The hydration heat evolution curves of composite cementitious materials containing copper tailing powder (CT) and graphene oxide (GO) with different contents are measured and analyzed in this paper. The hydration rate and total hydration heat of the composite cementitious materials decrease with the increase of CT dosage, but improve with the increase of CT fineness and GO dosage. The hydration process of the cementitious systems undergoes three periods, namely nucleation and crystal growth (NG), phase boundary reaction (I), and diffusion (D), which can be simulated well using the Krstulovic–Dabic model. The hydration rates of the three controlling processes of the composite cementitious system decrease with the increase of CT content, but improve slightly with the increase of CT fineness. GO enhances the controlling effect of the NG process of the cementitious systems with or without CT, thus promotes the early hydration as a whole. Copper tailings are waste materials generated during the purification of precious copper from the copper ores, and 128 t copper tailings will be left over per 1 t refined copper . The cumSome studies regarding the use of copper tailings as cement substitution have been conducted, and the results show that the pozzolanic activity of copper tailing powder is fairly low and its optimal replacement ratio is 5% without strength and durability reduction; however, the replacement ratio can reach up to 30–50% in mass concrete with consideration of the temperature control ,7,8. MorAs a result, copper tailing powder (CT) shows some adverse effects on early hydration and strength of the cement-based materials, but GO can improve their microstructure and properties. What will happen when the positive and the negative elements interact? How does GO promote the hydration mechanism of a cement-CT composite system? We suppose that GO also has reinforcing and toughening effects on the composite cementitious materials containing CT. In order to investigate the effect of CT on the early hydration mechanism of cement, as well as the enhancing effect of GO on the hydration of cement and cement-CT binder, the hydration heat evolution rate and cumulative hydration heat of composite cementitious materials containing CT and GO at different contents are measured at 25 °C by an isothermal calorimeter. Based on the thermodynamic data, the hydration kinetics of the composite cementitious materials containing CT and GO are investigated in detail using the Krstulovic–Dabic model to reveal the effects of CT and GO on the early hydration.2, and Al2O3. While the total content of SiO2, Al2O3, and Fe2O3 is 53.03%, which is less than 70% of that put forward by ASTM C618-15 Standard Specification for Coal Fly Ash and Raw or Calcined Pozzolan for use in concrete [2 exists mainly in the form of andradite instead of active SiO2. In general, the CT used in this study has a low pozzolanic activity. GO dispersion is produced by Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, China. It has a GO content of 4 mg/mL and its morphology, size (about 1 μm) and thickness (about 1 nm) are characterized by the Atomic Force Microscope  as shown in Ordinary Portland cement (P.O 42.5) and CT supplied by China Construction Mining Corporation are used in the experiment. Their chemical compositions, determined by the X-ray fluorescence , are listed in concrete . Its XRD2/kg and 690 m2/kg, respectively. The specific surface area of cement is 440 m2/kg. The average size of CT ground for 30 min and 60 min is 6.79 μm and 3.47μm, respectively, and the average size of cement is 5.67 μm, which is similar to their specific surface area.The copper tailings were dried, first, at 60 °C and filtered through a 1 mm-square-hole sieve in order. Then, they were ground for 30 min and 60 min, respectively, in a small insulative ball mill . The ball mill has a speed of 48 r/min, with a loading capacity of 5 kg of sample. The powder morphology was investigated using scanning electron microscopy . As shown in Two paste systems, I and II, prepared for hydration heat determination are listed in 2+ concentration reduces and the time when Ca2+ reaches supersaturation extends, which leads to the ending time of the induction period being slightly prolonged [As shown in rolonged ,17,18.3S and fast formation of C-S-H and Ca(OH)2 [After the acceleration period, comes the strong hydration reaction of C Ca(OH)2 . Owing tMoreover, it is interesting that the heat release per g of cement of the cement-CT binder clearly improves with the increase of CT content and strengthens slightly with the increase of CT fineness, as shown in α is hydration degree; t is hydration time; t0 is the time when the induction period ends; R is the ideal gas constant; n is the crystal growth index that reflects the geometrical crystal growth, 1 ≤ n ≤ 2 [A hydration kinetic model is often used to analyze the influence of various factors on the reaction rate and reaction direction during the hydration process, in order to reveal its control mechanism . The Krs ≤ n ≤ 2 .α is differentiated with respect to t in the equations above, the hydration rate of each process is obtained as follows:When Q/dt obtained by isothermal conduction calorimetry, the hydration degree α and hydration rate dα/dt required for the kinetic simulation of hydration process are determined by the following equations [Q(t) is the heat released from the end of the induction period. Due to the fact that the dissolution progress is so fast that it is not always possible to be detected. Meanwhile, the induction period is also thought to make a small contribution to the total heat. Therefore, this simulation is conducted from the beginning of the second peak, namely the ending of the induction period [Qmax is the total hydration heat when the reaction has completely finished and is obtained by using the Knudsen extrapolation Equation (9) to linearly fit the hydration heat evolution curves [t50 is the time required for half of Qmax.Based on the total hydration emission quations :(7)α(t)n period ; Qmax isn curves : where tQmax and hydration degree α(t) is determined by Equations (7) and (9), respectively and successively at first, as shown in n during the nucleation and crystal growth (NG) process could be calculated by substituting α(t) into Equation (1) and linearly fitting the double logarithmic curve of α(t) into Equations (2) and (3) and fitting the double logarithmic curve α, are acquired. The relationships of In order to obtain the hydration kinetic equations of CTs, the From 2 becomes supersaturated in a few minutes and then the hydrates grow from a fixed number of nuclei [2+ dissolved from unhydrated particles to supply the hydration reaction, the supersaturation state of Ca2+ remains constant. The reaction mainly occurs at the boundary between the solid hydrates and the liquids. At that time, the phase-boundary-controlled I process plays the leading role [Cement reacts with water primarily, and Ca(OH)f nuclei . For thef nuclei ,31. As aing role . As the n reduces with the increase of CT dosage while improving with the increase of CT fineness, which indicates that high fineness may affect the crystal growth geometry. The rate of chemical reaction during the NG process is very fast. The rate of the NG process is about 4–5 times the rate of the I process, and about 20 times the rate of the D process. The hydration reaction during the NG process is an autocatalytic reaction. The continuous growth of the crystal nucleus leads to the increase of their boundaries, which in turn accelerates the hydration reaction of the NG process. Therefore, the hydration reaction during the NG process is fairly fast. However, the hydration reaction during the I process is mainly controlled by the ion concentration, crystal area, and growth space for hydrates. In comparison with the NG process, a lot of reactants and water are consumed and a large amount of hydration products are formed during the I process, leading to the ion concentration to decline and the growth space for hydration products to narrow. Thus, the hydration rate of the I process is much lower than that of the NG process. With the development of hydration, the hydration reaction proceeds to the D process. During this process, massive dense C-S-H is formed due to the hydration of cement and the pozzolanic reaction of CT, which wraps on the surface of unreacted particles and makes the ion immobility difficult. As a result, the hydration rate during the D process is even lower than that during the I process.The kinetic parameters of the hydration process of sample CTs are listed in As shown in activity . With thIt is also noted that the hydration duration for both the NG process and I process is shortened with the increase of CT content, indicating that the hydration reaction of the composite binder containing CT transforms from the NG to I process and from the I to D process at a lower hydration degree with the increase of CT content. The replacement of cement by CT increases the effective water to cement ratio and provides more space for hydration products during the early hydration stage. Meanwhile, CT with high fineness can also act as nucleation sites for hydration products during the NG process . TherefoThe kinetic parameters of the hydration process of composite cementitious materials are given in Overall, based on the data in (1)Copper tailing powder, as a replacement for cement, reduces the early heat release rate and heat discharge of the cementitious system. The hydration rate and the total heat release improve with the decease of the content of copper tailing powder and the increase of the fineness of copper tailing powder. At the same time, graphene oxide can further improve the hydration rate and hydration heat of the cementitious system.(2)The Krstulovic–Dabic kinetic model can be used to characterize the controlling process during the hydration. The hydration process of the composite cementitious materials containing copper tailing powder and graphene oxide is controlled by a multiple reaction mechanism, namely nucleation and crystal growth (NG), phase boundary reaction (I), and diffusion (D), in that order.(3)The hydration rates,


