【作者】 刘珩；

【导师】 许仲梓； 卢都友；

【作者基本信息】 南京工业大学 ， 材料学， 2003， 硕士

【摘要】 碱集料反应（AAR）作为导致耐久性下降的重要原因之一，半个世纪以来已在世界范围内造成了大量混凝土工程的破坏和巨大的经济损失。碱硅酸反应（ASR）作为最主要和最普遍的AAR类型，其预防措施的研究一直是混凝土耐久性研究的重要内容。大量研究表明，使用某些混合材（如粉煤灰、高炉矿渣和硅灰等）置换部分水泥，能够延缓或抑制ASR。目前混合材特别是粉煤灰在国内外被广泛使用，但国内外尚缺少使用混合材预防ASR的标准和科学有效地评价混合材抑制ASR效果的方法来指导混合材应用。评价混合材有效性的方法均是以快速检测集料ASR活性的方法为基础，比较掺加混合材后试体膨胀率的变化，并不能回答具体工程中实际配比的ASR安全性。混凝土棱柱体法采用的实验参数与实际工程最接近，以试体一年的膨胀率作为判据，被认为是评价集料碱活性最可靠的方法，但很多情况下不能满足工程需要。快速砂浆棒法采用了80℃1mol/LNaOH碱溶液养护，大大加快了反应的速度，缩短了评判的时间，而且大量实验结果表明在碱溶液养护条件下可以比较不同矿物外加剂抑制ASR的差别。本文选择工程中应用的并用多种集料碱活性鉴定方法鉴定为中低活性集料和潜在碱活性集料作为标准集料，结合混凝土棱柱体法和快砂浆棒法的优点，采用接近混凝土实际配比的小混凝土快速方法研究了粉煤灰在不同条件下抑制集料ASR膨胀的规律性，以期为建立快速可靠地评价粉煤灰及其它混合材抑制实际工程混凝土ASR安全性的新方法提供依据。主要研究内容和结论如下：1. 集料碱活性综合判定及检测方法间的相关性。通过采用岩相法、压蒸法、快速砂浆棒法和中国快速小砂浆棒法四种集料碱活性检测方法对六合砾石、武进和浙江砂岩等五种集料的碱活性进行了综合判定及对试体的SEM/EDS分析，确定六合砾石为中等活性集料，武进和浙江砂岩为低活性及潜在碱活性集料。压蒸法和中国快速小砂浆棒法都采用单级配细集料和多胶砂比参数，检测结果具有较好的相关性。碱含量对ASR膨胀及粉煤灰抑制ASR效果的影响。研究了不同碱含量水平的六合砾石ASR膨胀行为及粉煤灰对六合砾石ASR抑制效果。发现当混凝土碱<WP=4>2. 含量在5.5Kg/m3时，六合砾石ASR膨胀明显增加，综合考虑国际上的研究经验及加快反应速度，新方法中确定混凝土的碱含量为6.6 Kg/m3（水泥碱含量为1.5%）。3. 集料种类与抑制效果。研究了粉煤灰对活性不同的六合砾石、武进砂岩和佛堂砂岩ASR膨胀抑制效果的影响，明确了粉煤灰抑制ASR效果与集料种类有关，集料活性不同，其安全使用所需要的最小粉煤灰掺量不同。4. 养护方式与粉煤灰抑制ASR效果。在80℃1mol/LNaOH和40℃湿气两种养护条件下对比研究了粉煤灰抑制ASR膨胀规律，通过对快速强化条件下的实验结果与长期温和条件下实验结果的统计分析，发现若以快速条件下28天的膨胀率0.04%作为判据与长期条件下3个月的膨胀率0.04%或是6个月的膨胀率0.06%作为判据，两者之间具有较好的相关性。最终的龄期和判据还需要在实践中通过对大量的集料进行反复的验证并加以完善。5. 粉煤灰抑制ASR膨胀机理。采用SEM/EDS研究了掺加0、15%、25%、50%粉煤灰的六合砾石试体的ASR特征，发现掺加粉煤灰，甚至大量粉煤灰后，集料仍发生了反应，但和不掺粉煤灰的试体相比，产物的形貌和成分发生了变化。指出粉煤灰对ASR的抑制除了是对混凝土中碱和Ca(OH)2的作用外，对产物结构的改善也是粉煤灰抑制ASR的一个重要方面。6. 在初步系统研究基础上，提出了粉煤灰抑制实际工程混凝土ASR有效性评估方法草案。更多还原

【Abstract】 Alkali aggregate reaction (AAR) is one of the important factors to affect the durability of concrete structures. It has caused deterioration/damage of concrete structures and large money consumption around the world in past decades. Alkali-silica reaction (ASR) is the important and universal type of AAR . It has always been a hot topic in area of AAR study to avoid ASR expansion. Much work shows that replacing part of cement with some type of SCMS, such as fly ash (PFA), slag and silica fume etc., not only can delay or suppress ASR, but also has important meanings on saving resources and protecting environment. SCMS especially PFA are now widely used internal and abroad. However, there is no reliable method for assessing the effectiveness of PFA and other SCMS in suppressing ASR expansion. Based on testing aggregate reactivity, the method of assessing the effectiveness of PFA compares the sample expansion before and after the PFA added. It cannot solve the problem whether in some construction project have danger of ASR and how design the concrete to ensure the security of the project. By adopting similar parameter with field concrete, Concrete Prism method (ASTM C1293) was considered as the most reliable method to evaluate the potential reactivity of aggregates. However, the period of testing is too long to meet project requirement in many conditions. By storing the mortar-bar in 1mol/L NaOH solution at 80℃, Accelerating Mortar-Bar method(ASTM C1260) was considered as the more quick method to evaluate the potential reactivity of aggregates. In order to develop reliable and rapid method for assessing the effectiveness of PFA in suppressing ASR expansion, we combine the advantages of two methods and select moderate and potential reactivity aggregates which were appraised with several testing methods and largely used in real project as standard aggregate. A lot of work has been done and the main results are summarized as follows. i ) Identification of alkali reactivity of aggregate and correlation of methods.<WP=6>The alkali reactivity of siliceous gravel, Wujing(WJ) sandstone and Zhejiang(ZHJ) sandstones etc. were examined by Petrographic, Chinese Autoclaving Method, Chinese accelerating Mortar-Bar Method and Accelerating Mortar-Bar Method. It was found that siliceous gravel was moderate reactivity, where WJ sandstone was low reactivity, ZHJ sandstone was potential reactivity. It was also found that these testing methods had correlation each other. Chinese Autoclaving Method and Chinese accelerating Mortar-Bar had good relation for they using the similar parameters, such as single graded fine aggregate and various cement-aggregate ratio. ii) Effect of alkali level of concrete on ASR expansion and the suppressing effect of PFA. ASR expansion behavior and the suppressing effect of PFA on ASR expansion of siliceous gravel at different alkali levels is studied. Results show that ASR expansion of gravel increased greatly when concrete alkali is 5.5Kg/m3. Considered reaction rate and international experiences in ASR studying, it is suitable to select 6.6Kg/m3 as assessing method’s alkalinity. iii) Suppressing effect and the type of reactive aggregate. It has been studied that the effect of PFA on suppressing the expansion of concrete prisms with siliceous gravel, WJ sandstone and ZHJ sandstone. Results show that the suppressing effect of PFA on ASR expansion is closely related with the type of reactive aggregate, difference in the alkali reactivity of aggregate lead to differences of the minimum amount of PFA needed to control expansion. iv) Storage environment and the suppressing effect of PFA. The suppressing effect of PFA on ASR expansion in 1mol/L NaOH solution at 80℃and moist at 40℃ were respectively studied. It was found that these data had good relationship between expansion value of 0.04% at 28 days in 1mol/L NaOH solution at 80℃ and expansion value of 0.04% at 3 months in moist at 40℃ or 0.06% at 6 months. However, the final testing period and expansion value sh更多还原