【作者】 刘竞；

【导师】 邓德华；

【作者基本信息】 中南大学 ， 材料学， 2008， 硕士

【摘要】 国内外对既有海洋工程的大量调查得出:海洋环境中的Cl^-通过混凝土保护层渗入到结构内部引起钢筋腐蚀是导致构筑物过早破坏（20～30年）的最主要原因。通过综合分析认为,一定厚度的、低渗透性的混凝土保护层是延长海洋环境中混凝土构筑物服役寿命的关键。为此,本文基于铁道部科技司“东南沿海铁路混凝土结构耐久性设计参数与技术措施的研究”课题的要求,围绕混凝土保护层的抗渗与抗裂性能,从材料和施工的角度,进行了高抗渗抗裂混凝土及其影响因素和高耐久壳坚隔联保护层构造的研究,取得了如下成果:1.研究了湿棉絮覆盖、喷养护剂、塑料薄膜密封等三种养护方法对混凝土强度、收缩、中心温升和抗渗性的影响,并通过强度、氯离子渗透深度、钢筋腐蚀电位、加速腐蚀下保护层开裂时间的测试,研究了养护时间对未掺和掺矿渣（等量取代水泥40%）混凝土的强度、抗渗性和护筋性的影响。结果表明:湿棉絮覆盖养护的混凝土强度发展最快,收缩最小,氯离子渗透性最低,中心温度最低;塑料薄膜养护的混凝土的中心温度最高,其较好的保温作用有利于寒冷工况下混凝土的保温养护;喷养护剂养护的混凝土强度最低,收缩发展较早较快,抗滲性最差。养护时间越长,混凝土的抗渗性越高,尤其对于掺矿物掺和料的混凝土,因而,为提高混凝土抗渗性,应采取更长的养护。2.研究了木胶合模板（W）、竹胶合模板（B）、钢模板（S）、塑料模板（P）与透水模板（CP）对混凝土性能的影响,结果表明:由CP成型的混凝土表层最密实,外观平整度好,表面强度和抗渗性最高。由W、B、S、P成型混凝土的表面强度和抗渗性基本相同。分析认为CP对表层混凝土性能的改善主要源于其渗水、透气和初期保水养护作用。3.深度渗透密封剂（DPS）喷涂混凝土表面,能有效提高表层混凝土的强度和抗滲性。其合理喷涂剂量为200g/m²～300g/m²,最佳喷涂龄期为混凝土浇筑后的7d～14d,混凝土饱和面干时喷涂的效果稍好。4.通过抗压强度、Cl^-滲透、平板抗裂、冻融循环、护筋性试验以及SEM微观分析,发现单掺聚丙烯（PE）纤维能有效抑制早期塑性开裂和改善匀质性,但因PE引入的结合较弱、微结构疏松的纤维与基体间界面（FMIZ）,对混凝土的抗滲性有一定影响;在掺入PE纤维的同时再掺入硅灰,可显著提高混凝土的强度和抗渗性,其机理是硅灰明显改善了基体和FMIZ微结构的密实性,弥补了单掺PE纤维对抗渗性的不利影响,是改善混凝土抗裂抗渗性的有效措施,因此,将PE纤维增强硅灰高性能混凝土用于海洋环境中受破坏最严重的浪溅与水位变动区,通过对薄弱环节的增强来延长构筑物的服役寿命。5.在上述研究的基础上,提出了采用高耐久壳坚隔联保护层构造（HighDurable Separating-Coupling Cover Structure,简称SCCS）提高混凝土结构耐久性的构想;并从耐久性、强度、体积稳定性、变形协调性、工作性和多功能性等方面出发,建立了SCCS的设计准则;发明了混凝土结构具有高抗裂与低渗透的高耐久壳坚隔联保护层的施工方法,其要点有:采用自密实PE纤维增强硅灰高性能混凝土（SPSM）浇注保护层;构件的主钢筋以内采用普通混凝土浇注;采用隔联网分离实现同一构件中两种不同混凝土的一次性浇筑施工;采用传力杆有效解决由于隔联网引起的不同混凝土界面粘结问题。模拟试验证明具有SCCS的钢筋混凝土试件的力学和护筋性能显著提高,是大幅度延长在海洋环境中钢筋混凝土构筑物服役寿命的经济有效的技术措施。6.得出了28d抗压强度≥55MPa、90d的Cl离子扩散系数≤1.0×10^-12m²/s、抗裂等级为Ⅰ级、90d的收缩应变值≤400ε的自密实PE纤维增强硅灰高性能混凝土的组成配比和配制技术。更多还原

