HIGH-STRENGTH CONCRETE AND METHOD OF PRODUCING SAME

Abstract

There is described a high-strength concrete generally having: about 100 parts by weight of cement; about 60 to about 360 parts by weight of fine aggregates; about 90 to about 230 parts by weight of mineral powder having a diameter D50 below 150 .Math.m; about 0.1 to about 25 parts by weight of superplasticizer; and about 20 to about 65 parts by weight of water, the high-strength concrete has a cement content less than about 500 kg/m.sup.3 and having a compressive strength after 28 curing days of about 55 MPa or greater.

Claims

1. A high-strength concrete comprising: about 100 parts by weight of cement; about 60 to about 360 parts by weight of fine aggregates having an D50 diameter above 100 um; about 90 to about 230 parts by weight of mineral powder having a D50 diameter below 150 .Math.m; about 0.1 to about 25 parts by weight of superplasticizer; and about 20 to about 65 parts by weight of water, the high-strength concrete has a cement content less than about 500 kg/m.sup.3 and has a compressive strength after 28 curing days of about 55 MPa or greater.

2. The high strength concrete of claim 1 wherein the mineral powder includes above 20% by weight of one or more materials having a D50 diameter above the D50 diameter of the cement, and above 20% by weight of one or more materials having a D50 diameter below the D50 diameter of the cement.

3. The high strength concrete of claim 1 wherein the mineral powder has a D50 diameter within 30% of a D50 diameter of the cement and includes granite powder having a D50 diameter more than 5% above the D50 diameter of the cement, and at least one other material having a D50 diameter more than 5% below the D50 diameter of the cement.

4. The high strength concrete of claim 1 wherein the D50 diameter of the mineral powder is below 100 .Math.m, preferably below 50 .Math.m.

5. The high-strength concrete of claim 1 wherein the cement content is less than about 490 kg/m.sup.3, preferably less than about 480 kg/m.sup.3, and most preferably less than about 470 kg/m.sup.3.

6. The high-strength concrete of claim 1 wherein the parts by weight of mineral powder range between about 100 and about 220, preferably between about 125 and about 195 and most preferably between about 150 and about 170.

7. The high-strength concrete of claim 1 wherein the mineral powder comprises granite powder.

8. The high-strength concrete of claim 1 wherein the mineral powder comprises marble powder.

9. The high-strength concrete of claim 1 further comprising at least 0.2 % by volume of reinforcing fibers.

10. The high-strength concrete of claim 9 wherein the reinforcing fibers comprise steel fibers.

11. The high-strength concrete of claim 10 wherein the steel fibers have an aspect ratio ranging between 10 and 200, preferably between 50 and 100, and most preferably of about 65.

12. The high-strength concrete of claim 1 wherein the cement has an alkali concentration of less than 0.6 % weight percent with respect to a total weight of the cement.

13. The high-strength concrete of claim 1 wherein the mineral powder comprises at least 10 parts by weight of granite powder.

14. The high-strength concrete of claim 1 wherein the mineral powder comprises at least 35 parts by weight of limestone powder.

15. The high-strength concrete of claim 1 wherein a portion of the mineral powder and a portion of the water are provided in the form of a sludge.

16. A high-strength concrete mix comprising: about 100 parts by weight of cement; about 60 to about 360 parts by weight of fine aggregates; and about 90 to about 230 parts by weight of mineral powder having a diameter D50 below 150 .Math.m, which, when mixed with about 20 to about 65 parts by weight of water and about 0.1 to about 25 parts by weight of superplasticizer, forms a high-strength concrete having a cement content less than about 500 kg/m.sup.3 and having a compressive strength after 28 curing days of about 55 MPa or greater.

17. The high-strength concrete mix of claim 16 wherein the parts by weight of mineral powder ranges between about 100 and about 220, preferably between about 125 and about 195 and most preferably between about 150 and about 170.

