WO2023017550A1

WO2023017550A1 - Fibers cement nanocomposite and manufacturing method thereof

Info

Publication number: WO2023017550A1
Application number: PCT/IR2022/050027
Authority: WO
Inventors: Mohammad ASADI; Shoboo SALEHPOUR; Ali ASADI
Original assignee: Asadi Mohammad
Priority date: 2021-08-07
Filing date: 2022-08-07
Publication date: 2023-02-16

Abstract

A fibers cement nanocomposite comprising a cementitious matrix, a plurality of surface-modified cellulose fibers, and a plurality of silica particles dispersed inside the cementitious matrix. The plurality of surface-modified cellulose fibers comprise cellulose fibers and a plurality of hydrophilic nanosilica particles bonded to outer surfaces of the cellulose fibers.

Description

FIBERS CEMENT NANOCOMPOSITE AND MANUFACTURING METHOD

THEREOF

CROSS-REFERENCE TO REEATED APPEICATION

[0001] This application claims the benefit of priority from Iran Patent Application Ser. No. 140050140003003949, filed on August 07, 2021, and entitled “Production of cement nanocomposites containing nanosilica and cellulose fibers autoclaved on an industrial scale” which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure generally relates to a fibers cement nanocomposite and manufacturing method thereof, and more particularly, to a modified cellulose fibers reinforced cement nanocomposite and manufacturing method thereof.

BACKGROUND

[0002] In the last few years, an increase in interest has been given to the use of cellulose fibers as reinforcing agents in fibers cement nanocomposites. However, attempts to increase the use of cellulose fibers in fibers cement nanocomposite applications have met major challenges such as degradation of the fibers, and great water absorption leading to low durability of the cellulose reinforced cement nanocomposites. Modification of the surface of the cellulose fibers has been considered a method for solving the mentioned challenges when using the cellulose fibers dispersion.

[0003] In recent years, chemical treatments of the surface of the cellulose fibers using the nanosilica particles have received attention; however, for producing industrial applications such as construction and building products a reproducible, repeatable procedure may be highly required. Thereby, there is need to develop a highly robust fibers cement nanocomposite and preparation method thereof.

SUMMARY

[0004] This summary is intended to provide an overview of the subject matter of the present disclosure, and is not intended to identify essential elements or key elements of the subject matter, nor is it intended to be used to determine the scope of the claimed implementations. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later. The proper scope of the present disclosure may be ascertained from the claims set forth below in view of the detailed description below and the drawings.

[0005] In one general aspect, the present disclosure describes a fibers cement nanocomposite comprising a cementitious matrix, a plurality of surface-modified cellulose fibers dispersed inside the cementitious matrix, and a plurality of silica particles dispersed inside the cementitious matrix. The plurality of surface-modified cellulose fibers may comprise cellulose fibers and a plurality of hydrophilic nanosilica particles bonded to outer surfaces of the cellulose fibers. In an exemplary embodiment, the cellulose fibers may be prepared by fibrillating a plurality of cellulose pulps in water at ambient temperature for 120-240 minutes. In one or more exemplary embodiments, the nanosilica particles may have a diameter of 10-15 nm. In one or more exemplary embodiments, the fibers cement nanocomposite comprises 40% to 44% (w/w) cementitious matrix, 45% to 47% (w/w) of the plurality of silica particles, 6% to 10% cellulose fibers, and 5% to 8% colloidal nanosilica.

[0006] One or more exemplary embodiments describe an exemplary method for preparing a fibers cement nanocomposite sheet. An exemplary method may comprise fibrillating a plurality of cellulose pulps in water at ambient temperature for 120-240 minutes; producing a first mixture by mixing the fibrillated plurality of cellulose fibers with a colloidal nanosilica for a time duration of 8 to 24 hours; producing a second mixture by mixing the first mixture with silica particles for a time duration of 10 to 30 minutes; forming a fibers cement nanocomposite by mixing a cementitious matrix with the second mixture for a time duration of 10 to 30 minutes; forming a fibers cement nanocomposite sheet using a Hatschek process; preheating the fibers cement nanocomposite sheet at a temperature of 35 to 50 °C and a humidity of 15 to 25% for a time duration of 12 hours; and curing the fibers cement nanocomposite sheet in an autoclave at a temperature of 160 to 210 °C and a pressure of 8 to 12 bar for a time duration of 9 to 13 hours.

