It has become increasingly clear, that the recent consumption of mineral resources is unsustainable. The Czech Republic produces more than 217,000 tones of mineral wool annually, while its recycling stays unacceptably limited. This paper presents new possibilities how to recycle mineral wool from building insulation systems. Cladding of 30 years old building composed of FOS 125 facade was disassembled and its mineral wool boards were subjected to micro-milling in order to get filler and shortly chopped fibers to be the multifunction micro-aggregate in new design of plaster mortars. It was shown that mortars containing up to 1.2 wt. % of such waste exhibited decrease in pressure strength in the order of tens of percent than those made from reference mixture. On the other side, their bending strength was decreased slightly or oven improved. Other improvement was detected in thermal conductivity

Domonkos, Mária

Prošek, Zdeněk

Trejbal, Jan

Zobal, Ondřej

English

CTU Open Journal Systems (Czech Technical University, Prague / České vysoké učení technické v Praze)

https://doi.org/10.14311/APP.2022.34.0122Acta Polytechnica CTU Proceedings 34:122–126, 2022 © 2022 The Author(s). Licensed under a CC-BY 4.0 licencePublished by the Czech Technical University in PragueNEW POSSIBILITIES FOR RECYCLING OF MINERAL WOOLSEPARATED FROM THERMAL INSULATION WASTEJan Trejbala,∗, Ondřej Zobala, Mária Domonkosa, Zdeněk Prošeka,ba Czech Technical University in Prague, Faculty of Civil Engineering, Thákurova 7, 166 29 Prague 6, CzechRepublicb University Centre for Energy Efficient Buildings of Czech Technical University in Prague, Třinecká 1024,273 43 Buštěhrad, Czech Republic∗ corresponding author: jan.trejbal@fsv.cvut.czAbstract. It has become increasingly clear, that the recent consumption of mineral resources isunsustainable. The Czech Republic produces more than 217,000 tones of mineral wool annually, whileits recycling stays unacceptably limited. This paper presents new possibilities how to recycle mineralwool from building insulation systems. Cladding of 30 years old building composed of FOS 125 facadewas disassembled and its mineral wool boards were subjected to micro-milling in order to get fillerand shortly chopped fibers to be the multifunction micro-aggregate in new design of plaster mortars.It was shown that mortars containing up to 1.2 wt. % of such waste exhibited decrease in pressurestrength in the order of tens of percent than those made from reference mixture. On the other side,their bending strength was decreased slightly or oven improved. Other improvement was detected inthermal conductivity.Keywords: Construction and demolition waste, ETICS, mineral wool, recycling.1. Introduction1.1. Mineral wool waste productionThere is still increasing interest to save material re-sources and environment across all industries. Sucha phenomenon is also clear in civil engineering whichis strongly dependent on mineral resources. It is es-timated that civil engineering consumes as many ofthese resources as it corresponds to the consumptionof all other industrial fields together. Therefore, build-ing stone and gravel have become critical row material.Such a situation is further complicated by deprecia-tion of society to open new mines and quarries due toeconomical and aesthetic reasons. It is worth mention-ing that no new quarries were opened in the CzechRepublic during last 30 years [1].Mineral insulations thus may become an endangeredproduct. These materials occupy ca. 60 % of themarket with insulations globally [2]. According to datacollected by Eurostat of the European Commission,the Czech Republic produced more than 217,000 tonesof wools from mineral fibers during yr. 2020. In othercountries, the data are following: Germany, 615,472;France, 351,010; UK, 250,000 tones [3]. It has to bestressed out that such data do not contain glass woolssince these are classified into a different group togetherwith glass fibers for textile production. It is thereforehard to determine which part of them is made forinsulations. However, some scientists estimate thatglass fiber insulations create approx. 