LIGHTWEIGHT AND/OR THERMALLY INSULATING STRUCTURAL CONCRETES HAVING A HIGHER RESISTANCE/DENSITY AND/OR RESISTANCE/CONDUCTIVITY RATIO, AND METHODS FOR THE PRODUCTION THEREOF

Abstract

A disclosed structural and light concrete includes a binding matrix and light aggregates. The binding matrix has a volume fraction from approximately 20% to approximately 50% of a concrete total volume and include: (1) a Portland Type I, II, III, IV or V cement or a mixture thereof, in a dose of at least 100 kg/m3 of concrete; (2) supplementary cementitious materials in a proportion of up to 4 times by volume of Portland cement; (3) a water component having a volume fraction relative to cement and supplementary cementitious materials in a range from approximately 0.2 to approximately 0.7; and (4) a maximum volume fraction of calcium hydroxide (CH) of approximately 10%. The light aggregates correspond to a volume fraction a range from approximately 30% to approximately 80% of the total concrete volume. Properties include increased compression resistance, decreased density, lower thermal conductivity and higher quotient of density resistance.

Claims

1. A method of manufacturing a structural, lightweight, low thermal conductivity concrete, the method comprising: a. providing aggregates and a dosage of a binding matrix for the concrete, the dosage including a water/cementitious matrix material mixture with a ratio of water to cementitious matrix material in a range from approximately 0.2 to approximately 0.7; b. performing an analysis of the lightweight aggregates by size fraction to determine a pore size distribution of each fraction of a plurality of fractions; c. performing an analysis of the binding matrix to determine a content of calcium hydroxide (CH) and a pore volume of the binding matrix; d. defining absolute and relative aggregate fractions according to the following function of pore sizes: for pore sizes of up to 10 m, defining a minimum volume fraction of distributed air to be approximately 15% and defining a minimum fraction of accumulated air content to be approximately 10%; for pore sizes of up to 40 m, defining a minimum volume fraction of distributed air to be approximately 50% and defining a minimum fraction of cumulative air to be approximately 20%; for pore sizes of up to 100 m, defining a minimum volume fraction of distributed air to be approximately 75% and defining a minimum fraction of cumulative air to be approximately 30%; for pore sizes of up to 200 defining a minimum volume fraction of distributed air to be approximately 90% and defining a minimum fraction of cumulative air to be approximately 40%; for pore sizes of up to 300 m, defining a minimum volume fraction of distributed air to be approximately 100% and defining a minimum fraction of cumulative air to be approximately 43%; e. determining whether the following criteria are met based on the analysis performed in stages b) and c): i. a total volume fraction of air in the light aggregates is in a range from approximately 50% to approximately 99%; ii. a total volume fraction of air in the concrete provided by the light aggregates is in a range from approximately 25% to approximately 75%; iii. a volume fraction of binding matrix is 50% or less of a total volume of the concrete; iv. a total volume of pores in the binding matrix is in a range from approximately 10% to approximately 30% of a total volume of the matrix; v. a maximum volume fraction of calcium hydroxide (CH) in the binding matrix is approximately 10%; f. when these criteria are not met, repeating stages a) to e), and when these criteria are met, selecting the aggregates analyzed and the dosage for the binding matrix analyzed as the selected components of light structural concrete and with low thermal conductivity; and g. manufacturing a concrete with said selected aggregates and said matrix selected according to said dosage.

2. The method according to claim 1, wherein the analysis of the light aggregates in stage b) is performed by measuring a porosity distribution using computed tomography.

3. The method according to claim 1, wherein the analysis of the binding matrix in step c) in which a content of calcium hydroxide (CH) and pore volume is determined, further comprises: performing simulations to determine a predicted content of hydration products; and performing XRD, XRF and/or TGA measurements on samples of candidate binding matrices.

4. The method according to claim 1, wherein the aggregate of smaller size has a size of at least half of the largest fraction of said aggregate.

5. The method according to claim 1, wherein the aggregates provided in step a) include amorphous components and the analysis in stage b) further comprises: measuring the pore size distribution of each fraction of amorphous components; performing computed tomography measurements to determine the porosity distribution of amorphous components; and measuring thermal conductivity of amorphous components.

6. The method according to claim 5, wherein in stage e) a further criterion includes specifying that the thermal conductivity of the amorphous components is less than 0.2 W/mK.

