Keywords: modeling, self-compacting, mortar, concrete, rheology, high flow, Bingham model.

Self-compacting concrete (SCC) [1] is very popular in japan. This concrete is a special case of high flowing concrte (HFC). The detail rheology study of HFC is not available covering wide mix proportion. It is expensive to prepare this kind of concrete. So, if the final behavior of concrete before casting could be predicted it would save a lot of money. There has been no attempt to relate the mix proportion ratio to the rheology property so that if a designer knows the mix proption he can predict the rheology of the final mortar and concrete. With these in mind, effort has been made to propose generalized analytical models of rheology from the mix proportion, assuming the mortar and concrete behaves as Bingham fluid.

For viscosity model, Farris model [2] has been employed. The Farris model is based on the concept that "the viscosity of a multimodal suspension of particles can be calculated from the unimodal viscosity data of each size as long as the relative sizes in question are sufficient to have this condition of zero interaction" [2]. The modes Farris alludes to are the different sizes of particles within the suspension. Since the Farris model is based on the theory that the particles within the solid phase of the suspension can be divided into two or more specific size fractions, and concrete is typically divided into coarse and fine aggregate, this model seemed applicable.

As no model is available that predicts the yield stress of a material having Bingham characteristics, this research attempted one. The yield stress of the concrete was assumed to be a function of yield stress of mortar and the volume fraction of aggregate. The yield stress of the concrete must be equal to the yield stress of mortar if the gravel content is zero. With these model conditions in place, the development of a yield stress model was explored. This model is completely empirical one based on experimental data on mortar and concrete.

An effort has also been made to study the rheology and its relation to traditional test methods of HFC.The concrete was referred as HFC not the SCC; as the variation of mix proportion used in this study does not fall into the small range of mix proportion of SCC. HFC has high slump flow and self-leveling capacity in U-box without reinforcement. The main difference, between these two concretes, is that the SCC has the ability to pass the blocking test, but HFC does not.

This research has been divided into two main parts. First - tests on mortar, and second - tests on concrete. The mortar has been prepared to achieve the same mortar property of previously tested concretes. Wet screening has been evaded to obtain the mortar, instead separate mixes have been used. In the process of wet screening time was required from the time of mix and vibration was required to separate the mortar from the coarse aggregate. These two factors affect the mortar property, which were there during the mixing time. The main objective of mortar preparation was to keep the same mortar inside the concrete.

In this research slump flow test, V-funnel test, rheology test have been performed on both mortar and concrete to observe its relation with rheology of mortar and concrete. The materials used in combination to create the concrete were coarse aggregate, fine aggregate, Ordinary Portland Cement (OPC), Ground Granulated Blast Furnace Slag (GGBS), a liquid superplasticizer, and water. The physical composition of materials remained constant throughout this research and varied by weight and volume during the experimental phase.

1

H. Okamura and K. Ozawa, "Self-compactable High Performance Concrete in Japan", Proceedings of ACI seminar, Bangkok, 1971.

2

R.J. Farris. Prediction of the Viscosity of Multimodal Suspensions from Unimodal Viscosity Data. Transactions of the Soc. of Rheology, 12(2):281-301, 1968. doi:10.1122/1.549109

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