Effects of calcining conditions on the microstructure of sugar cane waste ashes (SCWA): Influence in the pozzolanic activation (original) (raw)
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Investigation on the pozzolanic properties of rice straw ash prepared at different temperatures
Materials Express, 2018
This study explains the influence of different temperature on the engineering properties of rice straw ash (RSA) and its reactivity as a pozzolanic material. Rice straw ash is used as natural pozzolana, prepared by burning at open atmosphere and three different controlled temperatures (400 C, 600 C and 750 C), as this process is economic. For construction purposes, it will be difficult to extract huge amounts of silica material from rice straw by putting it in acid or basic treatment. The physiological and mineralogical aspects of rice straw ash samples were studied throughout the research. The particular size analysis and field emission gun-scanning electron microscope (FEG-SEM) identify that that the average diameter of RSA particles prepared at 400 C to 750 C, are within the range of 400-800 nm. X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and Fourier Transform Infra-Red Spectroscopy (FTIR) analysis ratify that the main composition of RSA is silica. And most of the silica particles are amorphous and porous in nature, which fit the nature of a pozzolanic material. The pozzolanic reactivity of RSA shows that the compressive strength of RSA blended with lime mortar increases as the number of curing day increases.
This paper reports on the influence of calcining temperature (800 and 1000°C) on the pozzolanic activation of sugar cane straw (SCS). The reaction kinetics of SCS ash-lime mixtures were inferred from physicochemical characteristics (X-ray diffraction patterns and thermogravimetry analysis. The fitting of a kinetic-diffusive model to the experimental data (fixed lime versus time) allowed the computing of the kinetic parameters (reaction rate constant) of the pozzolanic reaction. Results obtained confirm that the sugar cane straw ash (SCSA) calcined at 800 and 1000°C have properties indicative of very high pozzolanic activity. No influence of calcining temperature on the pozzolanic activity was observed. Also, no crystalline compounds during the pozzolanic reaction were identified up to 90 days of reaction. Environmental durability and strength of the consequential mortars remain to be assessed.
Rem: Revista Escola de Minas, 2014
The effect of calcination temperature and air flow on the content of organic material, morphology of particles, degree of crystallinity and the reactivity with lime solution of the sugar cane bagasse ash is evaluated. The results show that the long fibers of the bagasse and organic material are retained when calcination occurs without sufficient air flow. Calcining with forced air-flow breaks the fibers, removes organic material and produces fine particles at a temperature of 600ºC. The non-organic material observed in the ash displays a high degree of crystallinity. Experiments show that the crystalline structure observed in the ashes is due to adhered sand which was not previously washed away. The reduction on the conductivity in lime solution and X-rays diffraction pattern suggest that amorphous silica is formed at temperatures lower than 600 o C and cristobalite is formed at higher temperatures.
ACS Sustainable Chemistry & Engineering, 2016
Biomass has gained in importance as an energy source in recent years. One of the crops that presents interesting opportunities with regard to biomass is sugar cane. In Brazil, sugar cane production is increasing for alcohol and sugar manufacture. Some by-products, such as sugar cane straw, also are obtained during harvesting. Due the calorific value of the sugar cane straw, its use as biomass is increasing. After the straw is burned to produce energy, an ash is obtained: sugar cane straw ash (SCSA). This waste needs an appropriate destination and, since the recent publication of successful studies using biomass derived-ashes as pozzolanic material, the present study aimed to assess the pozzolanic reactivity of sugar cane straw ash. The pozzolanic activity was assessed using a new and simple recently proposed method: evaluation of the electrical conductivity of calcium hydroxide (CH) and pozzolan suspensions, in which solid CH is initially present. These results were compared to those of two other well-established techniques: Fourier transformed infrared spectroscopy and thermogravimetric analysis. The evaluation by all three techniques is similar and shows that sugar cane straw ash is a good pozzolanic material: high lime fixation values for CH:SCSA mixes were determined by thermogravimetric analysis and unsaturation respect to CH in 3.5:6.5 CH:SCSA suspension was achieved at 60ºC. According to this behaviour, a bright future for SCSA as a replacement for Portland cement is expected.
A structural investigation relating to the pozzolanic activity of rice husk ashes
Various factors determine the applicability of rice husk ash (RHA) as a pozzolanic material. The amount and accessibility of reactive sites is thought to be a key factor. A structural study of RHA samples in relation to their reactivity has been performed; Silica in RHA formed by burning rice husk in a laboratory furnace under continuous supply of air have been characterized as a function of incineration temperature, time and cooling regime. The characterization methods included chemical analyses, conductivity measurements, microscopic analysis, X-ray diffraction (XRD) and 29 Si magic-angle spinning (MAS) nuclear magnetic resonance (NMR). In line with earlier observations, the analyses show that the highest amounts of amorphous silica occur in samples burnt in the range of 500°C-700°C. The 29 Si NMR data allow direct identification of the reactive silanol sites in the RHA samples. De-convolution of the NMR spectra clearly shows that the quickly cooled RHA resulting from burning rice husk for 12 h at 500°C has the highest amount of silanol groups. This sample also induced the largest drop in conductivity when added to a saturated calcium hydroxide solution giving an indication of its reactivity towards lime. Therefore, this RHA is the favorable sample to be used as pozzolanic cement additive.
