| Concrete is the most widely used in construction industry because of its excellent properties, such as convenience, low cost, high strength, durability, and easy to make. Concrete plays an irreplaceable role in construction. However, during the process of production and service, concrete might have become loose, peeling, and have cracks in it. If the defect couldn’t be repaired, concrete would become degradation quickly with water and corrosive medium penetrating into it. Concrete structure might lose efficacy due to its defect, and this not only brought huge economic losses to the country, but also a serious threat to people’s safety,In recent years, many experts research on the fixing the concrete structure to find out new materials and new process. Among them, polymer modified cementitious material received more attention because of its good flexural and folding performance, strong cohesive force and lower economic. However, polymer will hinder the cement hydration, and will affect the compressive strength of cementitious materials. In this research, nano-material which can promote cement early hydration will be added into polymer modified cementitious material, curing at either standard temperature,20℃or the average temperature in Hangzhou winter,6℃. The effects of nano-SiO2on the properties and microstructure of polymer modified cementious materials.This research mainly divided into three stages. First, the effects of nano-SiO2on macro-properties would be studied by testing the flow properties and mechanical properties. Secondly, the effect of nano-SiO2on microstructure would be studied by several micro tests, and the mechanism would be analyzed. Last, the effects of concrete beam repaired with nano-SiO2modified PMC would be evaluated.The data presented in this study showed that:1. The effect of EVA polymer on the properties of cementious materials. In the early age, EVA inhibited cement hydration, which leaded to less hydration products. So the compressive and flexural strength of cementious significantly declined. In the middle and later periods, when the humidity in cementious reduced, EVA could prevent water from inside, that could promote hydration. Therefore, the ratio of strength increasing improved. As the same time, the polymer film gradually formed, which could let the flexural strength of mortar significantly improved.Curing at6℃, low temperature affect the hydrolysis and filming of polymer. So the flexural strength of polymer modified mortar couldn’t be improved curing at low temperature.2. The effect of nano-SiO2on the properties of polymer modified cementious materials. In the early days, nano-SiO2can enhance the cement early hydration rate, improve the arrangement of Ca(OH)2and pore structure, which could significantly increase the strength. In the middle and later periods, the effect of nano-SiO2was becoming weaker, so strength was close to the one without nano-SiO2. Curing at6℃, nano-SiO2improved the degree of hydration and the arrangement of Ca(OH)2, and was good for the hydrolysis and filming of polymer, so the addition of nano-material improved strength and microstructure observably.3. The synergistic effect nano-SiO2and EVA polymer could improve the technical properties of the repaired reinforced concrete beam. EVA can enhance the bending crack resistance of concrete beam, and improve the bearing capacity a little. Nano-SiO2adding simultaneously with polymer can improve the bending crack resistance, the bearing capacity, and cohesive force of the combination, which reflected good repair effect... |
PDF Full Text Request