18. The high-strength concrete mix of claim 16 wherein the mineral powder comprises granite powder.

19. A method of producing a batch of high-strength concrete, the method comprising: mixing concrete ingredients into a drum, the concrete ingredients having about 100 parts by weight of cement, about 60 to about 360 parts by weight of fine aggregates, about 90 to about 230 parts by weight of mineral powder having a diameter D50 below 150 .Math.m, about 0.1 to about 25 parts by weight of superplasticizer, and about 20 to about 65 parts by weight of water, with a cement content less than about 500 kg/m.sup.3 of cement.

20. The method of claim 19 further comprising, prior to said mixing, drying a mineral powder containing sludge thereby obtain said mineral powder.

Description

BRIEF DESCRIPTION OF THE FIGURE

[0036] FIG. 1 is a graph of the particle distribution (cumulative % in function of diameter) for limestone filler (LF/F and LF/UF), granite powder (Gr. P), fly ash (FA), NRS, silica fumes (SF), and cement (CEM GULA).

[0037] FIG. 2 is a graph of the particle distribution (cumulative % in function of diameter) for sands and other fine aggregates.

[0038] FIG. 3 is a graph of the particle distribution (cumulative % in function of diameter) of recycled powders, namely granite powder (Gr. P), white granite powder (W Gr. P), limestone filler (LF) recycled, and quartz powder (Qz. P).

[0039] FIG. 4 is a graph of the particle distribution (cumulative % in function of diameter) of fillers compared to CEM GULA.

[0040] FIG. 5 is a dot plot showing the packing density of binary mixes combining CEM GU and fillers (d.sub.90 < 150 mm) with 3% SP content.

DETAILED DESCRIPTION

[0041] There is described a high-strength concrete. The high-strength concrete has: about 100 parts by weight of cement; about 60 to about 360 parts by weight of fine aggregates; about 90 to about 230 parts by weight of mineral powder having a diameter D50 below 150 .Math.m; about 0.1 to about 25 parts by weight of superplasticizer; and about 20 to about 65 parts by weight of water. As discussed further below, the high-strength concrete has a cement content less than about 500 kg/m.sup.3 and a compressive strength after 28 curing days of about 55 MPa or greater. In some embodiments, the high-strength concrete can be a high-performance concrete (HPC) meeting durability and workability requirements in addition to the strength requirement as defined by dedicated standardization organisms.

[0042] In some embodiments, the cement content is less than about 490 kg/m.sup.3, preferably less than about 480 kg/m.sup.3, and most preferably less than about 470 kg/m.sup.3. The cement can be any type of cement including, but not limited to, ordinary Portland cement (OPC), Portland pozzolana cement (PPC), rapid hardening cement, extra rapid hardening cement, low heat cement, sulfates resisting cement, white cement and the like. In preferred embodiments, the cement is a low-alkali cement such as a GU low-alkali cement. The most common alkalis in cement are Na.sub.2O and K.sub.2O. The term “low-alkali” as used herein in the context of cement can be defined as a cement having less than 0.6 weight percent of total alkali with respect to the total weight of the composition. In some embodiments, the total alkali weight can be calculated with Na.sub.2O only or with Na.sub.2O + 0.658K.sub.2O.

[0043] In some embodiments, the parts by weight of mineral powder range between about 100 and about 220, preferably between about 125 and about 195 and most preferably between about 150 and about 170. Examples of mineral powders can include, but are not limited to, granite powder, marble powder, quartz powder, limestone powder, or a combination thereof. The mineral powder stone is inert. An inert material is defined as having no or very limited pozzolanic activity. The particles of the mineral powder are defined as having a diameter D50 below 150 .Math.m. However, in some other embodiments, the D50 diameter of the mineral powder can preferably be below 145 .Math.m, and most preferably below 140 .Math.m in some other embodiments. The mineral powder used in the high-strength concrete can have a D10 diameter below 100 .Math.m, preferably below 10 .Math.m, and most preferably below 5 .Math.m. The mineral powder used in the high-strength concrete can have a D90 diameter below 250 .Math.m, preferably below 150 .Math.m, and most preferably below 100 .Math.m. The use of mineral powder in the ranges disclosed herein can provide the advantage of providing enhanced granulometry and structure to the concrete composition which allows to reduce the amount of cement while still achieving desirable compressive strength properties. Moreover, the mineral powder is a cost effective alternative to cementitious materials (such as supplementary cementitious material including, but not limited to, silica fume, fly ash, and glass powder) which are relatively costly.