7. A method of manufacturing structural and light concretes, the method comprising: a. providing aggregates and a dosage of a binding matrix for the concrete, said dosage including a mixture of water and matrix cementitious material in a ratio of water to matrix cementitious material in a range from approximately 0.2 to approximately 0.5; b. providing an analysis of the lightweight aggregates by size fraction to determine a pore size distribution of each fraction; c. measuring a mechanical strength of the binding matrix; d. defining absolute and relative aggregate fractions according to the following function of pore sizes: for pore sizes of up to 10 m, defining a minimum volume fraction of distributed air to be approximately 15%; for pore sizes of up to 40 m, defining a minimum volume fraction of distributed air to be approximately 50%; for pore sizes of up to 100 m, defining a minimum volume fraction of distributed air to be approximately 75%; for pore sizes of up to 200 m, defining a minimum volume fraction of distributed air to be approximately 90%; for pore sizes of up to 300 m, defining a minimum volume fraction of distributed air to be approximately 100%; e. determining whether the following criteria are met based on the analysis performed in stages b) and c): i. a total volume fraction of air in the selected light aggregates is in a range from approximately 30% to approximately 99%; ii. a total volume fraction of air in the concrete provided by the lightweight aggregates is in a range from approximately 15% to approximately 75%; iii. a volume fraction of binding matrix is 50% or less of a total volume of the concrete; f. when these criteria are not met, repeating steps a) to e), and when these criteria are met, selecting the aggregates analyzed and the dosage for the binding matrix analyzed as the selected components of the light structural concrete; and g. manufacturing a concrete with said selected aggregates, said selected matrix and said dosage.

8. The method according to claim 7, wherein the analysis of the light aggregates in stage b) is performed by measuring a porosity distribution by computed tomography.

9. The method according to claim 7, wherein the aggregates provided in step a) include amorphous components and the analysis in stage b) further comprises: measuring the pore size distribution of each fraction of amorphous components by performing computed tomography measurements to determine a porosity distribution; and measuring thermal conductivity of amorphous components.

10. The method according to claim 9, wherein in stage e) a further criterion includes specifying that the thermal conductivity of the amorphous components is less than 0.2 W/mK.

11. A structural and light concrete, comprising: a) a binding matrix component having a volume fraction from approximately 20% to approximately 50% of a concrete total volume, the binding matrix component comprising: i. a Portland Type I, II, III, IV or V cement or a mixture thereof, according to ASTM C 150 standard, in a dose of at least 100 kg/m.sup.3 of concrete; ii. supplementary cementitious materials in a proportion of up to 4 times by volume of Portland cement; iii. a water component having a volume fraction relative to cement and supplementary cementitious materials in a range from approximately 0.2 to approximately 0.7; iv. a maximum volume fraction of calcium hydroxide (CH) of approximately 10%; and b) light aggregates corresponding to a volume fraction a range from approximately 30% to approximately 80% of the total volume of the concrete, wherein the concrete has a compression resistance, after 28 days of age, of at least 10 MPa, a density lower than 1.4 t/m.sup.3, a thermal conductivity lower than 0.288 W/(m*K) at 23 C. and 50% of relative humidity, and a quotient of density resistance Q/ of at least 17 (MPa*m.sup.3/t).

12. The concrete of claim 11, wherein the concrete has a compression resistance, after 28 days of age, of at least 13 MPa.

13. The concrete of claim 11, wherein the concrete has a thermal conductivity less than 0.185 W/(m*K) at 23 C. and 50% of relative humidity.

14. The concrete of claim 11, wherein the concrete has a quotient of density resistance Q/ of at least 25 (MPa*m.sup.3/t).

15. The concrete of claim 11, wherein the concrete has a low thermal conductivity and has a conductivity resistance quotient of at least Q/=60 (MPa*m*K)/W.

16. The concrete of claim 15, wherein the concrete has a conductivity resistance quotient of at least Q/=70 (MPa*m*K)/W.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0032] FIG. 1 illustrates a diagram of the distribution of pores volume provided by the light aggregates in the concrete according to the pore size, according to an embodiment of the disclosure.

[0033] FIG. 2 shows the distribution of the volume of air in the pores according to the pore size for concrete with different lightweight aggregates, according to an embodiment of the disclosure.

DETAILED DESCRIPTION

[0034] The disclosure provides lightweight structural concretes and thermal insulators that have quotients Q/, and/or Q/ higher than those of conventional concrete or existing lightweight concrete and its method of obtaining it. It allows to obtain a concrete with structural strength and superior to that of ceramic bricks and characteristics of good thermal insulation. Likewise, it is possible to obtain a concrete with compressive strength of structural range according to the ACI318 standard and with densities lower than 1.0 t/m.sup.3.

