9 The Indian Concrete Journal September 2017 TECHNICAL PAPER Importance of rheological properties of fresh concrete - A review S. Girish and N. Ajay 1. INTRODUCTION Concrete of today has transformed itself into advanced type with new innovative ingredients added either singularly or in combination. The traditional four ingredient mix of cement + water + fine aggregate + coarse aggregate mix-design is the thing of the past [1]. Basically, the modifications with the addition of new ingredients like filler material, mineral and chemical admixtures were designed to improve the quality of concrete in the backdrop of rapidly growing concrete construction and demand for the requirement of new properties (both in fresh and hardened state). Nevertheless the concrete behavior is complex and workability of fresh concrete is a critical property that has a direct impact on the strength, durability, appearance and cost. Even to this day the workability of concrete is defined as “that property of freshly mixed concrete which determines the ease and homogeneity with which it can be mixed, placed, consolidated, and finished.” Still the measuring tool to assess the workability of concrete has not changed significantly in the last century and is measured using the simplistic test method, the slump The Indian Concrete Journal, September 2017, Vol. 91, Issue 9, pp. 09-17. The workability is a critical property and there is a need to characterize the fresh concrete by its rheological properties based on material science approach to overcome the inadequacies of traditional empirical tests like slump test. The fresh property can be characterized by its flow behavior, and fluid rheology approach is the most fundamental one and describes the concrete flow by at least two parameters, namely, yield stress and plastic viscosity. Understanding and controlling these two fundamental fresh concrete properties is vital for better performance of concrete mixes in designing a more economical and complex structures and improving the construction processes. This paper emphasizes the importance of rheology of fresh concrete in the backdrop of concrete being transformed itself into advanced type, with the addition of new innovative ingredients. Keywords: Workability; slump test; yield stress; plastic viscosity; rheology and rheometer. test, the apparatus of which was developed in USA around 1910 and it is believed that it was first used by Chapman, although in many countries the test apparatus is associated with Abram [2]. Later on, other workability test methods like re-mould test, flow table test, compacting factor test, vee-bee test, ball penetration test etc., were developed and were more sensitive, but depended on the dimensions of apparatus [3, 4, 5]. The majority of tests developed since the 1920s are empirical, that is, they attempt to simulate a field placement condition and measure a value such as time or distance, which serves as an index of workability [6]. In 1983, Tattersall interpreted and divided the workability test into three Classes [7] namely, Qualitative, Quantitative Empirical and Quantitative Fundamental science and argued that the empirical tests are single point test and suggested quantitative fundamental science approach for characterizing the fresh concrete. Fundamental science approach requires minimum two parameters to describe the material. The advent of advanced concrete production like high performance concrete has not eliminated the need to monitor concrete workability in the field. But on the contrary, it has made the monitoring even more critical, since