Nanomaterial for strength and durability improvment of cementitious materials

Abstract

The invention provides a cementitious product and additive designed to enhance the strength, wear resistance, and durability of cementitious materials. This is achieved by using a combination of: (a) nanoplatelets of graphene, graphene oxide, reduced graphene oxide, or inorganic materials with a lateral size larger than 1 µm; (b) inorganic particles with an aspect ratio of at least 5 and hardness of at least 900 Hv, such as silicon carbide; and (c) hollow flexible microspheres with an average size of 5-120 µm. The synergy of these components significantly improves the mechanical properties of cementitious products, especially those with reduced Portland cement content in favor of sustainable binders like volcanic ash and recycled industrial waste. The additive is suitable for use in pumpable water-based dispersions for cementitious and ceramic materials, offering a pathway towards more sustainable construction materials.

Description

[0001] NANOMATERIAL FOR STRENGTH AND DURABILITY IMPROVMENT OF CEMENTITIOUS MATERIALS

[0002] Technical field

[0003] The present invention relates generally to a product containing a mix of 2D nanomaterials , use of a product based on a mix of 2D nanomaterials in cementitious materials and the resulting cementitious product . The cementitious products have improved wear resistance , strength and durability .

[0004] Background

[0005] Improved wear resistance of surfaces laid with cementitious materials is crucial for areas with high traf fic density as well as for many other areas . Examples of such surfaces include but are not limited to busy roads , drive-through businesses , bus stops , airports , and various loading zones . The costs related to refinishing these surfaces are often much higher than the actual material costs , due to implications of stopping or re-routing traf fic .

[0006] Graphene , one of many two-dimensional materials , has many unique properties regarding for instance thermal and electrical conductivity, barrier properties as well as mechanical properties . It has an exceptionally high tensile strength and is at the same time the thinnest two-dimensional material known . Graphene and graphene oxide have previously been evaluated in cementitious materials and proven to improve various material properties including bending strength and compression strength (WO 2019 / 175564 Al ) .

[0007] One example of an inorganic nanoparticle of high hardness is silicon carbide ( SiC ) . SiC can be made acicular, i . e . with a high aspect ratio of at least 5 or at least 10 , and it has an exceptionally high hardness . Measuring 9 . 5 on the Mohs scale of hardness , or Vickers hardness well above 2000 , it is close to that of diamond . Patent US 4 , 666 , 520 "Cemetitious composite material with silicon carbide aggregate" describes some benefits by adding SiC to cementitious materials .

[0008] CN 109678439 discloses cement concrete comprising sulphoaluminate cement , fine sand, medium-coarse sand, mineral powder, graphene oxide , hollow glass beads , gypsum, water and concrete fibers .

[0009] In cementitious products where Portland cement is partially exchanged for more environmentally sustainable binding materials like natural volcanic ashes and calcinated clays as well as recycled industrial waste materials like slag and fly ash, the properties of such cementitious products may deteriorate and there is a need to address this .

[0010] Even though cement additives according to the state of the art can improve the properties of cementitious products , there is still room for an improvement regarding various properties such as for instance the wear resistance , strength and durability .

[0011] Summary

[0012] It is an obj ect of the present invention to obviate at least some of the disadvantages in the prior art and to provide an additive that can provide improved strength, higher wear resistance and durability of today' s cementitious materials . It is also the obj ect of the present invention to obviate at least some maj or disadvantages with concrete and other cementitious products made with low content of Portland cement , where Portland cement is exchanged for more environmentally sustainable binding materials like natural volcanic ashes and calcinated clays as well as recycled industrial waste materials like slag and fly ash . In a first aspect there is provided a cementitious product comprising a cement binder and at least two additives selected from the group consisting of a) , b) , and c) below: a) nanoplatelets of a material selected from the group consisting of graphene, graphene oxide, reduced graphene oxide, and an inorganic material, wherein the nanoplatelets have a lateral size as measured according to ISO / TS 21356-1:2021 larger than 1 pm, preferably larger than 2 pm, b) particles comprising an inorganic material, wherein the particles have an aspect ratio of at least 5, wherein the aspect ratio is the maximum Feret diameter to the minimum Feret diameter XFeretmax / XFeret min, wherein the minimum Feret diameter and the maximum Feret diameter are measured according to ISO 13322-1:2014, wherein the particles have a hardness as measured according to ASTM E384-22 of at least 900 Hv, preferably above 1300 Hv and most preferably above 2000 Hv, c) hollow flexible microspheres with an average size in the range 5-120 pm, preferably in the range 10-60 pm, wherein the average size is measured by determining a particle size distribution from laser diffraction according to ISO 13320:2020 and then calculating the average size from the particle size distribution according to ISO 9276-2:2014 using the method of moments.

[0013] In a second aspect there is provided an additive, for use in production of cementitious materials or ceramic materials, based on a pumpable water-based dispersion of a) and b) below; a) nanoplatelets of a material selected from the group consisting of graphene, graphene oxide, reduced graphene oxide, and an inorganic material, wherein the nanoplatelets have a lateral si ze as measured according to ISO / TS 21356- 1 : 2021 larger than 1 pm, preferably larger than 2 pm, b ) particles comprising an inorganic material , wherein the particles have an aspect ratio of at least 5 , wherein the aspect ratio is the maximum Feret diameter to the minimum Feret diameter XFeretmax / XFeret min, wherein the minimum Feret diameter and the maximum Feret diameter are measured according to ISO 13322- 1 : 2014 , wherein the particles have a hardness as measured according to ASTM E384-22 of at least 900 Hv, preferably above 1300 Hv and most preferably above 2000 Hv .

[0014] Advantages include that strength, wear resistance and / or durability of cementitious materials is improved .

[0015] For concrete and other cementitious products made with low content of Portland cement , where Portland cement is exchanged for more environmentally sustainable binding materials like natural volcanic ashes and calcinated clays as well as recycled industrial waste materials like slag and fly ash, the properties are improved .

[0016] Detailed description

[0017] Before the invention is disclosed and described in detail , it is to be understood that this invention is not limited to particular compounds , configurations , method steps , substrates , and materials disclosed herein as such compounds , configurations , method steps , substrates , and materials may vary somewhat . It is also to be understood that the terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting since the scope of the present invention is limited only by the appended claims . It must be noted that , as used in this speci fication and the appended claims , the singular forms "a" , "an" and "the" include plural referents unless the context clearly dictates otherwise .

[0018] I f nothing else is defined, any terms and scienti fic terminology used herein are intended to have the meanings commonly understood by those of skill in the art to which this invention pertains .

[0019] As used herein the term 2D materials refers to solids consisting of a single layer or a few layers of atoms .

[0020] As used herein graphene nanoplatelets^ ( GNP ) , are short: stacks of platele t “shaped: graphene sheets ,

[0021] It was found by the inventors of the present invention that , by combining 2D nanoplatelets of graphene or graphene oxide with inorganic acicular / lamellar ( i . e . with a high aspect ratio of at least 5 ) nanoparticles of high hardness it is possible to drastically improve compression strength, bending strength and wear resistance of cementitious material based on Portland cement . The combination of the two types of additives gives a much stronger ef fect on compression strength than the sum of the ef fects of the two additives alone .

[0022] The ef fect of the two types of additives together is even more pronounced when traditional Portland cement binder is exchanged for more environmentally sustainable alternative binding materials like natural volcanic ashes and calcinated clays as well as recycled industrial waste materials like slag and fly ash . Concrete made with low content of Portland cement and high content of recycled binding materials tend to become more brittle and prone to crack more easily . This is a well- known global challenge and limits the development of environmentally friendly, low CO2 concrete ( cementitious ) products . The invention presented here , a combination of two nanomaterials , has the potential to signi ficantly reduce brittleness , reduce crack formation and crack propagation and improve strength and wear resistance , and ultimately improve durability of these materials and thus open for a big technical leap towards a carbon neutral concrete industry .

[0023] It is generally well known by now that graphene nanoplatelets can be used to reinforce cementitious materials and improve tensile- , flexural- and compression strength . Graphene nanoplatelets can also help retain water in the cement mix during curing as well as reducing water absorption for cured cementitious products . Reduced water absorption will reduce performance degradation and durability-related damage , creating a stronger, more long-lasting product . Similar ef fects have been described also from addition of graphene oxide nanoplatelets and platelets of reduced graphene oxide .

[0024] In the first aspect there is provided cementitious product comprising a cement binder and at least two additives selected from the group consisting of a ) , b ) , and c ) below : a ) nanoplatelets of a material selected from the group consisting of graphene , graphene oxide , reduced graphene oxide , and an inorganic material , wherein the nanoplatelets have a lateral si ze as measured according to ISO / TS 21356- 1 : 2021 larger than 1 pm, preferably larger than 2 pm, b ) particles comprising an inorganic material , wherein the particles have an aspect ratio of at least 5 , wherein the aspect ratio is the maximum Feret diameter to the minimum Feret diameter XFeretmax / XFeret min, wherein the minimum Feret diameter and the maximum Feret diameter are measured according to ISO 13322- 1 : 2014 , wherein the particles have a hardness as measured according to ASTM E384-22 of at least 900 Hv, preferably above 1300 Hv and most preferably above 2000 Hv, c) hollow flexible microspheres with an average size in the range 5-120 pm, preferably in the range 10-60 pm, wherein the average size is measured by determining a particle size distribution from laser diffraction according to ISO 13320:2020 and then calculating the average size size according to ISO 9276-2:2014 using the method of moments.

[0025] In one embodiment the cementitious product comprises a) and b) above .

[0026] In one embodiment, the nanoplatelets comprise one or more layers, and wherein the nanoplatelets comprise at least one selected from the group consisting of graphene, graphene oxide, and reduced graphene oxide.

[0027] In one embodiment, the particles comprise silicon carbide.

[0028] In one embodiment, the nanoplatelets comprise one or more layers, and wherein the nanoplatelets comprise at least one selected from the group consisting of graphene, graphene oxide, and reduced graphene oxide, and wherein the particles comprise silicon carbide.

[0029] In one embodiment, the nanoplatelets comprise one or more layers, and wherein the nanoplatelets comprise at least one selected from the group consisting of graphene, graphene oxide, and reduced graphene oxide, wherein the particles comprise silicon carbide, and wherein the cementitious product comprises hollow flexible microspheres.

[0030] In the second aspect there is provided an additive, for use in production of cementitious materials or ceramic materials, based on a pumpable water-based dispersion of a) and b) below; a) nanoplatelets of a material selected from the group consisting of graphene, graphene oxide, reduced graphene oxide, and an inorganic material, wherein the nanoplatelets have a lateral size as measured according to ISO / TS 21356-1:2021 larger than 1 pm, preferably larger than 2 pm, b) particles comprising an inorganic material, wherein the particles have an aspect ratio of at least 5, wherein the aspect ratio is the maximum Feret diameter to the minimum Feret diameter XFeret max / XFeret min, wherein the minimum Feret diameter and the maximum Feret diameter are measured according to ISO 13322-1:2014, wherein the particles have a hardness as measured according to ASTM E384-22 of at least 900 Hv, preferably above 1300 Hv and most preferably above 2000 Hv.

[0031] The particles are acicular or lamellar, i.e. needle like or plate like and this is expressed so that the aspect ratio is at least 5. This is measured according to ISO 13322-1:2014 so that the minimum Feret diameter XFeret mm and the maximum Feret diameter XFeret max are measured from image analysis according to ISO 13322-1:2014 and then the aspect ratio is calculated as the ratio of the maximum Feret diameter to the manimum Feret diameter XFeret max / XFeret mm- The aspect ratio can for instance be measured and calculated using two-dimensional Environmental Scanning Electron Microscopy (ESEM) images.

[0032] The aspect ratio is at least 5. In one embodiment, the aspect ratio is at least 10. In one embodiment, the aspect ratio is at least 20.

[0033] In one embodiment, the dispersion comprises hollow flexible microspheres . In one embodiment , the nanoplatelets comprise one or more layers , and wherein the nanoplatelets comprise at least one selected from the group consisting of graphene , graphene oxide , and reduced graphene oxide .