[0007] This Summary is provided to introduce a selection of concepts in a simplified form; these concepts are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is disclosed more in detail with reference to the drawings in which: [0008] FIG. 1 illustrates a schematic illustration of a fibers cement nanocomposite comprising modified cellulose fibers, silica particles and cementitious matrix, in consistent with one or more exemplary embodiments of the present disclosure.

[0009] FIG. 2 illustrates a flowchart diagram of an exemplary method of manufacturing exemplary fibers cement nanocomposite and sheet provided using the said fibers cement nanocomposite, consistent with one or more exemplary embodiments of the present disclosure. [00010] FIG. 3A illustrates field emission scanning electron microscope (FE-SEM) image of surface of an exemplary unmodified cellulose fibers (UMF), consistent with one or more exemplary embodiments of the present disclosure. [00011] FIG. 3B illustrates FE-SEM image of the surface of an exemplary modified cellulose fibers (MF), consistent with one or more exemplary embodiments of the present disclosure.

[00012] FIG. 4A illustrates Energy-dispersive spectroscopy (EDS) spectrum of the surface of exemplary unmodified cellulose fibers (UMF), consistent with one or more exemplary embodiments of the present disclosure.

[00013] FIG. 4B illustrates the EDS spectrum of the surface of exemplary modified cellulose fibers, consistent with one or more exemplary embodiments of the present disclosure. [00014] FIG. 5A illustrates FE-SEM image of cross-section of exemplary fibers cement nanocomposite comprising unmodified cellulose fibers (FCC), consistent with one or more exemplary embodiments of the present disclosure, respectively.

[00015] FIG. 5B illustrates FE-SEM image of cross-section of exemplary fibers cement nanocomposite comprising modified cellulose fibers (FCC+NS), consistent with one or more exemplary embodiments of the present disclosure, respectively.

[00016] FIG. 6A illustrates EDS spectrum of cross-section of exemplary fibers cement nanocomposite comprising unmodified cellulose fibers (FCC), consistent with one or more exemplary embodiments of the present disclosure, respectively.

[00017] FIG. 6B illustrates EDS spectrum of cross-section of exemplary fibers cement nanocomposite comprising modified cellulose fibers (FCC+NS), consistent with one or more exemplary embodiments of the present disclosure, respectively.

[00018] FIG. 7A illustrates FTIR spectra of the unmodified cellulose fibers (UMF) and modified cellulose fibers (MF), consistent with one or more exemplary embodiments of the present disclosure.

[00019] FIG. 7B illustrates Fourier Transform Infra-Red (FTIR) spectra of exempalry fibers cement nanocomposite comprising unmodified cellulose fibers (FCC) and fibers cement nanocomposite comprising modified cellulose fibers (FCC+NS), consistent with one or more exemplary embodiments of the present disclosure.

[00020] FIG. 8A illustrates X-Ray diffraction (XRD) patterns of exemplary unmodified cellulose fibers (UMF) and modified cellulose fibers (MF), consistent with one or more exemplary embodiments of the present disclosure.

[00021] FIG. 8B illustrates XRD patterns of exemplary fibers cement nanocomposite comprising unmodified cellulose fibers and exemplary fibers cement nanocomposite comprising modified cellulose fibers, consistent with one or more exemplary embodiments of the present disclosure.

[00022] FIG. 9 illustrates water uptake behavior of exemplary fibers cement nanocomposite comprising unmodified cellulose fibers and exemplary fibers cement nanocomposite comprising modified cellulose fibers, consistent with one or more exemplary embodiments of the present disclosure.

[00023] It is understood that the following description and references to the figures concern exemplary embodiments of the present disclosure and shall not be limiting the scope of the claims.

DETAILED DESCRIPTION

[00024] In the following detailed description, numerous specific details are set forth by way of examples to provide a thorough understanding of the relevant teachings related to the exemplary embodiments. However, it should be apparent that the present teachings may be practiced without such details. In other instances, well-known methods, procedures, and components have been described at a relatively high-level, without detail, in order to avoid unnecessarily obscuring aspects of the present teachings.

