Chemical and Microstructural Effects of Different Calcinating Temperatures on Selected Pozzolans (original) (raw)
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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.
Nigerian Journal of Technology, 2018
Recycling of agricultural wastes such as rice husk ash as pozzolan is being increasingly encouraged, particularly in developing countries. In this paper, preliminary investigation on the physical and chemical compositions of rice husk ash using different techniques was carried out. Scanning Electron Microscopy (SEM) images of the rice husk ash showed residual pores to be distributed within the ash sample, indicating that the silica is a highly porous material with a large internal surface area. Samples burnt at 400 0 C for 6 hours and 600 0 C for 4 hours for 'Bukus' and 'Soro/ Olomo nla' show aggregates with clearly defined layers of loose flakes compared to 'Faro 58'. The Energy dispersive xray spectroscopy (EDX) analysis of rice husk ash performed to determine percentages of silica present in the samples were graphically represented. Nine elements (Al, Si, K, Ca, Br, Fe, Mg, Na, Mn) and their corresponding oxides (Al2O3, SiO2, K2O, CaO, Br, Fe2O3, MgO, Na2O, MnO) were detected with varying concentrations. The three varieties, on the average possess good silica content of over 50% considering the two varied temperature and time. Therefore, the chemical analysis results show that burning at combustion temperature of 600 0 C for 4hrs, gives optimal result than at 400 0 C for 6hrs because all the samples show high Silica content (Faro 58; 61.9, Bukus; 62.6 and Soro/Olomo nla; 59.5).
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.
American Journal of Civil Engineering and Architecture, 2016
In this study, the effect of the calcination temperature of rice husk on the pozzolanic properties of the resulting rice husk ash (RHA) especially its silica content was investigated. Rice husk was collected from a rice milling plant and washed to remove sand and other impurities, beneficiated using the water beneficiation method and calcined at temperatures of 400, 500, 600, 700and 800°C, respectively for three hours. Samples were taken for XRF analysis, setting time determination and specific gravity test. The result of XRF analysis revealed that RHA calcined at temperatures between 400°C and 800°C contains more than 70% silica as stipulated by ASTM C618 for pozzolanas. The silica content though varies slightly with different calcination temperature of the rice husk ash. Also, calcination removed impurities present in the rice husk. Besides that, the specific gravity of RHA decreases with increasing calcination temperature from 2.00 at 400°C to 1.05 at 800°C. Setting times of RHA mortars at 15% replacement of OPC with RHA shows no definite pattern with increasing temperature. However, the initial and final setting times of OPC-RHA mortars at all calcination temperatures were higher than that of OPC mortar. As a whole, calcination improves the silica content of rice husk ash for use as a pozzolana as well as removes mineral impurities that may affect the pozzolanic properties of the rice husk ash.
Effect of Calcination on the Chemical and Microstructural Properties of Rice Husk Ash
Journal of Engineering Research and Reports, 2021
This research study is aimed to evaluate the effects of different calcination temperatures on the properties of rice husk ash such as the chemical and microstructural properties. Rice husk ash is not utilized properly; it is not dumped with proper handling which is also causing environmental issues. Currently researchers are working on supplementary cementitious materials in concrete, in light of which, this research study is aimed to evaluate the effects of burning on Rics Husk Ash (RHA) structure and its pozzolanic reactivity for utilizing it in concrete. The rice husk is burnt at temperatures of 600-800°C for a duration of 8, 16 and 24 hours and for evaluating different chemical and structural properties through tests of X-ray Diffraction (XRD), X-Ray fluorescence (XRF) and Fourier Transform Infrared Spectroscopy (FTIR). It is concluded that burning of rice husk at 600-800°C for duration of 24 hours gives us more reactive and amorphous material and can be used as a cement substit...
Cement & Concrete Composites, 2009
In this paper a study of calcining conditions on the microstructural features of sugar cane waste ash (SCWA) is carried out. For this purpose, some microparticles (<90 lm) of sugar cane straw ash and sugar cane bagasse ash of samples calcined at 800°C and 1000 are studied by combining the bright field and the dark field images with the electron diffraction patterns in the transmission electron microscopy (TEM). It is appreciated that the morphology and texture of these microparticles change when silicon or calcium are present. Furthermore, it is observed that iron oxide (magnetite Fe 3 O 4 ) is located in the calcium-rich particles.
Use of Processed Biomass Ash as a Sustainable Pozzolana
Current Science, 2019
The industrial waste generated from sugar production, i.e. bagasse is further used as a biofuel. This generates a huge amount (44,000 tonnes/day) of waste in the form of sugarcane bagasse ash (SCBA). Asreceived boiler SCBA shows lower performance in terms of pozzolanic characteristics. In this study, the role of mechanical and thermal treatment in improving the pozzolanicity of SCBA has been examined. The preliminary characterization of SCBA was done using laser granulometry, SEM, XRF, XRD and TG analysis. The four methods were adopted to quantify the pozzolanic behaviour, viz. reactive silica determination, pozzolanic activity index, electrical conductivity drop and Chapelle activity. Further, the experimental data were analysed using ANOVA. The coefficient of regression (0.86-0.99) reflects effective and significant logarithmic models. The study concludes that the adopted processing of SCBA is highly effective in improving the pozzolanicity. Thus the processed SCBA is a sustainable solution to the cement industry.
BioResources, 2015
The construction industry is one of the largest and most active growth sectors worldwide. It presents an important environmental impact, and one way to reduce the impact of the construction activity is to substitute pozzolanic materials for ordinary Portland cement. In this work, barley straw, barley straw ash, and other natural and artificial pozzolans from Mexico were characterized and compared. Also, the pozzolanic activity of barley straw ash was compared with the pozzolanic properties of some natural and artificial pozzolans from Mexico. Materials considered included recycled dust of fired clay brick, fly ash, volcanic ash, and wheat straw ash.
Pozzolanic properties of Waste Agricultural Biomass - African Locust Bean Pod Waste
2017
The increase in agricultural waste such as African locust bean pod have resulted in endangering the life of plants and animals. Researchers have found out ways that this environmental pollution can be of positive relevance by recycling the waste to be re-used or reduce to ensure a cleaner and healthier environment. African locust bean pod was ashed and the pozzolanic properties were investigated. The pod was dried, blended and ashed in a furnace at 500°C for two (2) hours; different analysis was carried out on the ash obtained to prove the pozzolanic properties, such as sieve analysis to determine the particle size distribution; reaction of calcium hydroxide with the ash in relation to time which proved that pozzolanic reactivity increases with time, comparison of hydration of Portland cement with ashed locust bean pod mixture and compressive strength test.
Thermal Analysis and Pozzolanic Index of Rice Husk Ash at Different Grinding Time
Procedia Engineering, 2012
Thermo-gravimetric and differential thermo-gravimetric analyses were performance to study the effect of temperature on the mineralogical compositions of rice husk ash subjected to different grinding time. Eight rice husk ashes with different grinding time, i.e. coarse original rice husk ash (RHA0), RHA1, RHA2, RHA3, RHA4, RHA5, RHA6, and RHA7 were used for the study. The TGA/ DTA analysis and X-ray fluorescence (XRF) was used through this investigation. On the other hand, the pozzolanic activity index of the RHA was assessed in accordance with ASTM C 311-11a. From the experiment, it was found that the greater the weight loss, the less the crystallinity of the RHA. In addition, there are no significant differences in chemical compositions of the rice husk ashes with different grinding time. Furthermore, when the grinding time increased from 1 hour and 30 minutes to 5 hours, there was a significant drop in the pozzolanic index.