[0035] According to an embodiment, the structural lightweight and heat insulating concretes have a quotient Q/ greater than 60 (MPa*m*K)/W, preferably greater than 70 (MPa*m*K)/W.

[0036] The present disclosure also consists of lightweight structural concretes having a quotient Q/ greater than 17 (MPa*m.sup.3/t), preferably greater than 25 (MPa*m.sup.3/t).

[0037] The parameters of the criteria indicated below are determining factors in the physical behavior related to the density, mechanical behavior and/or thermal conductivity of concrete, these parameters are used in the method of the present disclosure.

[0038] According to an embodiment, the method of manufacturing lightweight structural concretes and thermal insulation includes the following stages: [0039] a. Providing aggregates that can include amorphous components and a dosage of a binding matrix for the concrete; said dosage consists of the water/cementitious matrix material ratio and should be in the range 0.20-0.70; [0040] b. Performing an analysis of the lightweight aggregates and said amorphous components present per size fraction by measuring the pore size distribution of each fraction; [0041] c. Performing an analysis of the binding matrix, measuring its CH content and pore volume; [0042] d. Defining the absolute and relative amount of the aggregate fractions in order to meet the following requirements: for pore sizes of up to 10 m, a minimum volume of distributed air volume of 15% and a minimum accumulated air content of 10% must be present; for pore sizes of up to 40 m, there must be a minimum content of distributed air volume of 50% and a minimum cumulative air content of 20%; for pore sizes of up to 100 m, a minimum content of distributed air volume of 75% and a minimum cumulative air content of 30% must be present; for pore sizes of up to 200 m, a minimum distributed air volume content of 90% and a cumulative minimum air content of 40% must be maintained; for pore sizes of up to 300 m, a minimum distributed air volume content of 100% and a minimum cumulative air content of 43% must be achieved; [0043] e. Considering the analysis carried out in stages b) and c) and to evaluate if the following criteria are met: [0044] i. a total volume of air in the selected light aggregates between 50% and 99%; [0045] ii. a total volume of air in the concrete provided by the light aggregates between 25% and 75%; [0046] iii. a maximum volume of binding matrix of 50% of the concrete total volume; [0047] iv. a total volume of pores in the binding matrix of 10-30% with respect to the matrix total volume; [0048] v. a maximum percentage of CH in the binding matrix of 10%; [0049] f. If these criteria are not met, repeating stages a) to e), if these criteria are met, selecting the analyzed aggregates and the dosage for the binding matrix analyzed as the selected components of light structural concrete and with low thermal conductivity; and [0050] g. Manufacturing a concrete with said candidate aggregates and said candidate matrix according to said dosage, as it is known in the state of the art.

[0051] According to an embodiment of the present disclosure, said analysis of the light aggregates in stage b) is carried out by measuring the porosity distribution by computed tomography (CT scan). This test allows to analyze in 3D the volume and distribution of pores greater than 1 m (it depends on the particle size). The air volume of pores smaller than 1 m is calculated by the difference in porosity measured by CT scan and the total porosity of the aggregate measured according to ACI213.

[0052] According to an embodiment of the present disclosure, said analysis of the other amorphous components in stage b) is measured from the porosity distribution by CT scan and its thermal conductivity is measured. The thermal conductivity of these must be 0.2 W/mK maximum.

[0053] According to an embodiment of the present disclosure, said analysis of the binding matrix in stage c) by measuring its CH content and pore volume, is carried out by measuring the content of the hydration products by simulations and samples of candidate binding matrices are analyzed by XRD, XRF and/or TGA.

[0054] According to an embodiment of the present disclosure, it is recommended that the smaller aggregate have a size of at least half of the largest fraction of said aggregate.

