Bentonite

Red, ball, kaolin, and bentonite are four types of clay that were obtained from quarries in Egypt’s Aswan, Abuznima, and Fayoum governments. They were stoned, ground to powder size, and sun-dried. The samples were sieved to 100 μm size, then they were thoroughly mixed with water, sectioned into sectors, and dried in the sun rays. Afterwards temperatures of 500 °C were used to bake the samples. Figure 1 illustrates bentonite, red, ball and kaolin clay samples labeled as A,B,C and D respectively. The porosity, P of the sample known as the ratio between the void volume and the total volume and can be calculated using the following equation [23 ,24 (link)].
$$P(\%)=\frac{W-D}{V}\times 100$$
where W (g), is the saturated mass of clay sample (the sample immersed in boiling water for 2 h), D (g), is the dried mass of clay sample (the sample dried in the oven at 110 °C for 48 h) and V(cm³) is the exterior (total) volume of the sample (V = W × S), where S (g), is the suspended weight of sample in water.
A scanning electron microscope (SEM, was used to show the distribution of particle inside each clay type as shown in Figure 2. To determine the elemental compositions of these clays, energy dispersive X-ray (EDX) analysis was used. The compositions are tabulated in Table 1. By knowing these compositions, the MAC can be calculated theoretically using the WinXCom program [25 (link),26 ,27 (link)]. On the other hand, to calculate the MAC experimentally, the HPGe detector and three point sources of different energies were used. The sample was placed between the source and the detector as shown in Figure 3 and the measurement was done for a sufficient time so that the statistical uncertainty of the area under the peak was less than 1% and the counting rate was calculated in the presence and absence of the sample. The MAC is calculated according to the following equation [28 (link),29 (link),30 (link)]: $$MAC=\frac{-1}{x.\rho }\ln \frac{A}{A_o}$$
where, A and A o represent the areas under the peak or the count rates obtained from the spectrum in presence and absence of the absorbing sample respectively, x (cm), the thickness of the measured clay sample and ρ (g/cm³) the density. The linear attenuation coefficient or LAC defined as the probability of photons with matter per unit path length and was calculated to determine other important shielding parameters (such as HVL and TVL) where the LAC equal MAC*ρ. The HVL and TVL represent the thickness needed to attenuate 50% and 90% of initial photon intensity, respectively, and can be evaluated by the following equations [31 ,32 (link)]: $$\mathrm{HVL}=\frac{\ln 2}{\mathrm{LAC}} , \mathrm{TVL}=\frac{\ln 10}{\mathrm{LAC}}$$
The radiation protection efficiency (RPE) was determined for the studied clays to show the most efficient clay from the following equation [33 ].
$$\mathrm{RPE}=\frac{I_o-I}{I_o}\times 100$$

To evaluate the interaction between gamma radiation and incident matter, the linear attenuation coefficient (μ) is a key parameter and can be calculated by Beer–Lambert’s Law [18 (link)] as follows: $\mathsf{\mu }=\frac{1}{\mathrm{x}}\ln \left(\frac{\mathrm{I}}{{\mathrm{I}}_0}\right)$
where I₀ is the intensity of incident γ-ray photon while I is transmitted γ-ray photons through a target of absorber thickness x. I and I₀ were calculated by determining the peak count rate in the presence and absence of the bentonite sample, respectively.
The mass attenuation coefficient (μ/ρ) was calculated to check the ability of the studied materials as shielding to rays without depending on the density of the material, by dividing the experimental calculated (μ) for a given material by its density (ρ). The (μ/ρ) can also be calculated theoretically using Equation (2) [19 (link)]: $\frac{\mathsf{\mu }}{\mathsf{\rho }}={\displaystyle \sum }_{\mathrm{i}}{\mathrm{w}}_{\mathrm{i}}{\left(\frac{\mathsf{\mu }}{\mathsf{\rho }}\right)}_{\mathrm{i}}$
where (μ/ρ)_i and (w_i) are the mass attenuation and the weight-fraction of the ith constituent element in the sample, respectively.
The half-value layer (HVL) is an important parameter when making a siutable radiation protecting material. This factor is the absorption thickness required to decrease the incident radiation to 50% of its initial value and is evaluated using Equation (3) [20 (link)]: $\mathrm{HVL}=\frac{\ln 2}{\mathsf{\mu }}$
When the photons pass through the sample, they travel a certain distance; the middle distance that a radiation travels between two consecutive interactions is known as the MFP and is described by Equation (4) [21 (link)]: $\mathrm{MFP}=\frac{1}{\mathsf{\mu }}$
When designing and selecting the shielding material, the EBF and EABF should be taken into account to correct the attenuation calculations due to the buildup of secondary photons generated by Compton scattering [22 (link)]. The minimum value of the buildup factor is 1 (BF ≥ 1); in this case, the absorption ratio of the buildup photons is 100%, and the greater the buildup factor more than one, the higher the scattering ratio of the buildup photons. Both exposure and energy absorption buildup factor can be estimated by phy-x software depending on the chemical composition of sample and its density [23 (link)].

