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Industrial minerals
Published in Francis P. Gudyanga, Minerals in Africa, 2020
Natron is an admixture of sodium carbonate decahydrate Na2CO3·10H2O, sodium bicarbonate NaHCO3 together with small quantities of sodium chloride and sodium sulphate. It occurs in saline lake beds in association with thermonatrite, nahcolite, trona, halite, mirabilite, gaylussite, gypsum, and calcite. It is the source of soda ash (sodium carbonate anhydrate N a2CO3) as a result of calcination.
Characterization of factors determining the durability of brick masonry
Published in Jan Kubica, Arkadiusz Kwiecień, Łukasz Bednarz, Brick and Block Masonry - From Historical to Sustainable Masonry, 2020
Determining the type of salt present in the wall is an important element of wall diagnostics as it makes it possible to determine the sources of moisture in the construction object and significantly facilitates this process. Chlorides usually take the form of halite, sylvin, salmiac and bischofite, nitrates in the form of nitronatrite, nitrocalcite, nitrommagnezite, sulphates in the form of mirabilite, acarnite, epsomite, kizerite, tenardite and gypsum, whereas carbonates often take the form of micrite, thermonatrite and natron (Szostak & Trochonowicz 2015). Depending on the structure or degree of hydration, crystals can take various mineralogical forms, e.g. calcium carbonate take the form of calcite, aragonite or micrite.
Salt Decay and Salt Mixtures in the Architectural Heritage: A Review of the Work of Arnold and Zehnder
Published in International Journal of Architectural Heritage, 2022
The potential effect of modern building materials as sources of salts is an aspect the two authors give plenty attention to. Indeed, materials with a high alkali content such as Portland cement, but also waterglass, siliconates and alkaline cleaning products, can give rise to three main kinds of chemical reactions from which soluble salts, carbonates, sulfates, nitrates and chlorides, are formed (Arnold 1981, 1995; Arnold and Zehnder 1991): the alkali in these materials react with the carbonic acid formed in moist walls when the air CO2 reacts with water, thus giving rise to alkali carbonates such as natrite, thermonatrite, nahcolite, trona or kalicinite;the alkali carbonates can further react with an acid atmosphere, producing sulfates of sodium and potassium;the alkali carbonates can also react with autochthonous salts in the wall, namely sulfates, nitrates and chlorides of magnesium and calcium, thereby forming sulfates, nitrates and chlorides of sodium and potassium, as well as magnesium carbonates such as hydromagnesite and nesquehonite; the new salts are more harmful than the native nitrates and chlorides of magnesium and calcium as the later are highly hygroscopic and therefore cannot crystallize under normal conditions.