Evaluation of Mechanical compressive strength of cementitious matrix with 12% of IER formulated by modified polymer (NEPS) at different percentages

During this paper, we improved the compressive strength of cementitious matrix based on ion exchanging resin (IER) at 12% and formulated by the modified novolac epoxy polymer surfactant (NEPS) at various percentages (0, 1, 2, 3, 4 and 5%). The results show that the introduction of 1% and 2% of NEPS in the cementitious matrix with 12% of IER increases the compressive strength compared to that of the basic matrix (from 7 to 90 days). However, the formulations 3, 4 and 5% show the compressive strength is less than that of the basic matrix (from 28 to 90 days).

During this paper, we improved the compressive strength of cementitious matrix based on ion exchanging resin (IER) at 12% and formulated by the modified novolac epoxy polymer surfactant (NEPS) at various percentages (0, 1, 2, 3, 4 and 5%). The results show that the introduction of 1% and 2% of NEPS in the cementitious matrix with 12% of IER increases the compressive strength compared to that of the basic matrix (from 7 to 90 days). However, the formulations 3, 4 and 5% show the compressive strength is less than that of the basic matrix (from 28 to 90 days).
Epoxy polymers cover various industrial areas such as: electronics, coating, inhibition, space construction and radioactive waste [1][2][3][4][5] . Epoxy polymers have many properties, including viscosimetric, thermal, morphological, rheological and mechanical compressive of strength [6][7][8][9] . At this time, the most widely employed process for the synthesis of epoxy polymers is the condensation of epichlorohydrin on structures having at least two mobile hydrogen atoms such as diamines, diacids and polyphenols. Also, the oxidation of polyunsaturated compounds and/or the condensation of glycidol with halogenated compounds 10,11 . Novolac epoxy polymers are obtained by the condensation of phenol with formaldehyde in an acid medium 12,13 .
The objective of this paper is to improve the chemical compressive of strength of the cementitious matrix based on ion exchanging resin (IER) at 12% formulated by novolac epoxy polymer surfactant (NEPS) modified at various percentages (1, 2, 3, 4 and 5%) [14][15][16] . We have studied the properties of mechanical of compressive strength, varying the polymer amounts incorporated in cementitious matrix formulations. This gave us the reflection to introduce the modified novolac epoxy polymer in surfactant form into the cementitious matrix. Besides, the results obtained show an increase in mechanical compressive of strength after 7, 14, 28 and 90 days of confinement compared to the basic matrix.

Material and Methods
Ion exchange resin (IER). Ion exchange resin is a crosslinked macromolecular water insoluble matrix which, upon contact with a solution, can exchange the ions it contains with other ions of the same sign from the solution used in water purification of the reactor vessel Mark TRIGA II 16 . Their physicochemical properties are shown in Table 1.
Molds. The used molds are cylindrical with a diameter of 5 cm and a height of 10 cm, which are illustrated in Press carver 4350 L. The used press carver 4350 L is manual hydraulic which makes it possible to determine the compressive strength of the mortar from the force measured in view of the surface.

Preparation of surfactant.
The synthesis of modified novolac epoxy polymer surfactant (NEPS) based on novolac epoxy polymer (NEP) was carried out in two steps. The first step consists of condensing of 0.004 mol of novolac epoxy polymer with 0.026 mol of acrylic chloride in the presence of Lewis acid (AlCl 3 ) by Friedel and Craft acylation reaction with magnetic stirring for 4 hours at 100 °C. Besides, in the second step, 3.014 mol of para-aminophenol were added to the previously product obtained (I) according to the first step by reaction of 1, 4-Mickael addition under magnetic stirring for 3 hours at 70 °C (Scheme 2) 18,19 . All the employed chemicals products were purchased from Aldrich Chemical Co.
Calculation of compressive strength. The strength is applied to the matrix by two cylindrical metal plates and the reading of the force is either pound or Pound per Square Inch (PSI). Moreover, we calculate the compressive strength (R) from the displayed force value which is expressed by using Eq. 1.
With R, F and S denote compressive strength (MPa), force applied (Pound) and surface of the test piece (cm 2 ), respectively.

