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Nondestructive Test in Geopolymer Concrete with Aid of Ultrasonic Waves

Nouri, Ali | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54260 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Toufigh, Vahab
  7. Abstract:
  8. In recent decades, particle composite materials have a wide range of applications in engineering. Particle composites are a group of heterogeneous materials with different length scales and are characterized by particles that are randomly distributed in a matrix phase. Geopolymer concrete is a special type of concrete that its binder is made by reacting alumina and silicate carriers with an activating agent and in recent years with the expansion of its use has reduced the amount of cement consumption. In addition to the many advantages of geopolymer concrete, it has disadvantages in terms of setting time. That is why the use of cement has been proposed as a solution to the problem. This additional cement changes the properties of the geopolymer adhesive. Experimental findings show that wave propagation is dispersed in heterogeneous materials with components of different length scales. In this research, the dispersive behavior of particle composite materials with rotational degrees of freedom has been analyzed. For this purpose, the energy functions of the Lagrange equation were determined by the discrete element method. These functions include both the degree of freedom of movement and the degree of freedom of rotation. Taylor expansion was applied to transfer equations from a discrete to continuous medium. The use of Taylor expansion is such that the structure of the equations remains stable. Among the available methods for finding the equation in a closed form, the method of using alternating network structure was chosen. The specific constraint determines the possible network structure. These constraints are selected from the original equations themselves. Then, with the presented method and with the help of constraints, the coefficients related to the equations were obtained. Experimental data of fresh and hardened geopolymer concrete were obtained from different grain and adhesive ratios. Concrete samples are prepared using a special processing method in order to achieve the maximum strength and resistance by considering the construction characteristics and characteristics of geopolymer materials. Equation coefficients were obtained using the characteristics of aggregates in geopolymer concrete. Laboratory data related to the velocity of the hardened concrete phase and fresh geopolymer mortar were compared with the prediction curve of the introduced sample. As a result, using the obtained parameters for the prediction curve, the best relationship between the experimental data and the theoretical line was obtained. The results were also compared with the scattering curve of the slope model with higher order inertia, which in previous studies to some extent predict the phase velocity in concrete. The comparison between the two theoretical curves also showed a good agreement between them. As a result, a parameter was obtained to estimate the curing step and determine the percentage of cement used in geopolymer concrete. This parameter was able to predict the characteristics of the geopolymer product with cement both in terms of setting and in terms of the percentage of cement impurities
  9. Keywords:
  10. Geopolymer Concrete ; Phase Velocity ; Multiscale Modeling ; Dispersive Wave ; Three Dimentional Lattice Structure ; Heterogeneous Materials

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