cement systems enables an enhanced thermal stability. In an even harsh condition, where imposed deformations occur in addition to high temperatures, it is desirable that cementitious systems present high ductility, which can be achieved for example by adding polymers. The aim of this paper, is to better understand the rheological behavior of ductile cement slurries, designed for oil wells subjected to cyclic steam stimulation. The studied cement formulations contain Silica Fume and two different copolymers (Styrene-Butadiene and its carboxylated version). The influence of each copolymer content on the rheological parameters was investigated. Isothermal calorimetry was used to measure the induction period to guarantee that rheological parameters were carried out in the same hydration period. As the rheometer test was carried out in a non-isothermal condition together with a vane applied shear rate, increased reaction rates are expected. However, it is plausible to assume that the pastes remained in the induction period otherwise they would be in the acceleratory period where pastes start to set. Attempts have been made to correlate properties found by rheometry in the mini-slump test. It was observed that the XSBR delays and decreases the ettringite formation in the first hours of cement hydration, leading to lower yield stress values and increased viscosity and thixotropy. Good correlations were established between parameters measured by rheometry and mini-slump tests, which show promising results for potential use in on-site yield stress and plastic viscosity tests in Oil Well applications

Influência da substituição parcial de cimento por cinza ultrafina da casca de arroz com elevado teor de carbono nas propriedades do concreto

Este trabalho descreve o emprego de cinza ultrafina da casca de arroz com elevado teor de carbono em concretos de resistência convencional e de alta resistência. Estudou-se a influência do emprego da cinza ultrafina (10%, 15% e 20% de substituição de cimento, em massa) nas propriedades reológicas (tensão de escoamento e viscosidade plástica), na resistência à compressão (7, 28, 90 e 180 dias) e na penetração acelerada de íons cloreto. Além disso, a elevação adiabática da temperatura de um concreto convencional com 15% de cinza ultrafina foi comparada com a elevação de um concreto de referência. Os resultados indicaram que a cinza ultrafina produz melhorias significativas nas propriedades dos concretos para ambas as classes de resistência

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.FAPEAMCoordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)CNP

Compósito trifásico baseado em resíduo de goma de mascar-sbr e partículas de quartzo

O elevado consumo de produtos industrializados e o seu rápido descarte produzem grandes quantidades de resíduos sólidos, dos quais, os principais constituintes são os materiais poliméricos. Dentre estes, as borrachas de butadieno estireno merecem destaque. Esse material é usado em diversos setores, entre eles, o alimentício, para produção de chicles. A reciclagem desses materiais deve ser sempre pesquisada, buscando, principalmente, novas aplicações. Assim, este trabalho usou a borracha residual (BP) como matriz para cristais de quartzo. Os materiais preparados foram estudados por diversas técnicas, como, por exemplo, a Análise Termogravimétrica (TGA) e a Espectroscopia no Infravermelho por Transformada de Fourier (FTIR). Além disso, os materiais tiveram suas propriedades elétricas medidas. Foram feitas medidas de capacitância, campo elétrico, resistividade e densidade de corrente. Entre os materiais testados, o compósito carregado com 44,4% de quartzo apresentou a resposta mais linear e mais intensa de variação de carga elétrica em função da pressão aplicada. Portanto, os resultados mostraram que foram obtidos materiais com potencial aplicação no campo de sensores capacitivos de pressão.Palavras-Chave: SBR, goma de mascar, partículas de quartzo, sensor

Cinzas de biomassa geradas na agroindústria do cacau: caracterização e uso em substituição ao cimento

Cinza de biomassa é um resíduo sólido gerado em grande quantidade em caldeiras para produção de energia e calor. Na indústria de processamento de cacau, que usa casca de amêndoa de cacau (20%) e madeira de eucalipto (80%) como combustível, são geradas cinzas volantes e cinzas de fundo, cujas propriedades são pouco conhecidas, o que limita sua correta disposição ou aplicação. Neste trabalho, cinza fornalha (fundo) e ciclone (volante) foram coletadas, durante o processo de limpeza da caldeira, e caracterizadas quanto a composição química, morfologia (MEV), granulometria e mineralogia (DR-X) com o objetivo de avaliar a potencialidade das cinzas para uso como adição mineral. As cinzas foram beneficiadas com moagem e queima controlada a 500, 700 e 900o C. Para avaliação do efeito da cinza, foram moldadas quatro argamassas com 5% de substituição de cimento por cinza ciclone e cinza fornalha, in natura e moídas. Os resultados dos testes de absorção de água e resistência mecânica (compressão e tração na flexão) demonstraram um aumento da absorção e da porosidade para todas as misturas, mas a manutenção das propriedades mecânicas para mistura com cinza ciclone moída, quando comparada com a argamassa sem adição, demonstrando a potencialidade desta cinza como adição mineral

PCM-Impregnated Textile-Reinforced Cementitious Composite for Thermal Energy Storage

The growing global energy demand requires solutions that improve energy efficiency in all sectors. The civil construction sector is responsible for a large part of global energy consumption. In this context, phase change materials (PCMs) can be incorporated into construction materials to improve the energy efficiency of buildings. The purpose of this study was to incorporate a PCM to jute fabric, applying it in civil construction as a reinforcement for cement matrices. In order to do that, a method of immersing jute fabric in liquid phase change material, and then coating it with a polymer, was proposed. Treated jute fabric was then used to produce a laminated composite with a cementitious matrix. Morphological, mechanical and chemical characterization of jute textiles was performed, as well as an analysis of the composites’ mechanical and thermal behavior. The results verified that jute textiles absorbed 102% PCM in weight, which was successfully contained in the capillary porosity of jute. The PCM was able to delay the composite’s temperature increase by up to 24 °C. It was concluded that this method can be used to incorporate PCM to natural textiles, producing composites with thermal energy storage properties