This study demonstrates that the highest values of d33 are obtained when thinner films, produced with a lower concentration of polymer in the solvent , go through quenching in water, at room temperature. Whereas, in the case of higher polymer concentration , the best value of d33 (~30 pm/V) was obtained through quenching in liquid nitrogen, at the temperature of 77 K. We believe that in the former case, phase inversion is mainly originated by electrostatic interaction of PVDF with the polar molecules of water, due to the low viscosity of the polymer solution. On the contrary, in the latter case, due to higher viscosity of the solution, mechanical stretching induced on the polymer during spin-coating deposition is the main factor inducing self-alignment of the β-phase. These findings open up a new way to realize highly efficient devices for energy harvesting and wearable sensors.In the present work, poly(vinylidene fluoride) (PVDF) films were produced by spin-coating, and applying different conditions of quenching, in order to investigate the dominant mechanism of the β-phase formation. The influence of the polymer/solvent mass ratio of the solution, the rotational speed of the spin-coater and the crystallization temperature of the film on both the β-phase content and the piezoelectric coefficient ( Dipoles orientation is usually obtained by electrical poling. This technique is based on the application of a strong DC electric field (~106 V/m) at elevated temperatures (~393 K) on the polymer through a top and bottom electrode, in order to induce the alignment of the dipoles along the direction of the electric field  and spin-coated  with an acceleration of 7500 rpm/s2 for 10 s. After the deposition the sample was immersed immediately in an opportune bath  held at various quenching temperatures  for 30 min. The samples were produced as follows: firstly, PVDF in powder form  was dissolved in N,N dimethylformamide  by magnetic stirring  for 3 h at 343 K. Then, 1 mL of the produced polymer solution was cast over a PET/ITO substrate  and considering the following three quenching conditions—(i) 303 K in a water bath; (ii) 253 K in an ice/glycerol bath; and (iii) 77 K in a liquid nitrogen bath.The produced samples are schematically summarized in A Field Emission Scanning Electron Microscope  operating with an accelerating voltage of 3 kV was used to assess the morphology of the PVDF films. A Quorum Technologies Q150T ES sputter coater  was used to metallize the PVDF films prior to SEM imaging with 20 nm of Cr, in order to prevent charging.−1.The rheological behaviour of the material was assessed using a Modular Compact Rheometer . The measurement setup was composed of a 25 mm parallel plate system with 1 mm gap between the plates. Rheological tests were carried out at room temperature, in the steady shear regime. The rheological behaviour of the two different PVDF-DMF solutions was assessed as a function of the shear rate from 0.01 to 100 s−1 range with a resolution of 1 cm−1 .FT-IR characterizations were performed as described in References ,13,14. I2 in size on each sample, with 256 × 256 acquisition points per scanning area, and with a scan rate of 0.5 Hz, in order to obtain an estimate of the average value of The piezoelectric coefficient MA, USA) ,15. FollMA, USA) , we scan(i)d33PPLN), is conducted over the amplitude voltage range from 2 V to 10 V;At first, a calibration measurement of a reference periodically poled lithium niobate  sample, with a known value of the piezoresponse coefficient ((ii)Then, the sample under investigation is tested, and the amplitude of the PFM signal (iii)The PPLN is measured again and the new vertical piezoresponse force microscopy signals (VPFM), for each value of the applied voltage (iv)If the difference between the two piezoelectric calibration signals is less than 20%, the measurement of the sample under test is considered reliable;(v)Next, the calibration factor (vi)d33 value of the sample under test is finally calculated, using the following expression:The The procedure applied for PFM characterization can be summarized as follows: Once the PFM measurements were performed in each selected areas of the sample, we estimated the average PFM response as:The standard deviation of The rheological analysis showed a Newtonian behavior of the produced polymer-DMF solutions for both PVDF concentrations of 20 wt.% and 30 wt.% The increase in the PVDF to solvent ratio produced an increase in viscosity of the solution, regardless of the shear rate, as shown in 3 and the one of DMF 3.The calculated densities are: 3 and 3. Therefore, from Equation (4) and using the measured values of viscosity, we estimate the thickness of the samples, as reported in On the basis of the rheological characterizations, considering the high values of the spin-coater rotation speed (either 2500 rpm or 7500 rpm), the relatively short deposition time of 10 s and the low volatility of DMF at room temperature , we can assume that the solvent evaporation is negligible during deposition and that the viscosity of the solution is nearly constant. Therefore, the film thickness eference :(4)h=h0 studies  and usinThe produced samples are generally characterized by a porous spherulitic structure, which is originated by solvent evaporation. Size and morphology of the spherulites observed over the surface of the samples are significantly influenced by both spin-coating rotation speed and quenching process.In particular, it was observed that among the samples produced with the 20 wt.% of PVDF , the one2 at 77 K. We also observed that samples produced at a lower angular speed (2500 rpm) and quenched at lower temperature  are characterized by a more evident stretching and alignment of the polymer chain along the substrate than the ones produced at higher speed (7500 rpm). In particular, the length of the polymeric filaments is limited to ~1 μm in samples H and I, produced at 7500 rpm; whereas, they reach several microns in samples M and N, produced at 2500 rpm. Moreover, the averaged diameter of such polymeric filaments is around 300–400 nm in sample M and it reduces to 100–200 nm in sample N quenched in liquid nitrogen at 77 K.As regards the films produced with a PVDF content of 30 wt.% , we noti−1 and at 1275 cm−1. The α-phase is generally present in a low amount, as underlined from the relative amplitude of the characteristic peaks, located in the range between 1423 and 763 cm−1 [−1.The results of FTIR characterizations are reported in 763 cm−1 ,18,19. T−1) associated to the main peaks of the α-and β-phases, respectively, using the following formula [The relative volume fraction of the β-phase  formula :(5)F(β)=The obtained values of uenching ,11.2 are reported in acV  μmd in Vac . The val in F(β) ,14.F(β) is always higher than 70%. Furthermore, among the samples quenched at 303 K , the ones containing the lower polymer concentration , show a better piezoresponse. On the contrary, if the samples are quenched at 77 K, the higher piezoelectric response is obtained when the highest polymer concentration (30 wt.%) is used samples . The highest value of F(β) = 97.82%.It is interesting to observe that the samples produced at 253 K show lower piezoelectric coefficient, although the 2–CH2 groups of PVDF and polar molecules of water.Electroactive phase formation in PVDF films produced through spin-coating and quenching has been investigated in order to assess the main factors that affect phase inversion. In fact, several studies highlighted that β-phase formation in PVDF films is the result of the action of several factors, such as ,10,11: 2O is the dominant polarization factor during polymer crystallization;Quenching at room temperature in water: The electrostatic interaction with the polar molecules of H(2)Quenching at 253 K in a water/glycerol solution: The temperature gradient across the sample combined with the electrostatic interaction with water molecules are the main polarization factors acting during polymer crystallization;(3)Quenching at 77 K in liquid nitrogen: Neither the temperature gradient, nor the electrostatic interaction, are present. In this case, quenching has only the function of producing an instantaneous crystallization of the polymer, so that mechanical relaxation after spin-coating deposition is inhibited.For this purpose, we considered three different quenching conditions:Therefore, from the combined analysis of the morphological, FTIR and PFM investigations, we can draw the following conclusions.2 and CH2 in PVDF. Therefore, the rapid freezing of the PVDF film at very low temperature in liquid nitrogen, which is an apolar molecule, produces an instantaneous crystallization of the material, thus preventing elastic relaxation of the polymeric chains. This phenomenon is the dominant one, especially for the case of solutions with a higher viscosity, containing 30 wt.% of PVDF. This is confirmed by the high value of β-phase content, by the high value of measured piezoresponse coefficient, and by the formation of spherulites over the sample surface, interconnected by polymeric filaments that have a diameter below 200 nm, and lengths exceeding a few microns.The best stretching and alignment of the polymeric chains along the substrate is obtained producing the film by spin-coating at a lower angular speed . During spin-coating deposition, due to the very different molecular mass of fluorine and hydrogen, the centrifugal force induces orientation of the polar groups of CFIn the case of a more dilute solution, made with PDVF solution of 20 wt.%, the effect of mechanical stretching during spin-coating is limited, due to the low viscosity of the polymeric solution. Actually, samples with 20 wt.