Arenesulfonic acids could be used as accelerators or retarders due to addition of different concentrations to ordinary portland cement (OPC) pastes. High concentration (0.25...1 mol/l) have an retarding effect and lower concentrations down until 10-6 mol/l activate the hydration reactions in the cement paste. More over the structural properties of the sulfonic molecules allow at constant concentration a division in 2 groups:
1). Benzenesulfonic and toluene p-sulfonic acids act at high additive concentrations (about 1 mol/l) as retarders. Benezenesulfonic acid contains no CH3-group and on the aromatic ring of the toluene p-sulfonic acid the CH3- and SO3H group are sited in opposition.
2). Xylenesulfonic and mesitylenesulfonic acids are built up one aromatic ring substituted by 2 CH3 and one SO3H, respectively 3 CH3 and one SO3H group. That means the number of CH3 groups and the orientation of the substituents decrease the retarding effect in comparison with group 1.
Alkenesulfonic acids CnH2n+1SO3H with n = 1,2,3,5 can act as accelerators but behave in the investigated range of 10-3...1 mol/l as retarders. The retarding effect increase due to the enlargement of the aliphatic chain CnH2n+1 until n = 9.
Detailed studies on temporary heat evolutions demonstrate that as a result of the addition of arenesulfonic acids the heat liberation in the range "minimum of the induction period...48h" is strongly decreased. The addition of alkenesulfonic acid sodium salts show that as a function of the chain length CnH2n+1 the heat liberation in the range 0...minimum of induction period increase and the heat evolution in the time period "minimum of the induction period...48h" is strongly decreased, too. It is an indication that the formation of C-S-H phases, usually formed in the time period "minimum of the induction period...48h" in high amounts, is drastically influenced by the addition of alkenesulfonic acid sodium salts and arenesulfonic acids.
Ettringite crystallise as a first hydration product of C3A and possibly C4AF with CaSO4·2H2O and water in OPC pastes containing 0.25...1mol/l arenesulfonic and alkenesulfonic acids with n=1,2,3,4.At later stages AFm-phases ([Ca2Al(OH)6]+[X·nH2O]-) with X = inorganic or organic anion) with a layer structure are formed and both arenesulfonic and alkenesulfonic acid anions are in-situ chemically fixed in the crystal structure. The identification of the newly formed AFm- phases is based on the characteristic peak scheme of purely synthesised AFm-phases.
Pure AFm-phases containing methane-, ethane-, 1- propane- and 1-butanesulfonic acid anions, toluene p-sulfonic, xylenesulfonic, mesitylenesulfonic acid anions and naphthalene1-sulfonic and naphthalene 2-sulfonic acid anions were synthesised and characterised.
The results on the phase formation and possible formation of solid solutions in binary systems are shown in table 1.
- Binary Systems: Exchange of OH-<=> Sulfonic acid anion
Formation of the end members [Ca2Al(OH)6]+[OH·nH2O]- and [Ca2Al(OH)6]+[X·nH2O]-:
No formation of solid solutions
|
Binary Systems |
Anions |
[Ca2Al(OH)6]+[OH·nH2O]--[Ca2Al(OH)6]+[X·nH2O]-
|
X = C7H7SO3-, C8H9SO3- and C9H11SO3-
|
[Ca2Al(OH)6]+[OH·nH2O]--[Ca2Al(OH)6]+[Y·nH2O]-
|
Y = CH3SO3-, C2H5SO3-, C3H7SO3-
|
[Ca2Al(OH)6]+[OH·nH2O]--[Ca2Al(OH)6]+[Z·nH2O]
|
Z = C10H7-1-SO3-
|
However, solid solution occurred in the system [Ca2Al(OH)6]+[OH·nH2O]-- [Ca2Al(OH)6]+[C10H7-2-SO3-·nH2O] with the composition [Ca2Al(OH)6]+[OH·nH2O]-- [Ca2Al(OH)6]+[(1-x)C107-2-SO3- xOH-·nH2O] x = 0 - 0.9 at different relative humidities.
In binary systems containing two different arenesulfonic acid anions a formation of solid solutions at different relative humidities occurs (tab.2).
- Binary Systems: Exchange of Sulfonic acid anion <=> Sulfonic acid anion
Formation of solid solutions:
[Ca2Al(OH)6]+[(1-x)X·xY·nH2O]- x = [0.1,0.9]
|
Binary Systems
|
[Ca2Al(OH)6]+[C6H5SO3·nH2O]-- [Ca2Al(OH)6]+[C7H7SO3·nH2O]-
|
[Ca2Al(OH)6]+[C6H5SO3·nH2O]-- [Ca2Al(OH)6]+[C8H9SO3·nH2O]-
|
[Ca2Al(OH)6]+[C6H5SO3·nH2O]-- [Ca2Al(OH)6]+[C9H11SO3·nH2O]-
|
[Ca2Al(OH)6]+[C7H7SO3·nH2O]-- [Ca2Al(OH)6]+[C8H9SO3·nH2O]-
|
[Ca2Al(OH)6]+[C7H7SO3·nH2O]-- [Ca2Al(OH)6]+[C9H11SO3·nH2O]-
|
[Ca2Al(OH)6]+[C8H9SO3·nH2O]-- [Ca2Al(OH)6]+[C9H11SO3·nH2O]-
|
Keywords:
Hydratation, lamellare Calciumaluminathydrate, AFm-Phasen, AFt-Phasen, Sulfonsäuren, Sulfonatsalze, Additive, Beschleuniger, Verzögerer
hydration, lamellar calciumaluminatehydrates, AFm-phases, AFt-phases, sulfonic acids, sulfonic acid salts, additives, admixtures, accelerators, retarders
Online-Dokument im PDF-Format (21.564 KB) mit integrierter Gliederung und im PS-Format (30.394 KB, 3 PS-Dateien im ZIP-Format gepackt).
Inhaltsverzeichnis
Inhaltsverzeichnis, Abkürzungen und Nomenklatur
1. Kurzzusammenfassung (1-2)
2. Einleitung (3-7)
3. Experimentelle Methoden (8-19)
4. Ergebnisse (20-156)
5. Zusammenfassung (157-169)
6. Literaturverzeichnis (170-178)
7. Anhang (179-231)