2.1. Materials
The National Cement Company's ordinary Portland cement (OPC) was used as a material in this experiment and basalt powder (BP) was produced from Aswan quarries (Egypt). The chemical analysis of (OPC) and (BP) are depicted in Table (1).
Table (1): Chemical composition of (OPC) and (BP)
Oxides
|
SiO2
|
ZrO2
|
MnO
|
SO3
|
TiO2
|
V2O5
|
Cr2O3
|
CaO
|
Fe2O3
|
P2O5
|
Al2O3
|
OPC
|
10.89
|
2.39
|
3.32
|
9.91
|
2.98
|
1.50
|
2.05
|
20.25
|
46.71
|
-
|
-
|
BP
|
46.75
|
-
|
1.07
|
0.63
|
9.81
|
1.60
|
1.57
|
14.68
|
11.14
|
2.03
|
10.72
|
2.2. Preparation of Cement Pastes
In the beginning, a cement weight was put to a seamless, impermeable surface, a crater was created. With the aid of a trowel, The crater was filled with the required amount of mixing water. After being gently towelled to take up the water for about a minute, the dry cement was thoroughly mixed vigorously and continuously for approximately three minutes by hand. After the top layer had been compacted, the mould was filled with cement paste. and left there until a homogeneous specimen was created. Using an edgeless trowel, the top of the paste was smoothed off and brought level with the top of the mould. These percentages were substituted for the dry cement weight after mixing cement with tap water to make pastes of 5, 10, and 20% basalt powder additions. After adding and thoroughly combining basalt powder, the mixture was used with the mould. Moulding samples were immediately dried in a humidifier at an ambient temperature for 24 hours. When the moist curing time has ended, de-moulded cubes were used and curing was continued underwater for the needed time of testing. During the result of aggressive medium, the cube 2.5 cm (1 inch-sides length) was de-moulded and curried underwater for about 28 days, then the cube was submerged in different solutions (5% NaCl and 5% MgCl2) shown in Fig. 1. Samples were investigated at specified intervals up to 9 months.
2.3. Preparation of Reinforcing Steel for EIS
High tensile steel bars (reinforcing steel 38), measuring 12 mm in diameter and 100 mm in height, were the reinforcing steel employed in this experiment. The surface of the rods was mechanically cleaned to remove the heavily adhered mill scales and cleaned with bi-distilled water, dried with acetone then covered in epoxy while 1 cm2 was not coated. The coating by cement pastes was used with steel reinforcement in mouldier (cylindrical) have a 6 cm width and a 10 cm length shown in Fig. 2 and Table (2) lists the chemical compositions of reinforcing steel.
Table (2): Chemical composition of reinforcing steel.
Element
|
C
|
Si
|
Mn
|
P
|
S
|
Cr
|
Ni
|
Al
|
Fe
|
Wt %
|
0.323
|
0.169
|
0.782
|
0.032
|
0.019
|
0.0188
|
0.0135
|
0.033
|
98.58
|
2.4. Methods of Physico- Mechanical Properties
2.4.1. Bulk Density
Bulk density is defined as the mass of the dry solids divided by the total volume of the entire wet sample. By dividing the mass of dry cement particles by the volume of the cement sample, the bulk density can be calculated from Eq. 1 [9].
Bulk Density g/cm3 = Md / V (1)
Where; Md = mass of dry cement sample (g) and V = sum of the wet sample's volume cm3.
Each measurement was conducted on three equivalent individuals of the same preparing conditions and the average of the three results was calculated.
2.4.2. Water Absorption and Total Porosity.
The water absorption was established according to Davraz et al. [10]. Samples used were either boiled for five hours or submerged in water for 24 hours. The water was then allowed to drain following the removal of the samples from it. Any apparent surface water was removed using a cloth that has been dampened. The samples' weight was recorded as saturated weight (Ws). The used samples were dried for one day at 80°C in a ventilated oven. Dry weight (Wd), the final weight of the samples, was recorded. The water absorption percent is calculated from the following Eq. 2:
Water absorption % = [(Ws-Wd) / Wd] x100 (2)
The equation could be utilised to calculate the overall porosity of the cured cement pastes once the specimens' water absorption was established by Eq. 3:
Total Porosity % = Ws -Wd / ρwV (3)
Where; ρw is the water density and V is the volume of the sample.
