【作者】 李涛；

【导师】 黄政宇；

【作者基本信息】 湖南大学 ， 土木工程， 2016， 硕士

【摘要】 本文采用模拟海水作为UHPC的拌合用水进行内掺氯离子的试验研究:一方面,研究了内掺氯离子在UHPC基体中的结合特性;另一方面,通过半电池电位法、宏电池法及钢筋锈蚀实际观测结果进行了对比分析,研究了UHPC中钢筋的锈蚀情况;同时通过混凝土的抗压试验研究了内掺氯离子的UHPC抗压强度,通过钢筋混凝土的电化学快速锈蚀试验研究了UHPC的抗裂性能、相对电阻等。具体结论如下:(1)从测试方法、养护条件、氯离子含量、掺合料品种等方面研究了采用模拟海水拌合的UHPC基体中氯离子的结合特性,结果表明:由于高温使UHPC基体中Friedel’s盐分解,试样干燥温度为100℃时的自由氯离子含量比50℃的高;早期高温湿养降低了最终UHPC基体中氯离子的结合;随着龄期的增长,氯离子的结合会逐渐增大,且氯离子的含量越高,氯离子的结合度也越大;在掺合料组成方面,硅灰的加入由于降低了C-S-H凝胶的钙硅比值及基体的PH值、稀释了铝酸三钙而降低UHPC基体中氯离子的结合;粉煤灰中较高含量的氧化铝促进了UHPC基体中氯离子的结合;偏高岭土富含的氧化铝与氯离子可以加速反应生成Friedel’s盐,从而促进UHPC基体中氯离子的结合。(2)混凝土水化基本完成后,内掺0%、1%、3%氯离子的UHPC中钢筋的半电位均在-100m V到-200m V之间,宏电流均小于10u A;而普通混凝土中钢筋的半电位在-300m V到-500m V之间,宏电流均大于10u A。参照美国的ASTMC876-91腐蚀评判标准、Hartt W.H和Nam.I的研究以及混凝土破型后取出钢筋的实际锈蚀情况,通过对250天龄期混凝土破型后取出钢筋发现,普通混凝土中的钢筋已经锈蚀,而UHPC中的钢筋没有锈蚀,说明在UHPC中仅有氯离子而没有氧气和水的存在,钢筋发生锈蚀的可能性很低;进一步说明,用半电池电位法,宏电池法判别混凝土中钢筋的锈蚀状况具有一定的可行性。(3)从养护条件、氯离子掺量两个方面研究了普通混凝土、高性能混凝土、超高性能混凝土的抗压强度差异,研究发现:UHPC的抗压强度是OPC、HPC的3到4倍;早期高温热水养护的UHPC28天抗压强度与标准养护的基本相同;标准养护时,内掺3%氯离子的UHPC抗压强度比不掺氯离子的要高;早期高温热水养护时,内掺3%氯离子的UHPC28天抗压强度比不掺氯离子的要低;由于氯离子具有早强作用,7天龄期时,内掺3%氯离子的普通混凝土、高性能混凝土抗压强度比不掺的高,但是28天龄期时结果刚好相反。(4)通过对OPC、HPC、UHPC三种混凝土通0.1A的电流进行电化学快速锈蚀试验,结果发现:混凝土开裂时,普通混凝土及高性能混凝土的开裂裂缝宽度比较均匀,破坏沿着保护层最薄处开裂,且裂缝发展速度较快,而UHPC的开裂破坏是一条曲折的曲线,裂缝宽度不均匀,且破坏随时间的增长而缓慢进行。更多还原

【Abstract】 In order to study the steel corrosion in UHPC, The paper use simulated seawater as mixing water of UHPC to research,On the one hand, the chloride bounding properties of UHPC matrix were studied. On the other hand, the corrosion of steel bar in UHPC is studied by using half cell potential method, macro current method and the actual observation,At the same time, through the compression test of concrete, the compressive strength of UHPC doped with chloride ion was studied, and the cracking resistance and relative resistance of UHPC were studied by electrochemical corrosion test of reinforced concrete.Specific conclusions are as follows:(1) It studied the binding property of chloride in ultra high performance concrete matrix which mixing with simulate seawater from test method, curing condition, chloride content, admixture composition. Th e result showed:High temperature decomposed the Friedel’s salt and final the free chloride content at 100 degree was higher than that at 50 in sample. Early high temperature humidity curing will reduce the final chloride binding. but with the increase of a ge, the chloride binding will increase gradually, and the more chloride is added, the greater the degree of chloride binding. For the composition of admixture, The addition of silica fume decreased the chloride binding in UHPC matrix by decreasing the calc ium silicon ratio of C-S-H gel and the p H value of the matrix, and dilution of three calcium. The higher alumina content in fly ash promotes the chloride binding in UHPC. For metakaolin, the chloride can accelerate the formation of Friedel’s salt which promotes the chloride binding in UHPC matrix.(2) After the hydration of concrete was completed, the half potential of the steel in UHPC with 0%, 1%,3% chloride ions are all between-100 m V to-200 m V, and the macro current is less than 10 u A, The half potent ial of the steel in ordinary concrete is between-300 m V and-500 m V, and the macro current is more than 10 u A.Referring to the United States ASTMC876-91 corrosion evaluation standards, Hartt W.H and Nam.I research and actual observation,Over 250 days of age, the steel in concrete was found:The steel in ordinary concrete has been corroded, but the steel in UHPC are not corroded,It shows that if there is not oxygen and water in UHPC, the possibility of corrosion in UHPC is very low. Further shows that using hal f cell potential method and macro cell method to detect the corrosion of steel in concrete has a certain feasibility.(3) The difference of compressive strength of ordinary concrete, high performance concrete and UHPC was studied from two aspects of curing condition and chloride content,The study found:The compressive strength of UHPC was 3 to 4 times of OPC, HPC. The compressive strength of UHPC 28-day in early high temperature hot water curing is same as the standard curing.When standard curing, The compressive strength of UHPC with 3% chlorine ion is higher than 0% chloride ions one.In early high temperature curing, the compressive strength of the UHPC doped with 3% chloride ion is lower than that of the UHPC without chloride ion.Because of the early strong effect of chloride ion, the ordinary concrete and high performance concrete with 3% chloride ions in the 7-day age were higher than that of 0% chloride ions, but the 28-day compressive strength was just the opposite.(4) Ordinary concrete and high performance concrete cracking is relatively uniform, destruction along the protective layer of the thinnest part of cracking,and the cracking develops rapidly, but cracking failure of UHPC is a tortuous curves, cracking is not uniform,And the damage is slow with the time passing.更多还原