[00025] The following detailed description is presented to enable a person skilled in the art to make and use the formulations and methods disclosed in exemplary embodiments of the present disclosure. For purposes of explanation, specific nomenclature is set forth to provide a thorough understanding of the present disclosure. However, it will be apparent to one skilled in the art that these specific details are not required to practice the disclosed exemplary embodiments. Descriptions of specific exemplary embodiments are provided only as representative examples. Various modifications to the exemplary implementations will be plain to one skilled in the art, and the general principles defined herein may be applied to other implementations and applications without departing from the scope of the present disclosure. The present disclosure is not intended to be limited to the implementations shown, but is to be accorded the widest possible scope consistent with the principles and features disclosed herein. [00026] Exemplary embodiments of the present disclosure describe a fibers cement nanocomposite and a method for preparing a fibers cement nanocomposite sheet. Exemplary embodiments may encompass exemplary nanocomposite materials formed with loaded modified cellulose fibers, and an exemplary method for manufacturing an exemplary fibers cement nanocomposite sheet. In one or more exemplary embodiments, the present disclosure describes an exemplary formulation of a fibers cement nanocomposite that may be used for the production of products used in building and construction. An exemplary formulation may comprise a cementitious matrix, a plurality of surface-modified cellulose fibers, and a plurality of silica particles. The said surface-modified cellulose fibers and silica particles are uniformly dispersed in the cementitious matrix as a binder.

[00027] FIG. 1 illustrates a schematic illustration 100 of an exemplary modified fibers cement nanocomposite (FCC+NS) 110 comprising a cementitious matrix 120, silica 130, and modified cellulose fibers (MF) 140, in accordance with one or more exemplary embodiments of the present disclosure. Referring to FIG. 1, the modified fibers cement nanocomposite 110 may comprise a cementitious matrix 120, a plurality of surface-modified cellulose fibers 140 dispersed inside cementitious matrix 120, and a plurality of silica particles 130 dispersed inside cementitious matrix 120, consistent with one or more exemplary embodiments of the present disclosure. Each respective surface-modified cellulose fibers 140 may comprise cellulose fibers 150, and a plurality of hydrophilic nanosilica particles 160 bonded to an outer surface of cellulose fibers 150.

[00028] In one or more exemplary embodiments, the fibers cement nanocomposite comprising modified cellulose fibers (FCC+NS) may comprise by weight 40% to 44% cementitious matrix, 45% to 47% silica, 6% to 10% cellulose fibers, and 5% to 8% colloidal nanosilica. The cementitious matrix may be Portland cement but may also be, but is not limited to, high alumina cement, lime, high phosphate cement, and ground granulated blast furnace slag cement, or mixtures thereof. In one or more exemplary embodiments, the colloidal nanosilica may have an exemplary diameter of about 10-15 nm. The colloidal nanosilica may have an exemplary density of about 1 g/cm³-1.2 g/cm³. The colloidal nanosilica may have an exemplary specific surface area of about 70 m²/g-100 m²/g. The colloidal nanosilica may have an exemplary pH of about 8-9.

[00029] In one or more exemplary embodiments, an exemplary method for manufacturing an exemplary fibers cement nanocomposite and fibers cement nanocomposite sheet is disclosed. FIG. 2 illustrates a flowchart diagram of an exemplary method 200 for manufacturing the fibers cement nanocomposite and fibers cement nanocomposite sheet, consistent with one or more exemplary embodiments of the present disclosure. Exemplary method 200 may include one or more steps with regards to exemplary aspects and embodiments described above. In an exemplary embodiment, exemplary method 200 may include: fibrillating a plurality of cellulose pulps in water at ambient temperature for 120-240 minutes (step 201); producing a first mixture by mixing the fibrillated plurality of cellulose fibers with a colloidal nanosilica for a time duration of 8 to 24 hours (step 202); producing a second mixture by mixing the first mixture (mixture obtained from step 202) with silica particles for a time duration of 10 to 30 minutes (step 203); forming a fibers cement nanocomposite by mixing a cementitious matrix with the second mixture (mixture obtained from step 203) for a time duration of 10 to 30 minutes (step 204); forming a fibers cement nanocomposite sheet using a Hatschek process (step 205); preheating the fibers cement nanocomposite sheet at a temperature of 35 to 50 °C and a humidity of 15 to 25% for a time duration of 12 hours (step 206); curing the fibers cement nanocomposite sheet in an autoclave at a temperature of 160 to 210 °C and a pressure of 8 to 12 bar for a time duration of 9 to 13 hours (step 207).

