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Hydration of the cement paste with Na2CO3 addition
This research provides a fundamental understanding of the early stage hydration of Portland cement paste modified by 2 and 4 wt-% of sodium carbonate. An excess of CO3(2-) ions retards the Ca(OH)2 development and enables an intensive rise and growth of CaCO3 crystals in hydrated cement. This process lasts very intensivley from 6 to 24 hours. A high conversion of uncreated clinker materials minerals to hydration products in the cement - Na2CO3 pastes takes place rapidly between 1 and 24 hours. Later the conversion of clinker minerals to the hydrate phase is reduced and higher contents of calcite and vaterite relative to that of Ca(OH)2 in comparison with those found in the Portland cement paste are observed. As a consequence of this, differences in strength, dynamic modulus of elasticity and porosity between hardened Portland cement paste and those modified by Na2CO3 are found. The decrease in two-year compressive strength and elasticity modulus of cement - Na2CO3 pastes relative to Portland cement pastes by the loss in binding capability due to the preferential CaCO3 formation at the early stage of cement hydration and consequent growth of CaCO3 crystals due to gradual carbonation, particularly in air with 60 % of relative humidity. In this respect the higher volume of non-affected products of the hydration process by the action of CO2, the better compressive strength and elasticity modulus the cement paste becomes.
Hydration of the cement paste with Na2CO3 addition
This research provides a fundamental understanding of the early stage hydration of Portland cement paste modified by 2 and 4 wt-% of sodium carbonate. An excess of CO3(2-) ions retards the Ca(OH)2 development and enables an intensive rise and growth of CaCO3 crystals in hydrated cement. This process lasts very intensivley from 6 to 24 hours. A high conversion of uncreated clinker materials minerals to hydration products in the cement - Na2CO3 pastes takes place rapidly between 1 and 24 hours. Later the conversion of clinker minerals to the hydrate phase is reduced and higher contents of calcite and vaterite relative to that of Ca(OH)2 in comparison with those found in the Portland cement paste are observed. As a consequence of this, differences in strength, dynamic modulus of elasticity and porosity between hardened Portland cement paste and those modified by Na2CO3 are found. The decrease in two-year compressive strength and elasticity modulus of cement - Na2CO3 pastes relative to Portland cement pastes by the loss in binding capability due to the preferential CaCO3 formation at the early stage of cement hydration and consequent growth of CaCO3 crystals due to gradual carbonation, particularly in air with 60 % of relative humidity. In this respect the higher volume of non-affected products of the hydration process by the action of CO2, the better compressive strength and elasticity modulus the cement paste becomes.
Hydration of the cement paste with Na2CO3 addition
Hydratisierung von Zementpaste mit Zusatz von Na2CO3
Janotka, I. (author)
Ceramics Silikaty, Prag ; 45 ; 16-23
2001
8 Seiten, 10 Bilder, 3 Tabellen, 33 Quellen
Article (Journal)
English
Portlandzement , Hydratisieren , Kristall , Natriumcarbonat , Carbonat , Ion , Elastizität , Wasser
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