The Experts below are selected from a list of 7827 Experts worldwide ranked by ideXlab platform
Haim Cohen - One of the best experts on this subject based on the ideXlab platform.
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coal fly ash as a potential fixation reagent for radioactive wastes
Fuel, 2015Co-Authors: Roy Nir Lieberman, Uri Green, Giora Segev, Mehmet Polat, Yitzhak Mastai, Haim CohenAbstract:Abstract Israel produces ∼1.3 Mt/year of fly ash (FA), a byproduct of its coal-fired power plants. Due to increasing environmental regulations, these imported coals are processed to reduce the sulfur concentration (∼0.6%). These processing methods result in a material that has an enriched alkali/alkali earth component with pozzolanic and basic properties (pH > 10.5). FAs are utilized worldwide, mainly as a Cement Additive for the construction industry. Recently, it was demonstrated that Class F FA can act as an excellent fixation reagent for acidic wastes from the phosphate or the oil regeneration industries. In the current work the potential utilization of Class F FAs as fixation reagents for low-activity radioactive waste from the nuclear industry was examined. Aqueous solutions containing radionuclide simulants: cesium (Cs + ), strontium, (Sr 2+ ), and cerium (Ce 3+ , Ce 4+ ) were used as case studies with promising results. It is suggested that the primary fixation mechanism involves the aluminate/silicate anions at the FA surface. A novel experimental fixation approach utilizing the formation of carbonates is demonstrated and a new interaction mechanism is suggested based on the electrostatic interactions of the positively charged fine precipitates with the negatively charged FA surface.
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synergetic effect of coal flyash as a scrubber to acidic wastes of the phosphate fertilizers industry
2003Co-Authors: Haim Cohen, Eli Lederman, Mike Werner, Ithamar Pelly, Mehmet PolatAbstract:Fly ash is produced in Israeli power stations via bituminous combustion At present 1.5 million tons of fly ash are produced annually in 4 power stations and only ~50% of it is used as a Cement Additive. The rest is utilized in the construction industry. Environmental regulations in Israel define fly ash as a non hazardous material but still the regulations impose that any potential utilization needs special permit from the Ministry of Environmental Affairs. Thus the regulations imply that the ash to be used will be in accordance with the CALWET or the improved EPA-TCLP1311 leaching methods. The fly ash produced in Israel is very basic due to the low sulfur appreciable (up to 12%) mineral matter of the imported coals. Thus it is a good potential chemical scrubber to acidic wastes. The fertilizer industry in Israel produces mainly phosphate based products. The production methods rely heavily on dissolution of phosphate rock in strong acids. Thus large quantities of acidic wastes are produced. These wastes have to be treated before final storage. We have checked the possibility of using the fly ash to neutralize the acidity and fix the heavy toxic elements contained within the wastes. The results show that the fly ash is an excellent scrubber and also that it's large surface area serves as a very efficient absorber to the toxic heavy metals from
A P M Kentgens - One of the best experts on this subject based on the ideXlab platform.
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a structural investigation relating to the pozzolanic activity of rice husk ashes
Cement and Concrete Research, 2008Co-Authors: Deepa G Nair, A L A Fraaij, A A K Klaassen, A P M KentgensAbstract: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 {sup 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 deg. C-700 deg. C. The {sup 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 deg. 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 ismore » the favorable sample to be used as pozzolanic Cement Additive.« less
B Ambedkar - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation on rice husk ash as Cement replaCement on concrete production
Construction and Building Materials, 2016Co-Authors: Josephin Alex, J Dhanalakshmi, B AmbedkarAbstract:Abstract The emission of CO 2 has increased due to Cement manufacturing and improper disposal of rice hush ash (RHA) leads to air pollution and land fill problem. To mitigate these issues, the RHA has been used as Cement Additive in concrete making. A Taguchi L 27 fractional-factorial matrix was designed to assess the individual effects of key process variables like RHA loading, pozzolanicity, curing time, bulk density and RHA size. From the results, mechanical strength increased with decreasing RHA size and 20 wt% RHA replaCement is optimum for 15 and 60 min grounded sample. The morphology of RHA are also discussed.
Pei Chen - One of the best experts on this subject based on the ideXlab platform.
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studies on effects of burning conditions and rice husk ash rha blending amount on the mechanical behavior of Cement
Cement & Concrete Composites, 2015Co-Authors: Xingfei Song, Xiaoyu Ji, Pei ChenAbstract:Abstract The properties of RHA samples obtained at different conditions in muffle furnace and their effects on the mechanical behavior of Cement have been studied. The properties were characterized by SEM, XRF, XRD and specific surface area. The effect of using RHA as a partial replaCement for Cement has been investigated by compressive and flexural strengths test. It is showed that in muffle furnace 600 °C is the appropriate temperature for RHA preparation with large specific surface area due to the existences of nanoscale and amorphous SiO 2 . While, long combustion time could increase pozzolanic activity of RHA. The presence of K could decrease the specific surface area and increase the residual carbon content which content should be control strictly. RHA obtained in proper conditions can be used as Cement Additive to increase compressive and flexural strengths of Cement mortar specimens. It is verified that RHA replaCement ratio of 10% (by weight) has the best enhanCement effect on Cement strength.
Rui Yu - One of the best experts on this subject based on the ideXlab platform.
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influence of agglomeration of a recycled Cement Additive on the hydration and microstructure development of Cement based materials
Construction and Building Materials, 2013Co-Authors: Rui Yu, Zhong He ShuiAbstract:Abstract This paper presents a study, including experimental and mechanism analysis, on investigating the effect of agglomeration of a recycled Cement Additive on the hydration and microstructure development of Cement based materials. The recycled Additive is firstly produced form waste hardened Cement paste subjected to high temperature environment, namely original dehydrated Cement paste (DCP). Then, to reduce the amount of agglomerated particles, the original DCP is dispersed by the method proposed in this study. The experimental results show that due to the agglomeration of the DCP particles, much free water can be trapped into the flaky layers, which cause that the Cementitious system with original DCP need more water to maintain the normal consistency. Additionally, due to the nucleation effect of small DCP particles, the hydration and microstructure development of Cement can be effectively promoted, which directly cause the enhanCement of the mechanical properties of the Cementitious system. However, this promotive effect of the fine particles in DCP could be obviously reduced by its particle agglomeration.