Fibercement specimens were made with a mass of 300 g, Cemex Vertuá plus hydraulic cement type MM/B(P–C)-28 plus silica in different forms 80.2%. Calcium carbonate (marmoline CaCO₃ 90%) 14.70%. Glass fiber Cem-FIL 60 filament diameter: 14 μm and length of 12 mm 3.10%. Bentonite 1.60%, and high-range water-reducing plasticizer based on polycarboxylates of very high fluidity and water reduction from Sumiglas S.A 0.4%. A water/cement ratio of 0.3 was used, and other concentrations of the different forms of silica 0%, 3%, 5%, and 7% were taken based on previous work [25 (link)]. For each formulation (see Table 1), the design of experiments was performed, with four replicates, for a total of 40 samples for the compression test, and 40 samples for the flexure test, the samples were randomly selected for the analyses. The fibercement components were mixed according to ASTM standard C305–20, 2020 [26 (link)].Table 1

The formulation for fibercement with a total mass of 300 g.

Table 1

Samples	Cement (g)	Calcium carbonate (g)	Water (mL)	Plasticizer (mL)	Fiberglass (g)	Bentonite (g)	Sílice form (%) (g)
MC	240.60	43.80	165.0	1.20	9.30	4.80	0	0.000
MCA-3	233.38	43.80	165.0	1.20	9.30	4.80	3	7.220
MCA-5	228.57	43.80	165.0	1.20	9.30	4.80	5	12.03
MCA-7	223.76	43.80	165.0	1.20	9.30	4.80	7	16.84
MCE-3	233.38	43.80	165.0	1.20	9.30	4.80	3	7.220
MCE-5	228.57	43.80	165.0	1.20	9.30	4.80	5	12.03
MCE-7	223.76	43.80	165.0	1.20	9.30	4.80	7	16.84
MM-3	233.38	43.80	165.0	1.20	9.30	4.80	3	7.220
MM-5	228.57	43.80	165.0	1.20	9.30	4.80	5	12.03
MM-7	223.76	43.80	165.0	1.20	9.30	4.80	7	16.84

*MC = Control sample, MCA-3, MCA-5, MCA-7 sample rice husk at 3%, 5%, and 7%, MCE-3, MCE-5, MCE-7, sample with ash at 3%, 5%, and 7%, MM-3, MM-5, MM-7, sample with micro-silica at 3%, 5%, and 7%.

All of the above components were accurately mixed following the experimental design presented in Table 1. The raw materials were placed in an aluminum mixing vessel and mixed for 5 min with an electric mixer. The mixture was stirred at a frequency of 13 at 0 rpm and room temperature until homogeneity and moldability were achieved, according to ASTM Standards ASTM C109/109 M −16a, 2016 [27 ]. The specimens were compacted in a triple plastic mold with a 2" (50.8 mm) rim. The ASTM Standards ASTM C78/C78 M − 21, 2010 [28 ] was employed for the preparation of specimens subjected to the flexural test. Then, the specimens were compacted in a prism shape with dimensions of 150 mm × 50 mm × 10 mm. Finally, the samples were left to set for 28 days at room temperature and with a relative humidity of $70\pm 10\%$ .

Sodium alginate (SA) (15% loss during drying at 105 °C, 30% ignition residue and 0.004% heavy metal content) was purchased from Panreac Quimica (Barcelona, Spain). The polymer presented intrinsic viscosities of 1.03 × 10³ mL/g and 5.39 × 10³ mL/g in 0.1 M sodium chloride and distillate water, respectively, measured using an Ubbelohde capillary viscometer at 25 °C. The values of the typical molecular weight are 5.48 × 10⁴ g/mol and 3.38 × 10⁵ g/mol for 0.1 M sodium chloride and distillate water, respectively. In addition, the M/G ratio was determined using infrared spectra and was equal to 1.37. The raw bentonite was taken from the Azzouzet deposit (Nador, Morocco), previously characterized [21 (link)], purified and exchanged before the experiment to obtain a sodic clay. The main parameters of the raw and purified/exchanged clay are shown in Table 1.
Rosmarinus officinalis L. essential oil (REO) was obtained from a distillation unit in Jerrada (eastern region of Morocco) and was stored at −1 °C until examination. Tween 80 (density of 1.06 and viscosity of 300–500 mPa⋅s at 25 °C) was provided by Panreac Quimica (Barcelona, Spain) and calcium chloride (powder, 97% with a molar mass of 110.99 g/mole) was acquired from Riedel-de-Haën (Seelze, Germany).