32 research outputs found
Oxyfuel Combustion Residues as Supplementary Cementitious Materials for the Production of Blended Portland Cements
No full textOxyfuel combustion represents one of the most interesting processes aimed at CO2 capture and storage to mitigate greenhouse effects ascribable to the process industry. In a different technical area, searching for new processes aimed at producing low-CO2 cements has comparable relevance, due to the huge generation of greenhouse gases related to cement production. This paper proposes an integration of these two aspects, with an approach new in the pertinent literature. The possibility of reusing ashes, issued by a pilot plant fluidized bed oxyfuel combustion process, as a source of material in the production of low-CO2 cements is investigated. Ashes were tested as substitutes for natural pozzolan in blended cements. They were mixed with an industrial Portland clinker and natural gypsum in order to evaluate their hydraulic behavior at different curing temperatures (20–40°C) and times (2–28 days). Pozzolanicity tests together with differential thermal–thermogravimetric and X-ray diffraction analyses were employed to explore the hydration behavior of oxyfuel ashes-based blended cements
Use of Fluidized Bed Combustion Residues and Alumina Powder as Components of Ettringite-Based Aerated Building Elements
No full textThe use of industrial wastes and by-products for making construction materials unequivocally gives a
pronounced environment-friendly character to their manufacturing process. Two binary (M1, M2) and one
ternary (M3) mixtures, based on alumina powder, fluidized bed coal combustion fly- and/or bottom-ash were
submitted to hydrothermal treatments in order to generate aerated building elements based on ettringite
(6CaO·Al2O3·3SO3·32H2O); ettringite is a compound characterized by low density, water insolubility, high fire
resistance and significant mechanical strength. The M1 – M3 systems were hydrated in a thermostatic bath
(100 % R.H) at 55 °C and 70 °C for aging periods ranging from 2 h to 28 d; the hydrated samples were
submitted to both differential thermal–thermogravimetric and X-ray diffraction analyses for assessing the
formation of the hydration products. In this regard, the ettringite generation, being also dependent on the
operating temperatures and times, was observed within all the investigated systems. Furthermore, the best
results in terms of both ettringite concentration and formation rate were exhibited by the M2 system at 70 °C
after 2 d of curing
Factors influencing charge capacity of vanadium pentoxide thin film during lithium ion intercalation/deintercalation cycles
No full textXPS study of the Li intercalation process in sol-gel-produced V2O5 thin film: influence of substrate and film synthesis modification
No full textUse of solar energy to sustain limestone calcination for ordinary Portland cement production
No full textCement manufacture is one of the most raw materials- and energy-intensive industrial processes; moreover, its contribution to global anthropogenic CO2 emission is estimated as high as 6%. Most of energy requirement and CO2 generation are mainly associated with limestone calcination (LC). The use of solar energy as non-carbogenic renewable source for LC was evaluated in this paper; to this end, a directly irradiated fluidised bed (FB) reactor has been employed as limestone precalciner upstream of a cement clinker production kiln. LC was carried out at 940°C in an atmosphere containing about 70% CO2. The experimental activity was devoted to assess the reactivity of calcinated lime toward the main clay components for the Portland clinker (PCl) production process, as compared to lime from ordinary calcination. Portland cements (obtained by mixing PCls with 5% natural gypsum) were hydrated for periods ranging from 2 to 28 days (water/cement mass ratio=0.5). Parameters as lime saturation factor, burnability, clinker phase composition and cement pastes hydration behaviour were assessed
Use of oxyfuel combustion ash for the production of blended cements: A synergetic solution toward reduction of CO2 emissions
No full textIn this paper, it is investigated the possibility of reusing ashes, issued by an oxyfuel combustion process aimed at
mitigating CO2 emission, as substitutes for natural pozzolan in the production of low-CO2 blended cements. To
this end, the oxyfuel plant (a 95kWth pilot-scale fluidized bed reactor) was operated under controlled conditions
by feeding blends of anthracite or lignite and biomass corn stover. Characterization of fly and bottom ashes revealed
that the latter showed properties able to make them considerable for obtaining blended cements by
mixing themwith Portland clinker and natural gypsum. The cements were subjected to pozzolanicity and hydration
tests for curing times ranging from2 to 28 d at 20° and 40 °C. X-ray fluorescence and diffraction, differential
thermal–thermogravimetric analyses and scanning electron microscopy were employed as characterization
techniques. With reference to a standard blended cement, and with particular eye on the blended cement containing
bottom ashes obtained from the lignite–biomass mixture combustion, it was observed a good similarity
in the ability of the silico-aluminous fraction to react with Ca(OH)2 produced by Portland clinker hydration, to
yield the desired calcium silicate hydrates among the hydration products
Oxyfuel combustion residues as supplementary cementitious materials for the production of blended Portland cements