[00030] Referring to FIG. 2, step 201 may comprise fibrillating a plurality of cellulose pulps in water at ambient temperature for 120-240 minutes; which results in improving the mechanical properties of the cellulose fibers. In one or more exemplary embodiments, the cellulosic pulps may be obtained from Northern bleached softwood kraft with a refining level of about 683 ml CSF and 2 mm in length. In one or more exemplary embodiments, fibrillation of the cellulose pulps may carry out for a period of time ranging from 100 to 200 minutes, and more efficiently, from 150 to 200 minutes.

[00031] Again, referring to FIG. 2, step 202 may comprise producing a first mixture by mixing the fibrillated plurality of cellulose fibers with a colloidal nanosilica for a time duration of 8 to 24 hours. As a result, a plurality of nanosilica particles are bonded with the fibrillated cellulose fibers. In one exemplary embodiment of step 202, the fibrillated cellulose fibers obtained from step 201 are mixed with colloidal nanosilica. Accordingly, a plurality of hydrophilic nanosilica particles bonded to an outer surface of the cellulose fibers. In one or more exemplary embodiments of the present disclosure, the colloidal nanosilica may have an exemplary diameter of about 10-15 nm.

[00032] Step 203 may comprise producing a second mixture by mixing the first mixture (first mixture obtained from step 202) with silica particles for a time duration of 10 to 30 minutes. Further, the said method comprises step 204 comprising forming a fibers cement nanocomposite by mixing a cementitious matrix with the second mixture (second mixture obtained from step 203) for a time duration of 10 to 30 minutes. In one or more exemplary embodiments, ordinary Portland cement may be used for the preparation of the fibers cement nanocomposites. It should be mentioned that other types of cement may also be used as a binder, and the scope of the present disclosure is not limited to Portland cement. As previously mentioned, all the solid particles meaning silica particles and modified cellulose fibers are uniformly dispersed in the cementitious matrix. It should be noticed that the uniform dispersion of the solid particles especially the cellulose fibers is provided due to modification of the surface of the cellulose fibers. In one or more exemplary embodiments of the present disclosure, the dry weight ratio of modified cellulose fibers: silica particles: cementitious matrix in the fibers cement nanocomposite may be about 8%:33%:59%.

[00033] Again, referring to FIG. 2, step 205 may comprise forming a fibers cement nanocomposite sheet using a Hatschek process. Well- known Hatschek process used herein may comprise sub-steps as described below: after mixing the prepared fibers cement nanocomposite dispersion (fibers cement nanocomposite obtained from step 204) for 20 minutes, the said fibers cement nanocomposite is transported to a continuous belt, wherein vacuum is applied to remove water from the fibers cement nanocomposite. The Hatschek process further comprises transferring the fibers cement nanocomposite to the formation cylinder in layers with 0.6 mm thickness (163 cm diameter, pressure 3 bar) where the stacking is performed until sheets have 10 mm thickness. Finally, the sheet is cut, shaped and submitted for the next steps to preheating.

[00034] Again, referring to FIG. 2, step 206 may comprise preheating the fibers cement nanocomposite sheet at a temperature of 35 to 50 °C and a humidity of 15 to 25% for a time duration of 12 hours. In one or more exemplary embodiments, preheating may be carried out at 30 °C, for 8 hours. Also, preheating may be performed in a closed room for controlling the temperature, pressure, and humidity. Referring to FIG. 2, step 207 may comprise curing the fibers cement nanocomposite sheet in an autoclave at a temperature of 160 to 210 °C and a pressure of 8 to 12 bar for a time duration of 9 to 13 hours.

[00035] To better illustrate the objects, aspects and advantages of the present disclosure, the present disclosure will be further described with reference to specific examples. It will be understood by those skilled in the art that the specific embodiments described herein are merely illustrative of the present disclosure and are not intended to limit the present disclosure.

[00036] In the examples, the experimental methods used were all conventional methods unless otherwise specified, and the materials, reagents and the like used were commercially available without otherwise specified.

Example 1: Manufacturing method of an exemplary fibers cement nanocomposite and exemplary fibers cement nanocomposite sheet.

[00037] In this example, exemplary fibers cement nanocomposite formulation and preparation method of exemplary fibers cement nanocomposite sheet are described. The manufacturing method of said fibers cement nanocomposite sheet comprises: i) fibrillating a plurality of cellulose fibers in water at ambient temperature for a time duration of 120-240 minutes, wherein the cellulose fibers are obtained from Northern bleached softwood kraft with a refining level of about 683 ml CSF and 2 mm in length; ii) producing a first mixture by mixing the fibrillated plurality of cellulose fibers with a colloidal nanosilica for 2 hours; iii) producing a second mixture by mixing the first mixture with silica particles for a time duration of 10 minutes; and iv) forming a fibers cement nanocomposite by mixing a cementitious matrix with the second mixture for a time duration of 10 to 30 minutes. Specification of the colloidal nanosilica are shown in Table ITable 1. The colloidal nanosilica content is 5% (dry weight) of the whole formulation. The chemical composition of silica and cement are shown in Error!

