High-temperature protective hybrid impregnation and coating for carbon reinforcement in concrete structures

碳纤维增强混凝土是一种具有很大应用潜力的新型建筑材料，但由于材料耐高温性能差，在加固和新建建筑结构中的应用受到限制。混凝土剥落、聚合物软化和降解以及碳纤维的氧化可能在高温下发生，并导致复合材料的机械性能（如强度）劣化。还需要对高温下的材料行为进行进一步研究，以生成广泛和可靠的数据库。不幸的是，迄今为止已知的材料特性测试方法是不一致的，复杂的，几乎不适合高温实验。因此，标准化的测试程序的发展是一个研究aim.To防止过早失效的碳钢筋混凝土结构暴露在高温下，我们建议修改已知的和合适的细粒度的高强度混凝土混合物通过添加PP纤维。此外，碳纤维束将被温度稳定的混合颗粒浸渍饱和。其次，将施加基于高岭石混合颗粒的保护涂层。片状高岭石颗粒，每个化学功能化与阻燃剂，膨胀和炭化聚合物的组合，通过接枝程序，组装成一个堆叠片周围的纤维束，而粘合剂确保的吸引力浸渍和混凝土基质。在高温或火灾的情况下，所得到的致密和稳定的炭，由片状纳米粘土颗粒增强，具有优异的界面屏障，在一个方向上对氧气和在另一个方向上对挥发性燃烧产物。此外，它形成热屏蔽屏障。因此，它减缓了聚合物软化并防止其降解。阻燃剂部分可以抑制现有的火焰，防止易燃聚合物材料自燃，而膨胀成分仅补偿粘土在相变过程中的质量损失。新开发的浸渍和涂层将应用于纤维束，并通过开发的测试装置进行拉伸和粘合测试，以测试其耐高温性能（包括试样几何形状、载荷引入、测量系统、加热方法）。该项目将提供以下方面的基本知识：（1）高岭土涂层对混合二氧化硅颗粒浸渍碳纤维束的影响，作为高温下防止分解的保护层;（2）在室温和高温下检查嵌入混凝土中的此类纤维束的机械性能，以及（3）与减少剥落的碳纤维束组合的混凝土成分的建议。最后，改进的测试装置预计可用于确定高温荷载下碳钢筋混凝土的基本力学性能（4）。

Carbon reinforced concrete is an innovative construction material with high potential for future application, but the use for strengthening and new building structures is limited due to material’s poor high temperature resistance. Concrete spalling, polymer softening and degradation as well as oxidation of the carbon fibre can occur at high temperatures and lead to deterioration of the composite’s mechanical properties like the strength. Still further research on the material behaviour under high temperatures is needed to generate an extensive and reliable database. Unfortunately test methods for material characterisation known so far are inconsistent, elaborate and barely suitable for high temperature experiments. Hence, development of standardized test procedures is a research aim.To prevent premature failure of carbon reinforced concrete structures exposed to high temperatures we propose to modify known and suitable fine grained high strength concrete mixtures by addition of PP fibres. Furthermore, carbon fibre strands will be saturated with a temperature stable, hybrid particle based impregnation. Second, a protective coating based on kaolinite hybrid particles will be applied. The platelet-like kaolinite particles, each chemically functionalised with a combination of flame retardant, intumescent and charring polymers by grafting procedures, assemble into a stacked sheet all around the fibre strand, while adhesives assure the attraction to both impregnation and concrete matrix. In case of high temperatures or fire, the resulting dense and stable char, reinforced by platelet-like nanoclay particles, features an excellent interface barrier for oxygen in one direction and for volatile combustion products on the other way. Furthermore it forms a heat shielding barrier. Thereby, it decelerates the polymer softening and prevents its degradation. The flame retardant moiety smothers the existing flame and prevents spontaneous combustion of flammable polymeric material, while the intumescent component merely compensates for the mass loss of the clay during phase transition.The newly developed impregnation and coating will be applied on fibre strands and examined in tensile and bond tests regarding its high temperature resistance via the developed test setups (including specimen geometry, load introduction, measuring system, heating method). The project will provide a fundamental knowledge on (1) effect of kaolinite coatings on hybrid silica particle impregnated carbon fibre strands as a protective layer against decomposition at high temperatures; (2) mechanical properties of such fibre strands embedded in concrete examined at room and under high temperatures, and (3) recommendations for the composition of concrete in combination with carbon fibre strands with reduced spalling. Finally, improved test setups are expected to be available for determining the basic mechanical properties of carbon reinforced concrete under high temperature load (4).