[0034] In one embodiment , the particles comprise silicon carbide .

[0035] In one embodiment , the additive comprises hollow flexible microspheres .

[0036] This disclosure describes results from extensive lab evaluations of cementitious materials modi fied with graphene and graphene oxide 2D nanomaterials and combinations with hard acicular / lamellar inorganic nanomaterials . The results show that the morphology of the 2D nanomaterial has a signi ficant ef fect on how ef ficiently the material af fect strength properties of cementitious materials . A population of graphene platelets with few layers create higher strength ef fects per weight unit added compared to a population with multi-layer graphene . The results show that graphene material with high fraction of multi-layer graphene and / or nano-graphite may reduce strength rather than improving material properties .

[0037] Lab evaluations also show that by combining additions to cementitious materials of high-quality graphene or graphene oxide 2D nanoplatelets with acicular / lamellar inorganic nanoparticles of high hardness , strength properties , durability of the cementitious material and resistance to wear was drastically improved . These very powerful ef fects are surprising . The combination of the two types of nanomaterials is surprisingly more ef ficient than the sum of the ef fects of the two additives alone .

[0038] By combining high-quality graphene or graphene oxide 2D nanoplatelets with inorganic acicular / lamellar nanoparticles of high hardness it is thus possible to produce cement-based products that are stronger and more durable and wear resistant than what is available today . This new technology also opens for cementitious construction materials based on low ratio Portland cement and high ratio of alternative binding materials like natural volcanic ashes and calcinated clays as well as recycled industrial waste materials like slag and fly ash . It is known that cementitious materials with high ratio alternative binders tend to become more brittle and more prone to cracking, and consequently show relatively poor, resistance , and durability . With additions of a combination of high quality 2D nanoplatelets ( graphene / graphene oxide or reduced graphene oxide ) and inorganic acicular / lamellar nanoparticles of high hardness ( SiC ) , it is possible to overcome some of the quality limitations that comes with low CO2 cementitious materials with higher ratio recycled binding materials . It seems as i f graphene nanoplatelets and acicular / lamellar inorganic nanofibers help reduce crack formation and crack propagation caused by autogenous and drying shrinkage of cementitious materials . It is likely that enhanced strength properties with these nanomaterials to some extent comes with reduced formation of nano- and microcracks in the cementitious material .

[0039] Today, air entrainment technology is used to provide frost resistant properties to cementitious materials . Air entrainment technology is sometimes quite unreliable and is often connected to quality problems and liability issues . Many factors af fect the outcome ( formulation variables , handling aspects as well as physical factors ) and unfortunately the final answer to i f the quality meets the requirements comes months after the concrete is placed . One alternative solution to this issue is to use flexible hollow microspheres instead of entrained air to make cementitious materials frost resistant (Akzo 1979 , Ong et al 2015 ) . Flexible hollow microspheres are typically smaller than air voids stabili zed by air entrainment technology . The smaller pore si ze distribution of flexible hollow microspheres helps provide frost resistant properties at lower pore volumes ( around 1 volume! ) compared with pore volumes typically needed when air entrainment technology is used ( 4- 8 volume! ) , which in turn make a stronger cementitious material . It is stated in the literature that by reducing void volume in concrete by 1 volume! , compression strength is increased by up to 5! ( Ong et al 2015 ) . There are cementitious applications for which air entrainment technology may be too unreliable and where quality issues are common . The recipes for these applications often contain surface active components that interfere with the air entrainment additives . One example of applications where this issue is common is underwater concrete . Alternative binding materials like slag and fly ash may also interfere with air entrainment additives , as surface active components , such as activated carbon, are often used in the processes that generate slag and fly ash . The surfaces of slag and fly ash are typically more hydrophobic compared to surfaces of Portland cement and tend to attract surface active components ( air entrainment additives ) and disturb the system balance with poor air pore stability as a consequent .

