The Use of Crushed Cable Waste As a Substitute of Natural Aggregate in Cement Screed

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Article The Use of Crushed Cable Waste as a Substitute of Natural Aggregate in Cement Screed

Pavel Reiterman * and Martin Lidmila

Faculty of Civil Engineering, Czech Technical University in Prague, Thákurova 7, 166 29 Prague 6, Czech Republic; [email protected] * Correspondence: [email protected]

Abstract: This research is focused on the utilization of cable waste originating during the recycling of wires as a partial substitution of natural aggregate in cement screed. The main goal of the work performed was to find an optimal level of substitution in terms of freezing–thawing resistance, which is a significant aspect for such type of concrete mixtures. The studied artificial aggregate was gradually dosed in cement screed by 5% in a volume of up to 30% of substitution. The influence of the substitution was also evaluated in terms of compressive strength, flexural strength, bulk density determination, and the ultrasonic pulse method. Gradual substitution led to the reduction of the bulk density and studied mechanical properties due to the considerable air-entraining effect. The utilization of cable waste reduced the value of modulus of elasticity and modified deformation behavior of studied mixtures, which exhibited significant softening during the flexural test. Studied screed mixtures incorporating waste material exhibited slightly lower values of the coefficient of freeze-thaw resistance in comparison with the control mixture, however, the attained values comply with technical requirements. Keywords: cable waste; cement screed; freeze-thaw resistance; mechanical properties Citation: Reiterman, P.; Lidmila, M. The Use of Crushed Cable Waste as a Substitute of Natural Aggregate in Cement Screed. Buildings 2021, 11, 1. Introduction 190. https://doi.org/10.3390/ The protection of unrenewable sources has become the main issue throughout the buildings11050190 global scientific community. The re-usability of various materials performs a current trend in the research to reduce the negative impacts of human activities on the environment. Academic Editor: Łukasz Sadowski Cement-based composites, especially concrete, are one of the used building materials worldwide, with increasing annual consumption. Attention is on the reduction of cement Received: 23 March 2021 application due to high energy demand on its production and high amount of embodied Accepted: 29 April 2021 Published: 30 April 2021 carbon dioxide emissions. Portland cement production is responsible for approximately 7% of global CO2 [1]. In addition, the production of cement-based composites is responsible

Publisher’s Note: MDPI stays neutral for the high consumption of natural aggregate, accounting for approximately 80% of their with regard to jurisdictional claims in volume. The present shortage, from the sustainability point of view, is partially reflected by published maps and institutional affil- the massive effort to utilize recycled aggregate (RA) originating from demolition waste [2]. iations. Several studies have been conducted dealing with the substitution of natural aggregate by RA, however, predominantly coarse fractions are suitable for common use due to the physical properties [3,4]. Alternatively, the use of RA must be compensated by another technological approach [5]. Fine residues containing binding particles often essentially increase the dosage of water and entirely reduce the final mechanical and durability Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. performance of hardened concrete. However, Silva et al. (2021) reported exactly the This article is an open access article opposite trend, thus utilization of fine RA led to a similar mechanical performance in distributed under the terms and comparison with the reference mixture; respectively, utilization of coarse RA caused a conditions of the Creative Commons significant decay [6]. Similar results were reported by Khatib (2005) [7]. The various role Attribution (CC BY) license (https:// of fine and coarse RA is determined by very fluctuating properties and the nature of RA creativecommons.org/licenses/by/ that was also highlighted and documented by Fan et al. (2016) [8]. Nevertheless, it is still 4.0/). very important to find other possibilities for the replacement of natural sand with other

Buildings 2021, 11, 190. https://doi.org/10.3390/buildings11050190 https://www.mdpi.com/journal/buildings Buildings 2021, 11, 190 2 of 9