% of PVDF quenched at 77 K in liquid nitrogen, were characterized by a low piezoresponse coefficient. This confirms that β-phase crystallization is produced essentially through the electrostatic interaction of PVDF polar groups with polar molecules of water, occurring during quenching in a water bath at room temperature (303 K). In fact, the mechanism that is believed to be responsible for the increase of the piezoelectric coefficient in the sample at 20 wt.% of PVDF quenched at 303 K, is the formation of hydrogen bonds between the O–H groups of water with C–H groups of PVDF. The formation of these hydrogen bonds induce the PVDF molecules on the water to be oriented with C–F groups downwards to water, as described in References ,21. The From the histogram of In this paper, we demonstrated that the process that enables to obtain films with the highest β-phase and piezoresponse coefficient depends on the initial concentration of PVDF over DMF. In fact, the viscosity of the polymer solution plays a crucial role in the orientation of the polymer chains, due to mechanical stretching induced by spinning.d33 is associated with the highest amount of FT-IR and PFM data, in some cases, do not have the same trend as a function of the quenching temperature. This is due to the fact that although the FT-IR measurements give us information about the amount of β-phase in the sample, nevertheless they do not give us any information about the orientation of the polymeric chains. In any case, it is important to underline that the highest d33 among the samples produced with 20 wt.% of PVDF, indicating that the dominant factor in phase inversion is the electrostatic interaction between the polar groups of PVDF and water molecules. For the samples with a polymer/solvent mass ratio of 30 wt.%, the best d33 is obtained using a quenching temperature of 77 K, indicating a better orientation and alignment of the polymer chains, which are frozen using liquid N2. The samples quenched at 303 K showed the best d33 if compared with our previous studies [In this work, the combination of the deposition of thin films through the spin process, and the phase inversion through a quenching process, gave us a considerable enhancement of the  studies ,13,14,23 studies ,27,28,29d33, without the need of electrical poling or mechanical stretching, suitable to realize devices for energy harvesting and wearable sensors.The combination of spin-coating and phase inversion opensspi a new way to realize highly efficient piezoelectric PVDF thin films with an enhanced


In this paper, the influences of the graphite precursor and the oxidation method on the resulting reduced graphene oxide  are shown. Three types of graphite were used to prepare samples for analysis, and each of the precursors was oxidized by two different methods . Each obtained graphite oxide and reduced graphene oxide was analysed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy (RS). Carbon-based materials are very interesting due to their stable physicochemical properties and low cost, as well as other characteristics . These mrGO is obtained by the oxidation of graphite ) followed by reduction and exfoliation ,7. Curre−1) results from the presence of vacancies or dislocations in the graphene layer and at the edge of this layer. This band is also related to the presence of defects in the material [2 hybridized carbon atoms and is located near 1580 cm−1 [−1 [D/IG ratio (intensity of the D peak to the intensity of the G peak) is related to the amount of defects present in the material [2D/IG ratio (intensity of the 2D peak to the intensity of the G peak) is related to the number of graphene layers in the material [Based on the literature ,15,16,17material ,21,22. T580 cm−1 . The lascm−1 [−1 ,24. Basematerial ,26, whilmaterial ; when thmaterial .−1 (marked as D’) and two (according to other papers- three) additional bands above 2440 cm−1 become visible. There are discrepancies in the name of these latter peaks, where the first peak above 2440 cm−1 is marked as D* or G* and the next peaks are marked as D+D’ or D+G and 2D’ or G+D’ [2D/ID+G (I2D/ID+D’) ratio indicates the restoration of the sp2 hybridized structure [The literature indicates that additional peaks may be visible in the Raman spectra of some graphene-based materials after deconvolution. In our previous work , we pres or G+D’ ,22,28. ATwo types of natural graphite, scale graphite (S) and flake graphite (F), and one synthetic graphite; electrode graphite (E), were used for the measurements. The contents of carbon in these analytical samples in the dry and ashless state are 99.2, 99.5 and 99.5, respectively. These graphites are characterized by a high degree of crystallinity and large crystallite dimensions; however, their properties differ between materials. Due to the spatial arrangement of the flake graphite structure, the bonds between neighbouring planes can be easily broken, resulting in significant anisotropy in this graphite. The natural scale graphite has a coarse crystal structure with large crystals. The synthetic graphite is characterized by a high purity and close similarity to natural graphite; however, it is obtained in a synthetic method from a properly prepared mass in an Acheson electric resistance furnace at a temperature of 2500–3000 °C . The difGROS-A, GROF-A, GROE-A, GROS-B, GROF-B and GROE-B according to the type of graphite used and the method of oxidation. The diagram showing used abbreviations  is shown in Graphite oxides were obtained from scale, flake and synthetic graphites by two methods denoted A and B  and subsequently annealed at 900 °C for 5 min. The obtained rGOs are denoted X-ray diffraction measurements were conducted using an X’Pert PRO PW 3040/60 diffractometer . The samples were deposited onto glass and analysed by using Cu Ka1 radiation with a voltage of 45 kV and a current of 30 mA.XPS was performed using a PHI 500 VersaProbe spectrometer from ULVAC  using an Al Kα anode radiation beam (1486.6 eV).Spectroscopic studies were performed using an N-TEGRA Spectra platform . The vibrations of the molecules were excited using 532 nm wavelength. The exposure time was 10 s. Measurements were performed at ten different points of each sample.a), crystalline height (Lc) and interplanar distance (d002).The first step of the material characterization included determination of the crystallite diameter . The area under the G peak is approximately 7–8 times larger than the area under the D peak. For all analysed graphites, the intensity of the G peak is much larger than the intensity of the D peak.In the next step of the measurements, the Raman spectra of the graphite samples were collected . From thgraphite ). Howeve001) are obtained for the GROFs. The smallest crystallite diameter, La, is observed for the graphite oxides obtained from synthetic graphite, regardless of the oxidation method. The crystalline height (Lc) is similar for all the GROs.The first stage of measurements of the graphite oxides included analysis using the XRD method. Based on the obtained data , the larThe GROs were also analysed using the XPS method . All the2 and sp3 bonds of carbon. Moreover, peaks corresponding to carbon bonded to oxygen dominate the spectra of the GROs: three peaks  that correspond to hydroxyl/epoxy , carbonyl/quinone (C=O) and carboxyl (O=C–OH) groups are identified. Based on the obtained data, the hydroxyl and epoxy groups are the most abundant. Smaller amounts of carbonyl and quinone groups are present, and the carboxyl group content is the smallest (more carbonyl and quinone groups and fewer carboxyl groups are present in the GROs oxidized by method B). Furthermore, the lowest degree of graphite oxidation is observed for the GROSs.To determine the distribution of carbon and oxygen bonds, the C 1s XPS spectra of the graphite oxides were deconvoluted into five components. After deconvolution, two peaks appear at energies (284.5 ± 0.1 eV and 285.4 ± 0.2 eV) that correspond to the spD/IG, I2D/IG, and I2D/ID+D’) are shown in All of the experiments whose results were described above (XRD and XPS) were performed to obtain information about the tested graphites and graphite oxides. This knowledge was helpful for interpreting the data obtained from Raman Spectroscopy (RS). The RS method enables much more detailed analysis of the changes related the introduction of oxygen atoms into the graphite structure, thus increasing the understanding of the unstructured phase. 3 hybridized bonds as a result of the oxidation of graphite. Both the D and G bands of the GROs are wider than the D and G bands in the Raman spectra of graphite. Moreover, the G band of GRO is shifted towards lower wavenumbers, which confirms the presence of defects in the graphene layers.The spectra of GRO are characterized by intense D and G bands and a wide 2D band. Such an intense D band indicates the formation of defects in the structures. The increase in the intensity of the D band in relation to that of the G band indicates an increase in the amount of the disordered phase in the GROs. Unlike in the Raman spectra of the graphites, for the GROs, the D band is more intense than the G band, which is related to the formation of spThe presence of oxygen atoms causes both an increase in the interplanar distance and changes in the characteristics of the vibrations in the material’s lattice. For this reason, the Raman spectra of oxidized graphites are characterized by more intense D peaks in comparison to the D peaks of the unoxidized graphites. If the degree of oxidation is larger, the intensity of this peak is also larger ,31.−1. A D’ band is observed in the spectra of graphene materials obtained from the oxidation or direct exfoliation of graphites and subsequent reduction of the GROs, which confirms the formation of structural defects [The FWHM values of the D and G bands are larger for the GROs than for the graphites. The wide G bands in the GROs are accompanied by a D’ band, the intensity of which is proportional to the number of defects. The FWHM of the D’ peak is in the range from 61 to 66 cm defects ,23,31,32 defects .