Fly ash-based cementitious mixture
View Patent ↗A cementitious mixture for high-volume production of masonry products comprises a hydraulic binder accounting for 20 wt % or more of the cementitious mixture, the hydraulic binder comprising 75 to 100 wt % Class C fly ash with a CaO equivalent content of at least 15% by weight. The cementitious mixture also comprises one or more aggregates, and a set control system.
1. A method of forming a building product comprising:
providing a Class C fly ash with at least 15% by weight of CaO equivalent;
forming a cementitious mixture, wherein forming the cementitious mixture includes:
forming a hydraulic binder mixture comprising between 75 to 100% by weight of the Class C fly ash;
adding one or more aggregates comprising between 10 and 80% by weight of the cementitious mixture;
adding a set control system comprising between 0.04 and 5% by weight of the cementitious mixture, wherein the set control system includes a mixture of 1 part boron in salt or acid form and between 3 and 27 parts of dextro (L+) tartaric acid by weight;
adding between 3 and 25% by weight of water to the cementitious mixture;
mixing the mixture and water in air while applying shear forces;
vibration compacting the mixture into a shape under a confining pressure less than 345 kPa; and
hardening the vibration compacted mixture at a temperature below 100° C. and in the presence of water.
2. The method of claim 1 , wherein the mixing of the mixture and added water is performed for 5 to 600 seconds.
3. The method of claim 1 , wherein the vibration compacting further comprises variable frequency vibration compacting with a vibration force ranging from 5 to 88 kN for a time period ranging from about 1 to 60 seconds.
4. The method of claim 1 , further comprising at least one of antiquing, texturing, scoring, cutting, shaping, crushing, or grinding the hardened, vibration compacted mixture.
5. The method of claim 3 , wherein the mixture substantially retains its shape when removed from the mold at least 0.1 seconds after completion of vibration compacting.
6. The method of claim 3 , wherein the hardened, vibration compacted mixture has a density between 0.50 and 0.98 times a theoretical density.
7. The method of claim 1 , wherein the one or more aggregates include at least one of silica sand, limestone, granite, dolerite, basalt, sandstone, dolomite, quartz, recycled concrete, recycled foundry sand, recycled glass, recycled minerals, or mine spoils having particle sizes ranging from about one micrometer to about 3 centimeters.
8. The method of claim 1 , wherein comprising adding an efflorescence control agent, including at least one of an integral water repellent, an organic acid, a carbon containing base, or a salt.
9. The method of claim 8 , further comprising adding the integral water repellent, the added integral water repellent accounting for about 0.025% by weight to about 5% by weight of fly ash in the cementitious mixture and including at least one of Octyltriethoxysilane or a C14 to C18 organic fatty acid.
10. The method of claim 1 , wherein the hardening commences within a range of 10 to 240 minutes after the cementitious mixture is mixed with the water.
11. The method of claim 1 , wherein the added water is sufficient to provide a slump of 0 to 15 centimeters when tested by the standard cone method for measuring slump.
12. The method of claim 1 , wherein the shape includes a brick, a block, a paver, a segmented retaining wall block, a pipe, a roofing tile, a panel, or an architectural element.
13. The method of claim 1 , further comprising adding coloring agents including at least one of a pigment derived from a metal oxide, hydroxides or salts, or a colored organic compound.