[0040] By combining high-quality graphene or graphene oxide 2D nanoplatelets with inorganic acicular / lamellar nanomaterial of high hardness and flexible hollow microspheres , it is thus possible to produce cementitious products with guaranteed frost resistance , that are more sustainable , stronger, more durable and wear resistant compared to cementitious materials available today .

[0041] Examples of such flexible hollow microspheres include but are not limited to expandable microspheres marketed under the tradename Expancel® Microspheres by Nouryon . These particles may be pre-expanded particles , i . e . expandable particles , which have already been partially expanded, upon exposure to heat, e.g. by means of hot gases, such as steam. All known kinds of expandable microspheres, in particular all known types of expandable thermoplastic microspheres can be used in concrete according to the present invention, such as those marketed under the trademark Expancel® as said above. The expandable thermoplastic microspheres can be of fossil based or bio-based polymer material. Useful expandable microspheres are described in the literature, for example in U.S. Pat. Nos. 3, 615, 972, 3, 945, 956, 4,287,308, 5, 536, 756, 6, 235, 800, 6,235,394 and 6,509,384, 6, 617,363 and 6.984,347, in US Patent Applications Publications US 2004 / 0176486 and 2005 / 0079352, in EP 486080, EP 1230975, EP 1288272, EP 1598-405, EP 1811007 and EP 1964903, in WO 2002 / 096635, WO 2004 / 072160, WO 2007 / 091960, WO 2007 / 091961 and WO 2007 / 142593, and in JP Laid Open No. 1987-286534 and 2005-272633. All of which here explicitly incorporated herein by reference. Suitable expandable thermoplastic microspheres typically have a thermoplastic shell made from polymers or co-polymers obtainable by polymerizing various ethylenically unsaturated monomers.

[0042] Suitable monomers might also be those which have been obtained from renewable sources and, hence, are bio-based, such as for instance lactone-based monomers (e.g. in WO 2019 / 043235 Al) , itaconate dialkylester monomers (e.g. in WO 2019 / 101749 Al) , or tetrahydrofurfuryl (meth) acrylate monomers (e.g. in WO 2021 / 198487 Al and WO2021 / 198492 Al) . All of which here explicitly incorporated herein by reference. Any mixtures of the abovementioned monomers may also be used. In some embodiments, it is preferable that the expandable particles and / or pre-expanded particles comprise monomers from renewable sources. It may sometimes be desirable that the monomers for the polymer shell also comprise crosslinking multifunctional monomers. If present, such crosslinking monomers preferably constitute from 0.1 to 1 wt.%, most preferably from 0.2 to 0.5 wt . % of the total amounts of monomers for the polymer shell. Preferably, the polymer shell constitutes from 60 to 95 wt.%, most preferably from 70 to 85 wt.%, of the total microsphere. The softening temperature of the polymer shell, normally corresponding to its glass transition temperature (T) , is preferably within the range of from 50 to 250° C . , or from 70 to 230° C. The foaming agent encapsulated by the polymer shell in a microsphere is normally a liquid having a boiling temperature not higher than the softening temperature of the thermoplastic polymer shell. The foaming agent, also referred to as blowing agent or propellant, may be at least one hydrocarbon, such as n-pentane, isopentane, neopentane, n- butane, isobutane, n-hexane, isohexane, neohexane, n-heptane, isoheptane, n-octane and isooctane, or any mixture thereof. Particularly preferred foaming agents comprise at least one of isobutane, isopentane, isohexane, cyclohexane, isooctane, isododecane, and mixtures thereof. The foaming agent suitably makes up from 5 to 40 wt.% of the total weight of the microsphere. The boiling point of the foaming agent at atmospheric pressure may be within a wide range, preferably from -20 to 200° C . , most preferably from -20 to 150° C . , and most preferably -20 to 100° C. The thermally expandable thermoplastic microspheres are heated to effect expansion thereof. The temperature at which the expansion of the microspheres starts is called Tstart while the temperature at which maximum expansion is reached is called Tmax, both determined at a temperature increase rate of 20°C. per minute. The thermally expandable microspheres used in the present invention suitably have a Tstart of from 50 to 200° C . , preferably from 70 to 180° C . , most preferably from 70 to 150° C. The thermally expandable microspheres used in the present invention suitably have a Tmaxof from 70 to 300° C . , preferably from 80 to 250° C . , most preferred from 100 to 200° C. The expandable microspheres preferably have a volume median diameter of from 1 to 100 pm, more preferably from 2 to 50 pm, most preferably from 3 to 30 pm, as determined by laser light scattering on a Malvern Master si zer Hydro 2000 SM apparatus on wet samples . This instrument follows the standard ISO 13320 : 2020 for measuring a particle si ze distribution Shd^SiHdh is calculated according to ISO 9276-

