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| 2. |
- Andreas, Lale, et al.
(författare)
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Use of secondary materials in landfill constructions
- 2007
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Ingår i: SARDINIA 2007. - Cagliari : CISA, Environmental Sanitary Engineering Centre. - 9788862650038
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Konferensbidrag (refereegranskat)abstract
- Many landfills are subject to closure in the near future. Roughly 2,000 hectares of landfill area have to be covered only in Sweden, equivalent to about 100 million tonnes of construction material. In addition to material costs in the order of tens of billions Euro, this also puts a strain on the environment through the exploitation of non-renewable virgin construction materials. Many landfill operators are considering alternative cover designs and materials in order to reduce resource spending. However, there is a fair amount of uncertainty with regard to functional and environmental consequences of using alternative (secondary) materials, both from the side of the companies and the authorities. This paper gives an overview over potential waste based construction materials and the use of some of them in projects presently ongoing in Sweden.Research on the use of secondary materials in landfill covers is quite recent. Substitutes for natural or synthetic materials in a landfill cover can be various types of waste from process industry, construction and demolition, or comparable activities. Alternative materials that have been investigated are ashes, slags, sewage and fibre sludges, treated soils and compost. Table 1 gives an overview over potential waste based construction materials. The total of potential materials is well in excess of the material needs for landfill construction, but they may not be available at the right time, place or quality.Besides being economically viable, the substitute materials should have suitable technical and environmental properties in order to secure a proper function of the construction. Experiences from three field studies (landfills at Tveta/Södertälje, Hagfors and Alvkarleby) are discussed looking at relevant issues during 1) construction, 2) active after care phase, and 3) long term processes.Using SCM poses additional problems compared to using conventional materials. Often, the supply of material has to be planned in advance and the materials may have to be stored on site. Storing, however, can cause problems if the materials have properties that change over time e.g. due to climate. For other materials storing may be necessary in order to achieve desired properties. One example is the ageing of strongly alkaline materials that react with atmospheric carbon dioxide and thus obtain better leaching properties. Table 1 Overview over potential waste based construction materials and examplesSourceExamplesMining and mineral industryWaste rock, flotation sand, etc...Construction and demolition (C&D)Crushed concrete, gypsum, asphalt, reinforced polymers, woodProcess industryDifferent types of slag from steel making, green liquor and fibre sludge from paper production, ashes and foundry wastesWastewater treatmentDigested sewage sludge, sandIncinerationBottom ash, fly ashThe evidence is mounting that the desired technical function of a landfill cover can be attained using suitable combinations of secondary construction materials. So far, all three field tests indicate leachate amounts between less then one and 30 l (m2 yr)-1 below the liner. In comparison with the average annual precipitation of about 600 mm yr-1 at the Swedish East coast, only 0.2-5 % of the precipitation seeped through the liner so far; i.e. the leachate generation is reduced with about 90 % or more.The issue is more if the materials may cause adverse impacts of the landfill and its recipients. A low water infiltration through the liner means that the most of infiltrating water is removed as drainage water and thus the leaching of the layers above the liner are of the greatest concern.Infiltrating water will yield a liquid to solid ratio of about 1-2 l kg-1 in the layers above the liner after about 10 years. The most mobile elements, such as nitrogen, will be leached to a great extent already at such low L/S ratios, so a forecast with regard to the need of treatment of drainage water points at about two to three decades.In the long term perspective the mineral changes of the construction materials become important. E.g. one of the incentives for using fly ash in liners is their capacity for chemical-mineralogical changes leading to the formation of clay-like structures. This could mean that a liner built of ashes will attain a lower permeability over time. Other mineral changes that can occur in ashes include the trapping of metals in the structure, e g in clay and carbonate phases.Much is still to be learned about the long term processes and the factors that control them. Ongoing studies include the assessment of climatic variables, different material combinations as well as the impact of landfill gases.The following conclusions can be drawn:The use of secondary materials in construction is important due to substantial resource and environmental impacts. An increased use should be beneficial, provided that the problems of using such materials can be managed.In addition to legislative and bureaucratic barriers, there are also practical issues which need to be dealt with in order to pave the way for a wider use of alternative construction materials. In the construction phase more planning is needed due to temporal and geographical limitation of the material availability. Some materials are not ready for immediate use but need to be pre-treated. All of these factors may cause a need for more space and time. A system for quality assurance comparable to that of traditional construction materials is another issue that needs to be resolved. Most likely some kind of legislative pressure is needed for this.In the medium term leaching of pollutants from the construction materials may be the most important issue when using secondary construction materials, which underlines the double standards applied, since traditional construction materials will not be scrutinized in the same manner. Anyhow, the long term interactions between materials and their environment need to be considered and further studies are necessary for secondary construction materials as well as for conventional materials. Existing data indicate both possibilities and problems.In the long term issues of material interactions will remain and the mechanical impact of mineral changes in the secondary construction materials may be added to the list of issues to clarify. Some of the material changes may be beneficial for the function of the construction, e.g. clay formation in liner materials may make them more impervious, but there may also be negative changes caused by deteriorated material properties. The rate and extent of such processes and the factors that enhance or retard them need to be understood better.Secondary construction materials have always been used and some of the "traditional" materials used today were wastes before. There is no reason to believe that this development should not continue.
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- Eklöf, Ingemar, et al.