[0055] According to another object of the present disclosure, a method of manufacturing lightweight structural concretes includes the following stages: [0056] a. Providing aggregates that may include amorphous components and a dosage of a binding matrix for the concrete, said dosage consists of the water/cementitious matrix material ratio and should be in the range 0.20-0.50; [0057] b. Performing an analysis of the lightweight aggregates and said amorphous components present per size fraction by measuring the pore size distribution of each fraction; [0058] c. Performing an analysis of the binding matrix by measuring its mechanical strength; [0059] d. Defining the absolute and relative amount of the aggregate fractions in order to meet the following requirements: for pore sizes of up to 10 m, a minimum content of 15% of distributed air volume must be present; for pore sizes of up to 40 m, a minimum distributed air volume content of 50% must be available; for pore sizes of up to 100 m, a minimum distributed air volume content of 75% must be available; for pore sizes of up to 200 m, a minimum distributed air volume content of 90% must be available; for pore sizes of up to 300 m, a minimum distributed air volume content of 100% must be available; [0060] e. Considering the analysis carried out in stages b) and c) and to evaluate if the following criteria are met: [0061] i. a total volume of air in the selected light aggregates between 30% and 99%; [0062] ii. a total volume of air in the concrete provided by the lightweight aggregates between 15% and 75%; [0063] iii. a maximum volume of binding matrix of 50% of the total volume of the concrete; [0064] f. if these criteria are not met, repeating stages a) to e), if these criteria are met, selecting the aggregates analyzed and the dosage for the binding matrix analyzed as the selected components of the light structural concrete; and [0065] g. Manufacturing a concrete with said candidate aggregates, said candidate matrix and said dosage, as it is known in the state of the art.

[0066] According to an embodiment and similarly to the method for manufacturing lightweight structural concrete and thermal insulation previously described, said analysis of the lightweight aggregates in stage b) is carried out by measuring the porosity distribution by means of CT scan.

[0067] According to an embodiment of the present disclosure, said analysis of the other amorphous components in stage b) is measured from the porosity distribution by CT scan and its thermal conductivity is measured. The thermal conductivity of these must be 0.2 W/mK maximum.

[0068] Table 1 summarizes the aggregates conditions to be fulfilled in stage d) of the concrete manufacturing methods according to the disclosure, in absolute and relative amount of the aggregates fractions:

TABLE-US-00001 TABLE 1 Criteria for air volume and distribution of aggregates Minimum volume content of Minimum cumulative Pore size (m) air distributed (%) air content (%) 10 15% 10% 40 50% 20% 100 75% 30% 200 90% 40% 300 100% 43%

[0069] For the present disclosure, the matrix cementitious materials considered are Portland Cement Type I, II, III, IV, V or a mixture thereof, according to ASTM C 150 standard. In fact, the matrix may be composed by Portland cement, supplementary cementitious materials, chemical additives and water. The additional cementitious materials considered are: fly ash, micro silica, nano silica, pozzolan, natural, calcined clay, blast furnace slag, calcined shale, rice husk ash, wood waste ash or a mixture thereof and other materials that generate a pozzolanic reaction due to their content of silicates or aluminates.

[0070] The chemical additives considered are such as plasticizers, high-range plasticizers, air-entrainers, setting time (accelerating or retarding) modifiers, viscosifiers, shrinkage reducers, hydration facilitators, curing agents, either based on carboxylates, oleates, sulfonates, cellulose, styrenes-butadienes, among others typically used in concrete.

[0071] The aggregates considered are light aggregates and other aggregates of amorphous structure. As a whole, they include the aggregates of the concretes of the present disclosure. The lightweight aggregates have a higher porosity than the natural stone aggregates that are conventionally used. They can be of natural origin (pumice stone, vermiculite) or industrially produced (fly ash, micro silica, nano silica, pozzolana, natural, calcined clay, blast furnace slag, calcined shale, rice husk ash, glass). It is desired that the raw material of the aggregate is based on an amorphous material instead of a crystalline material, since the former normally have a lower thermal conductivity.

[0072] Other considered components of amorphous structure are thermoplastic polymers, elastomers or fibers, such as polystyrene, rubber, polypropylenes or acrylonitrile butadiene styrene. These components decrease the thermal conductivity of the concrete due to the low thermal conductivity they have, less than 0.2 W/mK.

[0073] The aggregates can be:

[0074] a) Artificial light aggregates: prepared by expansion, pelletization, sintering or other method, such as expanded clay, expanded shale, expanded slate, expanded perlite, expanded glass, vermiculite, diatomite, fly ash, blast furnace slag, glass microspheres, cenospheres, among others;

[0075] b) Natural light aggregates: pumice stone, vermiculite, diatomite, among others;

[0076] c) Thermoplastic polymers, elastomers or fibers, such as polystyrene, rubber, polypropylenes or acrylonitrile butadiene styrene.

[0077] Next, the present disclosure is illustrated by an example. This example should be understood as illustrative of the present disclosure and it is not intended to restrict the disclosure in any way.

Examples

[0078] Herein, Table 2 discloses examples of the present disclosure. The concretes 1, 3 and 4 were designed according to the method to obtain lightweight structural concretes and thermal insulators according to an embodiment. The concrete 3 was designed according to the method of manufacturing a lightweight structural concrete according to an embodiment. Concretes 2 and 5 are used to compare the effectiveness of the method. The aggregates of expanded clay and expanded glass are in the superficially dried saturated state (SSS), for which it was immersed in water for 24 hrs and then taken to the SSS condition.