[0044] In some embodiments, the mineral powder comprises or is granite powder. In some embodiments, the concrete comprises at least 10 parts by weight of granite powder, at least 20 parts by weight of granite powder, at least 30 parts by weight of granite powder, at least 40 parts by weight of granite powder, or about 50 parts by weight of granite powder. As can be seen in FIG. 1, granite powder (Gr. P) has a larger average diameter than cement (CEM GULA). Indeed, in the present concrete compositions with reduced concrete (less than 500 kg/m.sup.3). However, it was found that the addition of granite powder could reduce the workability of the mixture. In some embodiments considered, as shown in FIG. 1 the granite powder has a D50 diameter above the D50 diameter of the cement which it is intended to replace. In embodiments where one or more other mineral powder material having a smaller D50 diameter than the D50 diameter of the cement were used in addition to the mineral powder material having a D50 diameter above the D50 diameter of the cement, better workability was achieved. For instance, in some embodiments, the composition comprises, in addition to granite powder, fine and/or ultrafine limestone filler (LF/F, LF/UF) and/or silica fume which have a smaller diameter on average compared to cement, in a manner to provide an overall granulometry more consistent with the cement, which may limit the workability issues that may otherwise arise with the addition of granite powder. In further embodiments, the composition additionally to the granite powder comprises silica fume and limestone filler. For example, the composition can further comprise at least 35 parts by weight of limestone filler, more preferably at least 45 parts by weight of limestone filler, even more preferably 55 parts by weight of limestone filler, still preferably at least 65 parts by weight of limestone filler, and/or at least 5 parts by weight of silica fume, preferably at least 10 parts by weight of silica fume, more preferably at least 15 parts by weight of silica fume, and even more preferably 20 parts by weight of silica fume. Accordingly, more generally the mineral powder can comprise a first mineral powder that has a larger D50 diameter than cement on average (for example granite powder, white granite powder, quartz powder, coarse limestone or fly ash) and a second mineral powder that has a smaller D50 diameter than cement on average (for example fine and/or ultrafine limestone filler and/or silica fume) to obtain a granulometry of the mineral powder closer to the granularity of the cement (i.e. the granulometry of the combined first and second mineral powders).

[0045] Indeed, for instance, the high strength concrete can include mineral powders including above 20% by weight of one or more materials having a D50 diameter above the D50 diameter of the cement, and above 20% by weight of one or more materials having a D50 diameter below the D50 diameter of the cement.

[0046] Moreover, for instance, the mineral powders, overall, can have a D50 diameter within 30% of a D50 diameter of the cement, and includes both i) granite powder, white granite powder or quartz powder having a D50 diameter more than 5% above the D50 diameter of the cement, and at least one other material having a D50 diameter more than 5% below the D50 diameter of the cement, such as fine and/or ultrafine limestone filler and/or silica fume.

[0047] In some embodiments, the concrete compositions of the present disclosure contain no deliberate addition of fly ash or are free of fly ash. This can be an advantage as fly ash is becoming less common as the coal industry phases out and is replaced by other energy industries.

