Use of air-cooled blast furnace slag as supplementary cementitious material for self-compacting concrete production Paulo R. de Matos a,⇑ , Jade C.P. Oliveira b , Taísa M. Medina b , Diego C. Magalhães c , Philippe J.P. Gleize a , Rudiele A. Schankoski b , Ronaldo Pilar b a Laboratory of Application of Nanotechnology in Civil Construction (LabNANOTEC), Department of Civil Engineering, Federal University of Santa Catarina (UFSC), Brazil b Department of Civil Engineering, Federal University of Espírito Santo (UFES), Brazil c ArcelorMittal Global R&D, Espírito Santo, Brazil highlights  The use of ACS as SCM was evaluated in paste and self-compacting concrete.  ACS increased the yield stress and viscosity of paste, and the HRWR demand of concrete.  ACS led do similar cement hydration kinetics and strength compared to LF.  Blending ACS with LF evened the performance of concrete compared to pure limestone.  ACS did not significantly react up to 91 days. article info Article history: Received 8 April 2020 Received in revised form 24 June 2020 Accepted 28 June 2020 Keywords: Air-cooled blast furnace slag Self-compacting concrete Supplementary cementitious material Industrial waste abstract The manufacturing process of pig iron generates large amounts of slag. The slow cooling of this waste generates the air-cooled blast furnace slag (ACS). Since it is less reactive than granulated blast furnace slag (GBFS), ACS finds little use as supplementary cementitious material (SCM) and the existing studies use it only as aggregates in concrete. This work investigated the use of finely ground ACS as SCM for self- compacting concrete (SCC) production. Pastes and SCCs with GBFS, ACS in two grinding levels and lime- stone filler (LF) were produced, and their fresh state performance, hydration kinetics and compressive strength from 3 to 91 days were evaluated. ACS increased the yield stress and viscosity of the pastes com- pared with LF, also increasing the SCC’s superplasticizer content required to reach the target slump flow of 650 ± 50 mm. Nonetheless, this increase was from 0.95 up to 1.36 kg/m 3 of concrete, and all the mixes presented V-funnel time of 4–6 s and were highly stable in the fresh state (VSI = 0, with no segregation/ bleeding). Isothermal calorimetry indicated that ACS slightly shortened the induction period compared with LF, but led to equivalent peak values (6.7–6.9 mW/g cement). Concretes with ACS and LF had similar strengths at all ages, reaching 32 ± 1 MPa at 3 days and 41 ± 2 MPa at 91 days, indicating that no signif- icant reaction was observed for ACS up to the later age. Furthermore, blending ACS with LF in equal pro- portions resulted in a SCC with fresh performance equivalent to that containing only LF, in addition to increasing the strength by about 5% at all ages. In general, ACS had comparable performance to that of LF and can be used as SCM in SCC. Ó 2020 Elsevier Ltd. All rights reserved. 1. Introduction The steel industries generate millions of tons of slag as by- product during their production stages [1–4]. According to data published by The Brazilian Development Bank [5], the average pro- duction of such waste among the ten largest steel producers in the world is of 294 kg of slag per ton of liquid pig iron. This slag is clas- sified according to its origin and form of cooling (by air, water, or water + pressure). Much of the slag generated during the manufac- ture of pig iron is abruptly cooled and ground to be used as a bin- der by the Portland cement industry, generating the granulated blast furnace slag (GBFS). In turn, the slag that is not intended for this purpose is usually slowly cooled to reduce process costs, and is called air-cooled blast furnace slag (or simply air-cooled slag https://doi.org/10.1016/j.conbuildmat.2020.120102 0950-0618/Ó 2020 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail addresses: paulorm.matos@gmail.com, paulo.r.matos@posgrad.ufsc.br (P.R. de Matos), jadecenach@gmail.com (J.C.P. Oliveira), taisamedin@hotmail.com (T.M. Medina), diego.c.magalhaes@arcelormittal.com.br (D.C. Magalhães), p.gleize@ ufsc.br (P.J.P. Gleize), rudiele@gmail.com (R.A. Schankoski), ronaldo_pilar@hotmail. com (R. Pilar). Construction and Building Materials 262 (2020) 120102 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat