Organically modified concrete waste with oleic acid

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Organically modified concrete waste with oleic acid: Preparation and characterization F.J.H.T.V. Ramos1, L.C. Mendes1* 1

Instituto de Macromoléculas Professora Eloisa Mano, Universidade Federal do Rio de

Janeiro, Avenida Horacio Macedo, 2030-Centro de Tecnologia, Bloco J, Ilha

do

Fundão, 21945-970, Rio de Janeiro, Brazil *Corresponding author: [email protected], tel.: (55) 21 3938-7727, fax: (55) 21 2270-1317

Abstract This article focuses the preparation and characterization of organically modified concrete waste (CW) with oleic acid (OA). After crushing and sifting, the concrete particles were chemically modified by OA using a sonication process. X-ray fluorescence (XRF), infrared spectroscopy (FTIR), thermogravimetry (TG/DTG), differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray detector (EDX) were used to investigate the structure of the modified concrete particles. We noticed that silica is the predominant component of the concrete. The FTIR spectrum revealed that the OA was bonded to the CW surface by the carboxylate group. Thermal stability of the OA bonded molecules on the CW surface increased, as shown by TG/DTG. The SEM and EDX analysis showed the insertion of OA on the CW

surface.

The results suggest that CW-OA particles can be used as an eco-friendly material and have good potential to be an interesting filler in polymeric composites. Keywords: concrete waste, surface modification, oleic acid, thermal analysis Introduction Over time, modified fillers have been gaining importance due to their intrinsic properties. Regardless of the dimensions - micro or nano - they allow surface modifications that can assign special characteristics. Either organic or

inorganic 1

chemical reactions may be applied to change their morphology and/or 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65

chemical

constitution. One can find several examples of this kind of work in literature. Some authors modify montmorillonite - organically, or using polyaniline - to be used as filler in several polymeric composites. In general, the aim was to improve mechanical and/or barrier properties [1-4] of neat polymers. In other works, researchers modify

silica.

Konsinglark and co-workers reacted silica particles with silane and isoprene, and then hydrogenated it and used in nanocomposites [5]. Mendes et al. [6] synthesized silica through the sol-gel process, and modified its surface with acryloyl chloride. Silica nanoparticles were treated with oleic acid, and the authors reported that the modified nanoparticles were properly dispersed in mineral oil [7].

There are other inorganic fillers being modified in literature. Zinc oxide

surface

modified with silane was used to improve the filler dispersion in the nanocomposite [8]. Organically modified fluorohectorite was used to show an electric-field-induced alignment when suspended in silicone oil [9]. Zirconium phosphate was intercalated with octadecylamine to be used as filler in LLDPE nanocomposites [10]. Zeolite was treated with different coupling agents, to study its influence on the

mechanical

properties and flame retardant performance of polypropylene composites [11]. Silica oxide particles were functionalized with polystyrene and silane, to improve the stabilization of polybutadiene/polystyrene blend [12]. Tavares et al. used silica and niobium nanoparticles to prepare nanostructured materials [13]. Mineral filler was added to asphalt, in order to study its effect on hot mix asphalt (and led to changes in the fracture and moisture resistances and wettability) [14]. Ultra-fine calcium carbonate surface was treated with polyacrylic acid, inducing the reduction of its surface tension [15]. Canadian switch grass coated with polypyrrole was used to prepare a low-density polyethylene composite [16]. Silicon alkoxides were used to produce nanoparticles. Their sulfonation using direct sulfuric acid and chlorosulfonic acid was investigated by Dias et al. [17]. Supercritical carbon dioxide was employed for synthesizing polymer– inorganic filler nanocomposites [18]. Calcium carbonate was modified with several unsaturated acids and acid anhydrides. These materials were compounded with polypropylene and their mechanical properties were evaluated [19]. Several fillers (quartz, talc and wollastonite) were chemically modified on their surface with coupling agents and their effect on reinforcement of silicone rubber was investigated [20]. 2

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Concerning to the sustainable aspect of this issue, there is an abundant source of inorganic filler in the Brazilian urban solid waste. The disposal of concrete waste and other residues from the building industry has become an environmental problem. After reducing the particle size and modifying its surface, the concrete waste can be used as low-cost filler for composites. One of the main challenges on using this material in composites is the dispersion of the particles. The oleic acid has been used often for this purpose. The silver nanoparticles were successfully dispersed with oleic acid, when investigated by Anh-Tuan Le [21]. Monodispersed magnetite nanoparticles coated with oleic acid, and reduced the interactions among the nanoparticles [22]. Also the thermal transition and crystal arrangement of oleic acid were investigated by Tandon and coworkers [23]. Therefore, we expected that the modification of the surface of concrete waste particles with oleic acid would improve its dispersion in a polymeric matrix. Oleic acid has a long-chain, and can ease the dispersion of the concrete waste particles within the polymeric matrix.