Reference source not found.. Table 1:

Some specification of an exemplary colloidal nanosilica are used in manufacturing exemplary fibers cement nanocomposite and exemplary fibers cement nanocomposite sheet.

Table 2:

The chemical composition of exemplary silica and exemplary cement are used in manufacturing exemplary fibers cement nanocomposite and exemplary fibers cement nanocomposite sheet.

[00038] In an exemplary embodiment, an exemplary manufacturing method of an exemplary fibers cement nanocomposite sheet may further comprise: v) forming fibers cement nanocomposite sheet using a Hatschek process, wherein after mixing the prepared fibers cement nanocomposite dispersion for 30 minutes, it is transported to a continuous belt, wherein vacuum is applied to remove water from the fibers cement nanocomposite dispersion. Then, the fibers cement nanocomposite sheet is transferred to the formation cylinder in layers with 0.6 mm thickness (163 cm diameter, pressure 3 bar) where the stacking is performed until sheets have 10 mm thickness. Finally, the sheet is cut, shaped, and submitted for the next steps to preheating. In an exemplary embodiment, the manufacturing method of said fibers cement nanocomposite sheet may further comprise: vi) preheating the fibers cement nanocomposite sheet at a temperature of 35 to 50 °C and a humidity of 15 to 25% for a time duration of 12 hours; and vii) curing the fibers cement nanocomposite sheet in an autoclave at a temperature of 160 to 210 °C and a pressure of 8 to 12 bar for a time duration of 9 to 13 hours.

Example 2: Study the mechanical properties of exemplary fibers cement nanocomposite comprising unmodified cellulose fibers (FCC) and exemplary fibers cement nanocomposite comprising modified cellulose fibers (FCC+NS)

[00039] The modulus of rupture (MOR) of fibers cement nanocomposite comprising unmodified cellulose fibers (FCC) and modified cellulose fibers (FCC+NS) prepared according to the manner described in example 1, were measured based on standard EN- 12467 in both wet and dry conditions; results are shown in Table 3:.

[00040] The fibers cement nanocomposite containing modified cellulose fibers has a higher modulus of rupture than the other sample, in both wet and dry conditions. There are two main reasons for this observation. The hydroxyl functional groups of the nanosilica particles bond to the hydroxyl groups on the outer surface of the cellulose fibers via hydrogen bonding, eliminating the fibers-fibers interactions, improving the cellulose fibers dispersion in the cementitious matrix, and enhancing the mechanical properties of the fibers cement nanocomposite. On the other hand, the nanosilica particles chemically bonded to the surface of cellulose fibers may react with the calcium hydroxide which results in the formation of hydrated calcium silicate gel, reducing the porosity and also increasing the strength of the fibers cement nanocomposite. [00041] Also, the results show that the MOR in wet conditions is lower than that in dry conditions which may be attributed to the weakening of the cellulose fibers, and weakening of the interface of the cellulose fibers and cementitious matrix due to the water absorption.

Table 3:

The modulus of rupture (MOR) of exemplary fibers cement nanocomposite comprising unmodified cellulose fibers (FCC) and exemplary fibers cement nanocomposite comprising modified cellulose fibers (FCC+NS), consistent with one or more exemplary embodiments of the present disclosure.

Example 3: Morphological analysis of the cellulose fibers using field emission scanning electron microscope (FE-SEM)

[00042] FE-SEM images of the surface of the unmodified cellulose fibers and modified cellulose fibers are shown in FIGs. 3A and 3B, respectively. Modified cellulose fibers are prepared using the method described in example 1. Referring to FIGs. 3A-3B, the surface of the modified cellulose fibers is rougher than that of the Unmodified cellulose fibers which may be due to the presence of nanosilica particles on the outer surface of the modified cellulose fibers.

