Contribution of blended cement in sustainable cement production. Part I
The objective of this research is to establish the influence of blended cements, i.d. to determine the effects of combined dosages of mineral additions in cement production and the application of cement in concrete. The research has concentrated on the effects of mineral additions on the properties of blended cements as well as the environmental-sustainable effects of cement production with regard to the saving of natural resources and reduction of CO2 emission.
Acknowledging the literature data and the collected indicators about the developmental trends in this industrial area, the experimental research was conducted as industrial research into the clinker production. The objective was to collect the data about the change of the reduced consumption of thermal energy and electricity on change in CO2 emission resulting from different composition of raw material; it was also conducted as laboratory and industrial research into cement with the objective to increase the use of clinker with mineral cement additions.
Finally, it was laboratory research into concrete with the purpose of determining the infl uence of blended cements on durability properties. The theme of this paper is the research of secondary raw materials as cement additions and their role in the environmentalsustainable production of concrete. (...)
29Si and 27Al MAS NMR characterization of cement–State of art
This paper summarizes the information available on the application of solid-state nuclear magnetic resonance (NMR) techniques to the characterization of Portland, belite and calcium aluminate cement. The nuclei studied were 29Si and 27Al. The 29Si spectra of anhydrous cement (C2S and C3S) contain Q0 units, while both Q1 and Q2 units can be identified on the spectra for C-S-H gel. Further to the literature on the chemistry of cement, the chain comprising C-S-H gel normally has two, five or even eight links.
Aluminium taken up by the gel may replace silicon atoms in tetrahedral bridge bonds, giving rise to Q2(1Al) units. Moreover, the tetrahedral aluminium (AlT or Al(IV)) present in the anhydrous phases of cement converts to octahedral aluminium (AlO or Al(VI)) when different type of calcium sulfoaluminate, calcium aluminates hydrate and/or Al(OH)3 are formed.
EQUIPMENT PROVIDERS 1
ACS 2000 variable speed drive reduces energy consumption and improves process control of a cement plant
Jura Cement, Switzerland’s second largest cement producer replaced a 25-year old cascade converter with a variable speed drive from ABB. Cement plants use a lot of energy and technologies that help cut the high energy bills are well regarded. One of the biggest benefits of installing the ACS 2000 compared to the cascade drive is the energy saving potential. The kiln fan is one of the largest consumers of energy in a cement plant. Controlling a kiln fan with an electric variable speed drive can result in significant energy savings.
The kiln had to be stopped up to 30 times per year. Some stop pages were the result of brush changes to the slip ring motors. Based on the experience from the ACS 2000’s performance, Jura Cement will have no kiln stops because of the drive’s maintenance or performance.
EQUIPMENT PROVIDERS 2
Secondary fuels, energy for the cement industry
Due to decreasing resources and increasing market prices for primary fuels like oil, gas or coal, it is paramount for the cement industry to search for alternative energy sources. With regard to the CO2 emissions trading, a switch to energy sources which have a neutral CO2 balance can be rather profitable. Usually, these are non-fossil fuels. Industries with high energy consumption have made increasing use of alternative fuels during the last years. Accordingly, the use of so called secondary fuels (also waste derived fuels/wdf or refuse derived fuels/rdf) has gained importance.
EQUIPMENT PROVIDERS 3
Secondary fuel: where to get from and how to use
With this Vecoplan system, the RDF fuel quality control becomes a loop and the cement plant gains independency from the individual RDF fuel suppliers. In worst case the unloaded material will be dropped into a separate “quarantine” box inside the storage area in order to avoid that contaminated RDF will be mixed into good fuel. This box can be re-loaded into the same suppliers truck and returned to the RDF fuel supplier for re-working or disposal.
Even if the RDF quality will be proven with new preparation technologies we have to understand that the mixing of RDF is the most important step in order to substitute secondary fuel safely from different waste streams at high substitution rates.