For each measurement, the average of the three measurements was calculated. which was performed on three comparable specimens prepared under identical conditions.
2.4.3. Compressive Strength Measurements
In order to assess compressive strength, 2.5 x 2.5 x 2.5 cm neat cement cubes were prepared, de-moulded, and constantly cured in a humidity chamber until the time of testing as indicated in Fig. 3. For each assessment of compressive strength, a set of three cubes was used [11]. With a loading rate of 100 kg/min, compressive strength measurements were performed using two-ton Amsler testing equipment according to Khater H.M. [12].
2.5. Characterization of Hydrated Pastes Mix Design
2.5.1. Infrared Spectroscopic Analysis
The fingerprint of the compound's infrared spectrum is applicable to give both qualitative and quantitative examinations of the mixture. To be able to learn more about the hydrated products, IR spectral analysis was done on a sample of hydrated pastes. From the proper spectrum, it is occasionally feasible to draw inferences about structural elements. Alkali halide (KBr) pressed disc procedures are accustomed to preparing the samples because they further reduce IR scattering. 1.0 mg of the moist powder sample was mixed with 99 mg of potassium bromide in an agate mortar to form a homogeneous slurry. The mixture was compressed under a vacuum to provide a transparent disc with a diameter of 1.0 cm. Then, set the KBr disc in the spectrometer after moving it to a sample holder. The Jascoo FTIR 4600 was used to record the infrared spectrum analyses from KBr discs in the 400–4000 cm− 1 range.
2.5.2. X-ray Diffraction Instrument (XRD)
The sample being studied is focussed into a high-energy beam of charged particles, such as electrons or protons, or an X-ray beam, to cause the release of distinctive X-rays from it. An atom among the sample has ground state (or unexcited) electrons that are bonded to the nucleus in specific energy levels or shells when it is at rest. An electron's inner shell might be excited by the incident ray, ejecting the electron out of the shell and leaving an electron hole in its place. An electron from the outer, higher energy shell then fills the hole, and the energy may result in the production of an x-ray. In the phase experiment, we used a Bruker D8 Discover with a Cu radiation source, wave length1.54 A, the applied voltage was 40 kV and the filament current was 40 mA.
2.6. Electrochemical Impedance Spectroscopy
The Autolab 302N Potentiostat/Galvaniostat was accustomed to conducting electrochemical impedance investigations in a three electrodes system. The fundamental benefit of this strategy is that the electrode/electrolyte interface is represented by a completely electronic model. An electrical circuit with resistors and capacitors is frequently compared to an interface that is undergoing an electrochemical reaction. As a result, the equivalent circuit of an electrochemical system is a good way to express it. An impedance plot derived for a specific electrochemical system can be compared to one or more analogous circuits using AC (alternating current) circuit theory. The data is utilized to either confirm or at the very least disprove a mechanistic model for the system. Since the impedance data revealed to be reliant on the disturbance signal amplitudes in the vicinity of 5 to 15 mV, a 10 mV amplitude signal is typically employed for impedance measurements. The typical working frequency range used was from 1 mHz to 100 kHz. Data generation processes, including collection, processing, storage, retrieval, and analysis, have been automated by Metrhom Nova 2.1.5 software. After initial setup measurements, the electrode impedance data may be collected over a wide frequency range (1 mHz − 100 kHz).
2.7. Spectroscopic Analysis
The surface morphology and grain size were observed using the SEM. Energy dispersive X-ray analysis was used to identify the constituents on the surface of reinforcing steel in various corrosive media. The analysis was carried out using JEOL JSM 5410 (Japan).