钢筋增强ECC梁及ECC/混凝土复合梁的高温性能、损伤机理及火损后修复加固技术研究

ECC possess good ductility, control of micro crack, energy absorption capacity and durability, which greatly overcome the shortcomings (brittle and non-tensile) of traditional concrete material. Thus, ECC is regarded as a new building material researched and developed widely in the new century. However, the melting of polymer fibers in ECC at high temperature may lead to a significant decline in its mechanical properties, which will trigger concern for the safety of this new material. In this study, the mechanical properties at and after elevated temperatures and after realkalisation repairing, thermal behavior, microstructure of ECC, and bond-slip behavior between steel bars and ECC would be tested. And then static experimental research on mechanical of steel bars ECC beams under thermal-mechanical loading, after fire, after realkalisation repairing would be conducted, followed by the finite element analysis on these components. Based on the results from tests and finite element analysis, the development of mechanical properties, degradation mechanism at and after elevated temperatures and mechanism of realkalization repairing after fire damage of ECC material and components would be investigated. The bond-slip model between steel bars and ECC would be proposed. Finally, empirical formulas on duration of fire resistance of steel bars ECC beams, bending bearing capacity calculation method of steel bars ECC beams after 3-face heating and realkalization repairing would be established. The progress of this study would propel the development of ECC and its wider application in construction, and also provide the basis for design of ECC structure, thus this study will be of great theoretical significance and practical value.

ECC材料具有良好的延性、微裂缝控制特性、能量吸收能力和耐久性能，极大克服了传统混凝土材料脆性大、不抗拉的缺点，是新世纪广泛研究并发展的新型建材。但高温下ECC中聚合物纤维发生熔融，可能导致其力学性能大幅下降，引发人们对其安全性的担忧。本项目以此为研究目标，对ECC材料的高温及其经再碱化修复后力学性能、热工性能、微观结构和钢筋-ECC间粘结-滑移性能进行试验研究，开展钢筋-ECC梁热-力耦合作用下受火性能试验、高温后静载试验、火损经再碱化修复试验，及相关有限元模拟分析。基于实验研究和有限元分析结果，查明ECC材料和构件的高温损伤规律、损伤机理及其经再碱化修复机理，建立钢筋-ECC粘结-滑移模型，提出钢筋-ECC梁的耐火极限计算公式、三面受火后及其经再碱化修复加固后的受弯承载力计算方法。本项目的顺利开展将推动ECC材料更广泛的工程应用，为ECC结构设计提供参考，具有重要的理论意义和实用价值。

ECC材料重要组成部分的聚合物纤维耐火性能不佳、高温下易熔融，将导致ECC材料及其构件力学性能严重劣化。申请者通过采用工业和建筑固废、掺入高熔点玄武岩纤维等方法研发了新型绿色ECC材料：1）当陶粉掺量为50%时， ECC的导热系数降低了23.9% ~ 25.8%，比热容降低了23.6% ~ 26.4%；当陶粉掺量不变时，随着陶砂完全取代石英砂，ECC的导热系数降低了17.2% ~ 25.3%，比热容则降低了5.5% ~ 11.0%。2）当玄武岩纤维掺量为0.7% 时，随着作用温度在20 ~ 600 ℃范围内升高时，ECC的导热系数持续下降，其比热容呈现先增大后减小的趋势；600 ℃时，各配比ECC的导热系数仅为常温下的44.8% ~ 58.4%；600 ℃以上时，ECC导热系数的下降速度有所减缓。3）采用40 mm厚新研发的ECC加固的钢筋混凝土梁较砂浆加固钢筋混凝土梁的耐火极限延长了30 min，采用50 mm厚该ECC加固后混凝土梁的耐火极限延长了59 min。4）SFRCR-ECC容重为1410 kg/m3，仅为普通混凝土的56% 左右；SFRCR-ECC可无需任何粘合剂、以一定压力直接喷涂于防护构件表面，并在高温下保持良好的粘结性能而不发生剥离。 5）由于SFRCR-ECC具有优异的隔热性能，30 mm厚SFRCR-ECC防护下的CFST柱耐火极限超过210 min。通过本研究表明，与传统加固材料和防火涂料相比，因具有更高机械性能、粘结性能、可喷涂性和低导热性，新型ECC有望成为当前加固和钢结构防火领域中更经济、更耐久的选择，并具有广泛的应用前景。