In this article, we reported the preparation and characterization of concrete waste organically modified with oleic acid. It was intended to modify the surface of the concrete waste particles, and improve the dispersion of these particles in polymeric composites. We performed thermal, structural and morphological characterizations, to ascertain if the intended modification of the concrete waste particles was accomplished.

Experimental Materials Concrete waste (CW) was supplied by Lafarge Concreto Ltda. Oleic acid (OA, 99% purity) was supplied by Sigma Aldrich. Preparation of the CW The concrete waste was crushed in a C model Carver hydraulic press, with 18 ton capacity, in order to reduce the particle sizes. Then, the crushed material was studied by 3

size analysis in a Produtest apparatus, with an Abronzinox sieve of 270 mesh. The 1 2 3 4

particles which passed through the sieve were selected for chemical modification.

5 6 7

Surface modification with OA

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The CW particles were disaggregated through sonication, using ethanol. The resulting material was dried, and then 80 g of these sonicated particles were added to 450 ml of a

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0.33 % (v/v) ethanol / OA solution. This dispersion was kept under stirring during 24 hours. Then, it was filtered and washed with ethanol to remove the unreacted oleic acid. Finally, the resulting material was dried to constant weight. In order to make clear, the materials were referred, from this point on, as concrete waste (CW), oleic acid

(OA),

and concrete waste modified by oleic acid (CW-OA). Characterization X- ray Fluorescence The chemical composition of the concrete waste was evaluated using

X-ray

fluorescence analysis in a Rigaku RIX 3100 spectrometer. The amount of each oxide was determined and expressed in terms of percentage.

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Wide-angle X-ray diffraction (WAXD)

38

Wide-angle X-ray diffraction analysis was performed using a Rigaku Miniflex diffractometer with CuKα radiation (λ = 0.15418 nm). The experimental conditions

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used were: 30 kV, 20 mA, 2θ interval from 2 to 90° and resolution of 0.01°.

Fourier Transform Infrared Spectroscopy (FTIR) Infrared spectroscopy was performed with a Varian Excalibur FT-IR spectrometer, using a KBr disk. The spectra were taken from 500 to 4000 cm-1 with 50 scans and 2 cm-1 of resolution. Characteristic absorptions of the sample before and after modification were registered.

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Thermogravimetry/ Derivative Thermogravimetry (TG/DTG) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65

Thermal degradation of the materials was evaluated using a TA Instrument Q500 thermogravimetric analyzer. The analysis was carried out from 30 to 700°C, at 10°C min-1, under nitrogen atmosphere. We used samples weighing around 10 mg. Onset, maximum degradation and final temperatures (Tonset, Tmax and Tfinal) were registered. Differential scanning calorimetry (DSC) Calorimetric analysis was carried out using a TA Instruments Q1000 calorimeter. Three thermal cycles were used. The OA and the CW-OA were heated from -50 to 130°C at 10°C min-1, because the main transitions of the OA can be found between this range [21, 22]. The CW was heated from 0 to 300°C at 10°C min-1. Both OA and CW were heated, kept at the maximum temperature (130°C for OA, 300°C for CW) for 2 min and then cooled to the minimum temperature (-50°C for OA, 0°C to CW) at 10°C min-1. A second heating procedure, repeating the parameters of the first heating, was performed. As no change has happened in the CW curves after 130°C, the overlay of the curves is shown only between -50 and 130°C. Scanning electron microscopy (SEM) and energy dispersive x-ray detector (EDX) The morphology of the concrete, before and after modification, was evaluated by FEI QUANTA 400 microscope with electron beams of 15 kV and variable magnification. The sample was placed onto a carbon ribbon and covered with a layer of gold. The EDX analysis was also applied to confirm the metal oxides and the presence of oleic acid on the concrete particles. Results and discussion X-ray fluorescence data are reported in Table 1. Several oxides were detected, but SiO2, CaO, Al2O3 and Fe2O3 appeared in the largest amounts. According to literature, these oxides are the main components of conventional concrete [24, 25]. Table 1 – Chemical composition of the CW by X-ray fluorescence.