materials and protect non-renewable resources. Concurrently, the industry is generating a large scale of waste, which is accumulated, because of complicated or no practical use [9,10]. In recent years, various types of slags, rice husks, nutshells, etc., as partial substitution were studied [11,12]. However, plastic waste poses a crucial environmental problem. Plastic waste exhibiting thermoplasticity is widely recycled [13,14], however, plastic waste originating from wires is hard to reuse because of the content of antifouling addition and mercaptan, which is added as a burning indicator. This waste material originates when end-of-life cables are scrapped. The recycling of cables is predominantly motivated by the exploitation of conductive metal, especially copper, which forms approximately 70 wt.% of the cable [15]. Just about 3.5 million metric tons were generated in 2015, according to European Economic Community (EEC) [16]. The mechanical separation of the metal and plastic particles is a more frequent recycling technique, than especially floating. This separation technique is very simple and efficient, however, when the metallic phases are reclaimed, a small metallic residue up to 1 wt.% remains in the grit. It is caused by very small differences in the weight of single particles. The contamination of cable waste grit by metallic powder could have a negative impact on the hydration process of used cement, especially in the case of copper exhibiting retarding effect, alternatively aluminum with an accelerating effect and accompanying emission of hydrogen leading to uncontrolled air-entraining. The advantage of cable waste is the limited risks of the presence of undesirable impurities in comparison with other types of plastic wastes, e.g., plastic waste originating from PET bottles recycling often contains residues of paper, fats, sugar, etc. reducing cohesion with cement paste and final mechanical and durability performance of the hardened composite [17,18]. Originated plastic grit consists of various plastics—polyvinyl chloride (PVC), crosslinked polyethylene (XLPE), or thermoplastic form (PE) [14,16]. Individual plastic forms should be additionally, however separately, reused. Unfortunately, the separation of single plastics from the grit is very complicated due to the very similar physicochemical properties. The flotation seems to be a very promising separation technology, in which various modifi- cations were described by Barbakadze et al. [16]. However, a reliable procedure for the separation of the individual plastic forms from the grit has not been practically applied yet. Hence, the plastic grit originating from the life-end wires performs undesirable waste without practical use. Buildings 2021, 11, x FOR PEER REVIEW Studied waste material is of a granular nature with a grain size of up to 4 mm that3 of cor-10 responds well with commonly used natural sand. On the other hand, the studied material exhibits a significantly lower content of the fines, which is well visible in Figures1 and2.

100 natural sand

] 80 %

[ cable waste

Cumulative passing Cumulative 20

0 0 0.063 0.125 0.25 0.5 1 2 4 8 Sieve size [mm]

Figure 1. Cumulative passing of studied cable waste and replaced natural sand. Figure 1. Cumulative passing of studied cable waste and replaced natural sand.

Figure 2. Studied cable waste.

The low wettability is a specific property of contained plastics, which causes the fix- ation of air bubbles when they are immersed in water, especially in the form of grit. The present work partially follows previous work [19], which was focused on the air-entraining effect of rubber particles on fresh concrete and on final resistance to freezing–thawing. The present work is focused on the replacement of natural sand, non-renewable material, by waste plastic grit, which originates as a residue after the recycling of life-end wires. Previous research was predominantly focused on the determination of basic physical, mechanical, and thermal properties of final composites [20,21]. Záleská et al. (2018) also studied the hydrothermal properties of development lightweight composites [22], which was motivated by the reduction of the bulk density of the final composites [23]. However, response to freezing–thawing of cement-based composites incorporating this waste material has not been studied yet. This program is motivated by the reduced permeability of the concrete, reported by Zéhil and Assad [24], which is caused by the repellent nature of plastic particles.

Buildings 2021, 11, x FOR PEER REVIEW 3 of 10

100 natural sand

] 80 %

[ cable waste

Cumulative passing Cumulative 20

0 0 0.063 0.125 0.25 0.5 1 2 4 8 Sieve size [mm] Buildings 2021, 11, 190 3 of 9

Figure 1. Cumulative passing of studied cable waste and replaced natural sand.

FigureFigure 2.2. StudiedStudied cablecable waste.waste.

