【作者】 高英力；

【导师】 周士琼；

【作者基本信息】 中南大学 ， 道路与铁道工程， 2005， 博士

【摘要】 超细粉煤灰(Ultra-fine Fly Ash,简称UFA)因其优良的性能已被广泛应用于土木工程领域,用以配制UFA高性能混凝土,在高层建筑、桥梁、公路、水工、港工等重要的建筑物以及大型的基础设施建设中,已发挥出越来越大的作用。 本文以UFA等量取代水泥,配制了用于路面的高性能公路水泥混凝土,并通过系统的试验对UFA高性能公路水泥基材料及所配制的混凝土早期收缩变形和抗裂性能进行了综合研究。其中包括水泥浆体的早期化学收缩变形以及UFA公路混凝土早期的自收缩变形、塑性收缩变形、温度收缩变形以及各龄期的干燥收缩变形等。在收缩变形试验研究的基础上,引入有限元理论分析了UFA高性能公路混凝土早期的收缩应力及温度应力;并尝试研发了UFA-FG减缩抗裂专用掺合料,应用于公路混凝土的配制。另外,还引入模糊数学的理论建立了针对UFA高性能公路混凝土早期抗裂性能的模糊综合评判系统,并应用于实际工程的抗裂性能评价。最后,将UFA应用于现场的路面施工,跟踪观测了UFA高性能公路混凝土的早期及长期抗裂性能,并总结了相关的施工技术要点。 以下是本文取得的主要研究成果: 1.对UFA粉体作用效应的研究表明,UFA球形颗粒在水泥基材料体系中具有优良的密实填充和减水增强效应,其填充结构相比于纯水泥颗粒更接近于Horsfield最密填充;而减水增强效应使得UFA水泥浆体在获得相同流动度情况下,比基准水泥胶砂减水10～15%,28天强度高于基准胶砂。 2.自行设计并改进了水泥浆体化学收缩测定装置,首次系统测试了UFA水泥浆体的早期化学收缩变形。结果表明,UFA可有效抑制水泥反应体系的化学收缩变形,其收缩随UFA掺量增加而减小。并通过试验与理论计算相结合,探讨了UFA水泥浆体体系的减缩机理和收缩模型,为UFA的减缩效应提供了相应的理论依据。 3.引入电感调频式微位移传感器自行改进设计了自收缩测试装置,测试了UFA高性能公路混凝土试件硬化早期(7天以前)的自收缩。结果表明,UFA可抑制混凝土的自收缩变形;同时通过水泥石结构孔隙水的计算比较了UFA水泥浆体和基准水泥浆体早期的内部自干燥程度。结果表明UFA的掺入降低了水泥石内部的自干燥,更多还原

