# Effect of Magnetized Water on the Mechanical and Durability Properties of Concrete Block Pavers

^{1}

^{2}

^{3}

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## Abstract

**:**

## 1. Introduction

## 2. Materials and Sample Preparation

#### 2.1. Materials

#### 2.2. Experimental Design

^{3}of the concrete mix was 516 kg, 240 kg, 1150 kg, and 612 kg, respectively. The mix design variable is the number of times that water passed through the permanent magnet (10, 20, 40, and 80).

#### 2.3. Specimen Preparation

#### 2.4. Test Methods

#### 2.4.1. Compressive Strength

#### 2.4.2. Splitting Tensile Strength

#### 2.4.3. Flexural Strength

#### 2.4.4. Mass Loss

_{2}SO

_{4}solution with pH 1.0. The solution was monitored refreshed weekly in order to keep the pH constant for a period of 13 weeks at a temperature of 25 °C. Specimens were removed from the solution weekly, rinsed three times with regular tap water to remove loose reaction products, and left to dry for one hour at room temperature before measuring the mass loss. The mean of five specimens was reported as the mass loss of each mix. The mass loss percentage of each specimen was calculated by the following Equation (1):

_{t}(%) = ((M

_{t}− M

_{i})/M

_{i}) × 100

_{t}is the mass of the specimens at time t (g), and M

_{i}is the initial mass of the specimens before exposure to H

_{2}SO

_{4}solution (g).

#### 2.4.5. Water Absorption

## 3. Results and Discussion

#### 3.1. Effect of Magnetized Water on Compressive Strength

#### 3.2. Effect of Magnetized Water on Splitting Tensile Strength

#### 3.3. Effect of Magnetized Water on Flexural Strength

#### 3.4. Effects of Sulfuric Acid Immersion

#### 3.4.1. Mass Loss

_{2}SO

_{4}solution with pH 1.0 versus immersion time are shown in Figure 8. Each point of the plot is a mean value of five independent specimen readings per mix.

_{2}SO

_{4}attack and showed the worst resistance to acid attack compared to specimens with magnetized water, and had a mass loss of 10% after 91 days of exposure. This means that, regardless of the number of times that regular tap water passes through the permanent magnetic field, the magnetized water had a positive and significant effect on the resistance of specimens to acid attack. As seen in Figure 8, for mixes with magnetized water, mix No. 1 displayed the most positive effect from the magnetic field, and had the best resistance to acid attack. Mixes No. 2 to No. 5 displayed 53%, 44%, 37%, and 24% lower mass loss compared to the control mix after 91 days exposure to 5% H

_{2}SO

_{4}solution, respectively. Figure 8 also shows that for mixes with magnetized water, as the number of times that water passes through the permanent magnetic field decreases, the mass loss of the mixes declines gradually. This means that there is an inverse relationship between the number of times that water passes through the permanent magnetic field and the resistance to acid attack. When sulfuric acid reacts with the hydration products, dissolution of the hydrated composites and hydrogen ions occurs [33]. The speed of this action depends on the pore structure, porosity, sulfuric acid concentration, and pH value of the solution [34]. The higher resistance of specimens with magnetized water to acid attack may be attributed to the reduction of pores in the structure of the specimens with magnetized water, as a result of their greater density and higher degree of hydration. This is in good agreement with the results of Ahmed [15], which used magnetized water instead of regular tap water, and found a significant improvement in the microstructural properties of concrete mixes. Consequently, the structure of concrete with magnetized water becomes denser, and lower amounts of pores can be seen in concrete with magnetized water compared to concrete with regular tap water [6,8,15,18]. These differences explain why the magnetized water can increase the durability properties of concrete mixes. The subsequent decrease for more than 10 times the water passing through the permanent magnetic field has been explained in the discussion of the compressive strength results.

#### 3.4.2. Compressive Strength Loss

_{2}SO

_{4}solution after 28 and 91 days of exposure. Each point of the plot is a mean value of five independent specimen readings per mix. The percentage change in the compressive strength of each mix was determined by comparing the compressive strength of specimens after 28 and 91 days of exposure to H

_{2}SO

_{4}solution with the compressive strength of specimens after 28 days of water curing.

_{2}SO

_{4}solution, but the rate of decrease varied for different mixes. For all of the concrete mixes, the maximum loss in the compressive strength of concrete mixes was observed after 91 days of exposure to H

_{2}SO

_{4}solution, as expected. The reduction in the compressive strength of the mixes was likely due to dimension decrements and the loss of surface stiffness [35]. The reduction in compressive strength of the mixes may also be attributed to the reaction of sulfuric acid with Ca(OH)

_{2}[33]. Allahverdi and Škvara [36] reported that sulfuric acid attack causes the extensive formation of gypsum in the regions close to the surfaces, and tends to cause disintegrating mechanical stresses that ultimately lead to spalling and exposure of the fresh surface. The results also showed that, regardless of the number of times that water passes through the permanent magnetic field, the specimens with magnetized water had a lower loss in compressive strength compared with the ones with regular tap water. This may be attributed to the more compact and dense microstructure of the mixes with magnetized water, which reduced the effective pores in the concrete surface, and hence reduced its permeability. The lower loss in the compressive strength of the specimens with magnetized water may also be related to the lower mass loss of the specimens with magnetized water compared to the ones with regular tap water. The highest loss in compressive strength of the mixes after 91 days of immersion in H

_{2}SO

_{4}solution was registered for mix No. 1. For specimens with magnetized water, the compressive strength percentage loss decreased as the number of times that water passed through the permanent magnetic field reduced. After 91 days of exposure, differences of 11.5%, 9%, 6%, and 3.5% in percentage loss were noted between mix No. 1 and mixes No. 2, No. 3, No. 4, and No. 5, respectively. These results are in agreement with the mass loss results.