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Figure 1 and Table 2 present the WAXD patterns and the reflection angles of the CW, 1 2 3 4 5 6 7 8 9 10

before and after modification. The reflections of crystalline planes of the neat and modified concrete waste were similar and are associated to the oxides found in the x-ray fluorescence analysis - SiO2, CaO, Al2O3 and Fe2O3. The values of the reflection angles are in agreement with those reported by Wongkeo et al. [26] in an article about mechanical properties of environmentally friendly concrete blocks, and Sabai et al. [27],

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in a research on blocks produced from construction and demolition waste.

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water and associated to dehydration of calcium silicates (C-S-H). No transition was detected in the second heating. The curves of the CW-OA in both cycles resembled

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Figure 1 – Wide-angle X-ray diffraction (WAXD) patterns of the CW and CW-OA. Table 2 – Main WAXD reflection angles of CW and CW-OA.

Figures 2 and 3 show the DSC curves of the CW, OA and CW-OA. The OA showed two endothermic peaks, one around -14°C and the other around 12°C, in the first and second heating cycles, related to its melting temperatures (Tm). There were two peaks in the cooling cycle (-21 and 2°C). Evaluating the thermal curve of the CW (first heating cycle), there was a slight variation around 90°C, ascribed to the release of adsorbed

those of the neat CW. The disappearing of the Tm and Tc peaks of the OA in the thermal curves of CW-OA suggests that the OA was bond to the CW surface, and may mean that the intended functionalization was achieved. Figure 2 – Overlay of the DSC curves (2nd heating) of the CW, OA and CW-OA. Figure 3 – DSC curves of the CW (a), OA (b) and CW-OA (c). TG/DTG thermal degradation curves were shown in Figures

3 and 4, respectively. The

CW degraded in a single step. The TG/DTG curves of OA showed

single-step

degradation (between 150-275°C), with Tonset around 224°C and Tmax close to 257 °C. The CW-OA curve showed two steps of degradation. The first one until 400°C was ascribed to the decomposition of calcium hydroxide (Ca(OH) ),2 as reported by Barbhuiya et al. [28]. According to Mendes et al. [6], the mass loss between 400 and 700°C was due to the silica’s dehydroxylation,. As seen by Mendes et al. when studying the intercalation/exfoliation of zircon phosphate [29], the CW-OA curve stands between 6

the CW and the OA ones. The Tonset of the CW shifted from 612°C to 406°C due to the 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65

presence of OA. On the DTG curves, besides resembling the CW peak around 655°C, the CW-OA curve shows a peak around 451°C that does not exist on the CW curve. This peak can be ascribed to the chemical bond between the OA and the surface of the CW particles.

Figure 4 – Overlay of the TG curves of CW, OA and CW-OA. Figure 5 – Overlay of the DTG curves of the CW, OA and CW-OA.

Figure 6 shows the spectra of the materials. According to Horgnies et al. [32], high performance concrete presented bands at 3640 cm-1 (O–H; portlandite Ca(OH)2), 1410; 872 and 710 cm-1 (C=O; CaCO3), 1080–970 cm-1 (Si–O; silicates, CSH), 935 and 900 cm-1 (Si–O; C3S), 797 and 777 cm-1 (Si–O; silica). The spectrum of neat CW used here showed absorptions at 3489 cm-1 (O-H, stretching), 1640 (H-O-H, bending),1420 cm-1 (C=O and OH, stretching), 1100-1000 cm-1 (Si-O-Si, asymmetric stretching), 879

cm-1

(C=O, stretching, CaCO3), 779 cm-1 (Si-O-Si, symmetric stretching) and weak bands at 698, 580/458 cm-1 (Fe-O-Fe, stretching) [28-33]. The main absorptions of OA

were

2925, 2854, 2674 cm-1 (CH2 and CH, asymmetric and symmetric stretching), 1713 cm-1 (C=O, stretching); 1465 cm-1 (CH2 vibrational deformation), 1413 (OH, vibrational deformation), 1378 cm-1 (CH3 symmetric deformation), 1285 cm-1 (C-O, deformation), 938 cm-1 (OC-OH, vibrational deformation) and 723 cm-1 (C-[CH2]n-C,