Example 4: Elemental analysis of the surface of exemplary cellulose fibers using Energy - dispersive spectroscopy (EDS) technique

[00043] EDS spectra of the surface of the unmodified cellulose fibers (UMF) and modified cellulose fibers (MF) are shown in FIGs. 4A and 4B, respectively. Modified cellulose fibers (MF) are prepared using the method described in example 1. Referring to FIG. 4A, the surface of the unmodified cellulose fibers (UMF) are mainly composed of carbon (C) and oxygen (O), and also has insignificant amounts of sodium (Na), aluminum (Al), and silicon (Si). While there is a significant increase in the concentration of Si on the surface of exemplary modified cellulose fibers (MF) in comparison with unmodified cellulose fibers (UMF), which is evidence of the effective modification of the cellulose fibers with nanosilica and uniform distribution of the nanosilica particles on the surface of the fibers (FIG. 4B). Furthermore, the height of the carbon peak of the exemplary modified cellulose fibers (MF) (FIG. 4B) has been decreased which may be caused due to the reactions of the hydroxyl groups on the surface of the cellulose fibers with nanosilica particles.

Example 5: Morphological analysis of exemplary fibers cement nanocomposite using FE- SEM

[00044] FE-SEM images cross-section of exemplary fibers cement nanocomposite comprising unmodified cellulose fibers (FCC) and exemplary fibers cement nanocomposite comprising modified cellulose fibers (FCC+NS) prepared according to the manner described in example 1, are shown in FIG. 5A and 5B, respectively. The cross-section image of the fibers cement nanocomposite comprising unmodified cellulose fibers (FCC) shows a lack of coherency between cementitious matrix and cellulose fibers (FIG. 5A). Furthermore, in the fibers cement nanocomposite comprising unmodified cellulose fibers (FCC) a large amount of C-H crystals are well expanded, which means the porosity of fibers cement nanocomposites is relatively high and calcium hydroxide (C-H) crystals have enough space to grow. FIG. 5B shows a highly dense structure in the fibers cement nanocomposite comprising modified cellulose fibers (FCC+NS). Referring to FIG. 5B, the extent of calcium hydroxide silicate gel (H-S-C) formed by the pozzolanic reaction of nanosilica with C-H crystals is more compared to the fibers cement nanocomposite comprising unmodified cellulose fibers (FCC). Moreover, calcium hydroxide silicate gel (H-S-C) has been uniformly grown in fibers cement nanocomposite, improving the adhesion between modified cellulose fibers (MF) and cement, and subsequently increasing the mechanical strength of the nanocomposite.

Example 6: Elemental analysis of a cross-section of a surface of the fibers cement nanocomposites using EDS technique

[00045] EDS spectra of cross-section of exemplary fibers cement nanocomposite comprising unmodified cellulose fibers (FCC) and exemplary fibers cement nanocomposite comprising modified cellulose fibers (FCC+NS) are shown in FIG. 6A and 6B, respectively. The Si/Ca ratio in hydrates reflects the C-H content in calcium hydroxide silicate gels (H-S- C). Consequently, a higher amount of Si/Ca ratio indicates a higher CH content. Accordingly, the reduction of Si/Ca ratio of exemplary fibers cement nanocomposite comprising modified cellulose fibers (FCC+NS) in FIG. 6B may be attributed to the reaction between nanosilica particles and C-H crystals.

Example 7: Evaluation of the chemical structure of exemplary fibers cement nanocomposite using fourier-transform infra-red (FTIR) spectroscopy

[00046] FTIR spectroscopy is used for evaluating the functional group on the surface of the cellulose fibers before and after modification with colloidal nanosilica. Also, the chemical structure of exemplary fibers cement nanocomposite is compared in the presence of modified and unmodified cellulose fibers.

[00047] The FTIR spectra of exemplary unmodified cellulose fibers (UMF) and modified fibers (MF) according to the manner described in Example 1 are shown in FIG. 7A. Referring to FIG. 7A, the intensity of the characteristic peak of the hydroxyl group (-OH) at 3390 cm ¹ in the modified fibers has been decreased; and also the position of the hydroxyl group of the modified fibers has been slightly shifted to the higher wavenumber at 3430 cm ¹. This observation confirms the presence of nanosilica on the surface of the cellulose fibers, and also there is a strong interaction between OH groups of cellulose fibers and nanosilica particles. Furthermore, three main peaks may be seen in modified fibers FTIR spectra at 1112 cm ¹, 798 cm ¹, and 507 cm ¹ which are attributed to the stretching vibration of the Si-O-C, Si-O, and Si- O-Si, respectively. These peaks show that a strong chemical bond has been established between cellulose fibers and nanosilica particles via surface modification.

[00048] The FTIR spectrum of exemplary fibers cement nanocomposite comprising unmodified cellulose fibers (FCC) and exemplary fibers cement nanocomposite comprising modified cellulose fibers (FCC+NS), according to the manner described in Example 1, are shown in FIG. 7B. As shown in FIG. 7B, the peak at 3433 cm ¹ is related to the stretching vibration of OH groups of CH crystals formed during the hydration of CS3 and CS2 and free OH groups of water molecules in the mixture (both samples). The intensity of the said peak of exemplary fibers cement nanocomposite comprising modified cellulose fibers (FCC+NS) is lower than that of exemplary fibers cement nanocomposite comprising unmodified cellulose fibers (FCC), which is due to the reduction of the content of free OH groups and CH crystals and also increasing the amount of H-S-C bond.

Example 8: Measuring degree of crystallinity using X-Ray diffraction (XRD)

[00049] Degree of crystallinity of exemplary unmodified cellulose fibers (UMF) and modified cellulose fibers (MF) were measured using the XRD analysis. The XRD patterns of both unmodified cellulose fibers (UMF) and modified cellulose fibers (MF) are shown in FIG. 8A. The XRD studies confirmed that the unmodified cellulose fibers structure is same as that of unchanged cellulose (ip) with peaks at 18.8°, 22.6°, and 34.32° (2Theta). The degree of crystallinity of unmodified cellulose fibers (UMF) and modified cellulose fibers (MF) was calculated at 71% and 56%, respectively. It seems that the lower degree of crystallinity of exemplary modified cellulose fibers (MF) is due to the presence of amorphous nanosilica particles in the modified cellulose fibers structure. [00050] The XRD patterns of exemplary fibers cement nanocomposite comprising unmodified cellulose fibers (FCC) 803 and exemplary fibers cement nanocomposite comprising modified cellulose fibers (FCC+NS) 801 are shown in FIG. 8B. The intensity of the C-H crystals peaks is attributed to the relative content of C-H crystals in the hydrate, indicating the progress of the cement hydration process. Consequently, the reduction of the C- H content intensity may be due to the pozzolanic reaction between nanosilica and cementitious matrix. Furthermore, the intensity of the C-S-H peak of the fibers cement nanocomposite comprising modified cellulose fibers (FCC+NS) 801 is higher than that of fibers cement nanocomposite comprising unmodified cellulose fibers (FCC) 803, which may be the result of the reaction of the nanosilica and C-H crystals, leading to the formation of hydrated calcium silicate gel (C-H-S).

Example 9: Evaluating the water uptake properties of exemplary fibers cement nanocomposite

[00051] Water uptake behaviour of exemplary fibers cement nanocomposite comprising unmodified cellulose fibers (FCC) 901 and exemplary fibers cement nanocomposite comprising modified cellulose fibers (FCC+NS) 903 are shown in FIG. 9. The fibers cement nanocomposites comprising unmodified cellulose fibers (FCC) 901 showed a water uptake of about 29%, while this value was lower for exemplary fibers cement nanocomposite comprising modified cellulose fibers (FCC+NS) 903. Modification of the cellulose fibers using the nanosilica affects the water uptake behaviour of the fibers cement nanocomposite via different strategies. At first, the nanosilica particles are bonded to the hydroxyl groups on the outer surface of the cellulose fibers through hydrogen bonding, leading to the occupying and blocking of the water-absorbing sites of the fibers. On the other hand, increasing the adhesion between cementitious matrix and cellulose fibers in fibers cement nanocomposites results in the blocking of a large number of capillary tubes in the nanocomposite. Therefore, the process of penetration of moisture into the fibers cement nanocomposite may happen very slowly.

[00052] While the foregoing has described what are considered to be the best mode and/or other examples, it is understood that various modifications may be made therein and that the subject matter disclosed herein may be implemented in various forms and examples, and that the teachings may be applied in numerous applications, only some of which have been described herein. It is intended by the following claims to claim any and all applications, modifications and variations that fall within the true scope of the present teachings.

[00053] The scope of protection is limited solely by the claims that now follow. That scope is intended and should be interpreted to be as broad as is consistent with the ordinary meaning of the language that is used in the claims when interpreted in light of this specification and the prosecution history that follows and to encompass all structural and functional equivalents.