[0043] 2 : 2014 using the method of moments . By heating to a temperature above or around Tmax, it is normally possible to expand the microspheres from 2 to 5 times their original diameter or more , preferably from 3 to 5 times their original diameter .

[0044] The pre-expanded thermoplastic microsphere described here is one example of flexible hollow microspheres that can be used to make concrete frost resistant .

[0045] It is to be understood that this invention is not limited to the particular embodiments shown here . The embodiments are provided for illustrative purposes and are not intended to limit the scope of the invention since the scope of the present invention is limited by the appended claims .

[0046] Other features and uses of the invention and their associated advantages will be evident to a person skilled in the art upon reading the description and the examples .

[0047] Examples

[0048] True for all examples in the patent application is that the cement pastes were formulated with a water to cement ratio (wet ) of 0 . 4 . The pastes were allowed to cure in a mold placed in a humidity chamber at 20 ° C, with 100 percent relative humidity .

[0049] Example 1 ( comparative ) Suspensions of poor- and medium-quality graphene (multi-layer graphene and multi-layer graphene + nano-graphite) were evaluated separately in cement pastes based on Portland cement. Strength properties were not improved for the cured cement paste when adding the poor-quality graphene. Curing of cement pastes for 28 days in a humidity chamber at 20 °C (Table 1) •

[0050] Table 1. Effect on cement strength (compression strength, MPa) with addition of poor- and medium-quality graphene.

[0051] Three molds were prepared for each sample. Results are an average of the three.

[0052] All percentages are by weight.

[0053] Example 2 (comparative)

[0054] A suspension of high-quality graphene oxide was evaluated separately in cement pastes based on Portland cement (CEM II / A-LL 42,5 R) . Strength properties were improved for the cured cement paste when adding graphene oxide. Curing of cement pastes for 28 days in a humidity chamber at 20 °C (Table 2) .

[0055] Table 2. Effect on cement strength (flexural strength, kN) with addition of good-quality graphene oxide. Three molds were prepared for each sample. Results are an average of the three. Standard deviation in brackets.

[0056] All percentages are by weight.

[0057] Example 3 (comparative)

[0058] A suspension of good-quality graphene (few-layer graphene) and a suspension of good-quality graphene oxide was evaluated separately in cement pastes based on Portland cement (CEM II / A-LL 42,5 R) . Strength properties were improved for the cured cement paste when adding the graphene as well as when adding the graphene oxide. Curing of cement pastes for 28 days in a humidity chamber at 20 °C (Table 3) .

[0059] Table 3. Effect on cement strength (compression strength, MPa) with addition of good-quality (few-layer) graphene and graphene oxide. Six molds were prepared for each sample. Results are an average of the six. Standard deviation in brackets.

[0060] All percentages by weight.

[0061] Example 4 Good-quality graphene and good-quality graphene oxide from example 3 and inorganic hard acicular nanoparticles (SiC) were used as additives to cement pastes made from Portland cement (GEM II / A-LL 42,5 R) . The effect on strength when combining graphene / graphene oxide with hard acicular nanoparticles in cement are larger than the additive effects of the additives added separately. Curing of cement pastes for 28 days in a humidity chamber at 20 °C (Table 4) .

[0062] Table 4. Compression strength (MPa) for additives and combination of additives vs addition levels. Two molds were prepared for each sample. Results are an average of the two. Standard deviation in brackets.

[0063] All percentages by weight.