TheThe low wettability wettability is is a a specific specific property property of of contained contained plastics, plastics, which which causes causes the thefix- fixationation of ofair air bubbles bubbles when when they they are are immersed immersed in in water, water, especially especially in the form ofof grit.grit. TheThe presentpresent workwork partially partially follows follows previous previous work work [19 [19],], which which was was focused focused on on the the air-entraining air-entrain- effecting effect of rubber of rubber particles particles on on fresh fresh concrete concrete and and on on final final resistance resistanceto to freezing–thawing.freezing–thawing. TheThe presentpresent workwork isis focusedfocused onon thethe replacementreplacement ofof naturalnatural sand,sand, non-renewablenon-renewable material,material, byby wastewaste plasticplastic grit,grit, whichwhich originatesoriginates as a residueresidue after the recycling of life-endlife-end wires. PreviousPrevious research was was predominantly predominantly focused focused on on the the determination determination of basic of basic physical, physical, me- mechanical,chanical, and and ther thermalmal properties properties of final of final composites composites [20,21]. [20, Záleská21]. Zálesk et al.á et (2018) al. (2018) also stud- also studiedied the hydrothermal the hydrothermal properties properties of development of development lightweight lightweight composites composites [22], [ 22which], which was wasmotivated motivated by the by reduction the reduction of the of thebulk bulk density density of the of thefinal final composites composites [23]. [23 However,]. However, re- responsesponse to to freezing freezing–thawing–thawing of of cement cement-based-based composites composites incorporating incorporating this waste materialmaterial hashas notnot beenbeen studiedstudied yet.yet. ThisThis programprogram isis motivatedmotivated byby thethe reducedreduced permeabilitypermeability ofof thethe concrete,concrete, reportedreported byby ZZéhiléhil andand AssadAssad [[24],24], whichwhich isis causedcaused byby thethe repellentrepellent naturenature ofof plasticplastic particles.particles. 2. Materials and Methods 2.1. Materials and Mixture Design The performed experimental program focused on the resistance to freezing–thawing of cement-based screeds incorporating cable waste as replacement of natural sand. In order to evaluate the influence of studied waste material, a set of 7 mixtures was designed. The studied cable waste was collected in the recycling link, where the cables were cut by jaw recycling link and then crushed to grit; metallic particles were reclaimed from the resulting grit using a flotation separator. The studied waste material was documented in Figure1 . This material was a mixture of PVC, PE, and XLPE granules of grading 0–4 mm and exhibiting a bulk density of just about 690 kg m−3. The natural siliceous sand of grading 0–4 mm was partially replaced by cable waste up to 30% by mass. The composition and labeling of the mixtures are shown in Table1.

Table 1. Composition of studied screeds.

Component CWR CW05 CW10 CW15 CW20 CW25 CW30 CEM I 42.5 R 500 500 500 500 500 500 500 water 300 300 300 300 300 300 300 sand 0–4 mm 1500 1425 1350 1275 1200 1125 1050 Cable waste 0 20.8 41.6 62.4 83.2 104 124.8 Buildings 2021, 11, 190 4 of 9

2.2. Methods The content of air bubbles in fresh mixtures was determined using a pressure method in terms of CSNˇ EN 12350-7 [25] in order to assess the air-entraining effect of the increasing amount of cable waste. The air content was measured approximately 10 min after mixing. The compressive strength of hardened screeds was determined after 28 days of curing under humid conditions according to CSNˇ EN 12390-3 using a set of 3 cubic specimens of edge 150 mm [26], which were prior testing weighted to determine the bulk density of tested specimens. The flexural strength was determined by using prismatic specimens of dimensions 100 × 100 × 400 mm according to CSNˇ EN 12390-5. The test was organized as a 4-point bending test with a support span of 300 mm, and loads were placed in the thirds of the span [27]. A set of 3 specimens was used for each measurement. The deflection was recorded by using a couple of inductive sensors (HBK Company, Hoba, Quatar) and a data recording software Catman DAQ (2014) (HBK Company, Hoba, Quatar) during testing of prisms after 28 days. The main aim of the experimental program was the determination of freeze-thaw resistance, which was performed in terms of CSNˇ 73 1322 by using prismatic specimens of dimensions 100 × 100 × 400 mm [28]. The freeze-thaw resistance was expressed by the ratio of flexural strength determined on specimens subjected to freezing– thawing and a control set of specimens tested before freezing–thawing (non-cycled after 28 days). The set of 3 specimens was tested every 25 cycles. The loading cycle consisted of a freezing phase lasting 4 h. After that, the saturated specimens were cooled to −18 ◦C and then kept for 1 h. Subsequently, the climatic chamber was automatically flooded by water ◦ Buildings 2021, 11, x FOR PEER REVIEWat a temperature of 20 C, causing the thawing of the specimens. The climatic chamber5 of 10 was automatically drained down after approximately 2 h, and the next freeze-thaw cycle followed with saturated specimens. The loading regime is illustrated in Figure3.

30 ]

C 20 °

0 0 1 2 3 4 5 6

-10 Temperature [ Temperature

-20 Time [hours] FigureFigure 3. 3. TheThe regime regime of of a afreeze freeze-thaw-thaw cycle. cycle.

