Abstract
Alkali-activated materials (AAM) compared to Portland cement (PC) may significantly reduce the carbon dioxide emissions, as well as the consumption of non-renewable natural resources in civil engineering applications. Further environmental advantages are possible if natural aggregates used for mortars and concretes are replaced with residues and wastes from industrial or mining activities. This paper compares the performance of PC with AAM as binders in cementitious wall panels for external cladding in hot and humid climate. Three different cementitious matrices are proposed, consisting of either 100% Portland cement (PC), 100% alkali-activated metakaolin (MK) or 80/20 alkali-activated Metakaolin/Blastfurnace slag (80/20 MK/BFS). Mortars were produced with the addition of tailing from iron-ore mining activities in the state of Minas Gerais, Brazil, at an aggregate to binder ratio of 1.0 for all matrices. The thermal property determined for the three mortars was Thermal Conductivity using a heat flow meter (HFM) apparatus according to ISO 8301 (1999); their apparent density was also measured. After that, one-story house building simulation was carried out using the Energy Plus Software. The main room annual operative temperature provided by different panels used as cladding was compared to the adaptive comfort range established on ASHRAE Standard 55/2013 for a Brazilian and Portuguese hot and humid climate. According to the Climate Zone Definitions of ANSI/ASHRAE Standard 169/2006, Belo Horizonte (Brazil) and Funchal (Portugal) were selected as a sample of 2A zone that presents a hot and humid climate. Partial results of this research were presented in this paper. Results show that building simulations can effectively contribute to validate the selection of materials in the production of sustainable wall panels that provide suitable thermal conditions to the users in hot and humid climate.
Highlights
The diversity of concrete applications in construction is directly related to its wide range of variations in their physical characteristics according to their composition
The present study aims at measure the thermal conductivity and apparent density of three different matrices containing mine tailing as aggregate
The comparison between thermal comfort range according to the ASHRAE Standard 55/2013 and operative temperature of the main room simulated for 3 options of wall panels shows that 100 MK provided lowest indoor temperatures, throughout the year and 80/20 MK/blast furnace slag (BFS) the highest for Belo Horizonte (Figure 5)
Summary
The diversity of concrete applications in construction is directly related to its wide range of variations in their physical characteristics according to their composition. Several studies have analysed the physical and mechanical behaviour of alkali-activated materials (AAM). The growing interest in AAM is directly related to their low environmental impact when compared to PC-based materials. AAM are considered inorganic polymers obtained by the reaction between an aluminosilicate and an alkaline solution (activator solution). They can be produced by the activation of commercial materials such as metakaolin, fly ash, blast furnace slag and active silica [1,2,3,4]. In Brazil, most of the wastes that derive from the extraction and processing of ores are located in dams, which can cause risk such as infiltration of solutions containing heavy metals and cyanides in the soil beside the control of the pH of these solutions.
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