高碱含量水泥净浆的显微结构特征及碳化速率  

Carbonation Rate and Microstructural Characteristics of Hardened Cement Paste with High Alkali Content

作　　者：柳俊哲[1] 孙武[1] 陈剑斌[1] 巴明芳[1] 贺智敏[1] 袁伟静[1] 

机构地区：[1]宁波大学建筑工程与环境学院,浙江宁波315211

出　　处：《硅酸盐学报》2014年第8期1005-1010,共6页Journal of The Chinese Ceramic Society

基　　金：国家自然科学基金(51078189;51278255);宁波市重大科技计划项目(2013C51006)资助

摘　　要：将硬化后的水泥净浆分别浸泡在NaOH饱和溶液和水中,干燥后测定孔结构参数和碳化速率,评价孔结构特征相近时高碱含量对水泥净浆碳化速率的影响。结果表明:水灰比为0.3、0.4及0.5时,硬化水泥净浆孔结构特征相近时,碱含量越高,碳化速率越慢;NaOH溶液浸泡后的水泥净浆,孔结构和密实度均与同条件水中浸泡过的水泥净浆相近,水泥净浆内尚未出现氢氧化钠碳化后可能出现的碳酸钠晶体,未对水泥石孔结构产生影响。碳化由表向里进行过程中,水泥净浆的碳化区易出现微裂缝并延伸到试件内部,致使水泥净浆的各部位碳化深度不均匀,说明使用酚酞溶液的呈色反应评价水泥混凝土的碳化程度时应结合X射线电子计算机断层扫描和X射线衍射技术。明确了碳化不仅可以降低混凝土的pH值,而且由于碳化区易于出现裂缝使钢筋表面暴露于空气中,增加了钢筋腐蚀的概率。Pore structure parameters and carbonation rate of hardened cement paste soaked by saturated solution of sodium hy- droxide and water were investigated, respectively. The impact of high alkali content on the carbonation rate of hardened cement paste with the similar pore structure characteristics. The results show that the pore structures and density of hardened cement paste soaked under the above two conditions were similar. Sodium hydroxide in hardened cement paste soaked in saturated solu- tion is not carbonated yet, and cloes not affect the pore structure of cement stone. The higher alkali contents, the slower car- bonation rate for the cement stone soaked under the two conditions at various water to cement ratios of 0. 3, 0. 4 and 0. 5. The pore structures are similar before carbonation. The cracks in carbonation district are easily generated during carbonation pro- gress from outside to inside of cement stone, leading to the uneven carbonation depth. It is thus more rational to evaluate the carbonation rate by the Phenolphthalein colorimetric method and X-ray diffraction analysis and X-ray computed tomography a- nalysis. It is identified that the carbonation reduces the pH value of concrete, and the presence of the cracks in the carbonation zone to expose steel to air in order to improve the probability of steel corrosion in concrete.

关 键 词：硬化水泥净浆 碳化 高碱含量 孔结构 X射线电子计算机断层扫描 

分 类 号：TQ172[化学工程—水泥工业]