Abstract
Sheathing boards based on magnesium oxide (MgO) became very popular in the Danish market around the year 2010. However, it was realized a few years later that they condensed humidity from ambient air. The leakage from the boards led to severe problems with corrosion of metallic components and moisture uptake and degradation of wooden members. The boards have been banned from use in the Danish market since 2015, while damage cases valuing around 370 million EUR still need to be reconciled [1]. The binder in MgO board is formed by a chemical reaction between MgO and MgCl2. However, MgSO4 is a possible alternative to MgCl2, and such boards may have smaller moisture uptake, to reduce this issue. This paper gives an account of recent activities to compare properties of MgO boards, based on chlorides or sulphates. The investigations comprise: (1) Analysis of elemental composition and crystalline components, (2) Examination in optical microscope and scanning electron microscope, (3) Determination of moisture retention and water vapour permeability, (4) Analysis of chemical composition of leaked salt water from boards, and (5) Visual observation of decomposition and determination of dry mass change after exposure to high humidity.
Highlights
Around the year 2010, a new sheathing board product, the magnesium oxide (MgO) board, became a popular building material in Denmark to be used inside ventilated façades as sheathing behind a ventilated air gap
The binder in MgO board is formed by a chemical reaction between MgO and MgCl2
The binder in MgO-boards is formed by a chemical reaction between MgO and MgCl2, which was first produced by Stanislas Sorel in 1867 and is known as Sorel cement or magnesium oxychloride cement
Summary
Around the year 2010, a new sheathing board product, the magnesium oxide (MgO) board, became a popular building material in Denmark to be used inside ventilated façades as sheathing behind a ventilated air gap. The product is hard and strong but decomposes over time by contact with water or air at high relative humidity [3]. Https://doi.org/10.10 51/matecconf /201928202091 absorb an excessive amount of moisture from the air and form water drops that contain a high amount of chloride ions. This process is referred to as “crying” [4]. The purpose of this paper is to investigate the moisture properties of the different types of MgO-boards
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