Lateral pressure of nano-engineered SCC combining nanoclays, nanosilica and viscosity modifying admixtures

Abstract

Self-compacting concrete (SCC) is an energy efficient building technology widely used for multiple constructive applications. However, the large flowability of fresh SCC produces an increase of the lateral pressure exerted on the formwork regarding to conventional concretes. One solution to reduce the maximum lateral pressure (Pmax) is to modulate the fresh performance of SCC by the addition of rheology modifiers. Among them, nanocomponents highlight due to their larger efficiency derived from their tiny particle size. In this study, the efficiency of nano-engineered SCC (NE-SCC) combining small amounts of nanocomponents, as nanoclays and nanosilica, with viscosity modifying admixtures (VMAs) to decrease Pmax is explored. Lateral pressure exerted by NE-SCC on cylindrical columns subjected to self-weight and to air pressure was assessed using wall and capillary pressure sensors over time. It was found that the incorporation of attapulgite and bentonite nanoclays combined with VMAs could reduce Pmax. This reduction was measured with wall and capillary pressure sensors on self-weight column and air pressure column laboratory tests, and good correlation between them over time was obtained. A predictive model of the maximum lateral Pressure (Pmax) and its evolution over time (PL) was proposed, related to SCC paste thixotropy (Athix,p), casting height (H) and SCC pressure decay coefficient (Cd).