30 % of thatmade from basalt fibers [4].1.2. RecyclingAlthough the mineral wool waste (MWW) presentsonly a small share of construction and demolitionwaste (C&DW) production in the Czech Republic, asstated in VISOH system administered by Ministry ofthe Environment of the Czech Republic, it is neces-sary to find ways how to recycle such material [5]. Anumber of buildings insulated by systems with end-ing service life are still growing. Thus, it can beexpected that know-how in MWW recycling will bein demand [6]. As most of insulated building envelopeare made from composite system (including buildingadhesives, mechanical fasteners, reinforcing meshes,base-coats, finish-coat plasters, etc.), it is hard to sep-arate individual materials from each other. That isthe reason why these materials are rather landfilledthan recycled [4]. It has to be also considered that Eu-ropean Union requires the C&DW be recycled, whileits landfilling becomes more charged which also raisesinterest in recycling. It is worth noting that the chargefor mineral wool landfilling is 1,750 CZK per 1 tonein the Czech Republic [7].Despite the aforementioned difficulties, some re-searches dealt with recycling of mineral wool fromC&DW. As Wäntsi and Kärki summarized in theirreview paper [4], the MWW can be briquetted andthus returned into the wool manufacturing process.Adediran et al. [8] tested feasibility of incorporatingthe milled MWW into ceramic materials as a fluxingagent in the production of clay- and waste-based build-ing ceramics. Gebremariam et al. [9] used the milledMWW at the form of ultrafines as cement substitutionor as supplementary additives in concrete mixtures122vol. 34/2022 Recycling of Mineral Wool Wastesobtaining material with increased modulus of elas-ticity. Ramirez et al. [10] reinforced cement pasteswith residues of fibers from the recycled MWW. It wasshown that such modified material exhibited improvedmechanical properties and lower porosity.In this study, we present technology which is capa-ble to produce both fiber residues and filler from theMWW. Such a technology uses a micro-mill and a sep-arator that are together able to disintegrate individualmaterials in mineral wool based external thermal in-sulation composite system (ETICS). The MWW wasapplied into plaster mortar in order to improve itsthermal properties and tensile strength while keepingpressure strength, if possible.2. Materials and methods2.1. Mineral wool wasteThe MWW was provided from 34 meters high buildingin Kralupy nad Vltavou where the original externalETICS was replaced with new materials in 8/2020 dueto tightening requirements for heat transfer throughthe building envelope. The ETICS was realised in yr.1991 as the FOS 125 type which was composed frombasalt mineral wool boards (density 50 kg/m3) coveredwith sheet metal cladding, see Figure 1. Given thatthe insulation was anchored to the wall using steelframes, it was free of contamination with adhesivemortars, plaster, and other building materials.Figure 1. Building facade under reconstruction.2.2. RecyclingAfter the metal cladding was disassembled from thebuilding facade, insulation boards were removed fromthe steel frames and subjected to further processingusing the stationary recycling line LAV/K - 350 Tex(Lavaris, s. r. o., Czech Republic), which is shownin Figure 2. The whole line starts with an inputmodule (1) where the MWW is inserted. The mod-ule is equipped with the high-speed grinder LAV/K -350 Tex. The crushed mixture is then transportedinto a cyclone separator (2) which divides the mixtureinto two parts. The first is composed primarily ofthe chopped fibers which can be further reused forproduction of recycled insulation boards or as blowninsulation. Such a material is stored into the big bag(3). The second part is composed from mineral dustparticles – fillers – and short fibers that are capturedin a cyclone double-filter (4). The study deals withutilization of the second part and tries to find itseffective application in civil engineering.Figure 2. Scheme of recycling line LAV/K - 350 Tex.2.3. SpecimensThe filler and short fibers captured on the double-filterof the recycling line exhibit potential to be used asmicro-aggregate with other beneficial properties forproduction of plaster mortars (defined in ČSN EN 998-1 ed. 3), as the fibers can play the role of randomlydispersed and oriented micro-reinforcement and thusincrease tensile strength and ductility of the plasters.Moreover, heat insulation of such mortars can beincreased due to presence of clumps of fibers thatcreate air voids.Composition of mixtures was designed within ourprevious research (see [11, 12]). It was aimed to useas much recycled material as possible while keepingmortar mechanical properties similar to reference ma-terial (conventional mixture with no additives). Sixmixtures were designed differing from each other inthe amount of applied recycled MWW (from 0 to1.0 wt. % of the whole mixture). Their compositionis summarised in Table 1. Water to cement ratiowas increased with increasing amount of the recy-cled MWW in order to keep still the same mixtureworkability (classified using the flow test accordingto ČSN EN 1015-3). The last column of the Table 1presents density of hardened mortars after 28 days ofcuring.Three specimens with dimensions of40×40×160 mm were made from each mixtures. After123J. Trejbal, O. Zobal, M. Domonkos, Z. Prošek Acta Polytechnica CTU Proceedingscasting the mixtures in metal moulds, the specimenswere stored in water bath for 7 days. Next, they wereremoved from water and left for another 21 daysunder standard laboratory conditions (temperature22±1 ◦C, relative humidity approx. 