水胶比和粗骨料体积分数对混凝土内部相对湿度及扩散系数的影响  

Effects of Water-Binder Ratio and Coarse Aggregate Volume Fraction on Internal Relative Humidity and Moisture Diffusion Coefficient of Concrete

作　　者：韩宇栋[1,2] 张君[1,2] 罗孙一鸣[1,2] 

机构地区：[1]清华大学土木工程系,北京100084 [2]清华大学土木工程安全与耐久教育部重点实验室,北京100084

出　　处：《建筑材料学报》2014年第2期193-200,245,共9页Journal of Building Materials

基　　金：国家自然科学基金资助项目(51178248);国家重点基础研究发展计划(973计划)项目(2009CB623200);高等学校博士学科点专项科研基金资助项目(20130002110034)

摘　　要：为研究水胶比（质量比）和粗骨料体积分数对早龄期混凝土内部相对湿度和等效水分扩散系数的影响，测量了水胶比为0．62，0．43，0．30（分别标记为C3，C5和C8）的混凝土早龄期28d内部相对湿度的发展，进而求解了其水分扩散系数．结果表明：随着水胶比的增大，早龄期混凝土内部相对湿度饱和期的持续时间延长，自干燥引起的内部相对湿度下降减小，水分扩散引起的内部相对湿度下降增大，混凝土水分扩散系数也增大；自干燥单独作用下，C3，C5和C8混凝土密封试件28d内部相对湿度平均值分别为95．4％，93．3％和79．6％，而当自干燥和环境干燥共同作用时，其干燥试件对应值分别为70．0％，73．2％和73．0％；C3系列普通混凝土的水分扩散系数最大值Dmax约为C8系列高强混凝土的10倍．另外，早龄期混凝土中水分扩散过程主要由砂浆相控制，水分很可能绕开粗骨料进行扩散；单调增加石灰石粗骨料的体积分数（2．1％～50．0％）对同水胶比混凝土的旱龄期内部相对湿度发展和水分扩散系数的影响可以忽略．To investigate the effects of water-binder ratio and coarse aggregate volume fraction on internal relative humidity（IRH） and moisture diffusion coefficient of concrete, development of IRH of a series of three concretes with water-binder ratio of 0. 62, 0. 43 and 0. 30 respectively, labeled as C3, C5 and C8 ac- cordingly, was measured during early ages, and the moisture diffusion coefficient was obtained as well. The results show that with increased water-binder ratio, the duration of early-age moisture-saturated stage be- comes longer, self-desiccation-induced reduction of IRH decreases, moisture diffusion-induced reduction of IRH increases, and the moisture diffusion coefficient becomes larger. Due to self-desiccation only, the av- erage IRH of sealed specimens of series concrete C3, C5 and C8 at 28 days are 95.4%, 93.3%and 79.6% respectively, while the corresponding IRH of the dried specimens under the combined effects of self-desic-cation and moisture diffusion are 70.0%, 73.2% and 73.0% respectively. The maximum moisture diffu- sion coefficient（Dmax） of ordinary concrete C3 is 10 times of that of high strength concrete C8. Further- more, the moisture diffusion process inside early-age concrete probably mainly depends on the mortar phase, regardless of the limestone aggregate. Merely increasing the volume fraction of limestone aggre- gate, within the percentage from 2.1% to 50.0%, the variation of IRH and moisture diffusion coefficient is negligible for concretes with the same water-binder ratio.

关 键 词：早龄期混凝土 相对湿度 水分扩散系数 粗骨料体积分数 水胶比 

分 类 号：TU528.01[建筑科学—建筑技术科学]