[0064] Example 5

[0065] A suspension of good-quality graphene (few-layer graphene) was evaluated separately in cement pastes made from ultra-low- carbon, 100% circular cement (LCC high early from Cemvision) . The cement pastes were cured in a humidity chamber at 20°C.

[0066] Strength properties were found to be improved for the cured cement paste when adding graphene (Table 5) .

[0067] Table 5. Effect on cement strength (compression strength, MPa) with addition of good-quality (few-layer) graphene. Results in the table are calculated as the average result from two measurements, except for data points "28 days, 0.50%" and "48 days, 0.50%" which is the average from four and six measurements respectively. Standard deviation is below 1.0 for all data in the table, except for data points "28 days, 0.50%" and "48 days, 0.50%" for which standard deviation was 2,3 and 3.1 respectively.

Claims

CLAIMS1. A cementitious product comprising a cement binder and at least two additives selected from the group consisting of a) , b) , and c) below: a) nanoplatelets of a material selected from the group consisting of graphene, graphene oxide, reduced graphene oxide, and an inorganic material, wherein the nanoplatelets have a lateral size as measured according to ISO / TS 21356-1:2021 larger than 1 pm, preferably larger than 2 pm, b) particles comprising an inorganic material, wherein the particles have an aspect ratio of at least 5, wherein the aspect ratio is the maximum Feret diameter to the minimum Feret diameter XFeretmax / XFeret min, wherein the minimum Feret diameter and the maximum Feret diameter are measured according to ISO 13322-1:2014, wherein the particles have a hardness as measured according to ASTM E384-22 of at least 900 Hv, preferably above 1300 Hv and most preferably above 2000 Hv, c) hollow flexible microspheres with an average size in the range 5-120 pm, preferably in the range 10-60 pm, wherein the average size is measured by determining a particle size distribution from laser diffraction according to ISO 13320:2020 and then calculating the average size from the particle size distribution according to ISO 9276-2:2014 using the method of moments.

2. The cementitious product according to claim 1, wherein the nanoplatelets comprise one or more layers, and wherein the nanoplatelets comprise at least one selected from the group consisting of graphene, graphene oxide, and reduced graphene oxide .

3. The cementitious product according to any one of claims 1-2, wherein the particles comprise silicon carbide.

4. The cementitious product according to any one of claims 1-3, wherein the nanoplatelets comprise one or more layers, and wherein the nanoplatelets comprise at least one selected from the group consisting of graphene, graphene oxide, and reduced graphene oxide, and wherein the particles comprise silicon carbide.

5. The cementitious product according to any one of claims 1-4, wherein the nanoplatelets comprise one or more layers, and wherein the nanoplatelets comprise at least one selected from the group consisting of graphene, graphene oxide, and reduced graphene oxide, wherein the particles comprise silicon carbide, and wherein the cementitious product comprises hollow flexible microspheres.

6. An additive, for use in production of cementitious materials or ceramic materials, based on a pumpable water-based dispersion of a) and b) below; a) nanoplatelets of a material selected from the group consisting of graphene, graphene oxide, reduced graphene oxide, and an inorganic material, wherein the nanoplatelets have a lateral size as measured according to ISO / TS 21356-1:2021 larger than 1 pm, preferably larger than 2 pm, b) particles comprising an inorganic material, wherein the particles have an aspect ratio of at least 5, wherein the aspect ratio is the maximum Feret diameter to the minimum Feret diameter XFeretmax / XFeret min / wherein the minimum Feret diameter and the maximum Feret diameter are measured according to ISO 13322-1:2014, wherein the particles have a hardness as measured according to ASTM E384-22 of atleast 900 Hv, preferably above 1300 Hv and most preferably above 2000 Hv.

7. The additive according to claim 6, wherein the dispersion comprises hollow flexible microspheres.

8. The additive according to any one of claims 6-7, wherein the nanoplatelets comprise one or more layers, and wherein the nanoplatelets comprise at least one selected from the group consisting of graphene, graphene oxide, and reduced graphene oxide .

9. The additive according to any one of claims 6-8, wherein the particles comprise silicon carbide.

10. The additive according to any one of claims 6-9, wherein the additive comprises hollow flexible microspheres.

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