الفهرس 
Chapter 1 IntroductionOnly 14 pages are availabe for public view
 |  | from | 111 |  |  |
| | | from | 111 | | |
Abstract
Ultra-high-performance concrete (UHPC) has superior mechanical characteristics and durability but it is not an eco-friendly material because of its high cement content, which leads to an increase in the proportion of CO2 in the environment. To alleviate these problems, researchers attempted to decrease the cement content by substituting it with waste materials. However, the efficiency of the used industrial waste materials is still scattered and needs further investigation. This work aims to examine the impact of using different alternative filler materials such as quartz powder (QP), limestone powder (LP), granite powder (GP) and basalt powder (BP) along with silica fume (SF) as a cement replacement on mechanical characteristics and durability of UHPC and using optimization software to assess the optimum values of variables that achieve specified results of responses. The total powder content composed of 60% cement, 20% SF, and 20% filler materials (QP, LP, GP, and BP). Mixture design method in Minitab program was used to design concrete mixtures. Flowability, compressive strength, splitting tensile strength, flexural strength, water permeability, rapid chloride permeability, sulfate resistance and concrete microstructure were the tests performed on the concrete mixtures. The results indicated that UHPC with low environmental impact and compressive strength more than 120 MPa with higher durability could be produced using QP, LP, BP, and GP as a replacement of cement. Utilizing QP, LP, BP, and GP as a partial replacement of cement in the production of UHPC resulted in significant negative impact on concrete flowability. Mixture composed of 711 kg/m3 cement, 237 kg/m3 SF, 118.5 kg/m3 QP, 118.5 kg/m3 BP, 1017 kg/m3 sand, 142.2 kg/m3 water, 31.3 kg/m3 superplasticizer, and 156 kg/m3 steel fibers achieved the highest compressive strength at age 7, 90, 180 days, the strength were 85 MPa, 123 MPa, and 126.1 MPa respectively. In general, the partial replacement of cement with QP, LP, BP, and GP for almost all mixtures showed less results on splitting tensile strength compared to control mixture. The highest value of flexural strength was observed when LP and BP were incorporated at the dosages of 10% LP and 10% BP. The use of filler materials as a replacement of cement has a negligibly small impact on the water permeability of concrete mixtures. Also, test results show a significantly no negative effect in the penetration for chloride ions through the concrete mixes due to the incorporation of the utilized filler materials. The significance of each variable can be represented in the statistical models, along with the relationship between the responses and the independent parameters. The results show the possibility to use optimization software to assess the optimum values of variables that achieve specified results of responses.