[0048] In some embodiments, the high-strength concrete has a compressive strength after 28 curing days of at least 60 MPa, preferably at least 65 MPa and most preferably at least 70 MPa or greater. To increase the compressive strength, at least 0.2 vol. % of reinforcing fibers can be incorporated into the high-strength concrete in some embodiments. In some embodiments, the high-strength concrete can have at least 2 % by volume of reinforcing fibers, preferably at least 4 % by volume of reinforcing fibers, and most preferably at least 5 % by volume of reinforcing fibers. In some other embodiments, the reinforcing fibers can be omitted. By doing so, the compressive strength after 28 curing days can be at least 90 MPa, preferably at least 100 MPa and most preferably at least 110 MPa or greater depending on the embodiment. When the compressive strength of the concrete is above 120 MPa after 28 curing days, the high-strength concrete can be an ultra high-strength concrete. The reinforcing fibers can be any type of reinforcing fibers including, but not limited to, steel fibers, micro- or macro- fibers, polymeric fibers, composite fibers such as glass fiber and the like. In some embodiments, the reinforcing fibers have a single grading with a L10 to L90 length between about 6 mm and about 25 mm, preferably between about 8 mm and about 20 mm, and most preferably between about 10 mm and about 14 mm. The reinforcing fibers can have an aspect ratio ranging between 1 and 1000, preferably between 10 and 200 and most preferably between 50 and 100. It is noted that in embodiments where the reinforcing fibers are provided in the form of steel fibers, the aspect ratio can range between 10 and 200, preferably between 50 and 100 and most preferably of about 65. In some other embodiments, where the reinforcing fibers are made of polymer, the aspect ratio can be much greater. For instance, the aspect ratio of polymer reinforcing fibers can extend up to 1000.

[0049] In some embodiments, the fine aggregates have a single grading with a D10 to D90 between 0.05 mm and 5 mm, the finest fine aggregate having a D10 to D90 between 0.05 mm and 1 mm, and the coarsest fine aggregate having a D10 to D90 between 1 mm and 5 mm. However, these values can change from one embodiment to another. The fine aggregates can comprise sand in some embodiments. Examples of sand can include, but are not limited to, silica sand, masonry sand, river sand, crushed stone sand, utility sand, manufacturing sand, plastering sand, pit sand, coral sand, glass sand, gypsum sand, and the like.

[0050] In some examples, the high-strength concrete has about 90 to 230 parts by weight of coarse aggregates in addition to the other concrete ingredients. The coarse aggregates can have a single grading with a D10 to D90 between 5 mm and 35 mm, in some embodiments. However, these values can change from one embodiment to another. In some examples, the high-strength concrete can also have less than 150 parts by weight of cementitious powder. Examples of cementitious powder includes silica fume, fly ash and the like. The cementitious powder is pozzolanic. Pozzolanic materials are defined as materials which possess little to no cementitious value but which will, in powdered form and in the presence of water, react chemically with calcium hydroxide (Ca(OH).sub.2) at ordinary temperature to form compounds possessing cementitious properties. The quantification of the capacity of a pozzolan material to react with calcium hydroxide and water is given by measuring its pozzolanic activity. Mineral powders are known to be non-pozzolanic materials which have little or no pozzolanic activity.

[0051] In some high-strength concrete embodiments having about 100 parts by weight of cement, the parts by weight of fine aggregates range between about 80 and about 340; the parts by weight of mineral powder range between about 100 and about 220; the parts by weight of superplasticizer range between about 1 and 24; the parts by weight of water range between about 25 and about 60 and the cement content is less than about 490 kg/m.sup.3.

[0052] In some high-strength concrete embodiments having about 100 parts by weight of cement, the parts by weight of fine aggregates range between about 135 and about 285; the parts by weight of mineral powder range between about 125 and about 195; the parts by weight of superplasticizer range between about 7 and about 17; the parts by weight of water range preferably between about 30 and about 52; and the cement content is less than about 480 kg/m.sup.3.

[0053] In some high-strength concrete embodiments having about 100 parts by weight of cement, the parts by weight of fine aggregates range between about 200 and 220; the parts by weight of mineral powder range between about 150 and about 170; the parts by weight of superplasticizer range between 10 and 14; the parts by weight of water range between about 38 and 46; and the cement content is less than about 470 kg/m.sup.3.

[0054] In some embodiments, the high-strength concrete can be provided without water as a concrete mix. In these embodiments, the high-strength concrete mix has: about 100 parts by weight of cement; about 60 to about 360 parts by weight of fine aggregates; and about 90 to about 230 parts by weight of mineral powder having a diameter D50 below 150 .Math.m. The high-strength concrete mix, when mixed with about 20 to about 65 parts by weight of water and about 0.1 to about 25 parts by weight of superplasticizer, can form a high-strength concrete having a cement content less than about 500 kg/m.sup.3 and having a compressive strength after 28 curing days of about 55 MPa or greater. All the embodiments described above with respect to the high-strength concrete are applicable to the high-strength concrete mix.

