TY - CONF A1 - Carabba, L. A1 - Masi, G. A1 - Pirskawetz, Stephan A1 - Krüger, Simone A1 - Gluth, Gregor A1 - Bignozzi, M.C. ED - Serdar, M. ED - Stirmer, N. ED - Provis, J. T1 - Thermal properties and steel corrosion in light-weight alkali-activated mortars N2 - This study aims at investigating the use of coal fly ash-based alkali activated mortars as passive fire protection system for steel structures. These systems are used to slow down the temperature rise of the steel substrate in case of fire. In addition, the protective system should guarantee the ability to prevent and/or mitigate steel corrosion phenomena. The behavior of a light-weight mortar was compared to that of a normal-weight mortar. Density and porosity were measured to better characterize the physical properties of the mortars. The degree of protection in case of fire was assessed by performing medium-scale fire tests. Acoustic emission measurements were conducted to analyze cracking phenomena during the high temperature exposure. The corrosion process was evaluated using an electrochemical approach in order to monitor the durability of the developed material. Preliminary results show that a 20 mm-thick layer of light-weight mortar is able to protect the steel substrate from reaching the critical temperature of 500 °C for 38 minutes in case of cellulosic fire. In addition, alkali activated mortars provide protection for carbon steel in presence of aggressive environment (i.e. presence of chlorides). The corrosion resistance is strictly related to the physical properties of the developed mortars. T2 - International Conference on Sustainable Materials, Systems and Structures (SMSS 2019) CY - Rovinj, Croatia DA - 20.03.2019 KW - Fire resistance KW - Steel corrosion KW - Acoustic emission KW - Alkali-activated materials PY - 2019 SN - 978-2-35158-223-7 VL - 1 SP - 125 EP - 132 PB - RILEM Publications CY - Paris AN - OPUS4-47584 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Carabba, L. A1 - Pirskawetz, Stephan A1 - Krüger, Simone A1 - Gluth, Gregor A1 - Bignozzi, M.C. T1 - Acoustic emission study of heat-induced cracking in fly ash-based alkali-activated pastes and lightweight mortars N2 - Alkali-activated fly ashes have been proposed for various applications where resistance against high temperatures is required, yet several details regarding the response of these materials to heat-exposure need to be clarified. In the present study, heat-induced cracking in fly ash-based alkali-activated pastes and lightweight mortars was analyzed by in-situ acoustic emission (AE) detection during complete heating-cooling cycles (up to ∼1100 °C), augmented by thermogravimetry and ex-situ SEM and XRD analyses. The applicability of the lightweight mortars as passive fire protection coatings was assessed by recording temperature-time curves of mortar-coated steel plates. Cracking during heating was limited and associated exclusively with the dehydration of the materials in the temperature range ∼90–360 °C. However, samples heated to temperatures above ∼600 °C exhibited intense cracking on cooling. This was attributed to differential deformations caused by local sintering and partial melting at the glass transition temperature, and subsequent quenching on cooling. KW - Alkali-activated materials KW - Acoustic emission KW - Fire proofing KW - Heat resistance KW - Cracking PY - 2019 U6 - https://doi.org/10.1016/j.cemconcomp.2019.04.013 SN - 0958-9465 SN - 1873-393X VL - 102 SP - 145 EP - 156 PB - Elsevier AN - OPUS4-47904 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Winnefeld, F. A1 - Gluth, Gregor A1 - Bernal, S. A. A1 - Bignozzi, M. C. A1 - Carabba, L. A1 - Chithiraputhiran, S. A1 - Dehghan, A. A1 - Dolenec, S. A1 - Dombrowski-Daube, K. A1 - Dubey, A. A1 - Ducman, V. A1 - Yu, J. A1 - Peterson, K. A1 - Stephan, D. A1 - Provis, J. L. T1 - RILEM TC 247-DTA round robin test: sulfate resistance, alkali-silica reaction and freeze–thaw resistance of alkali-activated concretes N2 - The RILEM technical committee TC 247-DTA ‘Durability Testing of Alkali-Activated Materials’ conducted a round robin testing programme to determine the validity of various durability testing methods, originally developed for Portland cement based-concretes, for the assessment of the durability of alkali-activated concretes. The outcomes of the round robin tests evaluating sulfate resistance, alkali-silica reaction (ASR) and freeze–thaw resistance are presented in this contribution. Five different alkali-activated concretes, based on ground granulated blast furnace slag, fly ash, or metakaolin were investigated. The extent of sulfate damage to concretes based on slag or fly ash seems to be limited when exposed to an Na2SO4 solution. The mixture based on metakaolin showed an excessive, very early expansion, followed by a dimensionally stable period, which cannot be explained at present. In the slag-based concretes, MgSO4 caused more expansion and visual damage than Na2SO4; however, the expansion limits defined in the respective standards were not exceeded. Both the ASTM C1293 and RILEM AAR-3.1 test methods for the determination of ASR expansion appear to give essentially reliable identification of expansion caused by highly reactive aggregates. Alkali-activated materials in combination with an unreactive or potentially expansive aggregate were in no case seen to cause larger expansions; only the aggregates of known very high reactivity were seen to be problematic. The results of freeze–thaw testing (with/without deicing salts) of alkali-activated concretes suggest an important influence of the curing conditions and experimental conditions on the test outcomes, which need to be understood before the tests can be reliably applied and interpreted. KW - Alkali-activated materials KW - Sulfate attack KW - Alkali silica reaction KW - Alkali aggregate reaction KW - Freeze-thaw attack PY - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-515527 VL - 53 IS - 6 SP - 140 PB - Springer Nature AN - OPUS4-51552 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -