**3.2 Zeta (ξ) potential**

The process of the evolution of (ξ)-potential as a function of pH of the cement particles saturated with the SDBS surfactant are showing in **Figure 3**. The introduction of the SDBS during the preparation of samples passes by several stages. Indeed, for a low concentration of SDBS in order of 0.1 mmol/L, the (ξ) potential is 35 mV. This value results from the ionization of calcium during the hydration of the cement. When the concentration of the SDBS solubilized, Zeta potential decreased. This allows us to deduct the essential role of SDBS in the hydration of the cement, thus in the neutralization of these ions (Ca2+).

**Figure 3** shows the quantity adsorbed of surfactant as a function of initial concentration. We notice the existence of three zones:

**Figure 2.** *Particle size of wood fibers.*

*Thermal Conductivity and Mechanical Properties of Organo-Clay-Wood Fiber in Cement… DOI: http://dx.doi.org/10.5772/intechopen.102321*

**Figure 3.** *Variation of the zeta potential according to the initial concentration according to the initial concentration by surfactant.*

The first one for low concentration **(I)** we can see equilibrium. This phenomenon was attributed to the micelles, which gives an idea about the formation of micelles beyond a critical concentration. From a certain critical concentration, the hydrophobic interaction between the surfactant molecules of surfactant becomes important compared to the hydrophobic surfactant/water interactions that form spontaneously an association.

The second zone **(II)**, we observe an increase of the slope which is explained by the intercalation of the surfactant molecules with water to form the saturation of the first layer [22]. It is the beginning of mineralization. Thus we observed agglomerations of micelles together, this part is called the micellisation phase.

In the third zone **(III)**, of SDBS, we have (ξ*)* potential of negative charge (**Figure 4**).

In this case we can say that we have a neutralization of material by the existence of the electrostatic strengths. (The surfactant is cationic and the surface of fibers is negatively charged). The molecules of surfactant are adsorbed at the air/water interface and the superficial concentration increases. From a certain value, a monomolecular layer of surfactant occupies the surface and interfacial tension decreases linearly with the logarithm of the concentration.

#### **3.3 XRD**

The XRD patterns of natural clay and organoclay modified by the CTAB are shown in (**Figures 5** and **6**). It can clearly be seen that the natural clay characteristics peaks are present sat 2θ = 7.05°, 12.55°, 25.5° these peaks refer to the presence of Kaolinite

**Figure 4.** *Evolution of the quantity adsorbed by additive according to the concentration insolution.*

the peak at 2θ = 12,55° corresponding at Kaolinite contending Illite. Typical XRD patterns of organoclay after the treatment with the CTAB appears many diffraction peaks at 5.13° until 20°, this result due to the linear structure of CTAB (19 carbons). The CTAB Kaolinite matrix has the highest value of the interfoliar space d001 = 19.10 A° corresponds to the interplanar spacing [23].

*Thermal Conductivity and Mechanical Properties of Organo-Clay-Wood Fiber in Cement… DOI: http://dx.doi.org/10.5772/intechopen.102321*

**Figure 6.** *XRD patterns of Organoclay.*

#### **3.4 FTIR of wood Fibers**

The FTIR spectra in the range 4000 cm–500 cm−1 of the different samples are shown in **Figure 7**. The main characteristic bands of non-treated and treated wood fibers are listed as follows:

**Figure 7.** *FTIR spectra of the non-treated wood and the treated wood with NaOH.*

The presence of a large band in the 3386 cm−1 corresponds to hydroxyl group characteristics of polysaccharides. The band sat 2930 and 2898 cm−1 are due successively to sym and usym CH2 in polysaccharides and fats. The FTIR spectrum exhibits the presence of carbonyl and acetyl groups in the xylan component of (C=O stretching vibration) at 1732 cm−1. However, this peak almost disappears when these fibers are treated with 2% of NaOH. The band at 1635 cm−1 is characterized by the vibration of water molecules. Furthermore, the band at 1436 cm−1, assigned to the asymmetric C-H deformation in lignin and hemicelluloses structures. Concerning the FTIR of (WFNT), the peak at 1512 cm−1 is indicative of the presence of lignin and is attributed to the C=C aromatic skeletal vibration. In the spectra of WF treated 5% NaOH, this peak was reduced, due to the elimination of lignin by chemical treatments. The small peak sat 1375 cm−1 in the spectrum of untreated WF, WF treated 0.5%, 2% are related to CH2 vibration. The band at 1168 cm−1, which appears in all the FTIR spectra, corresponds to the C-O-C asymmetric stretching of the hemicelluloses and lignin. The peak at 1042 cm−1, is assigned to ether linkage (C-O-C) from lignin or hemicelluloses. The peak at 810 cm−1 is associated with cellulose, the C-H rock vibrations the cellulose.

#### **3.5 FTIR of Organoclay**

**Figure 8** shows the characteristics of natural clay and OC treated with CTAB. The peak assignments in the spectra represented OH stretching vibration (3624– 3390 cm−1. The treatments of the natural clay with the CTAB make the appearance of two peaks have (2921–2881 cm−1) two peaks attributed to OH stretching vibration. The bond OH (1633 cm−1) can be attributed to water molecules adsorbed on the biomaterial structure.

FTIR exhibits the existence, of a strong band in the range of 750–400 cm−1 it was associated with the characteristic Si-O-Si stretching vibration of pure clay. Peaks at 1420 cm−1 and 3434 cm−1 corresponding to the O-H stretching vibration. Peaks at 1263 cm−1, 2866 cm−1 and 2920 cm−1 corresponded to the stretching vibrations of –CH, –CH3 and –CH2 respectively. Moreover, characteristic band at 1470 cm−1 is assigned to the symmetric vibrations of the COO<sup>−</sup> group in the main chain of 1634 cm−1 is attributed to the OH bending vibration in the water chemically bond.

**Figure 8.** *Infrared spectral characteristics of natural clay and clay treated with CTAB.*

*Thermal Conductivity and Mechanical Properties of Organo-Clay-Wood Fiber in Cement… DOI: http://dx.doi.org/10.5772/intechopen.102321*

#### **3.6 Scanning electron microscopy (SEM)**

The micrograph (**Figure 9**) shows the morphology of the surface of raw clay and clay treated with the CTAB, modified by the addition of a low percentage of silica gel. This figure showed that the morphology of the clay surface appeared in the form of plaques, these plaques, of size of 200 nm is plied the some on the others in a characteristic package of structure sheet.

After this treatment by the CTAB and its modification by the addition of a silica gel, we can notice the good separation of some of plaques, layers, also, the appearance of spheres between these leaves in the micrometric size which asserts clearly that the silica gel is well inserted in to the OC.

### **3.7 Density and porosity**

The density values of WF reinforced cement are shown in **Figure 10**. Generally, the composites containing WF exhibit low density than these without WF. This could be attributed to the formation of void sat the interfacial are as between WF and cement matrix. For composite materials with 10% wt of WF, the density decreases by 43%. This indicates that WF has a filling effect on the density of cement composites with or without WF, where the density of cement composites is decreased by the addition of hemp fiber. In **Figure 10** the addition of 10% wt of WF decreased the density of cement composite. That improvement indicated that the addition of WF leads to decrease density and to obtain a composite material with a consolidated microstructure.

The results of porosity and water absorption of values of cement paste, WF reinforced composite, WF–OC reinforced composites are shown in **Figure 11**. Generally, the composites containing WF exhibit higher porosity than that without WF. This could be assigned to the formation of the voids at the interfacial are as between WF and matrices. For composite with 2 and 4% wt of WF, the porosity decreases by 1.82% (4%wt (WF)). The porosity of these composites indicates that WF has a felling effect on the porosity of cement paste composite [24] and this 2% wt and 4% wt are capable of saturating the surface and of reducing pores.

**Figure 11** shows that the addition of OC in the composite materials has reduced their porosity. The optimum addition was found as1% wt of OC, which decreased

**Figure 9.** *MEB micrographs of (a) natural clay and (b) Organoclay with silica gel.*

**Figure 10.** *Porosity and density as a function of treated wood fibers content for control cement and its composites.*

#### **Figure 11.**

*Porosity as a function of organo clay content for control cement.*

the porosity of composites by 18.75% when compared to the OPC. This implies that organo clay played a pore-filling role to reduce the porosity and to saturate pores. However, adding less than 1% wt of organo clay increased the porosity of all samples due to the agglomeration effect when less than 1% wt organo clay was added. This finding is comparable with the study where the porosity of the OPC is decreased due to the addition of 1% wt of organo clay to cement paste. We can say that composites containing 1% wt organo clay, are different from those of cement paste; the structure is less dense, and contain more pores. But composites with 1% wt of OC are different from those of OPC. The structure is more compact with few pores [25].
