Phlego: geomimetic cement
Phlego cement improves mechanical properties and reduces carbon footprint by controlling fiber entanglement through hydrothermal processing, enhancing ductility and reflectivity, providing a sustainable alternative to OPC.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-08-29
- Publication Date
- 2026-03-05
AI Technical Summary
Existing cement technologies, particularly Ordinary Portland Cement (OPC), have not adequately addressed the need for improved mechanical properties and reduced carbon footprint, and the specific aspects of Phlego cement production have not been fully explored.
The development of Phlego cement involves controlling fiber entanglement through in-situ growth of fibers via hydrothermal processing, using specific compositional and process parameter ranges to enhance ductility and whiteness, while maintaining cementitious phases found in OPC and geopolymers.
Phlego cement enhances ductility and reduces carbon emissions, offering a visually appealing, high-reflectivity alternative that addresses the carbon-intensive nature of traditional cement production without disrupting the manufacturing process.
Smart Images
Figure US2025044268_05032026_PF_FP_ABST
Abstract
Description
[0001] Phlego: Geomimetic Cement
[0002] FIELD OF THE INVENTION
[0003] This invention relates to Phlego cement.
[0004] BACKGROUND
[0005] Recently, Phlego cement has emerged as a promising alternative to ordinary Portland cement (OPC) as a construction material, providing important advantages of improved mechanical properties and reduced carbon footprint. See US patent publication US 2023 / 0013411, hereby incorporated in its entirety, for further details on Phlego cement .
[0006] Briefly, the composition of the raw meal for Phlego clinker is made of:
[0007] (a) silica (40% to 60% by weight) ;
[0008] (b) aluminum oxide (10% to 25% by weight) ;
[0009] (c) Sulfur oxide (0.5% to 2% by weight) , which together with the presence of CaO and AI2O3, has the capability of forming fibrous ettringite (C-S-A-H, calcium-sulfo-aluminate hydrates) . This provides a natural fiber reinforced mortar;
[0010] (d) Calcium oxide (5% to 16% by weight) , which together with the presence of AI2O3, forms Al-tobermorite (C-A-S-H, calcium-alumino-silicate hydrates) when mixed with pozzolanic ash;
[0011] (e) Alkali metal oxides (Na2O and K2O, 5% to 15% by weight) . Alkalis are important as they serve the dual purpose of (1) speeding up the hydration process of the C-A- S-H and (2) favoring chemical cross-linking, which leads to the formation of polymeric phases . In current clinkers , the presence of alkalis is ensured through the pyroprocessing of clay-rich rocks , which are added to the raw material , or through alkaline solutions . The presence of solid alkali metal oxides within a naturally blended CaO and AI2O3 mix such as Phlego ' s raw meal also ensures the formation of cementitious phases (N / K-A-S-H, sodium and potassium alumino-silicate hydrates ) being typical of geopolymers when the clinker is slaked under alkaline conditions and temperature as low as 80 ° C . By having approximately as much alkali metal oxides (Na2O and K2O) as CaO, together with the presence of AI2O3, this blend has the capability of producing a clinker that is , by its nature , hydraulic .
[0012] An important aspect of this raw meal is what ' s not in it -- carbon-containing chemical species in the raw meal are less than 1 % by weight , and are preferably as close to 0% by weight as possible .
[0013] To produce the Phlego cement one part of this new clinker can be mixed with two parts of poz zolanic ash, either from natural origin or industrial byproducts ( e . g . volcanic or fly ashes ) . Each lump of the clinker phase being dispersed within the poz zolan will then constitute a functional and structural unit of the cement . When slaked, each lump of clinker forms fibrous ettringite ( C-S-A-H, calcium-sul fo-aluminate hydrates ) , creating clusters of seeds of intertwined fibers being dispersed within the poz zolanic material and branching out to the surrounding areas . This results in a natural fiber-reinforced concrete material at the microstructural level . Due to the presence of alkali metal oxides (Na2O and K2O) and CaO, both in the clinker and poz zolanic ash, fibrous ettringite will result embedded in a crossbred or hybrid matrix made of a geopolymer or alkali-activated cements with gel-like ( C-N / K- A-S-H) phases and C-A-S-H ( C-A-S-H, calcium-alumino-silicate hydrates ) .