[00054] Except as stated immediately above, nothing that has been stated or illustrated is intended or should be interpreted to cause a dedication of any component, step, feature, object, benefit, advantage, or equivalent to the public, regardless of whether it is or is not recited in the claims.

[00055] It will be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study except where specific meanings have otherwise been set forth herein. Relational terms such as first and second and the like may be used solely to distinguish one entity or action from another without necessarily requiring or implying any actual such relationship or order between such entities or actions. An element proceeded by “a” or “an” does not, without further constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element. [00056] The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it may be seen that various features are grouped together in various implementations. This is for purposes of streamlining the disclosure, and is not to be interpreted as reflecting an intention that the claimed implementations require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed implementation. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separately claimed subject matter.

[00057] While various implementations have been described, the description is intended to be exemplary, rather than limiting and it will be apparent to those of ordinary skill in the art that many more implementations and implementations are possible that are within the scope of the implementations. Although many possible combinations of features are shown in the accompanying figures and discussed in this detailed description, many other combinations of the disclosed features are possible. Any feature of any implementation may be used in combination with or substituted for any other feature or element in any other implementation unless specifically restricted. Therefore, it will be understood that any of the features shown and/or discussed in the present disclosure may be implemented together in any suitable combination. Accordingly, the implementations are not to be restricted except in light of the attached claims and their equivalents. Also, various modifications and changes may be made within the scope of the attached claims.

Claims

What is claimed is:

1. A fibers cement nanocomposite, comprising: a cementitious matrix; a plurality of surface-modified cellulose fibers dispersed inside the cementitious matrix, wherein the plurality of surface-modified cellulose fibers comprise: cellulose fibers; and a plurality of hydrophilic nanosilica particles bonded to outer surfaces of the cellulose fibers, wherein the plurality of hydrophilic nanosilica particles are bonded to the outer surfaces of the cellulose fibers; and a plurality of silica particles dispersed inside the cementitious matrix.

2. The fibers cement nanocomposite of claim 1, wherein the cellulose fibers are prepared by fibrillating a plurality of cellulose pulps in water at ambient temperature for a time duration of 120 to 240 minutes.

3. The fibers cement nanocomposite of claim 1, wherein the nanosilica particles have a diameter between 10 nm and 15 nm.

4. The fibers cement nanocomposite of claim 1, comprising:

40% to 44% (w/w) cementitious matrix;

45% to 47% (w/w) of the plurality of silica particles;

6% to 10% cellulose fibers; and

5% to 8% colloidal nanosilica.

5. The fibers cement nanocomposite of claim 4, wherein the colloidal nanosilica has a diameter of 10-15 nm.

6. The fibers cement nanocomposite of claim 4, wherein the colloidal nanosilica has a density between 1 and 1.2 g/cm³.

7. The fibers cement nanocomposite of claim 4, wherein the colloidal nanosilica has a pH between 8 and 9.

8. The fibers cement nanocomposite of claim 4, wherein the colloidal nanosilica has a specific surface area in the range of 70 to 100 m²/g.

9. A method for preparing a fibers cement nanocomposite sheet, comprising: fibrillating a plurality of cellulose fibers in water at ambient temperature for a time duration of 120-240 minutes; producing a first mixture by mixing the fibrillated plurality of cellulose fibers with a colloidal nanosilica for a time duration of 8 to 24 hours; producing a second mixture by mixing the first mixture with silica particles for a time duration of 10 to 30 minutes; forming a fibers cement nanocomposite by mixing a cementitious matrix with the second mixture for a time duration of 10 to 30 minutes; forming a fibers cement nanocomposite sheet using a Hatschek process; preheating the fibers cement nanocomposite sheet at a temperature of 35 to 50 °C and a humidity of 15 to 25% for a time duration of 12 hours; and curing the fibers cement nanocomposite sheet in an autoclave at a temperature of 160 to 210 °C and a pressure of 8 to 12 bar for a time duration of 9 to 13 hours.

10. The method of claim 9, wherein the colloidal nanosilica has a diameter between 10 nm and 15 nm.

11. The method of claim 9, wherein the colloidal nanosilica has a density between 1 g/cm³ and 1.2 g/cm³.

12. The method of claim 9, wherein the colloidal nanosilica has a pH between 8 and 9.

13. The method of claim 9, wherein the colloidal nanosilica has a specific surface area between 70 m²/g and 100 m²/g.