#### 3.5. Effect of Magnetized Water on Water Absorption

#### 3.6. Effect of Magnetized Water on Microstructure of Concrete

## 4. Conclusions

- The mechanical performance of concrete showed an improvement due to using magnetized water instead of regular tap water: relative to the control mix, an average improvement of 12.5%, 13%, and 9% after 28 days of water curing was registered for the compressive strength, splitting tensile strength, and flexural strength, respectively;
- The results showed that as the curing age increases, the compressive strength, splitting tensile strength, and flexural strength of all of the mixes increases, as expected. However, the rate of increase varies for different mixes;
- The mass and compressive strength loss and water absorption results showed that magnetized water had a positive effect on the resistance to sulfuric attack and water absorption of the concrete mixes. The improvement grew as the number of times that water passed through the permanent magnetic field decreased;
- For the same mix proportions, concrete mixes with magnetized water will have a higher compressive strength, splitting tensile strength, and flexural strength, and a lower mass/compressive strength loss under acid attack and water absorption than control mix specimens, due to their greater density and more efficient degree of cement hydration;
- The SEM images showed that using magnetized water instead of regular tap water led to a significant improvement of the microstructure of the corresponding concrete mixes and resulted in a denser structure compared to the control mix;
- The cost of magnetizing water is very low because of the simple devices used. In this study, the following devices were used, with a total a cost of approximately ($600 USD): (a) an electric pump, (b) two water tanks, and (c) one permanent magnetic field. The cost would have to be adapted to the scale of the work involved. The time needed to pass 10 L of regular tap water through the permanent magnet in this study was about 28 s. This time would decrease as the strength of the electric pump increased.

## Author Contributions

## Acknowledgments

## Conflicts of Interest

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**Figure 5.**Compressive strength of concrete block pavers after 7, 14, and 28 days of curing in lime-saturated water.

**Figure 6.**Splitting tensile strength of concrete block pavers after 7, 14, and 28 days of curing in lime-saturated water.

**Figure 7.**Flexural strength of concrete block pavers after 7, 14, and 28 days of curing in lime-saturated water.

**Figure 8.**Percentage changes in the mass of the concrete block pavers exposed to 5% by weight of H

_{2}SO

_{4}solution with pH 1.0 versus immersion time.

**Figure 9.**Degradation and percentage changes in the compressive strength of concrete block specimens exposed to 5% by weight of H

_{2}SO

_{4}solution after 28 and 91 days of exposure.

**Figure 10.**Water absorption of mixes prepared with regular tap water and magnetized water after 28 days of curing.

**Figure 11.**SEM images (100×) of concrete mixes with (

**a**) regular tap water; (

**b**) magnetized water after passing 10 times; and (

**c**) magnetized water after passing 80 times through a permanent magnetic field at a constant speed of 2.25 m/s.

**Figure 12.**SEM images (5000×) of concrete mixes with (

**a**) regular tap water; and (

**b**) magnetized water after passing 10 times and (

**c**) 80 times through a permanent magnetic field at a constant speed of 2.25 m/s.

Material | Chemical Composition (%) | |||||||||
---|---|---|---|---|---|---|---|---|---|---|

SiO_{2} | CaO | Al_{2}O_{3} | Fe_{2}O_{3} | MgO | SO_{3} | K_{2}O | Na_{2}O | CL * | LOI ** | |

Cement (Type II) | 21.65 | 63.25 | 4.3 | 3.45 | 2.8 | 2.05 | 0.6 | 0.5 | 0.07 | 1.35 |

Properties | Fine Aggregates | Coarse Aggregates |
---|---|---|

Water absorption (%) | 4.15 | 1.63 |

Existent moisture (%) | 3.8 | 0.51 |

Modulus of fineness | - | 4.79 |

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**MDPI and ACS Style**

Ghorbani, S.; Gholizadeh, M.; De Brito, J.
Effect of Magnetized Water on the Mechanical and Durability Properties of Concrete Block Pavers. *Materials* **2018**, *11*, 1647.
https://doi.org/10.3390/ma11091647

**AMA Style**

Ghorbani S, Gholizadeh M, De Brito J.
Effect of Magnetized Water on the Mechanical and Durability Properties of Concrete Block Pavers. *Materials*. 2018; 11(9):1647.
https://doi.org/10.3390/ma11091647

**Chicago/Turabian Style**

Ghorbani, Saeid, Mostafa Gholizadeh, and Jorge De Brito.
2018. "Effect of Magnetized Water on the Mechanical and Durability Properties of Concrete Block Pavers" *Materials* 11, no. 9: 1647.
https://doi.org/10.3390/ma11091647