[0014] However, there are many aspects of this new approach for making cement and concrete that have not yet been considered in detail in the literature , and for which copying recipes from ordinary Portland cement technology is not expected to be appropriate .
[0015] SUMMARY
[0016] In this work, Phlego cement technology is further developed by producing a fibrous precursor and controlling fiber entanglement in Phlego cement by reinforcing it with in-situ growth of fibers through seeding, thereby enhancing ductility . We mimic natural processes of rock cementation in hydrothermal settings , while maintaining cementitious phases found in OPC, geopolymers , or alkali-activated cements .
[0017] Such controlled fiber entanglement can be provided via hydrothermal processing . The contribution of this work resides not in the mere use of hydrothermal synthesis , but in the identi fication and application of speci fic compositional and process parameter ranges . These ranges ( given below) -- were determined by systematic exploration of the experimental matrix, including degree of fill , temperature , and the composition of the nutrient solute -- and enable the formation of fiber entanglement directly from Phlego . Within this process , the fiber precursor acts as a heterogeneous nucleation site , thereby increasing nucleation density and facilitating the in-situ growth of ettringite , tobermorite , and gel-like C- (N, K) -A-S-H phases during mortar cementation from Phlego .
[0018] Further aspects of this work include : 1) Use of Phlego cement as a supplementary material. The use of Phlego as a replacement for OPC offers two key advantages: it enhances ductility due to the fibrous nature of Phlego and increases CO2 savings owing to its volcanic origin; and
[0019] 2) Control the whiteness of Phlego cement via composition. That allows aesthetically pleasing surfaces and helps reduce the urban heat island effect due to its high reflectivity, e.g., as shown on FIG. 4.
[0020] Significant advantages are provided. Phlego addresses the carbon-intensive nature of cement at the upstream stage of the manufacturing chain without disrupting it. This approach increases throughput, boosting transportation and fuel efficiency.
[0021] BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 schematically shows an exemplary process according to an embodiment of the invention.
[0023] FIGs. 2A-C are exemplary scanning electron microscope (SEM) images showing microstructure details of the fibrous precursor .
[0024] FIGs. 2D-F are exemplary scanning electron microscope images showing microstructure details of the resulting fibrous concrete.
[0025] FIG. 3A is an exemplary SEM image of the precursor with features labeled.
[0026] FIG. 3B is a ternary composition diagram.
[0027] FIG. 4 is measured reflectance data showing that Phlego concrete can be whiter than concrete from ordinary Portland cement . DETAILED DESCRIPTION
[0028] FIG . 1 schematically shows an exemplary process according to an embodiment of the invention . Here step 102 is calcining Phlego with limestone , step 104 is mixing the resulting calcined product with gypsum, and step 106 is performing hydrothermal synthesis on the resulting mixture .
[0029] More speci fically, an exemplary embodiment of the invention is a method of making a fibrous precursor for use in a Phlego cement mixture . A mixture of Phlego raw meal composition, limestone and gypsum is formed . This mixture is 42-47 % Phlego raw meal composition, 42-47 % limestone and 5- 10% gypsum by weight . The Phlego raw meal composition is 40- 60% silica, 10-25% aluminum oxide , 0 . 5-2 % sul fur, 5- 16% calcium oxide , 5- 15% sodium and / or potassium oxide , and 1 % or less carbon-containing species by weight . This mixture can be formed by calcining the Phlego raw meal composition with limestone to provide a calcined product and then mixing the calcined product with gypsum . Hydrothermal synthesis performed on this mixture provides the fibrous precursor . The water to mixture ratio (w / m) for this hydrothermal synthesis is in a range between 0 . 88 and 2 by weight .
