Optimization of autogenous shrinkage and microstructure for Ultra-High Performance Concrete (UHPC) based on appropriate application of porous pumice

摘要

In this study, optimization of autogenous shrinkage and microstructure for Ultra-High Performance Concrete (UHPC) based on appropriate application of porous pumice is addressed. The pumices with different water absorption rates are utilized to replace river sand by 10%, 20% and 30%, and its effect on the properties of the developed UHPC is investigated. The obtained experimental results show that the inclusion of pre-wetting pumice (particle size distribution is 0.6-1.25 mm) can significantly reduce the autogenous shrinkage of UHPC, without decrease the mechanical properties. Mercury Intrusion Porosimetry and Computed Tomography results indicate that the incorporation of 0.6-1.25 mm hydrous pumice can refine the pore structure and increase the fraction of interconnected pores. Environmental Scanning Electron Microscope, Super-high Magnification Lens Zoom 3D Microscope and Electron BackScattered Diffraction images revealed that the interfacial transition zone (ITZ) skeleton between hydrous pumice and UHPC paste is obviously improved. (C) 2019 Elsevier Ltd. All rights reserved.