[0055] In another aspect, there is described a method of producing a batch of high-strength concrete. The method has a step of mixing concrete ingredients. In some embodiments the step of mixing is performed with a drum. The concrete ingredients have about 100 parts by weight of cement, about 60 to about 360 parts by weight of fine aggregates, about 90 to about 230 parts by weight of mineral powder having a diameter D50 below 150 .Math.m, about 0.1 to about 25 parts by weight of superplasticizer, and about 20 to about 65 parts by weight of water, with a cement content less than about 500 kg/m.sup.3 of cement. In some embodiments, the method includes, prior to the step of mixing, a step of drying a mineral powder containing sludge thereby obtaining the mineral powder of the concrete ingredients. Accordingly, the mineral powder can be obtained from recycling residue of various stone manufacturing plants. In some embodiments, a portion of the mineral powder and a portion of the water are provided in the form of a sludge. As such, the sludge can contain water and mineral powder. In these embodiments, it is noted that the quantity of water required in the recipe of the high-strength concrete that is to be added separately of the sludge can be reduced to account for the water contained in the sludge. For instance, if the recipe dictates a total quantity of water, and that the sludge is estimated to contain a given quantity of water, then the given quantity of water can be subtracted from the total quantity of water of the recipe. In some embodiments, a portion of the mineral powder is provided in the form of dried mineral powders whereas another portion of the mineral powder is provided in the form of a mineral powder containing sludge.

[0056] The particle distribution of some of the concrete components used in the following examples are showed in FIGS. 1-4 and the packing density of binary mixes is shown in FIG. 5.

Example 1: Exemplary High-Strength Concrete Recipes

[0057] A first exemplary recipe comprised less than 500 kg/m.sup.3 of Portland cement, 300-1400 kg/m.sup.3 of fine aggregate (or sand, or mixture of sands) having a single grading with a D10 to D90 between 0.05 and 5 mm, 0-700 kg/m.sup.3 of a coarse aggregate having a single grading with a D10 to D90 between 5 and 35 mm, at least 500 kg/m.sup.3 of granite powder having a diameter D50 below 100 .Math.m, 0-500 kg/m.sup.3 of limestone filler having a diameter D50 below 150 .Math.m, 0-500 kg/m.sup.3 of marble filler having a diameter D50 below 150 .Math.m, 0-500 kg/m.sup.3 of quartz filler having a diameter D50 below 150 .Math.m, 50-900 kg/m.sup.3 of a combination of inert fillers made of natural stones, at least 600 kg/m.sup.3 of supplementary cementitious materials such as silica fume, fly ash and glass powder and 5 to 100 kg/m.sup.3 of superplasticizer as a dry composition. A corresponding wet composition contained additionally 100-250 kg/m.sup.3 of water. In some examples where a mixture of sands was used, the finest sand had a D10 to D90 between 0.05 and 1 mm and the coarsest sand had a D10 to D90 between 1 and 5 mm. Such exemplary high strength concrete recipes were determined to have a compression strength of at least 70 MPa. To obtain a ultra-high strength concrete with a compression strength of at least 120 MPa, at least 0.2 % by volume of fibers reinforcement was added to the concrete.

Example 2: Cement Optimization

[0058] The cement GU low-alkali and the cement GU were used to obtain concrete composition with granite powder with recipes as recited in Example 1. (CSA 3001 defines type GU). The concrete compositions were compared and it was found that the GU low alkali cement out performed the GU cement in terms compressive strength by a difference of up to 20 MPa in some cases. Indeed, two concrete compositions produced with 200 kg of granite powder, 280 kg of limestone powder and 400 kg of either GU low-alkali cement or GU cement were compared and a difference of 20 MPa in compaction strength was found in favor of the GU low-alkali cement. This is a surprising result considering both cements tested had similar granulometry and composition.

Example 3: Compression Strength Evaluation

[0059] Two compositions according to the present disclosure (compositions A and B) are shown in Table 1 below. Their compression strength was determined after 28 curing days. The units in Table 1 unless specified otherwise are kg.