【Abstract】 Untral-fine Fly Ash (UFA) has been used in civil engineering field because of its good performance and UFA high-performance concrete has been produced, which displayed tremendous role in some important structures and big basic buildings such as high-rise building, bridge, highway, hydro-structure and harbor work, etc.In this paper, high-performance concrete used for pavement was produced with UFA replaced equivalent cement. According to the data analysis in a series of experimental studies, the early shrinkage and cracking resistance of UFA high-performance highway cement-base materials and concrete were studied synthetically. The research contents include that the early chemical shrinkage of cement paste, the early autogenous shrinkage of UFA highway concrete, the early plastic shrinkage, the early thermal shrinkage and all age dry-shrinkage.On the basis of the shrinkage experiment, the early shrinkage and thermal stress of UFA high-performance concrete were analyzed by introducing the finite-element theory, and the UFA-FG special admixture using in shrinkage reducing and crack resisting, which was applied to the production of highway concrete, was attempted and developed. Moreover, the fuzzy comprehensive evaluation system about the early cracking resistance of UFA high-performance highway concrete was developed by making use of the fuzzy mathematics theory. In the end, UFA was used in the field pavement construction and UFA highway concrete was produced. The early and long-term cracking resistance of UFA high-performance highway concrete was tracking observed. Meanwhile, the correspondent construction technical requirements were generalized.The following are the main achievements in this paper:1. The research results of UFA powder technology effects proved that UFA spherical shape particle has good effects of dense packing, water reducing and strength increasing in cementitious materials, and the packing structure of UFA+cement particle is closer to "Horsfield packing" than that of the pure cement particle. Meanwhile, under thecondition of obtaining the same flow, UFA mortar can reduce 10—15% of water demand, and 28-days strength is higher than the reference cement mortar.2.The early chemical shrinkage of UFA cement paste is first tested systematically by experimental device of chemical shrinkage, which was designed and improved by the author. The results indicate that UFA can reduce the chemical shrinkage of cement hydration. The more UFA added, the less chemical shrinkage will be. On the other hand, the reducing-shrinkage mechanism and the shrinkage model of UFA cement paste were analyzed and researched. It supplied the correspondent theoretical supports for UFA’S reducing-shrinkage effect.3. The autogenous shrinkage test device was improved by introducing the inductance frequency-modulation type micro-displacement transducer, and the early autogenous shrinkage (before 7-days) of UFA high-performance highway concrete is tested with the improved test device. The results indicate that UFA can reduce the autogenous shrinkage of concrete. Meanwhile, the early internal autogenous desiccation degrees of the UFA cement paste and reference cement paste were compared according to the pore water calculating of hardened cement paste. It can be seen that the addition of UFA reduce the internal autogenous desiccation degree of hardened cement paste, which proved that UFA can reduce the autogenous shrinkage of concrete.4. The early plastic shrinkage, thermal shrinkage and dry-shrinkage of UFA high-performance concrete were tested systematically. It can been seen that the addition of UFA reduce the early plastic shrinkage and thermal shrinkage. UFA can depress dry-shrinkage effectively when the content of UFA is less than 40% of binding materials, but the dry-shrinkage increases with the growth of UFA content when the content of UFA is more than 40% of binding materials. On the basis of the dry-shrinkage test, the mutual relation of autogenous shrinkage and dry-shrinkage was studied, and the relation was compared systematically under the condition of fix and variable water-binding material ratio. At last, the total shrinkage prediction empirical model of UFA highway concrete was developed, and the playback of shrinkage test proved thatthe predictive value and empirical value is anastomotic well.5. The early shrinkage and thermal stress of UFA highway concrete desk were calculated with Ansys software by introducing the finite element theory, and two kinds of stress were coupled. The results proved further that the addition of UFA enhances the early ability of concrete against cracking compared to the reference concrete.6. Regarded UFA as the main body material and Fluoro Gypsum (FG) as the modifying material, UFA-FG special admixture using in shrinkage reducing and crack resisting was researched and developed according to the orthogonal test. The early shrinkage of concrete was reduced effectively and the cracking resistance of concrete was improved by making use of the shrinkage-compensated effect of UFA-FG.7. The fuzzy comprehensive evaluation system, which was developed by the fuzzy mathematics theory, can appraise the early cracking resistance of UFA high-performance highway concrete effectively. The system removes the "exclusive" evaluating of the ordinary evaluation methodology, which make the evaluation outcome more scientific. Moreover, it was used in the cracking resistance evaluating of the actual pavement project, and the evaluation outcome showed that the early cracking resistance of pavement is "excellent", which agreed to the practical observed outcome.8. UFA high-performance highway concrete was used in the field test pavement project successfully, which belongs to the 18th contract section of ChangNing interconnection, "HengZao" highway. And the construction technical requirements and quality monitoring technique used in the pavement construction process were generalized. From the actual project application it can be seen that the mechanical performance of UFA high-performance highway concrete meets the design requirement, the fractural strength of highway concrete, which is produced in the winter (<5°C), meets the requirement of 7-day opening traffic. The concrete’s workability is well, and the quality is stable. Moreover, the early cracking resistance of highway concrete is good, so the flaw can’t be discovered. Meanwhile the long-term performance is well. All in all, we can draw a conclusion that it is less in China that thelarge volume UFA which is used in the pavement project achieves success.9. The cost of concrete can be reduced effectively when UFA is added into concrete, In fact, the cost is cut down about 12.7% compared to the ordinary concrete pavement. Meanwhile, the addition of UFA can utilize waste materials, save energy, thus the environment benefits are obvious.更多还原