On the porosity of low-clinker shotcrete and accelerated pastes. (3rd March 2023)

• Record Type: Journal Article
• Authors: Steindl, Florian R.; Mittermayr, Florian; Sakoparnig, Marlene; Juhart, Joachim; Briendl, Lukas; Lindlar, Benedikt; Ukrainczyk, Neven; Dietzel, Martin; Kusterle, Wolfgang; Galan, Isabel
• Is Part Of: Construction & building materials. Volume 368(2023)
• Publication Date: 2023-03-03
• Subjects: Porosity -- Shotcrete -- Mercury Intrusion -- Durability -- SCMs; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2023.130461
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: New insights into porosity of dry- and wet-mix shotcrete and accelerated pastes. New deconvolution method for pore size distribution curves. Pore size distribution can be modelled by multi-modal Boltzmann distribution. Cement and binder composition significantly affect pore volume and pore size distribution of real-scale shotcrete. Spraying process and accelerator have a strong effect on the porosity of pastes and concretes. Abstract: Although the number and size of interconnected pores have been identified as the most important aspects of concrete microstructure, comprehensive datasets on shotcrete porosity and pore size distributions are still scarce and their key controls are poorly investigated. In this study we investigate the effects of the spraying process, setting accelerator addition and mix design on the microstructure of real-scale dry- and wet-mix shotcrete and hand-mixed and sprayed accelerated pastes. A newly proposed deconvolution analysis of the pore size distributions, measured by mercury intrusion porosimetry, offers increased precision in determining the critical and median pore diameter parameters. In total >50 samples were analysed. Results show that the dry-mix shotcrete exhibits a shift towards coarser pore sizes (∼100–1 μm) than wet-mix shotcrete. Combinations of different supplementary cementitious materials are favourable for producing wet-mix shotcretes with refined pore structures. The addition of setting accelerators, up to 10 wt-% of binder mass, and the spraying process cause systematic variations in the pore volume and pore structure of (sprayed) paste and shotcrete.