On the other hand, particles in concrete come in various sizes, shapes, and forms, e.g., cement, fine aggregate, and coarse aggregate. It also contributes to the plastic viscosity of high performance concrete. The recent trend of manufacturing high performance concrete mixtures is changing the common ready mix methodology by decreasing portions of coarse aggregate as well as Portland cement, which is achieved by incorporating supplementary cementitious materials.
As a method of controlling the plastic viscosity of cementitious materials, there are two well-known ways: increasing the sand-to-aggregate ratio for mix design and using a viscosity modifying admixture (Leemann and Winnefeld 2007). Hence it is very important to control not only yield stress but also the plastic viscosity of cementitious materials. 1999 Vikan and Justnes 2007 Mazanec et al. In practice, it is sometimes inconvenient to handle high performance cementitious materials with a very low water-to-binder ratio ( w/b): it shows extremely high plastic viscosity even though enough dosage of HRWRA is incorporated to achieve a sufficient fluidity (Yen et al. Incorporating such an HRWRA may control the yield stress and viscosity independently, but still the use of supplementary cementitious materials or filler is an in-hand solution in field. The recent trend of developing polycarboxylates, the main component of HRWRA, helps decrease viscosity as part of the overall effort to lower yield stress. HRWRA is the most widely used method to improve fluidity of cementitious materials due to its ability to decrease the yield stress (Winnefeld et al. ( 2011), many factors influence the yield stress or plastic viscosity of cementitious materials. After introducing the concept of rheology, the fluidity of cementitious materials can be controlled further with yield stress and plastic viscosity. The conventional approach was based on the mixture’s water control (both unit water content and water-to-cement ratio) thus, introducing a high-range water-reducing admixture (HRWRA or superplasticizer) was an innovative contribution.
For construction application, concrete development has focused on improving fluidity to assure a fresh state performance.
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