Contents lists available at ScienceDirect Theoretical and Applied Fracture Mechanics journal homepage: www.elsevier.com/locate/tafmec Micro-chemo-mechanical features of ultra-high performance glass concrete (UHPGC) William Wilson a,b, ⁎ , Nancy Ahmed Soliman a,c , Luca Sorelli d , Arezki Tagnit-Hamou a a Université de Sherbrooke, Sherbrooke, QC, Canada b École Polytechnique Fédérale de Lausanne, Lausanne, VD, Switzerland c Massachussetts Institute of Technology, Cambridge, MA, United States d Université Laval, Québec, QC, Canada ARTICLEINFO Keywords: Ultra-high performance concrete Glass powder Microstructure Nanoindentation Quantitative EDS Image analysis ABSTRACT ThedevelopmentofUltra-HighPerformanceConcrete(UHPC)openednewresearchdirectionsforenhancingthe architectural design, sustainability and serviceability of concrete structures. However, the costs and resource intensiveness trigger the need for innovative UHPC mix design incorporating alternative materials, such as post- consumption Glass Powder (GP). This works aims at disclosing the microstructure features of UHPGC, in which the constituents can be partially replaced by diferent fneness of GP without impacting the long-term strengths. By using the latest NI-QEDS technique (coupling NanoIndentation and Quantitative Energy-Dispersive Spectroscopy), as well as image analysis applied to EDS chemical mappings, it was possible to investigate me- chanical properties of the microstructure constituents and their volume fractions. A conventional UHPC mi- crostructure was compared to a similar system with 30% replacement of cement by GP and to another system with 50% replacement of silica fume by Fine GP (FGP). The results showed the key role of GP anhydrous particles contributing to the rigid skeleton of anhydrous inclusions, as well as their bond quality with the sur- rounding cement paste. The reduction of cement and silica fume was thus possible without impairing the mi- cromechanical properties of the hydrates, by improving the particle packing density in the hardened state. As major conclusion, replacing cement and silica fume with GP and FGP without impairing both micro-scale and macro-scale mechanical properties provides a promising means to reduce the environmental footprint of current UHPC mix design. 1. Introduction Ultra-High Performance Concrete (UHPC) is a class of cement-based composites which is endowed with ultra-high properties, such as compressive strength, e.g., above 150MPa. Such strength can be achieved by combining the removal of large aggregates from concrete (maximal particle size ~0.6mm), the reduction of the water-to-binder ratio (below 0.20, using efcient superplasticizers), and the optimiza- tion of the packing density with fllers and supplementary cementitious materials (i.e., fne quartz, cement and silica fume) [1]. However, re- placing the inexpensive part of concrete (the aggregates) by specialized powders in UHPC results in very high costs and environmental foot- print. In UHPC with low water-to-binder ratio (e.g. below 0.20), the degree of hydration of cement is limited to about 30% after 28days [2,3]. Thus, a major part of anhydrous cement clinker particles acts as fller, which can be potentially replaced by cheaper, less resource- intensive SCMs such as fy ash, slag, limestone, natural pozzolans, conventional quartz sand or post-consumption glass powder [2,4–20]. If mechanical properties are not compromised, such replacements can have strong economical and environmental potentials for construction using UHPC [7,11]. As for alternative SCMs, Soliman et al. [20] optimised diferent types of Ultra-High Performance Glass Concrete (UHPGC) and showed that cement in UHPC could be replaced by glass powder up to 50% without impairing strengths at 91days (similar results were obtained for 30% replacement by Kou and Xing [10]). Another investigated ap- proach was to replace quartz powder (also known as silica four) with glass powder, with compressive strength gains of 15–22% at later age [12,20]. Furthermore, Soliman et al. [5] showed how Silica Fume (SF) dosageinUHPCcouldbereducedby50%throughitsreplacementwith fne glass powder, without signifcant efects on strengths at all ages. Moreover, because of lower reactivity and lower water-absorption of https://doi.org/10.1016/j.tafmec.2019.102373 Received 5 June 2019; Received in revised form 24 September 2019; Accepted 24 September 2019 ⁎ Corresponding author at: Université de Sherbrooke, Sherbrooke, QC, Canada. E-mail address: William.Wilson@USherbrooke.ca (W. Wilson). Theoretical and Applied Fracture Mechanics 104 (2019) 102373 Available online 01 October 2019 0167-8442/ © 2019 Elsevier Ltd. All rights reserved. T