−1 [The 2D band is less intense than the D band. Based on the position, shape and intensity of the 2D band obtained from deconvolution of the Raman spectrum into components (Lorentz curves), the number of graphene layers can be determined ,34,35. I−1 . In cont−1), 2D (2695–2703 cm−1), D+D’ (2897–2910 cm−1) and 2D’ (3090–3118 cm−1), are obtained after deconvolution. The FWHM of the 2D peak is approximately 230 cm−1, which is much larger than that of the 2D peak of graphene (approximately 30 cm−1) [1 and 2D2 [In the spectra of the analysed GROs, four peaks: D*  as a consequence of the greater degree of exfoliation that occurs during high-temperature processing. The values calculated on the basis of the 002 band are in the range (0.3373–0.3393 nm) for method A and in the range (0.3421–0.3440 nm) for method B. The largest values of the interplanar distances (d00X) are observed for the rGOF materials, while the smallest ones are observed for rGOE. The maintenance of a large distance between graphene layers may be related to the presence of significant amounts of oxygen in the rGOs and a large degree of defect formation in the graphene layers. The crystallite sizes of the rGOs differ depending on the type of graphite used and the oxidation method. The smallest values of Lc and La are obtained for rGOs fabricated from synthetic graphite. Moreover, analysis of the obtained parameters reveals that higher values of Lc and La are obtained for the rGO-A series independent of the type of graphite. This result suggests that a lower degree of exfoliation occurs for the GROs obtained by method A. The resulting rGOs (method A) are characterized by a lower susceptibility to high-temperature exfoliation (larger number of layers).All reduced graphene oxides were examined by the same methods as those employed for the graphite oxides, and XRD measurements were performed first. The structural parameters of the rGOs are shown in Based on the data obtained using the XPS method , a large2 hybridized carbon (78% for A method and 80% for B method) occurs for these samples, and their percentage of sp3 hybridized carbon is the smallest among all the rGOs. Meanwhile, the largest amount of sp3 hybridized carbon in the rGOs is obtained for the samples prepared from synthetic graphite. As a reminder, the lowest degree of reduction, expressed as the C/O ratio, also occurs in the rGOEs.As was done for the GROs, the distribution of carbon and oxygen bonds was determined for rGO using the XPS method. Analysis of the XPS C 1s spectra after deconvolution , thereby confirming that both the reduction and oxidation process contribute to the formation of defects in the graphene layers.Reduced graphene oxides are made of graphene layers with residual oxygen groups attached to the planes and edges. The obtained materials exhibit intense G band and D bands, which confirms the presence of defects in the graphene layers. The FWHM values of the D and G peaks of the rGOs are smaller than those of the GROs, which indicates the presence of fewer defects in the structure (associated with a lower oxygen content). In the spectra of the rGOs, the intense G band is accompanied by a D’ band, the intensity of which is proportional to the amount of defects in the structure. The FWHM of this band is ~61–68 cmThe rGO-Bs are characterized by D* and 2D bands with larger FWHM values compared to those of the rGO-As, which indicates that these samples have fewer graphene layers in their aggregates (as a reminder: the average number of layers determined using the XRD method is 22–28 for the rGO-As and 8–11 for the rGO-Bs). Simultaneously, the FWHM values obtained for the rGO-Bs are larger than those obtained for the GRO-Bs. This result indicates that the aggregates of the rGOs contain fewer graphene layers than the aggregates of the GROs .D/IG ratios. The higher ID/IG ratios obtained for the rGO-B samples confirm that despite thermal reduction of these structures, more defects and imperfections are present in these samples than in the rGO-A structures. This difference can be explained by the higher oxygen content in the rGO-Bs, which is related to larger distances between the layers and a greater degree of exfoliation. The ID/IG values determined for the rGOs depend on the type of graphite used and increase in the order: flake (F) < scale (S) < synthetic (E) graphite . This trend can be related to the size of the graphene layers (La) determined using the XRD method, in which the opposite trend is observed . Based on the measurements performed, smaller graphite crystallites lead to larger amounts of defects in the obtained rGO structures. This relationship was also confirmed in the papers [The intensity of the D peak is lower for the rGO-A samples than the rGO-B samples, confirming that these materials contain fewer defects. This feature further results in lower Ie papers ,37, wher2D/IG ratio is related to the number of graphene layers, and larger values of this ratio are observed for the rGOs than for the corresponding GROs. The smallest values are obtained for rGOE-B, which indicates that this material has the fewest layers in its aggregates. Due to the type of graphite used, the I2D/ID+D’ ratio is the smallest for the GRO-Es. Please note that these materials are characterized by the smallest quantity of sp2 hybridized carbon and the largest quantity of sp3 hybridized carbon (determined by XPS measurements), indicating a high degree of destruction of the graphene layers. Furthermore, the I2D/ID+D’ ratios are the smallest in this case. Conversely, the rGO-Fs are characterized by the largest quantity of sp2 hybridized carbon and the smallest quantity of sp3 hybridized carbon, which indicates the presence of fewer defects in these graphene structures.Analysis of the Raman spectra of the rGOs shows that the intensity of the 2D band is much lower than that of the G band. The ID/IG ratio and the smallest I2D/IG and I2D/ID+D’ ratios are obtained for the oxides prepared from synthetic graphite (E), which indicates that this graphite is the most susceptible to oxidation and exfoliation. In the case of the oxides obtained from flake graphite (F), the smallest ID/IG ratio and the largest I2D/IG and I2D/ID+D’ ratios are obtained. Based on the Raman spectra, an increase in the D band is observed for the GROs in comparison to that of the unoxidized graphite. This increase is related to the formation of sp3 hybridized bonds as a result of the oxidation of graphite. The presence of oxygen atoms causes both an increase in the interplanar distance and changes in the characteristics of the vibrations of the material’s lattice.From comparison of the different oxidation methods, method B is determined to be more effective for introducing oxygen into the graphite structure (more carbonyl and quinone groups and fewer carboxyl groups are present). Furthermore, comparison of the type of precursor (graphite) used shows that the synthetic graphite (E) is the least susceptible to oxidation. This conclusion is confirmed by the results of RS. The largest I2, CO and H2O, which leads to a weakening of the van der Waals forces between graphene planes, and as a consequence, individual graphene sheets are obtained. In such a process, complete elimination of oxygen from the graphite structure cannot be achieved, and the obtained product may contain even several percent of oxygen depending on the degree of reduction.Please note that rapid degradation of the oxygen groups occurs during thermal exfoliation and reduction of GRO. This degradation is accompanied by an increase in pressure due to the evolution of COAnalysis of the data obtained from XPS measurements reveals that the degree of reduction (represented as the C/O ratio) changes in the order rGOE < rGOS < rGOF.D/IG values, which indicate the content of defects in the structure, of the rGOs increase in the order rGOF < rGOG < rGOE. This trend is related to the size of the graphene layers (La), which exhibits the opposite trend (rGOE < rGOS < rGOF).The IAs we have proven, both the type of graphite used and the method of oxidation have a fundamental influence on the properties of the resulting rGOs. Further research on the prepared materials will include studies of their electrical properties. The sensitivity of selected parameters to the surrounding environment will also be tested (the rGOs will be applied as sensor layers in gas sensing devices).This work involved various advanced research methods that enable deeper analysis of the changes related to the incorporation of oxygen atoms into graphite oxides and reduced graphene oxides.The research facilitated the development of preliminary criteria for the selection of a graphite precursor for the preparation of reduced graphene oxides with the desired textural and structural parameters. The reduced graphene oxides obtained from flake graphites, which had the largest crystallite diameter among the analysed graphites, were characterized by the highest degree of reduction and the fewest defects. Moreover, in each investigated case, large crystallite dimensions in the graphite precursor corresponded to large crystallite dimensions in the obtained reduced graphene oxide (regardless of the oxidation method).This work also showed that the oxidation method has a large influence on the studied parameters of the obtained materials. The research allowed to indicate which of three graphite precursors is the most susceptible to oxidation and what structural and textural parameters will graphene materials have after exfoliation/reduction process. Graphite oxides obtained by method B (modified Tour’s method) were characterized by higher content of oxygen groups in comparison to method A (Hummers’ method). The flake graphite, characterized by the largest diameter of crystallites, proved to be the most suitable material for the preparation of graphene materials. Reduced graphene oxides obtained from flake graphite are characterized by a greater reduction degree and less amounts of defect .


