Influence of Rheological Behavior of Mortar Matrix on Fresh Concrete Segregation and Bleeding
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REVIEW PAPER
Influence of Rheological Behavior of Mortar Matrix on Fresh Concrete Segregation and Bleeding Junzheng Pan1 · Xiaojian Gao1,2,3 · Huan Ye1 Received: 2 October 2019 / Accepted: 21 July 2020 © Shiraz University 2020
Abstract In this paper, the effect of water-binder ratio, sand ratio and high-range water reducer (HRWR) content on the rheological behavior of mortar formulated from concrete mixture was investigated by using a RheoCAD rheometer. The segregation of fresh concrete and hardened concrete was, respectively, measured by two different modified methods, coarse aggregate sieving-washing method and image processing method. The bleeding of fresh concrete was measured by two laser displacement sensors. The experimental results show that sand ratio and HRWR content have significant influences on yield stress whereas have little contribution to plastic viscosity. The segregation of concrete increases with the decrease of yield stress and is affected by plastic viscosity meanwhile. There is a weak relationship between bleeding rate and yield stress, but the bleeding rate decreases with the increase of plastic viscosity. Furthermore, it is convenient to analyze the degree of segregation and the distribution of coarse aggregate particles by image processing method and to real-timely monitor the bleeding and settlement of fresh concrete by laser displacement sensors. Keywords Fresh concrete · Rheological performance · Segregation · Bleeding
1 Introduction Cement concrete is globally the most widely used building material with an annual consumption of billions of tons. It is significant to ensure the homogeneity of cement concrete to guarantee the building structure with good mechanical properties and durability. However, cement concrete is a multiphasic material and the densities of the numerous components are very different, indicating that the gravity becomes the enemy of homogeneity (Roussel 2006). In the field of cementitious materials, heterogeneities induced by gravity can be divided into two categories: segregation and * Xiaojian Gao [email protected] 1
School of Civil Engineering, Harbin Institute of Technology, Harbin 150090, China
2
Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education, Harbin Institute of Technology, Harbin 150090, China
3
Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and Information Technology, Harbin Institute of Technology, Harbin 150090, China
bleeding. Segregation is commonly defined as the separation of some size levels of coarse aggregates from cement mortar. It can be induced during flow by shear forces, or at rest by gravity difference (Ovarlez 2012). Bleeding is one form of segregation and the phenomenon behaves the migration of water to the surface and the accumulation of particles at the bottom, and it is easily induced by excessive vibration or the presence of spaces between formwork boards. Generally, concrete consists of coarse aggregates, fine aggregates, cement pa
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