55 %).2.4. Testing of mechanical propertiesBasic mechanical properties – compressive and bend-ing strength – were examined following standardČSN EN 1015-11. Destructive three-point bendingstrength test was carried out using loading frameMTS 40 (MTS USA). The loading rate was set to1 mm/min. Both parts of broken specimens were sub-sequently subjected to pressure strength test usingpress EU 40 (VEB Werkstoffprüfmaschinen). In sucha case, the loading was controlled with force at therate of 0.1 MPa/sec.2.5. Testing of thermal propertiesTesting of heat properties was focused on determi-nation of thermal conductivity coefficient λ. Heattransfer analyzer ISOMET 2104 (Applied Precision)equipped with surface probe API210412 with measur-ing range 0.3–2.0 W/m.K and accuracy of ±5–10 %was used. Such a device applies a dynamic methodwhich is based on response monitoring of examinedmaterial on heat flow impulses. The measurementitself was carried out 28 days after the specimens weremade. Their temperature was equal to 22±1 ◦C (thesame as ambient air). Each specimen was measuredthree-times in a different position in order to obtainstatistically relevant data.3. Results and discussions3.1. Mechanical propertiesThe results of compressive strength test are shownin Figure 3. It is clear that with increasing amountof the recycled MWW incorporated into the mixture,compressive strength significantly decreased. Thespecimens marked as “I5” (those that contained thelargest amount of the recycled MWW) reached only onone third of the strength when compared to referencemixture REF. On the other side, even the I5 mixturecan be considered as plaster mortar of the highestcategory CS IV (required compressive strength is atleast 6 MPa) as defined in ČSN EN 998-1. It canbe therefore said that the decrease in compressivestrength as a result of the recycled MWW use ismassive, however still acceptable.A slightly different trend can be observed in thecase of bending strength test. As Figure 4 shows,specimens I1 overcome by ca. 13 % those made fromreference mixture. After addition more amount ofthe recycled MWW (all specimens I2–I5), bendingstrength decreased but significantly slower than incase of compressive strength. The highest detected de-crease was equal to ca. 37 %. Such a phenomenon canbe attributed to the function of short fibers that arerandomly distributed and oriented through the ma-trix, as assumed in Chapter 2.3. These fibers are ableto reduce creation of drying and shrinking cracks andthus contribute to the achievement of higher bending(tensile) strength. These findings are in accordancewith our previous research, see [13, 14]. Based on thecited researches, it can be assumed that matrices con-taining the milled MWW are able to exhibit ductilebehaviour because of short fibers bridging the cracksafter the matrix fails in tension. It will be the subjectof our further research.3.2. Thermal propertiesFigure 5 shows that thermal conductivity of testedspecimens decreases with increasing amount of the re-cycled MWW. While the reference mixture reached on1.82 W/m.K, those mixtures that contain the MWWexhibited improvement from ca. 10 to 40 %. Theirthermal insulation properties are thus improved. Sucha finding corresponds to changes in density of hard-ened mortars (see Table 1). As the amount of theMWW is increased, the density decreases by up to17 % as a consequence of increasing porosity.4. ConclusionsThe presented study deals with recycling of themineral wool waste (MWW) and thus tries to con-tribute in issues connected with a global deficit ofmineral resources and their unsustainable consump-tion. Recycling line LAV/K - 350 Tex developed byLavaris, s. r. o., Czech Republic, showed to be veryeffective in processing of the MWW from externalthermal insulation composite systems. A building inKralupy nad Vltavou older than 30 years was insu-lated with the new insulating system since the oldone (FOS 125) does