It is of great significance to study the consolidation characteristics of modified coastal cement-soil. A one-dimensional consolidation test and microscopic test were carried out. In the tests, the cement content was 20%, fly ash content was 0%, 5%, 10%, 20%, and 30%, and the water content was 80%. The consolidation test results showed that: (1) Compared with coastal cement soil, the deformation of coastal cement soil modified with a 20% fly ash content was reduced from 4.31 to 2.70 mm, and the vertical compression deformation was reduced by 1.61 mm. (2) During consolidation and compression, the e–p curve (pore ratio-pressure curve) of fly ash-modified coastal cement soil was slower than that of coastal cement soil and the rate of change of pore ratio. (3) The compression coefficient of fly ash-modified coastal cement soil was reduced from 0.780 to 0.598 MPa-1 compared with that of coastal cement soil. The microscopic test results indicate that after adding the proper amount of fly ash, a skeleton was formed between the microscopic particles of the sample, which improved its resistance to compression and deformation. The results of this study indicate that it is feasible to modify coastal cement soil with an appropriate amount of fly ash to improve its compression resistance. Coastal soft soil refers to the sludge formed by gradual deposition under the hydrodynamic effect of weak waves and tidal waves, which are widely distributed in coastal and lake areas all over the world, especially in east China and Southeast Asia ,2,3. DueMany studies have also been conducted on the properties of modified cement soil. Wang et al.  exploredCompared with the prevalence of studies on unconstrained compressive strength and direct shear strength, there have been fewer studies on the consolidation characteristics of cement soil, especially modified cement soil. However, it is worth noting that due to the high compressibility of coastal soft soil, the issue of excessive deformation should not be underestimated ,22,23,24Recently, a micromechanism analysis put forth a solid foundation for cement matrix composite materials. Wang et al. investigated the micromechanism of nano-magnesia for improving cemented seashore soft soil and silty clay by using of the SEM and EDS  methods ,11,12. KThe objective of this research was to take fly ash as the external admixture to modify coastal cement soil and to investigate its consolidation characteristics and microscopic mechanism under a high water content, both of which can be used as references for the reinforcement and treatment of coastal cement soil.The coastal soft soil samples were taken from the Jiangbin area of Binhai New Town in Shangyu District, Shaoxing City, China, as shown in Lanting composite Portland cement with a strength of P.O 32.5 was used in the test. The microgram of the cement surface morphology was obtained by SEM, as shown in The light gray fly ash used in the test was industrial waste. SEM and XRD analyses of fly ash were obtained through micro tests and are shown in All coastal soft soil samples had a curing age of 7 d, 80% water content and 20% cement content. The fly ash content was varied. Five sample groups of fly ash-modified coastal cement soil were prepared with fly ash contents of 0%, 5%, 10%, 20%, and 30%. Due to the randomness of the test and the discreteness of the data, 5 samples were tested for each group of tests, that is the data were repeatedly tested five times for each group of samples. The sample content and curing age are shown in The coastal soft soil samples were immersed in water for several days and sieved using 1 mm sieve. The large particles that remained in the sludge and impurities such as shells were removed, and the mixture was stirred evenly and allowed to stand for two weeks. The water content after two weeks was relatively stable. An appropriate amount of soft soil was taken to measure the actual water content.The proportion was calculated according to the designed test plan, and coastal soft soil, cement, fly ash, and water were weighed, mixed, stirred evenly, and then poured into a ring cutter with a diameter of 61.8 mm and a height of 20 mm. The sample was placed in a circular ring cutter and tapped, and the surface was smoothed, as shown in A full-automatic pneumatic consolidometer  was used in this test, and the pneumatic consolidation instrument used in this test is shown in In order to explore the influence of the fly ash content on the vertical compression deformation of the sample, the curve between the deformation and loading pressure of coastal cement soil modified with the fly ash content of 0%, 5%, 10%, 20%, and 30% is shown in It can be seen from Since the fly ash content affected the maximum vertical compressive deformation of the sample, the functional relationship between the fly ash content (x%) and the maximum vertical deformation (∆h) was derived by data fitting, as shown in It is evident form It was necessary to measure the pore ratio of the samples before the consolidation compression test of modified coastal cement soil with different fly ash contents of 0%, 5%, 10%, 20% and 30%. Referring to the measuring method of specific gravity of soil particle in soil mechanics, the particle specific gravity (ds) and sample density of coastal cement soil and fly ash-modified coastal cement soil samples after 7 d of curing were measured. According to Equation (2), the initial pore ratio of coastal cement soil and fly ash-modified coastal cement soil sample was obtained. According to Equation (3), the pore ratios of the samples under different loads were obtained. The results of the calculation are shown in s is the particle specific gravity of the sample, ω is the moisture content of the sample (%), ρω is the density of water (g/cm3), and ρ is the density of the sample (g/cm3).In Equation (2), d0 is the initial pore ratio of the sample, h0 is the initial height of the sample (mm), ∆h is the compression deformation of the sample (mm), and ei is the pore ratio at a certain pressure.In Equation (3), eAs shown in −1) of the pore ratio reduction to the increment of the effective compressive stress under the confinement condition , and its value varied with pressure. The more significant the pore ratio reduction, the higher the compressibility. In soil mechanics, the compressibility of soil is generally evaluated by the compression factor α1–2 when the pressure section p1 (100 kPa) is increased to p2 (200 kPa). Based on Equation (4), the compression coefficient of fly ash-modified coastal cement soil was calculated and analyzed.The compression coefficient was the ratio is the pressure at the current level, and p1 (MPa) is the upper pressure.In Equation (4), e−1. As can be seen from −1. After adding 5%, 10%, 20%, and 30% fly ash contents, the compression coefficients become 0.788, 0.665, 0.598, and 0.602 MPa−1, respectively. The 5% fly ash content had little effect on the compressive coefficient of the coastal cement soil. When the content was 10%, 20%, and 30%, the compression coefficient decreased and its compressibility reduced.The compression coefficient of coastal cement soil was 0.780 MPaIn order to investigate the relationship between the deformation and the pressurizing time under each load of fly ash-modified coastal cement soil, the deformation and time curves of CF-0-7, CF-5-7, CF-10-7, CF-20-7, and CF-30-7 are drawn as shown in It can be seen from In order to further explore the anti-compression modification effect of fly ash on coastal cement soil, it was necessary to conduct a microscopic analysis, apply the obtained microscopic particle shape and skeleton structure to macroscopic mechanics, and combine macroscopic and microscopic analyses to obtain persuasive research results ,36. ManyA vacuum scanning electron microscope and an energy spectrometer were used to magnify the images of the sample to 2000–5000 times by scanning electron microscopy. The SEM test was performed to obtain a micrograph of the required magnification. The elemental composition of the sample was obtained by EDS. The diffraction pattern of the sample was analyzed by XRD to elucidate its chemical composition.Prior to SEM and EDS tests, cuboid micro samples of 3 mm length, 3 mm width, and 2 mm height were cut, as shown in In order to explore the microscopic mechanism of the resistance of fly ash-modified cement soil, SEM, EDS, and XRD micro tests of the samples of CF-0-7, CF-5-7, CF-10-7, and CF-20-7 were carried out. 2 of cement to form a hydrating gel [In summary, the hydration product of cement combined with fly ash produced a large amount of clay particles, which increased the size of the soil particles, obviously improving the soil strength. The fly ash reacted with the hydration reactant Ca(OH)ting gel , which cBased on the consolidation test data and microscopic mechanism analysis, the following conclusions can be drawn:(1) After adding fly ash to coastal cement soil, the vertical compressive deformation and the rate of deformation decreased. Under a load of 800 kPa, the maximum vertical deformation of modified coastal cement soil with 20% fly ash content was 2.70 mm, and the deformation of coastal cement soil was 4.31 mm. The vertical compression deformation was reduced by 1.61 mm.(2) The change rate of the pore ratio of fly ash-modified coastal cement soil also had a significant decreasing trend compared with that of coastal cement soil, which decreased from 0.67 to 0.41. The e–p curve of fly ash-modified coastal cement soil was slower than that of coastal cement soil, and the compression deformation speed slowed down.(3) The compression coefficient of fly ash-modified coastal cement soil was also smaller than that of coastal cement soil. It could be seen that fly ash improved the deformation resistance of coastal cement soil and reduced the compressibility of the cement soil sample.(4) Fly ash reacted with calcium ions produced by the hydration of cement to form a hydrated calcium silicate gel, which caused skeleton formation among the particle pores and improved its resistance to compression and deformation.(5) At a short curing age, one appropriate range for added content of fly ash into cement soil existed. Only adding an appropriate fly ash content could produce good resistance to the compression and deformation behavior of coastal cement soil. In this study, the optimum fly ash content was 15%–20%. An excessive fly ash content delayed the setting time of cement, resulting in the slower hydration of cement and hence, a lack of considerable improvement of the anti-compression properties of cement soil.It should be noted that this study described the consolidation characteristics of fly ash-modified coastal cement soil based only on the results of the consolidation compression test and microscopic test, and it explored the modification effect under a high water content and a short curing age. Further research might involve the determination of the consolidation characteristics with a different water content and a prolonged curing age. What is more, in future work, the design of experiment method should be used to highlight the influences of parameters combination.


