China
Africa
Explore chapters and articles related to this topic
Durability of concrete
Published in Peter Domone, John Illston, Construction Materials, 2018
Thaumasite is a rare mineral that occurs naturally in some basic rocks and limestones. It is a compound of calcium silicate, carbonate and sulphate with the formula CaSiO3.CaCO3.CaSO4.15H2O. To be formed in concrete and mortar it requires: a source of calcium silicate, clearly available from the hydrated or unhydrated Portland cementa source of sulphate ions, for example from soil or groundwatera source of carbonate, most commonly limestone aggregate or fillers or formed from the bicarbonates arising from the atmospheric carbon dioxide dissolved in pore watera wet, cold (below 15°C) environment.
Durability of concrete
Published in Marios Soutsos, Peter Domone, Construction Materials, 2017
Thaumasite is a rare mineral that occurs naturally in some basic rocks and limestones. It is a compound of calcium silicate, carbonate and sulphate with the formula CaSiO3 ⋅ CaCO3 ⋅ CaSO4 ⋅ 15H2O. To be formed in concrete and mortar, it requires the following: A source of calcium silicate, clearly available from the hydrated or unhydrated Portland cementA source of sulphate ions, for example, from soil or groundwaterA source of carbonate, most commonly limestone aggregate or fillers or formed from the bicarbonates arising from the atmospheric carbon dioxide dissolved in pore waterA wet, cold (below 15°C) environment
Design of concrete mixtures for durability
Published in Mark Alexander, Arnon Bentur, Sidney Mindess, Durability of Concrete, 2017
Mark Alexander, Arnon Bentur, Sidney Mindess
Thaumasite sulfate attack is a particular form of sulfate attack that also involves the aggregates. Thaumasite is a complex calcium carbonate–silicate–sulfate hydrate (CaCO3 ⋅ CaSiO2 ⋅ CaSO4 ⋅ 15H2O). The necessary conditions for its formation are a cold (<15°C), wet environment, sulfates or sulfides in the ground, moisture in the form of mobile groundwater, and carbonate-bearing aggregates such as limestones or dolomites. This form of attack ends with the conversion of the concrete to a mushy paste, as the C–S–H breaks down in the presence of the sulfate and carbonate ions and the binding properties of the matrix are destroyed.
Sulfate transport assessment of cementitious materials-solidified saline soil
Published in Journal of Sustainable Cement-Based Materials, 2023
Fengjuan Wang, Jinyang Jiang, Aoning Zhang, Liguo Wang, Shiyu Sui
On the other hand, chemical reaction expansion is mainly caused by the sulfate reaction. Sulfate from soils reacts with tricalcium aluminate in cement to form the high-sulfur type calcium sulfoaluminate, also known as ettringite (3CaO·Al2O3·3CaSO4·32H2O) [23]. Ettringite is a needle-like crystal with strong expansibility, which could lead to the destruction of the soil. Another reaction is that calcium–silicate–hydrate (C–S–H) gel reacts with SO42− in sulfate solution below 15 °C, with sufficient water and carbonate, to form thaumasite. The molecular formula of thaumasite is CaSiO3·CaCO3·CaSO4·15H2O. The main hazard of thaumasite is that its reaction consumes the C–S–H gel, thus reducing the binding effect of the materials [24,25].
A case study on corrosion conditions and guidelines for repair of a reinforced concrete chimney in industrial environment
Published in Structure and Infrastructure Engineering, 2022
Maddalena Carsana, Matteo Gastaldi, Elena Redaelli
Sulphates in concrete may be due both to the gypsum present in the cement as regulator of setting time and to the possible penetration of sulphate ions (for example, those dissolved in the fumes condensate) which can produce expansion effects when reacting with the constituents of cement matrix. In particular, different destructive reactions due to sulphates penetration in concrete could develop gypsum bi-hydrate (CaSO4·2H2O), ettringite (3CaO·Al2O3·3CaSO4·32H2O) or thaumasite (CaCO3·CaSO4·CaSiO3·15H2O). The formation of thaumasite (Collepardi, 2006; Coppola, 2007; Neville, 2011), whose effects would have been more devastating, can be excluded considering that the fumes, although having high humidity and contaminants, are characterized by a high temperature which is not compatible with this specific reaction. Indeed, thaumasite develops in cold climate (0–5 °C) and wet environments (R.H.> 95%) rich of carbon dioxide.
Wood bioash effect as lime replacement in the stabilisation of different clay subgrades
Published in International Journal of Pavement Engineering, 2020
Martina Zagvozda, Tatjana Rukavina, Sanja Dimter
Even though linear swelling has been reduced and has stopped during 96 h measuring, a possibility of additional swelling problems due to sulphate-induced heave could limit the usage of this WA. Sulphate heave occurs from expansive mineral formation (ettringite, thaumasite) when sulphate minerals already present in soil react with lime or other calcium-based stabilisers (Little et al. 2010, Buttress et al.2013, Gadouri et al.2017). Expansion in stabilised soil can occur immediately after compaction or manifest months or years after binder addition (Nair and Little 2011). Even though used local soil is not sulphate bearing, a case for most of Croatia, chemical composition of WA shows that its application to soil presents external addition of sulphur. In soluble form and in the presence of water, this could result in long-term sulphate heave. To avoid possible detrimental effects, the ratio of lime substitution with WA should be restricted in order to keep the levels of sulphate under recommended levels of moderate to high risk (5000–8000 ppm) set by Little and Nair (2009). Maximum of around 3.5% WA in mixture would mean around 7500 ppm. Additionally, before in situ application, research to determine soluble sulphur could be done and techniques recommended by several authors or guidelines (Harris et al. 2004, Little and Nair 2009, Britpave 2011), to reduce the possibility of sulphate-induced heaving, such as increased water content, mellowing and other, should be conducted.