not meet current requirements.Old insulation boards from basalt fibers were removedfrom the sub-construction (steel frames) and subjectedto the recycled line in order to remove all impurities.The original fibers were chopped with a high-speedmill to achieve (i) fibers for recycled blown insula-tion and (ii) short fibers with dust particles – filler.The study focuses on the second mentioned materialsthat are considered to be hardly usable in technicalpractise. It was shown that they can play the role ofmultifunction micro-aggregate in plaster mortars.Mortar mixtures containing besides standard ma-terials also recycled aggregate at the amount of 0–1.2 wt. % of the whole mixture were designed forproduction of laboratory specimens with dimension of40×40×160 mm. These were after 28 days of curingand hardening tested in order to find out their pres-sure and bending strength and thermal conductivity.The finding are as follows:• Pressure strength massively decreased (over 60 %)with increasing amount of the recycled MWW. How-ever, even those specimens that contained the high-est amount of the MWW exhibited still acceptable124vol. 34/2022 Recycling of Mineral Wool WastesMixtureREF I1 I2 I3 I4 I5035Compressive strength [MPa]51015202530Trend lineStandard deviationFigure 3. Compressive strength of tested specimens.MixtureREF I1 I2 I3 I4 I50123456Bending strength [MPa]Trend lineStandard deviationFigure 4. Bending strength of tested specimens.MixtureREF I1 I2 I3 I4 I500.51.01.52.0Coefficient of thermal conductivity [W/(m.K)]Trend lineStandard deviationFigure 5. Thermal conductivity of tested specimens.125J. Trejbal, O. Zobal, M. Domonkos, Z. Prošek Acta Polytechnica CTU ProceedingsMixture Cement Sand 0-2 mm Concrete fines Water MWW Density[g] [g] [g] [g] [g] [kg/m3]REF225 900 375270 0 2,053I1 270 4.6 1,932I2 300 9.2 1,909I3 320 13.8 1,839I4 345 18.4 1,803I5 370 23.0 1,705Table 1. Composition of plaster mortar mixtures.strength (more than 10 MPa) to be considered plas-ter mortars according to relevant technical stan-dards.• Bending strength at first increased (by 12 %) withincreasing amount of the MWW, however, afterreaching the amount of 0.3 %, the strength de-creased very slightly (from ca. 19 to 35 %).• Coefficient of thermal conductivity decreased up to40 % with increasing amount of the MWW. Thermalresistance of the material was thus improved.Aforementioned findings prove that the recycledMWW can be processed into the form of micro-aggregate to be a part of plaster mortar mixtures.Based on achieved results, it can be concluded thatsuch material acts as randomly oriented reinforcement(short fibers), insulation aggregate (clumps of fibers),and substitution for fine fraction of virgin aggregates(dust particles).AcknowledgementsThis work was supported by the Technology Agency of theCzech Republic (research project No. TJ04000208) andthe support is gratefully acknowledged.Thanks go to Ing. Vladimír Vymětalík, Ph.D., Visco,s. r. o, Ing. Milan Pokrivčák, MBA, Knauf Insulation,s. r. o., and Ing. George Karra’a, Ph.D., Lavaris, s. r. o. fortheir technical and material support within the research.References[1] M. Škopán. Recycled construction and demolitionwaste as one oh the holders of the circular economy inconstruction industry. In Recycling 2020: circulareconomy in civil engineering, recycling and applicationof secondary building materials, pp. 9–17. ARSM, Brno,2020.[2] A. M. Papadopoulos. State of the art in thermalinsulation materials and aims for future developments.Energy and Buildings 37:77–86, 2005.doi:https://doi.org/10.1016/j.enbuild.2004.05.006.[3] Eurostat, European commission. Prodcom annualdata, 2020. https://ec.europa.eu/eurostat.[4] O. Wäntsi, T. Kärki. Mineral wool waste in europe: areview of mineral wool waste quantity, quality, andcurrent recycling methods. Journal of Material Cyclesand Waste Management 16:62–72, 2014.doi:https://doi.org/10.1007/s10163-013-0170-5.[5] Ministry of the Environment of the Czech Republic.Information system of waste management, 2021.https://isoh.mzp.cz/visoh.[6] A. Mueller, B. Leydolph, K. Stanelle. Recyclingmineral wool waste-technologies for the conversion ofthe fiber structure, part 1. International CeramicReview 58(6):378–381, 2009.[7] D. Průša, S. 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New possibilities for recycling of mineral wool separated from thermal insulation waste

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New possibilities for recycling of mineral wool separated from thermal insulation waste

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