The in vitro evaluations showed different roughness patterns between the groups, and the G3 group had the highest values. In vivo evaluations of the BIC% showed 50.45 ± 9.57% for the G1 group, 55.32 ± 10.31% for the G2 group and 68.65 ± 9.98% for the G3 group, with significant statistical difference between the groups (p < 0.0001). In the BAFO% values, the G1 group presented 54.97 ± 9.56%, the G2 group 59.09 ± 10.13% and the G3 group 70.12 ± 11.07%, with statistical difference between the groups (p < 0.001). The results obtained in the evaluations show that the surface with microgrooves stimulates the process of osseointegration, accelerating the healing process, increasing the contact between the bone and the implant and the area of new bone formation.The physical characteristics of an implant surface can determine and/or facilitate osseointegration processes. In this sense, a new implant surface with microgrooves associated with plus double acid treatment to generate roughness was evaluated and compared in vitro and in vivo with a non-treated (smooth) and double acid surface treatment. Thirty disks and thirty-six conical implants manufactured from commercially pure titanium (grade IV) were prepared for this study. Three groups were determined, as described below: Group 1 (G1), where the samples were only machined; group 2 (G2), where the samples were machined and had their surface treated to generate roughness; and test group 3 (G3), where the samples were machined with microgrooves and the surface was treated to generate the roughness. For the in vitro analysis, the samples were submitted to scanning microscopy (SEM), surface profilometry, the atomic force microscope (MFA) and the surface energy test. For the in vivo analyses, thirty-six implants were placed in the tibia of 9 New Zealand rabbits in a randomized manner, after histological and histomorphometric analysis, to determine the level of contact between the bone and implant (BIC%) and the bone area fraction occupancy (BAFO%) inside of the threads. The data collected were statistically analyzed between groups ( The rehabilitation of dental losses through osseointegrated implants has reached a fairly high level of confidence and has been used as a frequent treatment option in dentistry. For implantology concepts, the process of osseointegration for titanium implants is defined by the union between the implanted material and the bone tissue. The adequate union between them depends on the physical and chemical characteristics presented by the material, the surgical technique used and the patient’s conditions  ,2,3,4. RHowever, to improve the events required by the osseointegration process and to increase the quantity and quality of the union between the bone tissue and the surface of the implant, in view of possible adverse conditions, numerous propositions of implant surface changes were proposed . SeveralSome in vitro assays, such as surface microscopy, rugosity and wettability (surface energy), should be used to describe the proposed modifications and/or changes and thus be able to compare the results with other publications. Of these tests, surface wettability is the assay that may help to understand the behavior and ease (or not) of cell adhesion on the surface of the implant. Several studies have shown that there is a relationship between surface energy and cell adhesion on the surface ,13,14.The events related to optimal bone tissue healing using a treated implant surface are still unclear. The first stages of the osseointegration of implants involve some biological phases, such as protein adsorption, cell-surface interaction, progenitor cell recruitment and differentiation, and tissue formation at the interface between the body and the implanted material, which can be directly influenced by the physical-chemical characteristics of the material surface ,16,17.Although many findings on the behavior of different surfaces of titanium implants have already been made, there are still several points that need further scientific evidence, such as the relationship between cell culture results and the responses of these materials after being implanted in living organisms. In this way, based on cellular studies (in vitro), in which the benefits and the possibility of directing (guiding) the cellular growth with the elaboration of microgrooves on the surface of the implants were demonstrated ,18,19, wn = 10 per group) and the implants were 8.5 mm in length, 3.50 mm in diameter and used a conical design  (n = 12 per group). All the implants used presented the same macrogeometric design  were used in this study. The prepared disks were 5 mm in diameter and 2 mm in thickness , with controlled time and temperature, as determined by the manufacturing company , as described below: The implants were immersed in an 9.0 wt.% HF solution at ambient temperature for 45 s. The second immersion was made for 30 min at ambient temperature in a 30 wt.% H2SO4 solution containing 0.09 wt.% HF. Then, all samples were treated  in accordance with the sanitary standards required for the commercialization of the implantable products.The samples were divided into three groups in accordance with the surface treatment applied, which are as follows: Group 1 (G1), where the samples were only machined; group 2 (G2), where the samples were machined and had their surface treated to generate roughness; and group 3 (G3), where the samples were machined with microgrooves and the surface was treated to generate the roughness. The microgrooves (lines) of the G3 group had a maximum depth of 10 µm and a 10 µm distance between them during the machining of the implants in a CNC machine . The treatment of the surface of the G2 and G3 groups was performed with double acid conditioning, using hydrofluoric acid (HF) plus sulfuric acid  to obtain images and compare the morphological characteristics of the surfaces with different increases. Five other titanium disk samples from each group were used to determinate the roughness characteristics of the surface using a series of 3D images through AFM (Atomic Force Microscopy) analysis . These same samples disks were used to measure the surface roughness parameters  using an optical laser profilometer , where Ra is the absolute value of all profile points, Rq is the root-mean-square of the values of all points, Rz is the value of the absolute heights of the five highest peaks and the depths of the five deepest valleys and Rmax is the value between the maximum valley and maximum peak. These parameters are shown in the scheme in Surface wettability analysis: Surface wettability analysis was performed using a contact angle goniometer , which analyzes the static contact angles after the application of a drop of 5 μL of distilled water on the surface of the titanium disks, determining their hydrophilicity. Five disks from each group were used to make these measurements. The surface tension was calculated by measuring the contact angle formed between the drop and the disk surface . Images n = 12 per group) were installed in both tibias (n = 2 per tibia). The randomized distribution of the implants was performed using the site www.randomization.com. For the surgical procedures, the animals were anesthetized through the intramuscular injection of a combination of 0.35 mg/kg of ketamine  and 0.5 mg/kg of xylazine . In both medial area of the tibias, the hairs were scraped to facilitate surgical procedures and to avoid contamination. These areas were cleaned with a povidone-iodine solution. Then, the incision was performed with an extension of ~30 mm in length in each tibia and from 10 mm of the knee position to the distal direction. The soft tissues were separated and the bone was exposed. The beds to insert the titanium implants were prepared using the drill sequence and speed, determined by the manufacturer of the implant system, under intense distilled water cooling. The implants were manually inserted with ~15 N of torque and 10 mm between them . The suture was made using a simple point with nylon 4-0 . A single postoperative dose of 0.1 mL/kg of Benzetacil  was administered intramuscularly (I/M) in each animal. For the control of pain, the animals received three I/M anti-inflammatory doses (one per day) of 3 mg/kg of ketoprofen . All animals were euthanized 6 weeks after the implantation surgeries using an overdose of anesthesia. Then, the bone blocks of both tibias were removed and immediately immersed in a formaldehyde solution.Animal selection, surgical management and care: Nine white rabbits , weighing between 4 and 4.5 kg, were used for the in vivo analysis. The animals received the standard care and management applied in previous studies performed by our research group ,2,3. TheHistomorphometric and histological analysis: Three days after fixation in formaldehyde solution, the samples were washed in running tap water every 12 h and then gradually dehydrated in a progressive series of ethanol solution (60% to 100%). After dehydration, the blocks (bones with the implant) were embedded in historesin , polymerized and cut in the central region of the implants using a metallographical cutter . Then, the samples were polished using a sequence of abrasive paper (180 to 1200 mesh) in a polishing machine . The samples were stained using a picrosirius hematoxylin staining technique, as described below: First, the slides were dipped through either a methanol or ethanol gradient series . Second, 10 drops of Picrosirius were applied and left for 1 h. Third, the blades were washed and dried. Fourth, we applied 10 drops of hematoxilin which was left for 4 min. Finally, the blades were washed and dried once more. Images were taken using optical microscopy  and obtained for all samples. The percentage of bone-to-implant contact (BIC%) and the bone area fraction occupancy (BAFO%) inside of the threads were measured using the ImageJ program . For the BIC% calculation, the total perimeter around the implant was considered as 100%, and then the areas where the bone was in contact with the implant surface were measured. Whereas for the BAFO% calculation, the total area of threads was measured for the implant model used, and then the percentage of this area of threads occupied by the bone was used.Statistical analysis: A one-way ANOVA test was used to analyze the statistical differences between the groups. The comparison between the three groups in the same test was performed using the Mann–Whitney U test. These statistical analyses were performed using the software GraphPad Prism 5.01 . The level of significance was set at α = 0.05.The SEM images in different increases  of the three groups samples analyzed showed microscopic differences in the surface characteristics. However, the EDS (Energy Dispersive Spectroscopy) analysis of all groups showed a surface with high levels of titanium, without identification and/or the presence of other metal ions or contaminants.The G1 group (no treated surface) showed a small superficial undulation in the large magnification images produced by the cutting tools. In the G2 group, the surface showed a regular small porosity with a homogeneous distribution. The G3 group showed regularly distributed microgrooves and a similar rugosity to the G2 group samples, due to the same double acid treatment, with a deep and regular morphological pattern with small pores. Representative SEM images of the surface of each group are show in The characteristics of the surface of each group can be observed in the AFM images .The measured surface roughness showed different values of the analyzed parameters, which are summarized in The wettability analysis revealed the mean value of the contact angle over different periods time, which are presented in the comparative line graph and demonstrated in the schematic image in After the period determined by the osseointegration (6 weeks), all implant samples presented a good stability, without sample loss or failure of osseointegration. Then, all the implants could be evaluated histologically.In the G1 group, a few areas of new bone formation were visible close to the implant surface after the full time period, with poor new bone organization. In the G2 group, a large quantity of new bone formation was observed in comparison with the G1 group, with good organization of new tissue around the implant surface. In the G3 group, a great quantity of new bone formation was observed in comparison with the other two groups, with a good organization and a more advanced bone filling inside the threads in comparison to the other groups. Regards to the bone to implant contact (BIC%) and bone area fraction occupancy (BAFO%), the measurement and data analyses are summarized in The treatment to replace fully or partially edentulous patients using titanium implants has been applied with great frequency in dentistry practice, presenting good results and predictability. The production of these implants using titanium as a raw material has shown excellent results from a biological and mechanical point of view. However, the search for new knowledge and the improvement in the behavior of these materials in function, supporting the masticatory loads and the physiological reactions resulting from the medium where they are inserted , continues to challenge science. In this sense, the topographical changes in the surface of the implants have received special attention and are the main area of focus of research in the sense of improving and accelerating the processes of healing of the bone tissue. Thus, the present study had the purpose of comparing differently treated samples, through in vitro and in vivo assays, always using structures with the same macrodesign (disks and implants), but with different surface treatments. Similar with other studies about this subject ,14,15,20In the evaluation of the surface of the samples of each group by SEM, different morphological characteristics could be demonstrated, mainly in the G3 group, where the microgrooves were present and distributed in a regular and homogeneous way. As in other studies ,22,23,24The determination of surface roughness parameters of implantable biomaterials samples is an important point for the morphological characterization, considering that this condition will directly influence the adhesion, proliferation, differentiation and other cellular events resulting from the installation of the implant into the bone tissue. Several authors have demonstrated that an adequately machined titanium surface shows a Ra roughness parameter between 0.5 and 1.0 μm ,31. HoweStudies on the wettability of surfaces are commonly applied in materials engineering, as there is an influence of the roughness on the wetting properties, which are evaluated by the contact angle measured after the application of fluid on this surface. These studies could be used in many practical applications to adjust surface-fluid interactions . In implOther studies have shown that surfaces with rugosities have a spreading pattern of slower drop in comparison with less rough surfaces ,40, withStudies have shown that the surface topography of an implantable biomaterial can alter the local osteogenic response , dependiWithin the limitations of the present study, the results show that the implants with surfaces modified with microgrooves plus double acid treatment produced a significant enhancement in the process of osseointegration, accelerating healing, increasing the contact between the bone and the implant and the area of new bone formation.


