Cementitious binders for geopolymer, geopolymers, and uses thereof
Binders for geopolymers, which include: a) not less than 30 w % of a mixture of at least two chemically different aluminosilicates, b) not less than 20 w % of Ordinary Portland cement, and c) 8-20 w % of a mixture of calcium sulfoaluminate cement or calcium aluminate cement with a source of calcium sulfate, wherein in the mixture the weight ratio of calcium sulfate to calcium sulfoaluminate and/or calcium aluminate is between 0.08-1.5, preferably 0.3-1.1, more preferably 0.6-1.1. Also, geopolymers using such binders as well as their use in various construction methods.
1 . A cementitious binder for geopolymers, the cementitious binder comprising in each case relative to the total dry weight of cementitious binder
a) not less than 30 w % of a mixture of at least two chemically different aluminosilicates, wherein a first aluminosilicate is steelmaking slag and further aluminosilicates are selected from fly ash of class F according to ASTM C618 and/or calcined clay, and wherein a weight ratio of the steelmaking slag to the fly ash, if present, is from 1.5:1 to 1:2 and a weight ratio of the steelmaking slag to the calcined clay, if present, is from 2:1 to 5:1,
b) not less than 20 w % of Ordinary Portland cement,
wherein a weight ratio of the Ordinary Portland Cement to the mixture of the at least two chemically different aluminosilicates is from 0.3 to 2, and
c) 8-20 w % of a mixture of calcium sulfoaluminate cement or calcium aluminate cement with a source of calcium sulfate, wherein in the mixture the weight ratio of calcium sulfate to calcium sulfoaluminate and/or calcium aluminate is from 0.6 to 1.5.
2 . A cementitious binder as claimed in claim 1 , wherein the at least two chemically different aluminosilicates are selected from the steelmaking slag and the fly ash of class F according to ASTM C618.
3 . A cementitious binder as claimed in claim 1 , wherein the at least two chemically different aluminosilicates are selected from the steelmaking slag and the calcined clay.
4 . A cementitious binder as claimed in claim 1 , wherein the cementitious binder additionally comprises from 5 to 15 w % of silica fume, relative to the total dry weight of cementitious binder.
5 . A cementitious binder as claimed in claim 1 , wherein silica fume, the calcined clay, and the fly ash of class F according to ASTM C618 are present and wherein a weight ratio of the sum of the silica fume and the calcined clay to the fly ash is from 0.1 to 0.5.
6 . A cementitious binder as claimed in claim 1 , wherein the steelmaking slag is ground granulated blast furnace slag.
7 . A cementitious binder as claimed in claim 1 , wherein the source of calcium sulfate is anhydrite.
8 . A geopolymer composition comprising
a) the cementitious binder as claimed in claim 1 ,
b) aggregates and/or fillers,
c) optionally further additives.
9 . A method for repair of concrete or mortar structures or of masonry, the method comprising the steps of
a) providing the cementitious binder according to claim 1 or a geopolymer comprising the cementitious binder according to claim 1 , further comprising aggregates and/or fillers, and optionally further additives,
b) mixing the cementitious binder or the geopolymer composition provided in step a) with water,
c) applying the mixture obtained in step b) to the surface of a hardened concrete or mortar structure, and
d) optionally hardening the applied mixture.
10 . A method for protection of a structure, the method comprising the steps of
a) providing the cementitious binder according to claim 1 or a geopolymer comprising the cementitious binder according to claim 1 , further comprising aggregates and/or fillers, and optionally further additives,
b) mixing the cementitious binder or the geopolymer composition provided in step a) with water,
c) applying the mixture obtained in step b) to the surface of the hardened structure, and
d) optionally hardening the applied mixture.
11 . A method for waterproofing of a structure, the method comprising the steps of
a) providing the cementitious binder according to claim 1 or a geopolymer comprising the cementitious binder according to claim 1 , further comprising aggregates and/or fillers, and optionally further additives,
b) mixing the cementitious binder or the geopolymer composition provided in step a) with water,
c) applying the mixture obtained in step b) to the surface of the hardened structure, and
d) optionally hardening the applied mixture.
12 . A method for 3D printing of a mortar composition, the method comprising the steps of
a) providing the cementitious binder according to claim 1 or a geopolymer comprising the cementitious binder according to claim 1 , further comprising aggregates and/or fillers, and optionally further additives,
b) mixing the cementitious binder or the geopolymer composition provided in step a) with water, and
optionally conveying the mixture obtained in step b) to a print head,
c) applying the mixture obtained in step b) from the print head layer by layer to form a 3 dimensional object, and
d) optionally hardening the 3 dimensional object.
13 . A method for shotcreting, the method comprising the steps of
a) providing the cementitious binder according to claim 1 or a geopolymer comprising the cementitious binder according to claim 1 , further comprising aggregates and/or fillers, and optionally further additives,
b) mixing the cementitious binder or the geopolymer composition provided in step a) with water,
c) conveying the mixture obtained in step b) to a gun,
d) optionally intermixing an additional accelerator to the mixture obtained in step b),
e) spraying the mixture from the gun into a cavity and/or onto a surface, and
f) optionally hardening the applied mixture.