[0030] The fibrous precursor preferably includes fibrous ( C-A- S-H) and gel-like ( C-N / K-A-S-H) phases .
[0031] The method can further include oven-drying a moist product of the closed-chamber hydrothermal synthesis to provide a dried product , and grinding the dried product to provide the fibrous precursor .
[0032] The closed-chamber hydrothermal synthesis preferably includes elevating a chamber temperature of a closed reaction chamber to one or more elevated temperatures in a range from 150 °C to 250 °C . The temperature ramp rate for increasing and / or decreasing the chamber temperature is preferably between 2 and 4 ° C min-1. The closed reaction chamber is preferably held at the one or more elevated temperatures between 12 and 24 hours .
[0033] The closed-chamber hydrothermal synthesis preferably comprises filling a closed reaction chamber with 10- 17 % by volume of water and adding the mixture to the closed reaction chamber such that the water to mixture ratio is in a range between 0 . 88 and 2 by weight . However, it is also possible to mix the water and mixture in this proportion before adding the resulting wet mixture to the reaction chamber ( i . e . , there is no need to do the mixing with water in the reaction chamber ) .
[0034] A corresponding cement composition can be made by mixing the fibrous precursor with a Phlego clinker made from the Phlego raw meal composition and gypsum to provide the cement composition . Here the cement composition includes 5- 10% gypsum and at least 5% of the fibrous precursor by weight , with the balance being the Phlego clinker .
[0035] Example :
[0036] In one example , 5 grams of calcined Phlego raw meal + limestone is mixed with ~ 0 . 42 grams of gypsum to provide the mixture . This is placed in a 45 mL autoclave that also includes 5 grams of water ( equivalently, 5 mL of water ) . Then the autoclave was closed, placed in a furnace , heated to 200 ° C and left to react for 24 hours . The autoclave was allowed to cool to room temperature inside the furnace . After cooling, the moist material was removed from the autoclave and oven dried for 24 hours . Then the material was roughly ground with a mortar and pestle . Experiments were also carried out in a large autoclave reactor ( 450 mL ) to demonstrate scaling of the treatment using four times all material quantities described above.
[0037] FIGs. 2A-F are SEM images. Hydrothermally treated precursor material (FIGs. 2A-C) shows hollow structures with entangled fibers sprouting from the matrix (enlarged in FIG. 2B and detailed in FIG. 2C) . FIGs. 2D-F show Phlego cement paste, where tobermorite fibers are embedded in a gel-like matrix (enlarged in FIG. 2E) , with FIG. 2F highlighting fibers sprouting from hollow structures.
[0038] The morphological examination of the microstructure of the hydrothermally treated material by SEM reveals the presence of fibrous phases both within the matrix and inside hollowed and rimmed structures (FIGs. 2A-B) . Often, fibers exhibit spaghetti-like structures comprising long fibrils that form disordered and entangled patterns (FIG. 2B) . The outside rim in the structure reveals fibers sprouting from small, spherical grains (FIG. 2C) , suggesting that fibers might be serving as seeds for fiber growth. When the cementitious mix is allowed to cure for 28 days, fibers become embedded within a wrinkled, gel-like matrix (FIGs. 2D-E) , while maintaining their interwoven structure, visible in exposed hollowed structures (FIG. 2F) .
[0039] FIG. 3A is an SEM micrograph showing characteristic hollowed microstructures within the matrix of the fibrous, hydrothermally treated material. Labeled squares represent different features investigated via EMPA (electron microprobe analysis) : the rim (H) , the fibers within the structure (S) , and the fibers within the matrix (D) .