Herein an innovative process to develop a potential vitreous material with cementing properties is proposed. This process paves a production path through melting industrial waste and subsequently cooling the casting in water. The idea erases the need to reduce the environmental impact of the cement industry in terms of natural resources consumption as well as the re-utilization of abandoned wastes from other industries. The recycled industrial wastes were selected according to the amount of waste produced in the industrial field and its suitable chemical composition, such as construction and demolition waste and/or shells from shellfish. As a main result, the mechanical properties showed by our novel material were worse than those reported by blast furnace slag (25–28 MPa for two different proportions) for seven days and better (43–52 MPa for two different proportions) for 28 days. The rest of the properties evaluated were in agreement with the standards’ requirements. Hence, this novel process would help to minimize the environmental impact of these wastes at the same time that their use in the cement industry would reduce the consumption of raw materials. The cement industry has the challenge of reducing the environmental impact of its activity, both at the levels of intensive energy consumption and greenhouse gas (GHG) emissions reduction, as well as in the reduction of the use of raw materials from natural sources. This has motivated, for example, the development of non-Portland cement which is prepared using powders that are normally used as supplementary cementitious materials . Cement 2, and Al2O3 [Blast furnace slag is one of the most abundant solid by-products of the iron-making process, with between 300 and 350 kg of BFS per ton of pig iron produced . Blast fnd Al2O3 . Due to nd Al2O3 . Furthernd Al2O3 ,10. Greand Al2O3  by addin2O3 [Authors such as Lin et al. ,13,14 an2O3  or other2O3 ,16, fly-2O3 ,19, ligh2O3 .2), the solid waste stream generated in an aluminum recovery plant (AW) as the main source of aluminum (Al2O3), and mussel shell waste from the aquiculture industry (MS) as the main source of calcium (CaO). The CDW comes mainly from demolition of buildings or rejects of materials of new construction or small reforms in buildings. This type of waste is carried in its main part to landfills, causing a negative visual and landscape effect, in addition to the negative environmental impact, which rejects materials that, with a specific treatment, could be recycled. In general, there are two groups of CDW that are used in different applications: recycled aggregates and recycled ceramics or mixed aggregates. In particular, a mixture of fines smaller than 5 mm is used as cement component. This mixture is pulverized to obtain particles of similar size to BFS, fly ash or gypsum, which are other components used in the manufacture of cement [The main objective of this research work is to develop a new potential method to obtain a synthetic slag (SS) from a waste mixture vitrified with similar physicochemical properties to that of BFS. Three different wastes have been chosen as raw materials in order to facilitate their recycling as cement substitutes and reduce the amount of waste sent to landfills. These wastes are: construction and demolition waste (CDW) as a main source of silicon  is a high alumina mineral waste generated in the process of recycling salt slags from aluminum melting . This waste has a high content of alumina and it can be used in a lot of high value applications. The variability in the chemical composition depends on the raw material used .In the case of waste derived from aquiculture industry, mussel shells are used in construction, such as road surfaces  or as fiThe obtained materials were compared in terms of specific surface, particle size distribution, chemical composition, and vitreous phase percentage with a real BFS which come from the ArcelorMittal factory in Avilés (Asturias) and were provide by cement Portland Valderrivas . The performance of the synthetic slag in a slag-cement mortar with 25% and 50% replacement was evaluated according to the European standard EN 197-4: 2005  and usinAs previously stated, a mixture of three different wastes were used in order to manufacture a material with similar properties to the BFS.Construction and demolition waste were used as a source of silicon. A typical mixed aggregate sample was taken from the Environmental Complex of the Mancomunidad de la Vega, which is located between Guillena and Burguillos . Construction and demolition waste were taken from the first screening in the recycling plant, where plastics and wood were separated from the rest of the material, so the CDW used contained aggregates of concrete, mortars, ceramics, and gypsum. The AW used in the study came from a processing plant and was obtained from a recycling process of salt slags in order to recover free metals and melting slags. Mussel shell waste was supplied by a seashell recycling company. The shells were subjected to a heat treatment of 150 °C for sterilization prior to use, and they were grinded in order to get particles between 0.1 and 0.5 mm in size.In addition to the three mentioned wastes, commercial Portland cement type I 42.5 MPa (C), nominal strength according to the EN 197-1:2011 , and staFor the production of cementitious material, a manufacturing system that simulates the conditions for the production of BFS in the industry were developed. First, heating was performed to temperatures above the melting point of the waste mixture in an electric furnace . Then, the molten material was subjected to a rapid cooling which gave it a high vitreous phase. A high percentage in the vitreous phase provided high reactivity to the material to be used as an addition to cement. Once the cementitious material was obtained, it was used as an addition to the cement in different proportions (25% and 50%) and the physical, chemical, and mechanical properties were evaluated based on standards.The chemical composition of the wastes was determined using an X-ray Fluorescence Spectrometer . Thermal analyses were performed in order to study the behavior of the wastes during the process of heating and melting in order to establish the thermokinetic conditions of melting and to identify the occurrence of possible physical and chemical changes, both in the solid phase and molten phase throughout this process. For this purpose, a thermo-gravimetric study  of each waste and mixture was carried out with a heating rate of 20 °C/min while using air as a purging gas. In order to determine the melting point of the mixture of waste, a heating microscopy was carried out in a furnace  with silicon carbide resistances and 1700 °C as maximum operational temperature with a video-camera system  coupled to the furnace. An image analysis program was used to study the evolution of the fusion of solid samples as a function of temperature. Thus, different material characteristics were obtained, such as deformation temperature, the formation temperature sphere or hemisphere, and the flow temperature or sintering starting.A waste mixture adjustment methodology was defined in order to obtain an SS with similar chemical composition to BFSs. This methodology is schematized in 2, CaO, Al2O3, and loss on ignition (L.O.I) percentages of each of the wastes were employed as inputs for solving the mass balances. The material lost during the melting process was supposed to be equal to the sum of the loss of ignition values of each of the wastes. The calculation methodology consists of an iterative process. Firstly, SiO2, CaO, and global mass balances were calculated by imposing initial values for both SiO2 and CaO percentages in SS. These initial values were the intermedium concentration of the ranges reported in CDW (wt % CDW), mMS (wt % MS), and mAW (wt % AW) were employed to check if the Al2O3 concentration was in the range shown in 2 and CaO were increased or reduced if the Al2O3 was too high or too low, respectively. Following this methodology, the following waste mixture (WM) adjustment was employed to produce the synthetic slag: 37 wt % CDW, 53 wt % of MS, and AW 10 wt %.As shown in The furnace used for the melting of wastes was designed and manufactured specifically for this research and consists of six electrical resistances located in the upper part of the equipment and arranged in a hexagonal shape on the sides of the fusion chamber. The melting pot used for the fusion was made of silicon carbide and was placed on a vertically opening platform. 2, which is the minimum established by the standard additions of blast furnace slag-cements.After fusion and cooling with water, the material was carried to an oven for drying at 105 °C for 24 h. Then the material was milled to adjust the particle size to the requirements of the regulations. The first milling step obtained a material smaller than 3 mm. In a second operation, a vibratory mill  was used, and programmed with a speed of 1600 rpm for 3 min. The final sizing is done in a third step in a ball mill . The minimum size required for the material was imposed below 32 microns. The determination of the specific surface area was made based on the air permeability method (Blaine method), according to EN 196-6:2010 . The resParticle size distribution, chemical composition, and characterization of vitreous phase were carried out at the Technology and Innovation Research Center of the University of Seville. The particle size distribution was analyzed by a Mastersizer 2000 particle size analyzer . This equipment allows particle size analysis by the laser diffraction technique and can measure particles with sizes between 0.02 and 2000 microns. Chemical composition was determined using an X-ray fluorescence spectrometer . For the chemical characterization of the waste mixture, a technique of X-ray fluorescence was used with a sequential spectrophotometer. The characterization of the proportion of vitreous phase was estimated using X-ray diffraction. The experimental device used for the determination was a D8 Advance A25 . For this calculation a semi-quantitative method was employed to determine the area under the curve taken as a basic of the diffractogram.Different mixture proportions of SS and C were evaluated to test mechanical, physical, and chemical properties according to the relevant regulations. The tested samples were compared to mixtures with the same proportions of blast furnace slags and cement. All the samples were manufactured using a water/solid ratio of 50%. The mixture proportions are listed in The mechanical properties in the form of unconfined compressive