TABLE-US-00002 TABLE 2 Dosages of concretes Concrete 1 2 3 4 5 Cement 170 240 285 285 334 FA (fly ash) 192 145 172 172 0 SF (microsilica) 0 34 40 40 0 Water 145 167 199 199 132 Superplasticizer 1.80 2 2.30 2.30 0.67 Normal sand 0 0 0 0 214 Expanded clay 0-5 mm 0 0 0 0 297 Expanded clay 10-20 mm 0 0 0 0 400 Expanded shale 0 0 0 0 0 10-20 mm Expanded glass 160 0 117 0 0 0.1-0.3 mm Expanded glass 0 90 90 0 0 0.25-0.5 mm Expanded glass 0.5-1 mm 123 50 54 270 0 Expanded glass 1-2 mm 84 62 86 0 0 Expanded glass 2-4 mm 69 92 0 0 0

[0079] It can be seen in FIGS. 1 and 2 that, using the manufacturing method of the present disclosure, concretes 1, 3 and 4 meet the requirements of Table 1.

[0080] On the other hand, concrete 2 meets the requirements of the minimum content of the distributed volume of air, but does not comply with the minimum volume of accumulated air. Concrete 5 does not meet any of the above requirements. Concretes 3, 4 and 5 have a similar total air content, as can be seen in Table 3. However, in FIG. 1 and Table 3 it can be seen that a greater refinement of the accumulated air volume increases the efficiency of the quotient between resistance to compression and thermal conductivity. On the other hand, increasing the volume of air does not ensure greater efficiency either. Concrete 1 has a lower air content than concrete 2, but a greater volume of air for pore sizes smaller than 40 m. This results in concrete 1 having greater compressive strength and lower thermal conductivity than concrete 2.

[0081] On the other hand, concrete 3 is the only one of these examples that meets the requirements of lightweight structural concretes, since quotient Q/ is greater than or equal to 25.

TABLE-US-00003 TABLE 3 Concrete 1 2 3 4 5 Fresh density (t/m.sup.3) 0.94 0.95 1.18 1.12 1.31 Dry hardened density 0.76 0.78 0.86 0.82 1.21 (t/m.sup.3) Resistance to cylindrical 13.1 8.1 22.8 17.5 12.9 compression, 28 days (MPa) Dry thermal conductivity 0.17 0.19 0.24 0.23 0.44 (W/mK) Thermal conductivity 0.20 0.22 0.27 0.26 0.52 equilibrium (W/mK) Added air content (%) 52.7% 57.7% 45.0% 44.8% 45.2% Thermal conductivity 77 43 95 76 29 resistance ratio Q/ ((MPa * m * K)/W) Reason for resistance 17 10 27 21 11 to dry density Q/ (MPa/(kg/m.sup.3))

[0082] Table 4 shows the properties of the cementitious matrices used in the sample concretes. The concrete 1 has a matrix A, the concretes 2, 3 and 4 have the matrix B and the concrete 5 has the matrix C.

TABLE-US-00004 TABLE 4 Agglomerating Matrix A.sup.1 B.sup.2 C.sup.3 Dose Cement (kg/m.sup.3) 608 751 1392 Dosage Ash Flywheel (kg/m.sup.3) 686 452 0 Microsilica dose (kg/m.sup.3) 0 105 0 Water dose (kg/m.sup.3) 518 523 557 CH (%) 7.0 8.8 17.2 CSH (%) 20.9 26.8 47.1 CSH/CH 3.04 2.98 2.75 Fresh density (t/m.sup.3) 1.81 1.83 1.95 Dry hardened density (t/m.sup.3) 1.68 1.70 1.81 Cylindrical compressive strength at 28 days 45.6 62.0 73.1 (MPa) Dry thermal conductivity (W/mK) 0.43 0.45 0.68 Thermal conductivity at 23 C. and 50% 0.49 0.52 0.78 RH (W/mK)2 Quotient thermal conductivity resistance 105 138 107 Q/ ((MPa * m * K)/W) .sup.1Binding matrix present in mixture 1 of Table 2 .sup.2Binding matrix present in mixture 2, 3 and 4 of Table 2 .sup.3Binding matrix present in mixture 5 of Table 2

[0083] In Table 4 it can be seen that, using the design method of the present disclosure, the binding matrices A and B comply with a maximum percentage of CH volume in the binding matrix under 10%.