[0040] FIG. 3B is a ternary diagram representing the weight composition of SiCt, A120a, and CaO. The data points for this are from lOxlO-pixel squares in the image of FIG. 3A. Instead of showing all these data points, contours are drawn containing the densest 80% of the data for each region. Here the contour lines are labeled H, S, D according to which region of FIG 3A they come from. The compositional fields of typical cement phases (a-wollastonite, anorthite, gehlenite, C2S, and C3S) are overlayed, along with the compositional intervals of hydrated cementitious phases, including C-A-S-H (dashed straight line with arrows) , N-A-S-H (dotted straight line with arrows) , and their hybrid mix (solid line with arrows) . The fibrous material (S and D) aligns with the C-A-S-H / N-A-S-H mixture, while the halo (H) primarily falls within the Al-rich gehlenite field.
[0041] These fibers have a Ca / (Si+Al) ratio of 0.54 and 0.61 on average. The fibers within the rimmed structure (S) stand out for their higher Na2O content, reaching up to 20 wt% in a SiO2-A12O3-Na2O ternary diagram (not shown here) . In contrast, the fibers within the matrix (D) have a maximum Na2O content of 6%. The rim of the hollowed structure (H) is aluminum-rich and falls within the compositional range of gehlenite .
[0042] Phlego Cement distinguishes itself by its white composition, offering a brighter and more visually appealing alternative to the traditional grey Ordinary Portland Cement (OPC) , as is evident from visual observation of samples. It is also useful that Phlego cement is whiter than Portland cement in the infrared. FIG. 4 shows Reflectance Infrared Spectroscopy (FT-IR) measurements comparing the IR light reflection from OPC (dashed line) and Phlego (solid line) . Compared to OPC, Phlego has higher reflectance in the portion of the near-infrared region of the electromagnetic spectrum that goes from 1 pm to ~2 pm. As indicated above, this increased IR reflectance may help reduce the urban heat island effect. CLAIMS
[0043] 1. A method of making a fibrous precursor for use in a Phlego cement mixture, the method comprising: forming a mixture of Phlego raw meal composition, limestone and gypsum; wherein the Phlego raw meal composition is 40-60% silica, 10-25% aluminum oxide, 0.5-2% sulfur, 5-16% calcium oxide, 5-15% sodium and / or potassium oxide, and 1% or less carbon-containing species by weight; wherein the mixture is 42-47% Phlego raw meal composition, 42-47% limestone and 5-10% gypsum by weight; performing closed-chamber hydrothermal synthesis on the mixture to provide a fibrous precursor, wherein a water to mixture ratio (w / m) of the closed-chamber hydrothermal synthesis is in a range between 0.88 and 2 by weight.
[0044] 2. A method of making a cement composition, the method comprising : mixing the fibrous precursor of claim 1, a clinker made from the Phlego raw meal composition and gypsum to provide the cement composition; wherein the cement composition includes 5-10% gypsum and at least 5% of the fibrous precursor by weight.
[0045] 3. The method of claim 2, further comprising making a concrete using the cement composition, wherein the concrete is whiter than ordinary Portland concrete.
[0046] 4. The method of claim 1, wherein the closed-chamber hydrothermal synthesis includes: elevating a chamber temperature of a closed reaction chamber to one or more elevated temperatures in a range from 150 °C to 250 °C.
[0047] 5. The method of claim 4, wherein a temperature ramp rate for increasing and / or decreasing the chamber temperature is between 2 and 4 °C min-1.
[0048] 6. The method of claim 4, wherein the closed reaction chamber is held at the one or more elevated temperatures between 12 and 24 hours.
[0049] 7. The method of claim 1, further comprising: oven-drying a moist product of the closed-chamber hydrothermal synthesis to provide a dried product; grinding the dried product to provide the fibrous precursor .
[0050] 8. The method of claim 1, wherein the closed-chamber hydrothermal synthesis comprises filling a closed reaction chamber with 10-17% by volume of water.
[0051] 9. The method of claim 8, wherein the closed-chamber hydrothermal synthesis comprises adding the mixture to the closed reaction chamber such that the water to mixture ratio is in a range between 0.88 and 2 by weight.
[0052] 10. The method of claim 1, wherein the closed-chamber hydrothermal synthesis comprises mixing water with the mixture , then adding a resulting moist product to a closed reaction chamber, wherein the water used for this mixture has a volume in a range between 10% and 17 % of a volume of the closed reaction chamber .