strength (UCS) of the mixture between C and the SS made from waste were evaluated according to EN 196-1:2005 , using aThree physical properties were evaluated according to Reference . The ini3) (≤4.0%), and content in (≤0.10%) chloride ion. The methodology for determining the loss of ignition, insoluble residue, and sulfate ion content is collected in EN 196-2:2006 [The chemical properties of the material were determined according to Reference  and comp6-2:2006  while th6-2:2006 .Ra-226, CTh-232, and CK-40 were the activity concentrations of Ra-226, Th-232, and K-40 in Bq·kg−1 in the materials tested [Although in the normative use of cement the necessity to realize environmental tests is not mentioned, these were considered due to the nature of the used materials. The Netherlands Leaching Test (NEN 7345)  was carrs tested .2, CaO, and Al2O3 of CDW, AW, and MS, respectively.The chemical composition of wastes used is collected in The results of the thermo-gravimetric studies of each waste and of the waste mixtures are presented in 4·2H2O). Between 600 and 800 °C, the decomposition of the CaCO3  produced a substantial mass loss. The main mass loss was due to the de-carbonation of the calcite (14%).The MS consists almost entirely of carbonate . For this reason, the de-carbonation produced the most significant mass loss in this waste, as shown in In addition, a thermo-gravimetric study was performed on a sample with the mixture of the three wastes (SS). The results are shown in In order to determine the melting temperature of the waste mixture (WM), a study of microscopy heating was performed to gather data on the melting temperature as well as the temperature ranges in which the viscosity was suitable to allow the melted material to flow.The fusion of the WM with a particle size below 32 microns, to improve the homogeneity of the mixture, was carried out in an electric furnace, and a silicon carbide melting pot was used to contain the material. The furnace reached maximum temperatures of 1650 °C with a lower opening for the exit of the molten material. The heating microscopy tests determined the melting temperature of the material at around 1300 °C, as can be seen in the frames shown in 2, this specific surface value was used because it was obtained after milling process, which was above the minimum established by the standards.The specific surface of the material was an important property which affected the behavior of the mechanical properties of the resulting materials. The comparison between the UCS of SS and BFS mortars was conducted with samples which contained a specific surface larger than 4000 mg/cmThe specific surface is a very important parameter in the evolution of the compressive strength in cement pastes. The hydration process begins at the surface of the particles, so that the hydration rate will increase as the surface of contact between the particles and water increases, contributing mainly to the development of UCS .In relation to the particle size distribution of the material, the particle size distribution curve of the BFS is shown in The particle size distribution of cement used in the study is shown in 2, CaO, and Al2O3 were similar, which allowed for a good comparison of physical, chemical, and mechanical properties in the mixture with cement with the same proportions.2, which is released in the process of hydration of the clinker by the alkalis produced and by the addition of gypsum to control the setting time. This type of hydration is produced in slag-cement when Ca(OH)2 is not released, AC3 is not formed, and the K2O and Na2O that are formed remain inside a crystalline network and not in a free state. Therefore, it can be said that slag-cements have special properties, especially in terms of the heat of hydration, compressive strength, and durability [The characterization of the vitreous phase of the SS is necessary to explain the cementing behavior. The vitreous phase confers to the materials the reactive character to be used as additives in cement. The vitreous phase ratio is directly related to the type of cooling of the material. In rapid cooling the structure of the material is collapsed, and a high percentage of vitreous phase is obtained, which will make very reactive slag, and depending on the specific surface, it will have considerable pozzolanic properties . Coolingrability ,45.According to the X-ray diffraction tests, it can be said that BFS has a vitreous phase of 70% and a crystalline phase of 30%. The diffractogram corresponding to this material is shown in For SS, the vitreous phase estimated by the X-ray tested was around 85–90%. In order to prove if the cement made from the addition of SS could be classified as blast furnace slag-cement according to Reference , the mec2/g. Particle sizes smaller than 10 microns have the fundamental function of contributing mechanical resistance in the early stages; whereas particles with sizes between 10 and 45 microns contribute to the resistance developed at more advanced stages [2 of basic character, which serves as an activating element for slags. The slag hydration product is a C–S–H  gel with slightly less calcium and longer chains than that produced by the hydration of the cement. As a consequence of the slower hydration of the slags, the UCS at early ages of the slag-cements was not as strong as those of the conventional cements. However, at average ages of 28 days, the UCS was similar, achieving higher resistance values over a long term.UCS is the most important property of mortars and concretes made from cement. The variation in the UCS at 7 and 28 days with the proportion of BFS and SS added in the compositions is shown in d stages ,49. All d stages . A studyd stages . In cemeTwo types of setting times were defined: the initial setting time corresponding to the period in which the stiffness of the paste starts, and the final setting time in which the paste loses its workability. During the initial setting time, the first component to react was the C3S, reducing the available water and the plasticity of the mixture due to the reaction of hydration. The C3A is more reactive than C3S, with its activity ceased by the gypsum, which is used as an addition to control the setting time to achieve the desired workability .The initial and final setting times were characterized by the different proportions of the additions of SS (25SS and 50SS) to the cement, as well as the pastes obtained by the addition of BFS (25BFS and 50BFS) to the cement, and a 100% C, which serve as reference materials.The initial setting time is limited by Reference  accordinThe volume stability affects the potential application of the material as a construction product since volume changes could cause structural failures. The volumetric expansion of the samples is limited to 10 mm according to European standard . The samHeat of hydration is related to reactivity at early ages. The initial low values of UCS are indicative of a slower evolution of the heat of hydration. Therefore, the heat of hydration is a factor that has great importance at the practical level, since it has a self-accelerating effect on the hydration of the cement and can be better for use in cold environments. However, a high heat of hydration can have harmful effects on the internal part of the structure, especially in compact or solid concrete structures, which can cause mechanical stresses that may give rise to cracks in the structure. The heat of hydration, as well as other properties of the cement, is closely linked to its chemical composition, and above all, to the mineralogical composition of the four main components: C3S, C2S, C3A and C4AF. C3A has the highest heat of hydration of all of them, as well as the greatest variability, depending on the type of hydrate formed .The composition of the mixtures tested and the results obtained are shown in According to the results obtained, it can be said that, in the case of the addition of BFS and SS, as the proportion of addition increases, the heat of hydration decreases. The decrease is more pronounced in the case of SS mixtures than in the case of mixtures with BFS. According to the general cement requirements, in order for a cement to be considered as having low hydration heat, the value of this parameter should not exceed the characteristic value of 270 J/g. The samples that could be considered as low-heat hydration cements were those in which the proportions of additions studied were above 50%.The results of chemical properties are shown in As shown in In the case of the radioactive test, according to recommendations , the limThe concentration results were higher in BFS than in SS. In any case, the activities of the different radionuclides were below the European recommendations for standard concrete and aerated concrete . The resThe results obtained from this lab scale work have confirmed the technical feasibility of this innovative process to develop an innovative vitreous material from three industrial wastes such as CDW, MS, and AW. Indeed, a new waste mixture adjustment methodology was successfully defined in order to obtain an SS with similar chemical composition to BFSs. The result of this new adjustment proportioned a mix of 37 wt % CDW, 53 wt % MS, and 10 wt % AW. Regarding the mechanical properties studied, the samples tested after seven days showed worse UCS than the previous reported by BFS (25–28 MPa vs. 29–42 MPa). However, after 28 days this was reversed, and our proposed material showed stronger mechanical properties than BFS (43–52 MPa vs. 48–49 MPa). Both the physical and chemical properties, for example setting time and volume stability, were tested to confirm that the legislative requirement were successfully met. Additionally, environmental tests were performed to ensure the material viability obtained from waste, being not a future problem to be taken into account for the society.Therefore, it can be concluded that the waste mixture of CDW, MS, and AW has potential recycling as a raw material in the manufacture of slag cements. With this, the foundations for future works are laid and further efforts will be focused on scaling-up our work to an industrial application in which valuable by-products could be obtained from waste in order to contribute to a circular economy policy.Rodríguez-Galán, Mónica; Navarrete-Rubia, Benito; Vilches-Arenas, Luis Francisco; Leiva-Fernández, Carlos; Picón-bolaños, Juan Manuel; Díaz-Bautista, María Arantzazu. MATERIAL CEMENTANTE A PARTIR DE MEZCLAS DE RESIDUOS Y/O SUBPRODUCTOS INDUSTRIALES Y PROCEDIMIENTO DE FABRICACIÓN. 04.09.2017. Cementos Portland Valderrivas S.A. Cementos Portland Valderrivas (2592953B1).