Methods used
Fourier transform infrared spectroscopy. The used FTIR spectrometer is a BRUKER Fourier transform spectroscopy. The light beam passes through the sample to a thickness of about 2 μm. The analysis is carried out between 4000 cm −1 and 600 cm −1 .
Nuclear magnetic resonance. Analyzes of Nuclear magnetic resonance ( 1 H NMR and 13 C NMR) were obtained by using ADVANCE 300 Bruker like apparatus, and the product was solubilized in CDCl 3 . The chemical shifts are expressed in ppm. www.nature.com/scientificreports www.nature.com/scientificreports/ Scanning electron microscope. The scanning electron microscope was used to make photographic images. The observations were carried out on a JEOL-JEC-530 microscope. This technique is based on the use of a beam of electrons accelerated by a fixed potential that excites the surface of the sample.

Results and Discussions
Fourier transform infrared spectroscopy. The novolac epoxy polymer surfactant (NEPS) modified was characterized by Fourier transform infrared spectroscopy (FTIR) analysis (Fig. 2). The different bonds NEPS are grouped in Table 2.   www.nature.com/scientificreports www.nature.com/scientificreports/    Optimization of percentage of NEPS modified. The different formulations used for this study are 12% of IER, 67.92% of cement and 20.19% of water. In this study, we tried to introduce the novolac epoxy polymer surfactant (NEPS) modified into the cement matrix so as to improve the compressive strength. The used surfactant polymer is introduced in matrix at different percentages (1, 2, 3, 4 and 5%). Figure 5 shows the confinement matrix. The results of compressive strength for these 7, 14, 28 and 90 days matrix are shown in Table 3. According to these results, we concluded that the introduction of novolac epoxy polymer surfactant modified at various percentages (1, 2, 3, 4 and 5%) into the matrix increases the compressive strength with respect to the base matrix (Fig. 6) 20 . The matrix of 1% of NEPS modified has a superior compressive strength. Once again, we changed the configuration of the novolac epoxy polymer by modifying it in surfactant form to further improve  www.nature.com/scientificreports www.nature.com/scientificreports/ the compressive strength in the conditioning matrix. Moreover, the compressive strength increases with time for formulations of 1 to 5% novolac epoxy polymer surfactant and for base formulation. Furthermore, the compressive strength of the matrices with the novolac epoxy polymer surfactant of this test is higher than that of the basic matrix up to 28 days, from 28 days to 90 days, where as the tests' matrix 3, 4 and 5% is less than that of the basic matrix 14 . Besides, the evaluation of these results shows that the introduction of 1% and 2% of NEPS into the IER conditioning matrix increases the compressive strength with respect to the base matrix 16 . They, thus, make it possible to solubilized two immiscible phases. For this reason, we have given a good homogeneity of the conditioned cementitious matrix, as well as good dispersion.    www.nature.com/scientificreports www.nature.com/scientificreports/ Scanning electron microscopy. The dispersion of ions exchanging resin (IER) in the cementitious matrix formulated by novolac epoxy polymer surfactant at various percentages is presented in Fig. 7. The different formulations with addition of 0 to 5% of NEPS modified are analyzed by the scanning electron microscopy (SEM). According to SEM micrographs observations, the cementitious matrix formulated by NEPS clearly show the spherical IER loads on the analyzed surfaces 21,22 . The addition of 1% NEPS exhibits better dispersion, this confirms the higher compressive strength.
conclusion Several research studies have been conducted so as to determine which formulation has better compressibility resistance than the IER conditioning base formulation. Previous studies have evaluated the impact of the novolac epoxy polymer surfactant (NEPS) in different physical states on the formulation. The objective of this study was to improve the compressive strength of the containment matrix by setting the percentage of IER at 12%, the percentage of water at 20.19% and cement at 67.92%, and the introduction of the novolac epoxy polymer surfactant (NEPS) to different percentages (1, 2, 3, 4 and 5%). Besides, the results obtained in this study showed an increase in the compressive strength after 7, 14, 28 and 90 days of confinement with respect to the base formulation. In addition, the introduction of novolac epoxy polymer surfactant into formulation allowed an improvement in the compressive strength of 1% and 2% matrix of the NEPS and good homogeneity of the conditioned cementitious matrix, as well as good dispersion of IER in our formulations on the other hand.