[0053] 11 . The method of claim 1 , wherein the forming a mixture of Phlego raw meal composition, limestone and gypsum comprises : calcining the Phlego raw meal composition and limestone to provide a calcined product ; and mixing the calcined product with the gypsum .
[0054] 12 . The method of claim 1 , wherein the fibrous precursor includes fibrous ( C-A-S-H) and gel-like ( C-N / K-A-S-H) phases .
[0055] Phlego: Geomimetic Cement
[0056] FIELD OF THE INVENTION
[0057] This invention relates to Phlego cement.
[0058] BACKGROUND
[0059] Recently, Phlego cement has emerged as a promising alternative to ordinary Portland cement (OPC) as a construction material, providing important advantages of improved mechanical properties and reduced carbon footprint. See US patent publication US 2023 / 0013411, hereby incorporated in its entirety, for further details on Phlego cement .
[0060] Briefly, the composition of the raw meal for Phlego clinker is made of:
[0061] (a) silica (40% to 60% by weight) ;
[0062] (b) aluminum oxide (10% to 25% by weight) ;
[0063] (c) Sulfur oxide (0.5% to 2% by weight) , which together with the presence of CaO and AI2O3, has the capability of forming fibrous ettringite (C-S-A-H, calcium-sulfo-aluminate hydrates) . This provides a natural fiber reinforced mortar;
[0064] (d) Calcium oxide (5% to 16% by weight) , which together with the presence of AI2O3, forms Al-tobermorite (C-A-S-H, calcium-alumino-silicate hydrates) when mixed with pozzolanic ash;
[0065] (e) Alkali metal oxides (Na2O and K2O, 5% to 15% by weight) . Alkalis are important as they serve the dual purpose of (1) speeding up the hydration process of the C-A- S-H and (2) favoring chemical cross-linking, which leads to the formation of polymeric phases . In current clinkers , the presence of alkalis is ensured through the pyroprocessing of clay-rich rocks , which are added to the raw material , or through alkaline solutions . The presence of solid alkali metal oxides within a naturally blended CaO and AI2O3 mix such as Phlego ' s raw meal also ensures the formation of cementitious phases (N / K-A-S-H, sodium and potassium alumino-silicate hydrates ) being typical of geopolymers when the clinker is slaked under alkaline conditions and temperature as low as 80 ° C . By having approximately as much alkali metal oxides (Na2O and K2O) as CaO, together with the presence of AI2O3, this blend has the capability of producing a clinker that is , by its nature , hydraulic .
[0066] An important aspect of this raw meal is what ' s not in it -- carbon-containing chemical species in the raw meal are less than 1 % by weight , and are preferably as close to 0% by weight as possible .
[0067] To produce the Phlego cement one part of this new clinker can be mixed with two parts of poz zolanic ash, either from natural origin or industrial byproducts ( e . g . volcanic or fly ashes ) . Each lump of the clinker phase being dispersed within the poz zolan will then constitute a functional and structural unit of the cement . When slaked, each lump of clinker forms fibrous ettringite ( C-S-A-H, calcium-sul fo-aluminate hydrates ) , creating clusters of seeds of intertwined fibers being dispersed within the poz zolanic material and branching out to the surrounding areas . This results in a natural fiber-reinforced concrete material at the microstructural level . Due to the presence of alkali metal oxides (Na2O and K2O) and CaO, both in the clinker and poz zolanic ash, fibrous ettringite will result embedded in a crossbred or hybrid matrix made of a geopolymer or alkali-activated cements with gel-like ( C-N / K-
[0068] 2 A-S-H) phases and C-A-S-H ( C-A-S-H, calcium-alumino-silicate hydrates ) .
[0069] However, there are many aspects of this new approach for making cement and concrete that have not yet been considered in detail in the literature , and for which copying recipes from ordinary Portland cement technology is not expected to be appropriate .
