Effects of Supplementary Cementitious Materials on the Hydration of Ultrahigh-Performance Concrete

Abstract

With the variety of supplementary cementitious materials (SCMs) available, there have been fundamental questions regarding how they influence the hydration development of ultrahigh-performance concrete (UHPC), especially at early age. To provide a holistic perspective and side-by-side comparisons, the current study explored the partial replacement of cement with silica fume, natural zeolite, and limestone, which represented artificial pozzolans, natural pozzolans, and non-pozzolanic SCMs, respectively. To evaluate the most critical micro- and macro-scale properties of UHPC, the experimental investigations included temperature and free water measurements, further to thermogravimetric analyses (TGA) performed to determine the amount of physically and chemically bound water in the developed mixtures. Moreover, the X-ray diffractometry (XRD) method was employed to obtain the XRD patterns, which were then paired with the TGA results to quantify the crystalline phases of the UHPC mixtures using the Rietveld refinement method. With a detailed assessment of the UHPC’s degree of hydration over time, the outcome of this study shed light on how various SCMs are capable of reducing the heat of hydration, while enhancing the degree of hydration of cement particles.