【Abstract】 The durability survey of buildings in the marine environment at home and abroad indicates: many concrete structures appeared premature destruction and deterioration in 20 to 30 years after being built, far from reaching the designed service life and had to be rehabilitated costly. The main reason for premature deterioration is steel corrosion caused by chloride. To prolong the service life of buildings in marine effectively and economically, the pivotal approach is to improve the performance of cover concrete. The research of this paper comes from the project of "The parameters and construction techniques research on the concrete structure durability design in the Southeast coastal railway" supported by the Ministry of Railway. In order to improve the impermeable and cracking resistance performance of the cover concrete, The high performance concrete with high impermeable and cracking resistance and its factors and the new high durable firm shelling Separating—Coupling Cover Structure （SCCS） which will provide the more credible and effective protection for the internal reinforcement bars are studied by adopting both new materials and construction techniques. The main work and achievements of this paper are as follows:1. Three curing methods are used for concrete curing which are wet cotton mats, a curing agent and plastic film. The strength, shrinkage, central temperature and chloride permeability under various curing methods have been studied. The effect of wet curing duration on the strength, impermeability and corrosion resistance for protecting internal reinforcement of plain and slag-cement concrete （in which 40 % cement was replaced by blast furnace slag） are studied by experiments including strength, permeability, half-cell potential and concrete cover cracking time in the accelerated corrosion test. The results show the strength and chloride impermeability of concrete cured with cotton mats is the highest, while concrete cured with curing agent shows the lowest strength and chloride impermeability. Concrete cured with curing agent starts shrinking earlier and more quickly than the others, while the early shrinkage and its developing speed for concrete cured with wet cotton mats is the lowest. For the central temperature, concrete cured with plastic film is the highest, and then that cured with curing agent. Concrete cured with wet cotton mats shows the lowest. Plastic film shows the best effect for heat preservation, which may be very useful for concrete cast in a cold environment. Longer wet curing duration is essential to achieve higher strength, durability and corrosion resistance characteristics especially for slag-cement concrete. The plain cement concrete is relatively more tolerant to inadequate curing. The 14 days wet curing or more is necessarily especially when constructions in the deleterious environment.2. The influences of different formwork materials including Wood （W）, Bamboo （B）, Steel （S）, Plastic （P） and Controlled Permeability Cloth （CP） on the performance of the cover concrete are studied. The results show the cover concrete molded by CP is the densest and without any cracks on the surface. The strength and permeability of cover concrete molded by W, B, S and P are similar; however, those of cover concrete molded by PC are significantly improved. This improvement is mainly due to water seeping, air passing and wet curing action of CP on the fresh concrete.3. The Deep Penetrating Sealer （DPS） can increase the strength and impermeability of cover concrete effectively. The advisable spraying dosage range of DPS is 200 g/m²～300 g/m². The advisable schedule to spray DPS is during the 7～14 days after the concrete casting. If the cover concrete is in the surface dry saturated condition when spraying DPS, the effect will be better.4. The tidal zone of marine constructions used to be destroyed firstly. Polypropylene fibers （PPF） reinforced Silica Fume （SF）—high performance concrete is used to place the zone tentatively. The results show the addition of both PPF and SF significantly increase the concrete chloride resistance. The incorporation of fibers improves the performance of cracking resistance at the early age significantly, reduces the adverse influence of improper placement or consolidation and materials sedimentation on the homogeneity of concrete, however, just incorporating PPF has no obvious improvement on strength and impermeability and induce more porous fiber-matrix interfacial zone （FMIZ） by PPF which is detrimental to the chloride resistance, but the microstructures of both the matrix and the FMIZ in the concrete with PPF and SF are denser. Thus it is concluded that the significant increase of the chloride resistance of fly ash concrete due to the simultaneous addition of PPF and SF results from both the anti-cracking effect of PPF and the formation of denser microstructures of both the matrix and FMIZ by the high reactivity of silica fume.5. The new high durable firm shelling Separating—Coupling Cover Structure （SCCS）and its construction method have been designed based on the above reaearch. The materials of cover and the internal are dissimilated through the subtle Separating—Coupling steel meshwork. The concrete cover has been cast by Self—Compacting Polypropylene Fiber Reinforced Silica Fume High Performance Cement—based Materials （SPSM）.The upper and lower layers of the construction can place SPSM directly; the Separating—Coupling steel meshwork is used to separate the flowing concrete when the lateral cover and internal are placed by SPSM and ordinary cement concrete at the same time, respectively. The loading transferred reinforcement bar can solve the problem of the lower interfacial bonding strength caused the Separating—Coupling steel meshwork more than sufficiently. The simulative tests show the mechanical and steel bar protection performance of SCCS is better. The SCCS can improve the performance of the cover concrete and prolong the service life of the constructions significantly more effectively and economically.6. The mixing proportations and technique of SPSM have been studied. The main performance index of SPSM: self—compacting, the compressive strength of 28th day is more than 55 MPa, the chloride diffusion coefficient of 90th day is less than 1.0×10^-12m²/s, the grade of anti-cracking is the first level and the shrinkage value of 90th day is less than 400s.更多还原