Sugar Cane Wastes as Pozzolanic Materials: Application of Mathematical Model
ACI Materials Journal, 2008
This paper proposes a kinetic-diffusive model that allows for determination of pozzolanic activity as related to optimum calcining temperature on the activation of wastes from sugar cane industries and their use as pozzolanic material. Research based on the reaction kinetics between lime (calcium hydroxide [CH]), sugar cane straw ash (SCSA), and sugar cane bagasse ash (SCBA) calcined at 800 and 1000 °C (1472 and 1842 °F) is described. A pozzolanic activity method (accelerated chemical method) based on the measurement of the amount of CH reacted as the reaction proceeds is applied and the latter on the kinetic parameters are quantified by applying a kinetic-diffusive model to the process. The kinetic parameters that characterize the process (in particular, the reaction rate constant and free energy of activation) were determined with relative accuracy in the fitting process of the model. The pozzolanic activity is quantitatively evaluated according to the obtained values of the kinetic parameters. The results show good pozzolanic properties of the sugar cane wastes between 800 and 1000 °C (1472 and 1832 °F), and no influence of the calcining temperature on the pozzolanic activity for SCSA was observed. The correlation between the values of free energy of activation ΔG # and the reaction rate constants K are in correspondence with the theoretical studies about the rate processes reported in the literature.
Sugar cane bagasse ash as a pozzolanic material
DYNA
Este estudio tiene como objetivo verificar el potencial de uso del CBCA como sustitución parcial del cemento Portland. Por lo tanto, la campaña experimental fue dividida dos etapas; En la primera, se realizaron análisis mineralógicos y químicos con dos muestras de ceniza, crudas y calcinadas a una temperatura de 600°C durante 6h. En la segunda etapa, se observó que las cenizas calcinadas presentaban una mayor cantidad de material en estado amorfo, lo que posiblemente hizo que el material fuera el más reactivo. Por esta razón, sólo la ceniza calcinada se molió durante 1 y 2h. Adicionalmente estas muestras fueron estudiadas para verificar el índice de actividad puzolánica y la resistencia a la compresión, evaluando la sustitución de cemento Portland en proporciones de 10, 20 y 30% por SCBA. Los resultados mostraron un incremento demostrado que tanto la ceniza in-natura como la ceniza calcinada deben ser sometidas a un proceso de molienda para presentar actividad puzolánica.
Assessing the pozzolanic activity of sugarcane bagasse ash using X-ray diffraction
Construction and Building Materials, 2020
h i g h l i g h t s Calcination and grinding clearly increased SBA pozzolanicity. Methods to measure calcium hydroxide consumption by XRD analysis were studied. Relative decrease in calcium hydroxide peak intensity (CH RDPI) provided relevant information about SBA pozzolanicity. CH RDPI presented a strong correlation with data from other pozzolanic activity tests.
Pozzolanic behaviour of a bagasse ash from the boiler of a Cuban sugar factory
Advances in Cement Research, 2013
The paper presents a study of the pozzolanic reaction kinetics between calcium hydroxide and sugar cane bagasse ash (SCBAB) from the boiler of a sugar factory. A pozzolanic activity method (conductometric method) based on measurement of the electrical conductivity of the SCBAB/calcium hydroxide solution as the reaction proceeds is applied and the kinetic parameters are then quantified by applying a kinetic–diffusive model to the process. The kinetic parameters that characterise the process (in particular, the reaction rate constant and the free energy of activation) were determined with relative accuracy in the fitting process of the model. The pozzolanic activity is quantitatively evaluated according to the obtained values of the kinetic parameters. Other experimental techniques, such as X-ray diffraction and scanning electron microscopy, are also employed. Comparison with another bagasse ash calcined under controlled conditions in the laboratory is carried out. The results show th...
Cement and Concrete Composites, 2011
The effect of the particle size distribution and specific surface area on the pozzolanic activity of a residual rice husk ash (RHA) was investigated in this work. Different samples of RHA obtained from ultrafine grinding were characterized with respect to particle size analyses by laser granulometry, BET and Blaine specific surface areas, pore volume distribution by mercury intrusion porosimetry, surface texture by scanning electron microscopy, pozzolanic activity using the cement mortar method and activity with lime using the Chapelle method. From the results, it was concluded that a good correlation exists between the 'external' specific surface area, that is, the surface area associated with the measured particle size distribution, and the pozzolanic activity of the residual RHA. On the other hand, nearly no correlation was identified between the pozzolanic activity and the specific surface area measured using the BET method, an observation that is particularly related to the cellular nature of the internal structure of this RHA.