TheThe specimens specimens we werere visually visually checked checked after after each each set of set 25of cycles 25 cycles,, and the and loss the of lossstruc- of turalstructural integrity integrity was monitored was monitored by using by using non-destructive non-destructive testing. testing. The ultrasonic The ultrasonic pulse pulse ve- locityvelocity method method was wasapplied applied by using by using the PunditLab the PunditLab device device (Proceq, (Proceq, Schwerzenbach Schwerzenbach,, Swit- zerland)Switzerland) with a with couple a couple of 54 ofHz 54 transducers. Hz transducers. The dynamic The dynamic modulus modulus of elasticity of elasticity was cal- was culatedcalculated in accordance in accordance with with Equation Equation (1), (1), 22 −6−6 퐸E푑푦푛dyn == 훾γ푏b··v푣L퐿·10· 10 (1(1))

where Edyn is the dynamic modulus of elasticity (GPa), γb is the bulk density (kg m−3), and where E is the dynamic modulus of elasticity (GPa), γ is the bulk density (kg m−3), and dyn −1 b vL is the speed of the signal (m s −).1 vL is the speed of the signal (m s ).

3.3. Results Results PropertiesProperties of of Fresh Fresh Mixtures Mixtures. TheThe incorporation incorporation of of cable cable waste waste caused caused a asignificant significant air air-entraining-entraining effect, effect, illustrated illustrated inin Figure Figure 4.4 .It It was was confirmed confirmed that that each each 5% 5% rep replacementlacement by by mass mass increase increasedd the the content content of theof theair in air a infresh a fresh mixture mixture by approximatel by approximatelyy 1.2%. 1.2%. Although Although Zéhil Z andéhil Assaad and Assaad did not did reg- not isterregister the air the-entraining air-entraining effect effect of cable of cable waste, waste, it is it to is tonote note that that they they applied applied a areplacement replacement ofof aggregate aggregate from 22 upup toto 6% 6% by by mass, mass, thus thus quite quite lower lower [24 ].[24]. The The fixing fixing of air of was air explainedwas explained by Barbakadze et al. [16] through the hydrophobic nature of plastic particles and their tendency to attract air bubbles on the surface.

20 ]

% 18 [ 16 14.5 14.8 14 12.4 12 10.0 10 9.2 7.4 7.6 8 6 4 2

0 Air conctent in fresh mixtures fresh in conctent Air 0 5 10 15 20 25 30 Natural sand substitution [%]

Figure 4. Content of air in fresh mixtures.

The increased air content in the fresh mixture significantly influenced the properties of hardened mixtures. There were depicted relations of cable waste content and values of compressive strength and bulk density after 28 days in Figure 5. The aggregate formed a Buildings 2021, 11, x FOR PEER REVIEW 5 of 10

30 ]

C 20 °

0 0 1 2 3 4 5 6

-10 Temperature [ Temperature

-20 Time [hours] Figure 3. The regime of a freeze-thaw cycle.

The specimens were visually checked after each set of 25 cycles, and the loss of structural integrity was monitored by using non-destructive testing. The ultrasonic pulse ve- locity method was applied by using the PunditLab device (Proceq, Schwerzenbach, Swit- zerland) with a couple of 54 Hz transducers. The dynamic modulus of elasticity was cal- culated in accordance with Equation (1), 2 −6 퐸푑푦푛 = 훾푏 · 푣퐿 · 10 (1)

where Edyn is the dynamic modulus of elasticity (GPa), γb is the bulk density (kg m−3), and vL is the speed of the signal (m s−1).

3. Results Properties of Fresh Mixtures. The incorporation of cable waste caused a significant air-entraining effect, illustrated Buildings 2021, 11, 190 in Figure 4. It was confirmed that each 5% replacement by mass increased the content of5 of 9 the air in a fresh mixture by approximately 1.2%. Although Zéhil and Assaad did not reg- ister the air-entraining effect of cable waste, it is to note that they applied a replacement of aggregate from 2 up to 6% by mass, thus quite lower [24]. The fixing of air was ex- plainedby Barbakadze by Barbakadze et al. et [ 16al.] [16] through through the the hydrophobic hydrophobic nature nature of plasticof plastic particles particles and and their theirtendency tendency to to attract attract air air bubbles bubbles on on the the surface. surface.