No full textOxyfuel combustion represents one of the most interesting processes aimed at CO2 capture and storage to mitigate greenhouse effects ascribable to the process industry. In a different technical area, searching for new processes aimed at producing low-CO2 cements has comparable relevance, due to the huge generation of greenhouse gases related to cement production. This paper proposes an integration of these two aspects, with an approach new in the pertinent literature. The possibility of reusing ashes, issued by a pilot plant fluidized bed oxyfuel combustion process, as a source of material in the production of low-CO2 cements is investigated. Ashes were tested as substitutes for natural pozzolan in blended cements. They were mixed with an industrial Portland clinker and natural gypsum in order to evaluate their hydraulic behavior at different curing temperatures (20–40°C) and times (2–28 days). Pozzolanicity tests together with differential thermal–thermogravimetric and X-ray diffraction analyses were employed to explore the hydration behavior of oxyfuel ashes-based blended cements
Construction and Demolition Waste as Raw Materials for sustainable Cements
No full textIn 2014 about four billion tonnes of cement were produced [CEMBUREAU, 2014]. The use of industrial by-products, as a source of raw materials in the manufacture of portland and blended cements, is a research theme of significant relevance to the construction industry. Such industrial by-products can be employed as constituents of the final product or components of the raw feed in a cement kiln. Due to their hydraulic and/or pozzolanic activity, industrial by-products are utilized worldwide. Such by-products also increase durability and reduce costs for producing blended cements.
The use of such by-products as raw mixture component for the cement production has received comparatively little attention by researchers and engineers. There is currently an increasing interest towards searching for new categories of by-products, which would be able to provide reactive calcium, silicon, aluminum, and/or iron oxides, for portland cement clinker manufacture. In this regard, construction and demolition waste (C&DW) is worthy of consideration because, when obtained from a properly selective demolition process, they could be employed as alternative raw material for portland clinker production.
The present study deals with the use of two different kinds of C&DW, namely concrete waste (CW) and masonry waste (MW). In this study, C&DW is proposed to be employed as partial or total substitute for limestone and clay, respectively, in the portland clinker generating raw mixture. Four ternary mixtures containing limestone, as well as CW and MW, were subjected to laboratory tests in order to evaluate the clinker raw mixture produced and the performance of the related portland cement. A binary mixture, composed of limestone and clay, was used as a reference. All of these different cements displayed similar hydration behavior. Detailed results are presented and discussed
Synthesis and characterization of belite calcium sulfoaluminate cements produced by oxyfuel combustion residues
No full textIn this work, the possibility of reusing ashes issued by an oxyfuel combustion process (OC) as a source of material in the production of belite calcium sulfoaluminate BCSA cements has been investigated. OF process is one of the most promising combustion technologies for CO2 reduction from power plants. Combustion tests were carried out in an oxyfuel bubbling fluidized bed pilot plant. Four BCSA clinker-generating raw mixes were heated in a laboratory electric oven in the temperatures range 1150°-1350°C: one included only natural materials (limestone, clay, bauxite and gypsum), the others contained OC ashes as total substitute for clay. X-ray diffraction (XRD) analysis on the burning products showed high conversion of reactants toward the main BCSA clinker components (C2S and C4A3$), especially at 1200° or 1250°C. Moreover, physical-mechanical tests associated with XRD and differential thermal-thermogravimetric analyses accomplished on all the cements (obtained by adding natural gypsum to the clinkers produced at the best synthesis temperatures) generally displayed a similar hydration behaviour
Dolomite-based binders manufactured using concentrated solar energy in a fluidised bed reactor
No full textDolomite-based binders are characterised by interesting technical and environmental features. For their synthesis, sources of both CaO and MgO are required. The idea developed in this work is to couple the synthesis of dolomite-based binders, starting from a natural dolomite, through the concept of concentrated solar energy (needed to drive the endothermal dolomite calcination process) in fluidised bed reactors. To this end, a fluidised bed system, where the concentrated solar radiation is mimicked by the use of Xe-lamps (short-arc), has been set up and operated. Natural dolomite (sieved in the 420–590 μm size range) was calcined at a nominal temperature of 850 °C, and bed temperature profiles during solar-driven calcination were investigated. Then, four binders were prepared by mixing slaked dolomite (obtained from the hydration of solar calcined dolomite) with either blast furnace slag or coal fly ash as supplementary cementitious materials. The binders were hydrated for curing times ranging from 7 to 56 days. X-ray fluorescence, X-ray diffraction and combined differential thermal and thermogravimetric analyses were employed as characterisation techniques both to analyse the chemical composition of starting materials and to investigate the evolution of the hydration in the four systems
