فهرست مطالب amir khaghani boroujeni

Ultra-High Performance Concrete (UHPC), known for its superior mechanical and durability properties, is an appropriate material for different applications such as building and bridge construction. Investigating the possibility of UHPC production using available materials is an engineering challenge. This paper evaluates the applicability of some materials in making UHPC and the effectiveness of several parameters on the compressive strength of UHPCs. Then, by choosing the mixture yielding the highest compressive strength, the durability and mechanical properties of the mixture with 0-2.5% crimped steel fiber are investigated. The tests include compressive strength, flexural and tensile parameters, length change, rapid chloride ion migration, sorptivity, porosity, and sulfate resistance. The results reveal that the pozzolanic activity of silica fume and its synergetic effect with glass powder lead to the highest compressive strength. Moreover, it makes it possible to easily obtain a strength higher than 150 MPa. Utilization of 2.5% crimped steel fiber in UHPC mixtures remarkably enhanced mechanical performance so that the flexural and tensile strength were increased by about 95% and 25% compared to the plain UHPC, respectively. However, the incorporation of fibers increased the UHPC permeability.

Some of the nanoparticles such as zinc oxide have a significant antibacterial activity that can be used in removal of pathogenic organisms in certain water resources application. This study was specifically undertaken to investigate the use of cement matrix modified with Zinc oxide nanoparticles to prevent the growth of Pseudomonas aeruginosa and Bacillus cereus. The results showed that ZnO nanoparticles with the size lower than 20 nm were dispersed well in the cement matrix. Results also showed that inhibitory effect against gram-negative bacterium of Pseudomonas aeruginosa was higher than gram-positive bacterium of Bacillus cereus. Also, confinement of ZnO nanoparticles by cement materials reduced the photocatalytic activity slightly. Based on the preparation of antibacterial formulation of cement matrix containing ZnO nanoparticles, concrete surfaces with ZnO nanoparticles can be used in a wide range of aquatic environments for prevention of pathogenic bacterial growth.

In recent years, several researches have been carried out to investigate the applications of nano science in the concrete technology. It appears that by combination of nano science and concrete technology, new scientific horizons could be opened and high quality construction and building materials may be produced. . As a matter of fact, some types of nano materials have photocatalytic characteristics and could disintegrate the pollutants and various types of organic substances. Hence, utilizing nano technology, multi-purpose materials with enhanced characteristics and new applications such as self- cleaning surfaces could be produced.
Several types of nano materials have photocatalytic characteristics, which among them nano ZnO and TiO2 have found higher attention. The influence of TiO2 on the cement based materials has been the subject of several researches. However, nano ZnO was not considered appreciably. Thus, in the present study, the performance of different percentages of Nano ZnO on the mechanical and microstructural properties of concrete has been investigated. The studied properties were setting times, compressive strength, hydration degree, reaction with calcium hydroxide and microstructural analysis by scanning electron microscopy images (SEM). Moreover, with regards to the photocatalytical properties of this material, the influence of nano ZnO on the removal of a type of algae was scrutinized. The results indicate that nano-ZnO could significantly increase the initial and final setting times, leading to the slow formation of microstructure at very early ages.Furthermore, the photocatalytic investigation showed that the mortar surfaces containing these nanoparticles could prevent the growth of the blue-green algae.