20 ]

% 18 [ 16 14.5 14.8 14 12.4 12 10.0 10 9.2 7.4 7.6 8 6 4 2

0 Air conctent in fresh mixtures fresh in conctent Air 0 5 10 15 20 25 30 Natural sand substitution [%]

Figure 4. Content of air in fresh mixtures. Buildings 2021, 11, x FOR PEERFigure REVIEW 4. Content of air in fresh mixtures. 6 of 10

The increased air content in the fresh mixture significantly influenced the properties ofThe hardened increased mixtures. air content There in were the fresh depicted mixture relations significantly of cable influenced waste content the andproperties values of compressive strength and bulk density after 28 days in Figure5. The aggregate formed a of hardenedsolid skeleton mixtures. in the There traditional were depicted composite relations material, of cable however, waste incontent this case, and the values load of transi- solid skeleton in the traditional composite material, however, in this case, the load transition compressivetion wa sstrength ensured and by thebulk cement density paste after because 28 days of in the Figure significantly 5. The aggregate lower modulus formed of a elas- was ensured by the cement paste because of the significantly lower modulus of elasticity ticity of used cable waste. Hence, the loss of mechanical properties was expected. The of used cable waste. Hence, the loss of mechanical properties was expected. The gradual gradual decay of mechanical properties was reported by Zéhil and Assaad [24], Záleská decay of mechanical properties was reported by Zéhil and Assaad [24], Záleská et al. [29], et al. [29], Saikia and De Brito [30]. On the other hand, Azhdarpour et al. (2016) [31] re- Saikia and De Brito [30]. On the other hand, Azhdarpour et al. (2016) [31] reported a ported a slight improvement of compressive strength for replacement of up to 10%. This slight improvement of compressive strength for replacement of up to 10%. This anomalous anomalous behavior was explained by the reinforcing effect of the particles, which during behavior was explained by the reinforcing effect of the particles, which during loading exhibitedloading aexhibit similared strengthening a similar strengthening effect, such effect as the, such PVC as fibers. the PVC fibers.

50 2100 2060 45 2070 Compressive strength 2050 2031 38.8

40 Bulk density 2000 ]

1939 3 [MPa] 32.7 35 31.3 1950 1927

30 1900 [kg/m 1865 1849 y 22.9 25 21.6 1850 17.6 20 16.3 1800 15 1750 densit Bulk

Compressive strength strength Compressive 10 1700

5 1650

0 1600 0 5 10 15 20 25 30 Natural sand replacement [%]

Figure 5. Compressive strength and bulk density after 28 days. FigureThe 5. gradual Compressive decrease strength of mechanical and bulk density properties after 28 with days. an increasing amount of cable waste was well documented on the record of ﬂexural tests carried out after 28 days, Figure6. There wasThe obviousgradual decaydecrease of the of modulusmechanical of elasticityproperties and with change an increasing of deformation amount behavior. of cable waste was well documented on the record of flexural tests carried out after 28 days, Figure 6. There was obvious decay of the modulus of elasticity and change of deformation behavior. Mixtures with a higher amount of cable waste exhibited significant softening. Re- spectively, the brittle character of the rupture attained on the control mixture was reduced. Thus, the incorporation of cable waste had a similar effect as the use of fibers. The partial flexural-hardening effect of plastic waste was mentioned by Azhdarpour et al. [31]. These results indicated good cohesion of cable waste with cement paste. Such behavior was described during the utilization of rubber scraps. Buildings 2021, 11, 190 6 of 9

Mixtures with a higher amount of cable waste exhibited significant softening. Respectively, the brittle character of the rupture attained on the control mixture was reduced. Thus, the incorporation of cable waste had a similar effect as the use of fibers. The partial flexural- Buildings 2021, 11, x FOR PEER REVIEW hardening effect of plastic waste was mentioned by Azhdarpour et al.7[ of31 10]. These results Buildings 2021, 11, x FOR PEER REVIEW 7 of 10 indicated good cohesion of cable waste with cement paste. Such behavior was described during the utilization of rubber scraps. 25000 25000 CWR CW05 CWR 20000 CW05 20000 CW10 CW15 CW10 CW20 CW15 15000 CW25 CW20 15000 CW25 10000 10000