skeletal

vibration) [34, 35]. The spectrum of CW-OA showed absorptions at 3429, 2927, 2856, 1550, 1429, 1081, 1050, 880, 779, 581, 462 cm-1. The bands at 2927, 2856 and 1550 cm-1 are new. The two first are related to the CH2 and CH groups’ vibrations of the OA. The band at 1550 cm-1 is associated to the carboxylate group (resulting from reaction of hydroxyl groups on the CW surface and the carbonyl group of OA). Wen and coauthors [36] studied the modification of Fe3O4 nanoparticles with oleic acid and obtained similar FT-IR results. Figure 7 shows the reaction scheme of the hydroxyl groups on the CW surface and carbonyl groups of the OA molecules. Therefore, the covering of the CW surface with OA might have been successful, and the results were in an agreement with those found in thermal analyses.

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Figure 6 – FT-IR spectra CW, OA and CW-OA. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65

Figure 7 – Suggestion of reactional scheme between CW, OA and CW-OA.

Figures 8 and 9 show the SEM images of neat and modified CW, respectively. The neat CW particles resemble fragmented rock. They are heterogeneous in shape

and

dimension with some cleavage regions. The CW-OA particles look like snow flakes. The surfaces are smoothed, rounded and the particles have almost homogeneous distribution size. The EDX spectra of both CW and CW-OA (Figure 9) were similar. The spectrum of CW-OA presented a peak lower than 0.5 keV, ascribed to

the

hydrocarbon chain of the OA, which indicates that the covering of the particles’ surface might have been successful. Figure 8 – SEM image of neat CW.

Figure 9 – SEM image of CW-OA. Figure 10 – EDX spectra of CW (a) and CW-OA (b).

Conclusion Concrete waste was organically modified with oleic acid. Thermogravimetry analysis showed that the OA was successfully incorporated to the CW surface. The absence of melting and crystallization temperatures of OA in the CW-OA DSC curves points out the surface modification. SEM images and EDX spectra also allowed inferring that surface modification was accomplished. An eco-friendly material was obtained,

with

potential application in polymeric composites.

Acknowledgments We thank the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for supporting this work.

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Figure captions

Figure Captions

Figure 1 – Wide-angle X-ray diffraction (WAXD) patterns of the CW. Figure 2 – Overlay of the DSC curves of the CW, OA and CW-OA. Figure 3 – DSC curves of the CW (a), OA (b) and CW-OA (c). Figure 4 – Overlay of the TG curves of CW and OA. Figure 5 – Overlay of the DTG curves of the CW and OA. Figure 6 – FT-IR spectra CW, OA and CW-OA. Figure 7 – Suggestion of reactional scheme between CW and OA. Figure 8 – SEM image of neat CW. Figure 9 – SEM image of CW-OA. Figure 10 – EDX spectra of neat CW (a) and CW-OA (b).

Table 1

SiO2 CaO Al2O3 Fe2O3 K2 O SO3 MgO TiO2 MnO Others Total

Previous / % After / % 50.2 42.9 21.2 22.4 13.8 14.1 4.5 3.9 4.2 4.8 2.3 2.6 2.3 1.9 0.8 0.8 0.1 0.2 0.6 6.4 100 100

Table 2

Elements Ca1.979Al3.8Si8.2O24 SiO2 CaO Al2O3 Fe3O4

Cristallynity Peaks (2 theta) CW CW-OA 8.9 21, 26.8, 27.6, 29, 39.5, 45.2, 21, 26.4, 27.2, 29, 39, 45.4, 50, 60, 65, 67.8, 77, 81 50, 63.8, 67.7, 75, 81 28, 29.9, 36.5, 50.2, 55, 65, 28, 29.9, 50.4, 55, 65, 68.4 68.4 23.5, 36, 42, 65.5. 83.8 42, 83.5, 35 28, 35.8, 54, 57.5, 61.5 35, 60

New Peaks

20.7, 34.8, 41.4, 47, 48.2

Table Captions

Table 1 – Chemical composition of the CW by X-ray fluorescence. Table 2 – Main WAXD reflection angles of CW.