A Study on Engineering Properties with Impact Factors of Geopolymer and its Application on Repairing Concrete Defects

• Main Authors: Syuan-Jhih Lyu, 呂軒志
• Other Authors: 翁祖炘
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/267n85

博士 === 國立臺北科技大學 === 工程科技研究所 === 101 === Repair materials are key factors for structure restoration projects. Currently, however, no corresponding standards or methods exist for evaluating repair effectiveness. The formation of geopolymer is similar to concrete; it has low carbon dioxide emissions, high early strength, good durability, low volume change rate, and can be used as a pressure-bearing filler material. Geopolymer possesses great developmental potential for concrete defect repairs and has received much attention in recent years as an environmentally friendly material. Based on the framework of experimental design, this study investigates the influence factors, engineering and adhesion properties of geopolymer. First, statistical regression analysis is used to clarify the interaction between geopolymer constituents, and to understand the relationships between compositions, microstructure characteristics and mechanical properties. Secondly, a simple mechanical model is proposed to describe the repair properties of geopolymer on concrete cracks. After a series of adhesion tests with different layered angles, the adhesion properties and re-failure features of geopolymer-concrete interface are defined. In addition, the simulations of distinct element method are utilized to grasp the interface adhesion behavior of geopolymer after repairing concrete defects. Study results indicate that OH- (M) is the primary influential factor in geopolymer mechanical properties, and has an interaction with SiO2 (mol). As the OH- concentration increases, the geopolymer’s apparent cohesion and extent of polymerization also increased. Different proportions of OH- and SiO2 can form different Q4 (nAl) coordination structures, subsequently causing differences in mechanical properties. In addition, stress and extent of polymerizations had a significant effect on the geopolymer failure model. Under uniaxial compression conditions, geopolymer exhibited brittle fracture characteristics. As confining pressure increases it gradually changed to a slightly ductility characteristic. For repair adhesion, proposed mechanical models may consider the adhesion characteristics after repairing concrete defects with geopolymer. Plotting the stress damage envelope of layered specimens according to interface strength parameters can determine the damage model under different stress conditions. The experiments also showed that adding coal fly ash and granulated blast furnace slag to geopolymer lead to optimal interface adhesion strength. The normal stiffness of the adhesion interface and normal stress has an exponential relationship. Overall, the repair effectiveness can achieve above 95% regardless of confining pressure. For numerical simulation, the distinct element method can accurately simulate the mechanical behavior and damage pattern of specimens with different geopolymer, mortar substrate, and repair layer angles under uniaxial compression experiment conditions. The simulated results all conformed to the experiment value. This study used experimental design and statistical analysis. For geopolymer mechanical properties and numerical simulation, the proposed multiple regression equation achieved a model reliability of above 80%, which possesses reference value and significance.