Loading force [N] force Loading 5000 Loading force [N] force Loading 5000

0 0 0 0.1 0.2 0.3 0.4 0.5 0 0.1 0.2 0.3 0.4 0.5 Deflection [mm] Deflection [mm] Figure 6. The records of flexural tests after 28 days. FigureFigure 6. The 6. The records records of offlexural flexural tests tests after after 28 28days. days. The freeze-thaw resistance of cement-based screeds was a crucial technical parame- TheThe freeze freeze-thaw-thaw resistance resistance of of cement cement-based-based screeds screeds wa wass a a crucial crucial technical technical parame- parameter, ter, which was required for practical use [26]. The gradual deterioration of specimens sub- ter,which which was wa requireds required for for practical practical use use [26 [26].]. The The gradual gradual deterioration deterioration of specimensof specimens subjected subjected to freeze-thaw cycling monitored by non-destructive testing NDT is shown in Fig- jectedto freeze-thaw to freeze-thaw cycling cycling monitored monitored by non-destructiveby non-destructive testing testing NDT ND isT shownis shown in inFigure Fig-7 . ure 7. Studied mixtures exhibited the gradual reduction of the modulus of elasticity with ureStudied 7. Studied mixtures mixtures exhibited exhibited the gradual the gradual reduction reduction of the of modulus the modulus of elasticity of elasticity with increas-with increasing content of cable waste before freezing-thawing, which was caused by the re- increasinging content content of cable of cable waste waste before before freezing-thawing, freezing-thawing, which waswhich caused was bycaused the reduced by the re- bulk duced bulk density. Alongside, NDT measurement signalized slightly reduced freeze- duceddensity. bulk Alongside, density. Alongside, NDT measurement NDT measurement signalized slightly signalized reduced slightly freeze-thaw reduced resistance; freeze- thaw resistance; control mixture without cable waste reached decay after 50 cycles about thawcontrol resistance; mixture control without mixture cable without waste reached cable waste decay reached after 50 decay cycles after about 50 cycles 10.2%, about CW30 10.2%, CW30 with 30% of cable waste then 15.2%. However, results obtained from de- 10.2%,with CW30 30% of with cable 30% waste of thencable 15.2%.waste However,then 15.2%. results However, obtained results from obt destructiveained from testing destructive testing have relevance for the determination of final freeze-thaw resistance, thus structivehave relevance testing have for the relevance determination for the determination of final freeze-thaw of final resistance, freeze-thaw thus resistance, flexural strength, thus flexural strength, Figure 8. flexuralFigure strength,8. Figure 8.

40 34.3 33.340 34.3 0 cycles 35 31.333.3 0 cycles 3530.8 30.8 31.3 30.828.8 28.630.8 25 cycles 30 27.728.827.5 28.6 25 cycles 30 24.727.727.5 50 cycles 24.2 24.723.6 23.9 24.223.1 23.6 50 cycles 25 21.923.9 23.1 25 19.4 21.9 19.1 18.2 19.4 17.1 19.1 20 17.4 18.216.2 17.1 20 17.4 16.2 15 15 10 10

Modulus of elasticity [GPa] elasticity of Modulus 5 Modulus of elasticity [GPa] elasticity of Modulus 5 0 0 0 5 10 15 20 25 30 0 5 10 15 20 25 30 Natural sand replacement [%] Natural sand replacement [%] Figure 7. DynamicFigure modulus 7. Dynamic of elasticity modulus during of elasticity freezing during-thawing. freezing-thawing. Figure 7. Dynamic modulus of elasticity during freezing-thawing. The results of destructive testing correspond well with the results determined in The results of destructive testing correspond well with the results determined in terms of NDT. Thus, all studied mixtures exhibited slight decay of flexural strength dur- terms of NDT. Thus, all studied mixtures exhibited slight decay of flexural strength during freeze-thaw cycling. As in the NDT case, the destructive method confirmed the de- ing freeze-thaw cycling. As in the NDT case, the destructive method confirmed the decreasing trend of freeze-thaw resistance with an increasing amount of cable waste. The creasing trend of freeze-thaw resistance with an increasing amount of cable waste. The coefficient of freeze-thaw resistance of the reference mixture was 0.94 after 50 cycles; the coefficient of freeze-thaw resistance of the reference mixture was 0.94 after 50 cycles; the lowest value, 0.89, exhibited mixtures incorporating 15 and 20% of cable waste. However, lowest value, 0.89, exhibited mixtures incorporating 15 and 20% of cable waste. However, mixtures containing the highest replacement by cable waste exhibited a coefficient of mixtures containing the highest replacement by cable waste exhibited a coefficient of freeze-thaw resistance of just about 0.93, which produced a nearly similar value as the freeze-thaw resistance of just about 0.93, which produced a nearly similar value as the reference mixture free of the studied waste material. On the other hand, screeds exhibiting reference mixture free of the studied waste material. On the other hand, screeds exhibiting the coefficient of freeze-thaw resistance higher than 0.85 could be assessed as resistant to the coefficient of freeze-thaw resistance higher than 0.85 could be assessed as resistant to Buildings 2021, 11, x FOR PEER REVIEW 8 of 10

freezing–thawing [32]. Thus, all studied mixtures passed the required limit. It can be con- Buildings 11 2021, , 190 cluded that utilization had no significant negative impact on the freeze-thaw resistance, 7 of 9 thus the coefficient of freeze-thaw resistance was similar.

