Toward Development of Self-Compacting No-Slump Concrete Mixtures

No-slump concrete (NSLC) is one of the commercial types of concrete that is known as a type of concrete with almost zero flowability. No-slump concrete is normally used for typical applications, like pavements construction and massive dam structures. The specific feature of a no-slump concrete is its high shape holding ability. No fixed formwork is required for the construction. The main disadvantage of this type of concrete is that a great amount of energy is required for a proper compaction. Self-compacting concrete (SCC) is another commercial type of concrete that is known as a type of concrete that flows and fills the formwork under its own weight without applying any external energy. Although SCC is a relatively recent development, it has demonstrated substantial economic and environmental benefits in terms of faster construction, reduction of required manpower, better surface finishing, easier and vibration-free placing and reduced noise level. Therefore, SCC has recently found a wide use for different applications and structural configurations. However in comparison with NSLC, its demolding time for preserving its shape is much longer and fixed formworks are required for the construction. The first objective of this research project is to study the possibility of developing a self-compacting no-slump concrete (SCNSLC), which does not need compaction and also has a high shape holding ability shortly after placing in the formwork. The second objective is to develop a model, which can predict the rheological behaviour of a mixture based on the properties and proportion of the mix components. The study starts with a comprehensive study of mechanisms that govern the rheological behaviour of concrete in the dormant period, i.e. when the hydration effect is still ignorable. A fresh concrete mixture is considered as a two-phase system, paste and aggregates. The paste itself is divided into two components, the “void paste” and the “excess paste”. The void paste is the part of the paste which fills the void space between the aggregates in a compacted state. The excess paste is the rest of the paste used to form a nominal layer with an average constant thickness around every single aggregate particle. The void paste tries to keep the aggregate particles in their positions, while the excess paste tries to push the aggregate particles apart and promote their mobility. With respect to the dominant mechanism, mixtures are divided into three main classes: • Class 1: High Excess Paste volume mixtures, where the excess paste effect is dominant. For these mixtures the capacity to deform is maximal. • Class 2: Intermediate Excess Paste volume mixtures, where the effect of the void paste becomes significant and gradually increases with decreasing excess paste volume. The capacity of the intermediate excess paste volume mixtures to deform is lower than the high excess paste volume mixtures. • Class 3: Low Excess Paste volume mixtures, where the void paste effect is dominant and the excess paste does not significantly affect the rheological behavior. For these mixtures the capacity to deform is minimal. Mix design The shape holding ability of mixtures is characterized by the shape preservation factor 0