[0070] SUMMARY
[0071] In this work, Phlego cement technology is further developed by producing a fibrous precursor and controlling fiber entanglement in Phlego cement by reinforcing it with in-situ growth of fibers through seeding, thereby enhancing ductility . We mimic natural processes of rock cementation in hydrothermal settings , while maintaining cementitious phases found in OPC, geopolymers , or alkali-activated cements .
[0072] Such controlled fiber entanglement can be provided via hydrothermal processing . The contribution of this work resides not in the mere use of hydrothermal synthesis , but in the identi fication and application of speci fic compositional and process parameter ranges . These ranges ( given below) -- were determined by systematic exploration of the experimental matrix, including degree of fill , temperature , and the composition of the nutrient solute -- and enable the formation of fiber entanglement directly from Phlego . Within this process , the fiber precursor acts as a heterogeneous nucleation site , thereby increasing nucleation density and facilitating the in-situ growth of ettringite , tobermorite , and gel-like C- (N, K) -A-S-H phases during mortar cementation from Phlego .
[0073] Further aspects of this work include : 1) Use of Phlego cement as a supplementary material. The use of Phlego as a replacement for OPC offers two key advantages: it enhances ductility due to the fibrous nature of Phlego and increases CO2 savings owing to its volcanic origin; and
[0074] 2) Control the whiteness of Phlego cement via composition. That allows aesthetically pleasing surfaces and helps reduce the urban heat island effect due to its high reflectivity, e.g., as shown on FIG. 4.
[0075] Significant advantages are provided. Phlego addresses the carbon-intensive nature of cement at the upstream stage of the manufacturing chain without disrupting it. This approach increases throughput, boosting transportation and fuel efficiency.
[0076] BRIEF DESCRIPTION OF THE DRAWINGS
[0077] FIG. 1 schematically shows an exemplary process according to an embodiment of the invention.
[0078] FIGs. 2A-C are exemplary scanning electron microscope (SEM) images showing microstructure details of the fibrous precursor .
[0079] FIGs. 2D-F are exemplary scanning electron microscope images showing microstructure details of the resulting fibrous concrete.
[0080] FIG. 3A is an exemplary SEM image of the precursor with features labeled.
[0081] FIG. 3B is a ternary composition diagram.
[0082] FIG. 4 is measured reflectance data showing that Phlego concrete can be whiter than concrete from ordinary Portland cement .
[0083] 4 DETAILED DESCRIPTION
[0084] FIG . 1 schematically shows an exemplary process according to an embodiment of the invention . Here step 102 is calcining Phlego with limestone , step 104 is mixing the resulting calcined product with gypsum, and step 106 is performing hydrothermal synthesis on the resulting mixture .
[0085] More speci fically, an exemplary embodiment of the invention is a method of making a fibrous precursor for use in a Phlego cement mixture . A mixture of Phlego raw meal composition, limestone and gypsum is formed . This mixture is 42-47 % Phlego raw meal composition, 42-47 % limestone and 5- 10% gypsum by weight . The Phlego raw meal composition is 40- 60% silica, 10-25% aluminum oxide , 0 . 5-2 % sul fur, 5- 16% calcium oxide , 5- 15% sodium and / or potassium oxide , and 1 % or less carbon-containing species by weight . This mixture can be formed by calcining the Phlego raw meal composition with limestone to provide a calcined product and then mixing the calcined product with gypsum . Hydrothermal synthesis performed on this mixture provides the fibrous precursor . The water to mixture ratio (w / m) for this hydrothermal synthesis is in a range between 0 . 88 and 2 by weight .
[0086] The fibrous precursor preferably includes fibrous ( C-A- S-H) and gel-like ( C-N / K-A-S-H) phases .
[0087] The method can further include oven-drying a moist product of the closed-chamber hydrothermal synthesis to provide a dried product , and grinding the dried product to provide the fibrous precursor .