10.0 9.0 0 cycles 8.0 25 cycles 6.5 7.0 6.3 6.1 5.9 50 cycles 6.1 5.7 6.0 5.3 5.5 5.3 5.5 5.0 4.9 4.4 4.2 Buildings 2021, 11, x 5.0FOR PEER REVIEW 4.1 4.1 8 of 10 3.9 4.0 3.9 4.0 3.8 4.0 3.0

2.0 freezing–thawing [32]. Thus, all studied mixtures passed the required limit. It can be con- Flexural strength [MPa] strength Flexural 1.0 cluded that utilization had no significant negative impact on the freeze-thaw resistance, 0.0 thus the coefficient of freeze-thaw resistance was similar. 0 5 10 15 20 25 30 Natural sand replacement [%] 10.0 9.0 Figure 8. FlexuralFigure strength 8. Flexural during strength freezing during-thawing. freezing-thawing. 0 cycles 8.0 25 cycles 6.5 The utilizationThe results of cable of destructive waste as natural testing correspondsand replacement well with predominantly the results determined caused the in terms 7.0 6.3 6.1 5.9 50 cycles of6.1 NDT. Thus,5.7 all studied mixtures exhibited slight decay of flexural strength during freeze- 6.0 decay of all studied material5.3 properties5.5 5.3 of5.5 cement-based screeds that were expectable due 5.0 4.9 to the worsethaw cycling.technical As properties in the NDT of case,studied the destructivewaste material.4.4 method Similar confirmed4.2 results the were decreasing reported trend of 5.0 4.1 4.1 freeze-thaw resistance with an increasing amount of cable3.9 waste.4.0 The3.9 coefficient4.0 3.8 of freeze- 4.0 by a number of authors, who replaced natural aggregate with plastic waste material. On thaw resistance of the reference mixture was 0.94 after 50 cycles; the lowest value, 0.89, 3.0 the other hand, the main aim of the performed program was the determination of freeze- exhibited mixtures incorporating 15 and 20% of cable waste. However, mixtures containing 2.0 thaw resistance. Although there were lower mechanical properties with the increasing

Flexural strength [MPa] strength Flexural the highest replacement by cable waste exhibited a coefficient of freeze-thaw resistance of 1.0 amount of cable waste, all studied mixtures exhibited a nearly similar coefficient of freeze- just about 0.93, which produced a nearly similar value as the reference mixture free of the 0.0 thaw resistance after 50 cycles. The effect of the incorporation of cable waste on the prop- studied waste material. On the other hand, screeds exhibiting the coefficient of freeze-thaw erties0 of studied screeds5 is depicted10 in Figure15 9. 20 25 30 resistance higher than 0.85 could be assessed as resistant to freezing–thawing [32]. Thus, Natural sand replacement [%] all0.70 studied mixtures passed the required limit. It can be concluded that utilization had no Figuresignificant 8. Flexural negative strength impact during on freezing the freeze-thaw-thawing. resistance, thus the coefficient of freeze-thaw Compressive strength 0.60

] resistance was similar. -

[ Coefficient of freeze-thaw resistance TheThe utilization utilization of cable of cable waste waste as natural as natural sand sand replacement replacement predominantly predominantly caused caused the the 0.50 Flexural strength decaydecay of all of studied all studied material material properties properties of cement of cement-based-based screeds screeds that that wer weree expectable expectable due due to theto0.40 theworse worse technical technicalBulk density properties properties of studied of studied waste waste material. material. Similar Similar results results were were reported reported by a number of authors, who replaced natural aggregate with plastic waste material. On by0.30 a number of authors, who replaced natural aggregate with plastic waste material. On the the otherother hand,hand,the themain main aim aim of of the the performed performed program program was was the the determination determination of of freeze-thaw freeze- thawresistance.0.20 resistance. Although Although there there were were lower lower mechanical mechanical properties properties with with the increasing the increasing amount amountof cable of cable waste, waste, all studied all studied mixtures mixtures exhibited exhibited a nearly a nearly similar similar coefﬁcient coefficient of of freeze-thaw freeze- Loos of the property property the of Loos 0.10 thawresistance resistance after after 50 cycles.50 cycles. The The effect effect of theof the incorporation incorporation of cable of cable waste waste on the on propertiesthe prop- of ertiesstudied0.00 of studied screeds screeds is depicted is depicted in Figure in Figure9. 9. 0 5 10 15 20 25 30 0.70 Natural sand replacement [%] Compressive strength

Figure 9. The 0.60loss of compressive strength and freeze-thaw resistance.