Long-term deflections of concrete beams reinforced with fibre reinforced polymer bars
This paper presents and discusses procedures able to be applied to long-term defl ection calculation of flexural concrete members reinforced with fibre reinforced polymer (FRP) bars. Due to its simplicity and wide dissemination, most of the approaches so far are based on multiplicative coefficients applied to the values of instantaneous deflections. The suitability of the complementary methodology for long-term deflection calculation presented in the new Spanish code EHE to be applied to FRP reinforced concrete is discussed.
Comparative analyses with procedures from other design guidelines for FRP reinforced concrete structures are performed. Due to the mechanical properties of FRP bars, the use of the same coefficient as for steel reinforced concrete structures, or a single multiplicative coefficient, can lead to inadequate values in the calculation of long-term deformations.
Replacement of fossil fuels in the cement sector. A chance for dumping waste reduction
The main objective of this study is to determine the destination of different types of potentially recoverable wastes, that nowdays are being sending to landfi lls, and their potential use in cement kilns.
The list of potential wastes that can be used in cement plants is very extensive. Not all of them have been analyzed, only those which have specific existing management infrastructure. The types of wastes including in the study are the following:
- Used tyres.
- Mineral Oils.
- Industrial wastes.
- Meat flours.
- Vehicles out of use.
- Sewage sludge.
- Agricultural plastics wastes.
- Residue Derived Fuels (RDF).
One of the main conclussions of the study is the great potential of the RDF as an alternative fuel for the cement sector; the estimated supply of fuels derived from almost 20 Mt of urban waste (mainly from treatment plants) is in the order of 1,2 Mt yearly.
Use of wastewater sludge treated with CaO as a novel alternative raw material in the clinker manufacturing process
Cementos Molins Industrial is studying the industrial application of a novel alternative raw material that would replace lime in the clinker manufacturing process. This innitiative is framed in Sostaqua: a Cenit project lead by Aguas de Barcelona devoted to build technological developments focused to a self-sustainable urban water cycle.
In particular, Cmisa is aimed at studying the contribution of Cement Industry in the urban water cycle. The new alternative material under study (Neutral) is obtained from wastewater treatment plant sludge.
In the present study, in collaboration with Instituto Torroja de Ciencias de la Construcción (IETcc), a chemical and mineralogical study on Neutral has been performed, and calcination studies have been performed substitutind lime by Neutral and analyzing the clinker obtained. The results obtained at a lab scale show that Neutral can be introduced in the clinker manufacturing process as a calcium component substituting (totally or partially) lime. This interchange may bring up two fundamental advantages to the clinker formation process: the reduction in raw materials consumption and the lower CO2 emission.
Assessment in the experience of the use of alternative liquid fuels at the C.P.V. cement plant in Mataporquera (Cantabria)
To increase the alternative fuels consumption is one of the main future challenges for Portland Valderrivas Cement Group, particularly at its cement plant in Mataporquera (Cantabria). In November 2006, the alternative liquid fuels plant started functioning. Three years full of new experiences and hard work to optimize the use of residual fuels and guarantee the competitiveness of the cement plant.
Enerfuel: the source of the future
After having lower utilisation rates in the past, in 2009 Cemex Spain will reach a substitution rate close to 27 per cent for alternative fuels. A significant increase in usage began in 2008 with the use of refuse derived fuels (Enerfuel) at its Alicante plant. State-of-the-art technology will allow substitution rates above 40 per cent just for this secondary fuel, which is composed of a mix of paper, plastics, textiles and wood, on top of existing alternative fuels presently used.
The Torre Espacio in Madrid (2nd part)
The Torre Espacio (Space Tower), in Madrid, is one of the highest sky-scrapers in Europe. The building is located in the sky-scraper complex Cuatro Torres Business Area (CTBA) (Four Towers Business Area). It is 236 m high and has 57 floors above ground level.
These have a square shape in the base, which changes gradually as height increases to become eventually an ogive, following a curve represented mathematically by the cosine function. Construction processes and installations non habitual in Spain have been used, e.g. high strength concretes, special methods to pump concrete pumping, self climbing forms or modular façades. In the second part of the article the activities in the design phase are described, as well as the characteristics of the structure and of its construction process, the used concretes and the performance of the structure in a fire during their execution.