[0088] The closed-chamber hydrothermal synthesis preferably includes elevating a chamber temperature of a closed reaction chamber to one or more elevated temperatures in a
[0089] 5 range from 150 °C to 250 °C . The temperature ramp rate for increasing and / or decreasing the chamber temperature is preferably between 2 and 4 ° C min-1. The closed reaction chamber is preferably held at the one or more elevated temperatures between 12 and 24 hours .
[0090] The closed-chamber hydrothermal synthesis preferably comprises filling a closed reaction chamber with 10- 17 % by volume of water and adding the mixture to the closed reaction chamber such that the water to mixture ratio is in a range between 0 . 88 and 2 by weight . However, it is also possible to mix the water and mixture in this proportion before adding the resulting wet mixture to the reaction chamber ( i . e . , there is no need to do the mixing with water in the reaction chamber ) .
[0091] A corresponding cement composition can be made by mixing the fibrous precursor with a Phlego clinker made from the Phlego raw meal composition and gypsum to provide the cement composition . Here the cement composition includes 5- 10% gypsum and at least 5% of the fibrous precursor by weight , with the balance being the Phlego clinker .
[0092] Example :
[0093] In one example , 5 grams of calcined Phlego raw meal + limestone is mixed with ~ 0 . 42 grams of gypsum to provide the mixture . This is placed in a 45 mL autoclave that also includes 5 grams of water ( equivalently, 5 mL of water ) . Then the autoclave was closed, placed in a furnace , heated to 200 ° C and left to react for 24 hours . The autoclave was allowed to cool to room temperature inside the furnace . After cooling, the moist material was removed from the autoclave and oven dried for 24 hours . Then the material was roughly ground with a mortar and pestle . Experiments were also carried out in a large autoclave reactor ( 450 mL )
[0094] 6 to demonstrate scaling of the treatment using four times all material quantities described above.
[0095] FIGs. 2A-F are SEM images. Hydrothermally treated precursor material (FIGs. 2A-C) shows hollow structures with entangled fibers sprouting from the matrix (enlarged in FIG. 2B and detailed in FIG. 2C) . FIGs. 2D-F show Phlego cement paste, where tobermorite fibers are embedded in a gel-like matrix (enlarged in FIG. 2E) , with FIG. 2F highlighting fibers sprouting from hollow structures.
[0096] The morphological examination of the microstructure of the hydrothermally treated material by SEM reveals the presence of fibrous phases both within the matrix and inside hollowed and rimmed structures (FIGs. 2A-B) . Often, fibers exhibit spaghetti-like structures comprising long fibrils that form disordered and entangled patterns (FIG. 2B) . The outside rim in the structure reveals fibers sprouting from small, spherical grains (FIG. 2C) , suggesting that fibers might be serving as seeds for fiber growth. When the cementitious mix is allowed to cure for 28 days, fibers become embedded within a wrinkled, gel-like matrix (FIGs. 2D-E) , while maintaining their interwoven structure, visible in exposed hollowed structures (FIG. 2F) .
[0097] FIG. 3A is an SEM micrograph showing characteristic hollowed microstructures within the matrix of the fibrous, hydrothermally treated material. Labeled squares represent different features investigated via EMPA (electron microprobe analysis) : the rim (H) , the fibers within the structure (S) , and the fibers within the matrix (D) .
[0098] FIG. 3B is a ternary diagram representing the weight composition of SiCt, A120a, and CaO. The data points for this are from lOxlO-pixel squares in the image of FIG. 3A. Instead of showing all these data points, contours are drawn
[0099] 7 containing the densest 80% of the data for each region. Here the contour lines are labeled H, S, D according to which region of FIG 3A they come from. The compositional fields of typical cement phases (a-wollastonite, anorthite, gehlenite, C2S, and C3S) are overlayed, along with the compositional intervals of hydrated cementitious phases, including C-A-S-H (dashed straight line with arrows) , N-A-S-H (dotted straight line with arrows) , and their hybrid mix (solid line with arrows) . The fibrous material (S and D) aligns with the C-A-S-H / N-A-S-H mixture, while the halo (H) primarily falls within the Al-rich gehlenite field.