] -

[ Coefficient of freeze-thaw resistance Bulk density,0.50 compressiveFlexural strengthstrength , and flexural strength dropped with the increasing level of the0.40 replacementBulk, howeverdensity , the freeze-thaw resistance tended to be in the control mixture. Thus, an increasing amount of cable waste does not reduce the durability 0.30 performance in terms of freeze-thaw resistance. This is very important because the enhancement of0.20 sufficient freeze-thaw resistance is attained in practice with the increase of the cement content, respectively, by increasing the strength class, even though higher

Loos of the property property the of Loos 0.10 compressive strength is not required with respect to the nature of the use. Quite problematic would be0.00 the utilization for the production of structural concrete because the studied 0 5 10 15 20 25 30 Natural sand replacement [%] FigureFigure 9. The 9. The loss lossof compressive of compressive strength strength and and freeze freeze-thaw-thaw resistance. resistance.

Bulk density, compressive strength, and flexural strength dropped with the increasing level of the replacement, however, the freeze-thaw resistance tended to be in the control mixture. Thus, an increasing amount of cable waste does not reduce the durability performance in terms of freeze-thaw resistance. This is very important because the enhancement of sufficient freeze-thaw resistance is attained in practice with the increase of the cement content, respectively, by increasing the strength class, even though higher compressive strength is not required with respect to the nature of the use. Quite problematic would be the utilization for the production of structural concrete because the studied Buildings 2021, 11, 190 8 of 9

Bulk density, compressive strength, and flexural strength dropped with the increasing level of the replacement, however, the freeze-thaw resistance tended to be in the control mixture. Thus, an increasing amount of cable waste does not reduce the durability performance in terms of freeze-thaw resistance. This is very important because the enhancement of sufficient freeze-thaw resistance is attained in practice with the increase of the cement content, respectively, by increasing the strength class, even though higher compressive strength is not required with respect to the nature of the use. Quite problematic would be the utilization for the production of structural concrete because the studied solution cannot pass the requirements for aggregate for concrete, and in addition, the reduced values of modulus of elasticity are problematic with respect to the final deformation and probable significantly higher creep. On the other hand, the advantage of the utilization of cable waste grit lies in the production of cement-cement screeds of low strength classes, which exhibit sufficient freeze-thaw resistance allowing application in the exterior for various underlying beds. These screeds belong to the very frequently used building materials, and incorporation of waste material could bring interesting savings in natural resources.

4. Conclusions The performed experimental program dealt with the utilization of crushed cable waste as a partial replacement of natural siliceous sand in cement-based screeds. Attention was paid to the response of hardened composites to freezing–thawing. The attained results can be summarized as follows: • Utilization of cable waste has a signiﬁcant air-entraining effect on the fresh mixture, • The bulk density and mechanical properties of hardened screed have been reduced proportionally to the amount of the cable waste, • Freeze-thaw resistance of hardened screeds have been similar or slightly better with an increasing amount of cable waste in comparison with the control mixture, • The content of cable waste controls the mechanical properties of hardened screeds without loss of freeze-thaw resistance. The studied waste material seems to be prospective for utilization in cement-based screeds because its addition contributes to air-entraining, which ensures resistance to freezing-thawing. Although there was conﬁrmation of the ability to replace natural sand, the contribution of the studied waste material to that would be relatively low with respect to the extremely high global demands for natural sand. Hence, future research will be focused on milled powder prepared from grit as an alternative air-entraining additive to dry-ready mix screeds. In general, crushed cable waste is a prospective material, which could be successfully used in the building industry.

Author Contributions: Conceptualization, P.R. and M.L.; methodology, P.R.; investigation, P.R. and M.L.; writing—original draft preparation, P.R.; writing—review and editing, P.R.; supervision, M.L. All authors have read and agreed to the published version of the manuscript. Funding: Present work was supported by the project No. 19-00262S by Czech Science Foundation. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Conﬂicts of Interest: The authors declare no conﬂict of interest.

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