Investigation into the Effects of Materials and Mixing Procedures on Air Void Characteristics of Fresh Concrete Using Air Void Analyzer (AVA)
Investigation into the Effects of Materials and Mixing Procedures on Air Void Characteristics of Fresh Concrete Using Air Void Analyzer (AVA)
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DOI：
10.1520/jai100435
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发表时间：
2006-11
期刊：
影响因子：
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通讯作者：
S. Zhang;Kejin Wang
中科院分区：
文献类型：
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作者：
S. Zhang;Kejin Wang
利用空隙率分析仪（AVA）研究了混凝土原材料和拌和工艺对新拌混凝土空隙率特性的影响。用三种混合比例（有和没有C类粉煤灰或减水剂）制备二十七批混凝土，并且用五种混合程序（一步混合1、2或4分钟，两步混合4分钟和ASTM C 192实验室混合程序）和两种尺寸的盘式混合机（0.014和0.042 m3或0.5和1.5 ft3）混合它们。检查所有批料混合物的空气含量、粒度分布、比表面积和间距因子。结果表明，掺入15%的C级粉煤灰替代或推荐剂量的木质素基减水剂到混凝土中普遍降低了空隙的间距系数。两步混合法（先混合砂浆2 min，然后再混合砂浆与粗骨料2 min）产生的空隙间距系数低于一步4 min混合法（一次将所有混凝土材料混合在一起）。对于一次搅拌法配制的混凝土，随着搅拌时间的延长，混凝土的空隙率逐渐减小。对于给定的混凝土混合物和混合程序，使用不同尺寸的搅拌机提供具有不同空气含量和不同间距系数的混合物。相应的新鲜和硬化混凝土的空隙特性也分别使用B型压力计和RapidAir测试方法进行了检查。研究了AVA、B型压力计和RapidAir试验结果之间的相关性。
The air void analyzer (AVA) was used to investigate the effects of concrete materials and mixing procedures on air void characteristics of fresh concrete. Twenty-seven batches of concrete were made with three mix proportions (with and without Class C fly ash or water reducer), and they were mixed with five mixing procedures (one-step mixing for 1, 2, or 4 min, two-step mixing for 4 min and ASTM C 192 lab mixing procedures) and two sizes of pan mixers (0.014 and 0.042 m3 or 0.5 and 1.5 ft3). The air content, size distribution, specific surface, and spacing factor of all the batch mixtures were examined. The results indicated that incorporating 15 % Class C fly ash replacement or recommended dosage of a lignin-based water reducer into concrete generally reduced the spacing factor of air voids. The two-step mixing method (mixing mortar for 2 min first, and then mixing the mortar with coarse aggregate for another 2 min) produced a lower air void spacing factor than the one-step, 4-min mixing method (mixing all concrete materials together at once). For concrete mixed with the one-step mixing method, the air void spacing factor reduced with mixing time. For a given concrete mixture and mixing procedure, use of different sizes of mixers provided the mixtures with different air content and different spacing factor. The air void characteristics of the corresponding fresh and hardened concrete were also examined using the Type B pressure meter and RapidAir test methods, respectively. The correlations between the results from AVA, Type B pressure meter, and RapidAir tests were studied.