[0100] These fibers have a Ca / (Si+Al) ratio of 0.54 and 0.61 on average. The fibers within the rimmed structure (S) stand out for their higher Na2O content, reaching up to 20 wt% in a SiO2-A12O3-Na2O ternary diagram (not shown here) . In contrast, the fibers within the matrix (D) have a maximum Na2O content of 6%. The rim of the hollowed structure (H) is aluminum-rich and falls within the compositional range of gehlenite .
[0101] Phlego Cement distinguishes itself by its white composition, offering a brighter and more visually appealing alternative to the traditional grey Ordinary Portland Cement (OPC) , as is evident from visual observation of samples. It is also useful that Phlego cement is whiter than Portland cement in the infrared. FIG. 4 shows Reflectance Infrared Spectroscopy (FT-IR) measurements comparing the IR light reflection from OPC (dashed line) and Phlego (solid line) . Compared to OPC, Phlego has higher reflectance in the portion of the near-infrared region of the electromagnetic spectrum that goes from 1 pm to ~2 pm. As indicated above, this increased IR reflectance may help reduce the urban heat island effect.
[0102] 8
Claims
CLAIMS1. A method of making a fibrous precursor for use in a Phlego cement mixture, the method comprising: forming a mixture of Phlego raw meal composition, limestone and gypsum; wherein the Phlego raw meal composition is 40-60% silica, 10-25% aluminum oxide, 0.5-2% sulfur, 5-16% calcium oxide, 5-15% sodium and / or potassium oxide, and 1% or less carbon-containing species by weight; wherein the mixture is 42-47% Phlego raw meal composition, 42-47% limestone and 5-10% gypsum by weight; performing closed-chamber hydrothermal synthesis on the mixture to provide a fibrous precursor, wherein a water to mixture ratio (w / m) of the closed-chamber hydrothermal synthesis is in a range between 0.88 and 2 by weight.
2. A method of making a cement composition, the method comprising : mixing the fibrous precursor of claim 1, a clinker made from the Phlego raw meal composition and gypsum to provide the cement composition; wherein the cement composition includes 5-10% gypsum and at least 5% of the fibrous precursor by weight.
3. The method of claim 2, further comprising making a concrete using the cement composition, wherein the concrete is whiter than ordinary Portland concrete.
4. The method of claim 1, wherein the closed-chamber hydrothermal synthesis includes:9elevating a chamber temperature of a closed reaction chamber to one or more elevated temperatures in a range from 150 °C to 250 °C.
5. The method of claim 4, wherein a temperature ramp rate for increasing and / or decreasing the chamber temperature is between 2 and 4 °C min-1.
6. The method of claim 4, wherein the closed reaction chamber is held at the one or more elevated temperatures between 12 and 24 hours.
7. The method of claim 1, further comprising: oven-drying a moist product of the closed-chamber hydrothermal synthesis to provide a dried product; grinding the dried product to provide the fibrous precursor .
8. The method of claim 1, wherein the closed-chamber hydrothermal synthesis comprises filling a closed reaction chamber with 10-17% by volume of water.
9. The method of claim 8, wherein the closed-chamber hydrothermal synthesis comprises adding the mixture to the closed reaction chamber such that the water to mixture ratio is in a range between 0.88 and 2 by weight.
10. The method of claim 1, wherein the closed-chamber hydrothermal synthesis comprises mixing water with themixture , then adding a resulting moist product to a closed reaction chamber, wherein the water used for this mixture has a volume in a range between 10% and 17 % of a volume of the closed reaction chamber .11 . The method of claim 1 , wherein the forming a mixture of Phlego raw meal composition, limestone and gypsum comprises : calcining the Phlego raw meal composition and limestone to provide a calcined product ; and mixing the calcined product with the gypsum .12 . The method of claim 1 , wherein the fibrous precursor includes fibrous ( C-A-S-H) and gel-like ( C-N / K-A-S-H) phases .