Recycling and waste recovery in European cement and concrete sector
Spain is one of the low performance countries co-processing byproducts for the cement and concrete industry, far below other countries like Germany or Belgium which lead this tendency.
The construction market in Spain is changing to a quality-driven market and it involves many activities related to sustainability issues. In Spain there is experience with the usage of secondary cementicious materials in cement production but at a lower level than in other European countries. The use of alternative fuels as an energy source is less than 10% in comparision with up to 40% in other countries, which means that there is still much more to do. The use of recycled aggregates is another trend not fully exploited in Spain but which has succesful experiences in many other areas of Europe.
In general, the Spanish construction market can grow in sustainable practices just by following examples from other european countries which have proven their viability.
Obtaining backfill mixes using unclassified grading aggregates from aggregate crushing processes
In the aggregate extraction industry, the efficiency of the process looks for the maximum use of the aggregates produced, either used as extracted from deposits or from processing after quarrying. Usually, some percentage of unclassified material, which is not suitable for any of the common applications (mortar, concrete, road substrates) is produced, most of the time consisting in fine materials. Thus, it is necessary to find applications where these materials can be used. One of these possible applications is the use of unclassified gradings for the production of low-density backfills. These backfills are self-compacting materials of tailored strength, suited of high flowability, that can be used in lieu of the traditional compacted soil fill.
They can be readily placed into a trench, hole or other cavity. Compaction is not required; hence, the trench width or size of excavation can be reduced. Because of its fluidity, they are rapidly placed. Granular or site-excavated backfill, even if compacted properly in the required layer thickness, can not achieve the uniformity and density of these materials. They are easily reexcavated in case of need for place for future interventions. Its use is widely extended in some countries, and the ACI has even issued a recommendation guide. This work shows the advantage of fine aggregate unclassified fractions for the production of controlled low-strength materials for its use as backfill, when used in mixes with low cement content and with the help of a high activity foaming agent.
Effect of zeolite and zeolite – iron powder mixture on durability of cement suspension in carbon dioxide water
Cement-bentonite suspension is frequently used for the construction of slurry cut - off walls. Its disadvantage lies in relatively low resistance to aggressive liquid media. Hardened cement-bentonite suspension shows a marked loss in weight and compressive strength in water saturated by 50 mg of CO2
per liter of the solution.
The specimens are disrupted after 180 - day exposure. Contrary, weight and compressive strength losses are lower in the hardened cement-zeolite suspension. The specimens retain a rigid structure even after 365 days of CO2 water attack. The resistance of cement-zeolite suspension is further increased by the addition of finely ground iron powder. Zeolite addition contributes to reduction of Ca(OH)2 formation by pozzolanic reaction of zeolite consuming free CaO and developing microstructure with higher strength compared to that in cement – bentonite suspension with prevailing formation of Ca(OH)2 crystals. The positive effect of iron powder lies in changes in the formed microstructure of hydrated cement - zeolite suspension evoking the formation of voluminous rust products of iron - ferrous carbonate, ferrous bicarbonate, ferric oxide – hydroxide and consequently calcium ferric hydrate, decreasing the suspension permeability to CO2 and increasing its resistance to carbon dioxide water. (...)
The strength control of concrete in accordance with EHE-08
The possession of a recognised quality mark for the materials and deliveries of structural concrete implies advantages during the project and control in accordance with the new Structural Concrete Regulations EHE-08. The Strength control has different acceptance criteria when a recognised quality mark for the
The main aim of this paper is the study on the basic concepts of strength control through the Monte Carlo Simulation. The EHE-08 principles to take into account for the concrete manufacturer during the production process and delivery with acceptance probability are also considered in the exposed analysis.
The influence of using a concrete with recognised quality mark in testing results and the testing conditions by repeatability and bias, are also examined. Both construction and autocontrol tests are analysed. Finally, other non-statisticals methods of control will be shown, as well as the decisions arising from the quality control.
REACH, basics and implementation in the cement industry
REACH is the abbreviation for the new EU regulatory regime for the registration, evaluation, restrictions and authorisation of chemicals. This Regulation was adopted on 18 December 2006 and came into force on 1 June 2007.
The aim of this article is to provide an overview of the European regulation on the Registration, Evaluation, Authorisation and Restriction of Chemical substances (REACH) and, more specifically, implementation of REACH in the cement industry. In particular, provides recommendations and sets out conclusions with regard to the REACH obligations concerning the most important categories of raw materials, fuels and products used and produced by the cement industry. (...)
Study on emissions and its possible effect on the environment and health around cement plants
The aim of this study is to analyze the possible risk for health of those living around cement plants, resulting from their atmospheric emissions.
In order to undertake this study, four cement factories of different companies group, were selected: Vallacarca (Portland Valderrivas), Castillejo (Cemex), Lorca (Holcim) and Montcada (Lafarge). The criteria applied for the selection of the plants have been mainly three: Different geographical location and different environments (natural, rural, industrial and urban), Use of different types of fuel for the kilns and Four plants representative of the Spanish cement sector both because of the technology used and because of their emissions and associated control systems.
The methodology used for carrying out this study is internationally recognized and based on the methodology used by the French Environmental Administration for risks analysis on human health, and the one used by the U.S. Environmental Protection Agency (EPA). It is a complex methodology which includes: Information about the plant and its surroundings (climatology, production process, pollution control systems,...), Information on atmospheric emissions from the factorie´s kilns (including the situation of ´worst case scenario´), Exposure assessment (by inhalation or by ingestion, using internationally mathematical models) and Risk assessment (comparing the data obtained by these models with Toxicological Reference Values).
The results of the analysis conclude that for all pollutants, emissions from the four plants results in risk levels clearly lower than the internationally accepted values. For example, exposure levels obtained for dioxins and furans are between ten thousands an ten millions times below those defi ned as safe by the World Health Organization.
The study shows that it has not been identified a potential health risk for the people living and working in the surroundings of the four cement plants. This conclusion is the same in the case of plants that use fuels derived from waste instead of pet-coke.
The Navia viaduct (1st part)
The current trend to the construction of long viaducts of great longitude, originated by both the improvement of the standards of quality of the transport infrastructures and for environmental constraints, obliges to industrialize their construction. Deck execution by means of precast segments is a system broadly used throughout the world, although in Spain its development is small.
In the construction of the Navia viaduct this system has been used, for both the access viaducts 75 m long and main span 160 m long. By providing structural continuity to the deck and using the same precast elements for the whole viaduct, a simplification of both the production and the assembly processing has been obtained, resulting in a reduction of execution times and costs. The design and construction of the Navia viaduct are placed inside a line of work line started by FCC Construction, for the construction of viaducts by means of precast segements, initially intended for viaducts of average spans that in this case has been extrapolated to long spans.
In the first part of the article some general data of the work are provided, the different options considered in the previous study are analyzed, a general description structure of the chosen solution is made and the design process one is examined.