TABLE-US-00001 Comparison of compositions A and B were compared with prior art Compositions: A B Portland cement 400 400 Silica fume 80 80 Fly Ash 200 0 Fine glass powder 0 Unspecified inert filler 0 Limestone filler 260 165 Granite powder 200 200 Quartz powder 0 Glass powder 0 Glass sand 0 Sand 988 1280 Coarse aggregate 0 0 Water 168 176 HRWR 32 24 Steel fibers 2% 0% 28d strength (MPa) 128 97

[0060] A composition according to the present disclosure (composition C) is shown in Table 2 below. Its compression strength was determined after 28 curing days. The units in Table 2 unless specified otherwise are kg.

TABLE-US-00002 Comparison of composition C with prior art Composition: C Portland cement 354.2 Silica fume 30.8 Limestone filler 0 Granite powder 165 Sand 744 Coarse aggregate 1052 High Range Water Reducer (HRWR) 5.225 Water 152 28d strength (MPa) 70

Example 4: Composition Characterization

[0061] Exemplary compositions for ultra-high strength concrete (D-G) and high strength concrete (H-J) according to the present disclosure are presented in Table 3 and Table 5 respectively. Their properties are presented in Table 4 and Table 6 respectively.

TABLE-US-00003 Compositions E-G Compositions: [in relative mass] D E F G Cement GU 1 1 1 1 Supplementary cementing materials 0.7 0.7 0.7 0.2 Limestone powder 0.65 0.65 0.65 0.41 Granite powder 0.5 0.5 0.5 0.5 Fine aggregate 2.45 2.48 2.47 2.92 Superplasticizer 0.08 0.08 0.08 0.06 W/C ratio 0.48 0.48 0.42 0.44

TABLE-US-00004 Properties of compositions E-G Properties D E F G Static spread w/ fiber, mm [ASTM C1437] 175 205 240 245 Dynamic spread w/ fiber, mm [ASTM C1437] 215 230 > 250 > 250 Static spread with fibers, mm [ASTM C1437] 175 180 155 - Dynamic spread with fibers, mm [ASTM C1437] 210 215 190 - σ.sub.c 28 days, MPa [ASTM C39] 119.9 124.6 127.8 96.5

TABLE-US-00005 Compositions H-J Composition [in relative mass] H I J Cement GUb-8SF 1 1 1 Coarse aggregate 1.25 1.4 1.6 Fine aggregate 0.9 1 1.15 Granite powder 0.11 0.25 0.43 Superplasticizer 0.011 0.012 0.014 W/C ratio 0.31 0.35 0.39

TABLE-US-00006 Properties of compositions H-J Properties H I J s.sub.c 7 days, MPa [ASTM C39] 67.73 58.2 57.48 s.sub.c 28 days, MPa [ASTM C39] 81.02 68.85 72.46 Elastic Modulus 28 days, GPa [ASTM C469] 39 39.8 39.9 Electrical resistivity at 7 days, W m 101 79 67 Electrical resistivity at 28 days, W m 375 298 277 Slump, mm [ASTM C143] 185 227 208 Air content, % [ASTM C231 and ASTM C138] 1.89 2.39 1.9 Density, kg/m.sup.3 [ASTM C138] 2478 2459 2470 Volume of permeable voids, % [ASTM C642] 9.79 9.42 10.37

[0062] As can be understood, the examples described above and illustrated are intended to be exemplary only. In some embodiments, the concrete ingredients can be quantified in terms of density instead of in terms of parts by weight of cement. In these embodiments, nominal densities for the concrete ingredients can be used. For instance, cement can have a density of 3100 kg/m.sup.3, fine aggregates can have a density of 2650 kg/m.sup.3, mineral powder can have a density of 2650 kg/m.sup.3, superplasticizer can have a density of 1060 kg/m.sup.3, water can have a density of 1000 kg/m.sup.3, and coarse aggregates can have a density of 1450-2100 kg/m.sup.3. The scope is indicated by the appended claims.