(författare)
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Askor för konstruktionsändamål : slutrapport 2016-03-15
- 2016
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Vid förbränning av biobränslen och avfall genereras restprodukter, så kallade energiaskor, som kan användas som konstruktionsmaterial. I detta notat 8-2016 redovisas ett projekt som identifierat viktiga åtgärder i syfte att öka användningen av energiaskor för konstruktionsändamål. En stor andel av engergiaskorna har, i ursprunglig form eller efter sortering och behandling, goda konstruktionsmässiga egenskaper. För närvarande används energiaskor i Sverige till största delen som konstruktionsmaterial inom avfallsanläggningar; främst för sluttäckning av äldre avfallsdeponier. Men sluttäckningarna avslutas nu fortlöpande och behovet når sin kulmen inom de närmaste 5–6 åren. Därför behövs nya användningsområden för energiaskor, annars kommer askorna att deponeras i allt större utsträckning vilket är en dålig hushållning av resurser.Genom att använda energiaskor för konstruktioner, i exempelvis vägar, parkeringsplatser och för andra anläggningsändamål, kan man ersätta jungfruliga råvaror vilket gör energi- och avfallssystemet mer hållbart. Om inte andra avsättningsalternativ utvecklas ökar dessutom kostnaderna för askhanteringen, vilket belastar energiproducenterna och i slutändan också slutkonsumenterna.
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- Filipsson, Magnus, et al.
(författare)
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Efterbehandling av gruvavfall med morän/grönlutslam i tätskiktskonstruktionen : Massor med fördelar
- 2015
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Ingår i: Bygg och Teknik. - 0281-658X .- 2002-8350. ; :1, s. 66-70
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Dagens praxis för täckning av sulfidhaltiga gråbergsrester är att täcka med morän. Det görs som ”kvalificerad täckning” genom att lägga på ett tätskikt med lerig morän som packas tätt. I ett önskescenario finns siltig/lerig morän i anslutning till området som är tillräckligt tätt och som kan användas för att anlägga tätskikt. Erfarenhet visar dock att täta moräner förekommer sällan i gruvans närområde och funktionen som syrebarriär inte alltid uppfylls av lokalt förekommande morän. Alternativet är att använda andra tätskiktsmaterial, bentonitmatta, lera etcetera eller att modifiera lokalt förekommande morän. Ett alternativ är att modifiera lokalt förekommande morän genom inblandning av grönlutslam. Grönlutslammet har stor vattenhållande förmåga och en inblandning på cirka tio procent grönlutslam i siktad morän förbättrar moränens funktion som tätskikt avsevärt.Ett vanligt sätt att efterbehandla gruvavfall är att täcka det med ett skikt som hindrar syret att nå avfallet och därmed hindra oxidationen, även kallad kvalificerad täckning. Huvudfunktionkskravet är att minimera syretransporten och främst syrediffusionen över tid, vilket innebär i praktiken att tätskiktets hydrauliska konduktivitet ska vara under 10-8 m/s. I ett önskescenario finns siltig/lerig morän i anslutning till området som är tillräckligt tätt och som kan användas för att anlägga dessa skikt.
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| 6. |
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| 7. |
- Lidelöw, Sofia, et al.
(författare)
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Evaluation of leaching from four recycled materials used in full-scale road constructions
- 2008
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Ingår i: Proceedings of the 2nd International Conference on Engineering for Waste Valorisation. - Patras : University of Patras. - 9789605301019
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Konferensbidrag (refereegranskat)abstract
- The medium-term (5-10 years) elemental leaching from five different materials used in full-scale road applications was evaluated. Two materials, fayalite slag and blast-furnace slag, leached high concentrations of trace metals such as Cu and Zn throughout the study period. At several occasions, the blast-furnace slag generated leachates with acidic pH-values (<4). Leachate from crushed concrete and MSWI bottom ash contained elevated concentrations of e.g. Cr and Cu during the first 2-3 years. Enrichment of trace elements occurred in sediments of roadside drainage ditches, but the respective contribution from leachate and road surface runoff is unclear. Migration of the elements through subsoil and plants in the ditches was limited, but clear anthropogenic signals were observed for e.g. Cu and Zn at the BA section. Further studies are recommended to verify if laboratory tests used for impact assessments are able to predict the observed field leaching and how the road environment is affected by leaching from the road materials in the longer term.
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| 8. |
- Lidelöw, Sofia, et al.
(författare)
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Leaching behaviour of copper slag, construction and demolition waste and crushed rock used in a full-scale road construction
- 2017
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Ingår i: Journal of Environmental Management. - : Elsevier. - 0301-4797 .- 1095-8630. ; 204:1, s. 695-703
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Tidskriftsartikel (refereegranskat)abstract
- The leaching behaviour of a road construction with fayalitic copper slag, recycled concrete and crushed rock as sub-base materials was monitored over ten years. All studied materials used in the road construction, including crushed rock, contained concentrations of several elements exceeding the guideline values recommended by the Swedish EPA for total element concentrations for waste materials used in constructions. Despite that, leaching from the road construction under field conditions in general was relatively low. The leachates from the recycled materials contained higher concentrations of several constituents than the leachates from the reference section with crushed rock. The leaching of the elements of interest (Cr, Mo, Ni, Zn) reached peak concentrations during the second and fourth (Cu) years and decreased over the observation period to levels below the Swedish recommended values. Carbonation of the concrete aggregates caused a substantial but short-term increase in the leaching of oxyanions such as chromate. The environmental risks related to element leaching are highest at the beginning of the road life. Ageing of materials or pre-treatment through leaching is needed prior to their use in construction to avoid peak concentrations. Also, the design of road constructions should be adjusted so that recycled materials are covered with low-permeability covers, which would minimize the exposure to atmospheric precipitation and weathering.
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