Autogenous shrinkage, strength, and hydration heat of ultra-high-strength paste incorporating nano-zirconium dioxide

Abstract

Ultra-high-strength paste (UHSP) combined with nanomaterials has been extensively studied. However, the research on nano-ZrO2 is limited. In this study, UHSP with various nano-ZrO2 contents is analyzed. The motivation of this study is to clarify the effects of nano-ZrO2 on the hydration products, strength, autogenous shrinkage, and hydration heat of UHSPs. The water-to-binder ratio (w/b) of the specimens is 0.2. The nano-ZrO2 content is 0, 1.5, and 3 wt.%. The strength is measured at the age of 3, 7, and 28 days. The hydration heat is measured from the mixing stage to 3 days. The hydration products are analyzed by X-ray diffraction (XRD) and thermogravimetric analysis (TG). The autogenous shrinkage is measured from the mixing stage for 7 days using a new experimental device. The new experimental device can measure autogenous shrinkage, internal relative humidity, and internal temperature simultaneously. The following conclusions can be drawn based on the experimental studies: (1) Two stages were noticed in the autogenous shrinkage of UHSPs: a variable-temperature stage and a room-temperature stage. The cut-off point of these two stages occurred in roughly 1.5 days. Furthermore, in the room-temperature stage, there was a straight-line relationship between the autogenous shrinkage and internal relative humidity. (2) With the increase of the nano-ZrO2 amount, the compressive strength at 3 days, 7 days, and 4 weeks increased. (3) With the nano-ZrO2 increasing, the flow decreased. (4) With the nano-ZrO2 increasing, the hydration heat increased due to the physical nucleation effect of the nano-ZrO2. Furthermore, the nano-ZrO2 used in this study was chemically inert and did not take part in the cement hydration reaction based on the XRD, differential thermal, and TG data. This paper is of great significance for the development of high-strength cementitious materials doped with nano-ZrO2. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.