SCC and UHPC — Effect of Mixing Technology on Fresh Concrete Properties
SCC and UHPC — Effect of Mixing Technology on Fresh Concrete Properties
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DOI：
10.1007/978-3-540-72448-3_52
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
P. Schießl;O. Mazanec;D. Lowke
中科院分区：
文献类型：
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作者：
P. Schießl;O. Mazanec;D. Lowke
虽然许多法规和指南涵盖了混凝土及其组分的组成和性能，但混凝土生产的实际过程，即混合，实际上是留给用户的意图和目的。根据DIN EN 206，混凝土组分应进行混合，以产生均匀的混合物。选择混合持续时间，以充分混合材料。决定性的是水和高效减水剂均匀地分布到精细尺度，并且团聚体充分分散。如果使用的混合能量不足，则不能实现所选组合物的预期性能。搅拌所需的持续时间特别取决于搅拌机的类型以及混凝土的成分。由于相对于细粉（<0.125 mm）含量的低含水量和高掺量的外加剂，自密实混凝土（SCC）和超高强度混凝土UHPC的生产需要更多的搅拌能量以使混凝土组分均匀。在混凝土厂，SCC的搅拌时间超过4分钟，UHPC的搅拌时间超过12分钟并不罕见。与振捣混凝土相比，这限制了混凝土的生产速度，因此是一个重要的财务因素。研究了搅拌时间、搅拌速度和混凝土组成对超高性能混凝土均匀性的影响。此外，提出了一种基于搅拌功率的模型方法，用于计算不同混凝土组成所需的搅拌时间。
Although numerous regulations and guidelines cover the composition and properties of concrete and its components, the actual process of concrete production, i.e. mixing, is to all intents and purposes left to the user. According to DIN EN 206 the concrete components are to be blended so that a homogeneous mixture is produced. The duration of mixing is to be chosen to produce sufficient blending of the materials. It is decisive that water and superplasticizer are evenly distributed down to a fine scale and that agglomerates are sufficiently dispersed. If insufficient mixing energy is used, the properties expected from the composition chosen cannot be achieved. The necessary duration of mixing depends particularly on the type of mixer as well as the composition of the concrete. Due to the low water content with respect to the content of fines (<0.125 mm) and the high dosage of admixtures, the production of self-compacting concrete (SCC) and ultra high strength concrete UHPC requires more mixing energy to homogenise the concrete components. In concrete plants, mixing times above 4 min for SCC and 12 min for UHPC are not uncommon. This limits the rate of concrete production in comparison with vibrated concrete and is therefore an important financial factor. This paper considers the effect of mixing time, mixing tool speed and concrete composition on the homogenisation of ultra high performance concrete. In addition, a model approach based on mixing power is presented for the calculation of the necessary mixing time for different concrete compositions.