Mixture for anti-radiation pozzolon-polymeric cementitious material

Abstract

An anti-radiation concrete comprising a geopolymer is described. In an implementation, the anti-radiation concrete comprises a mixture of at least two aqueous alkaline activators, fine aggregate, and coarse aggregate from high density metal-containing rocks.

Claims

1. An anti-radiation concrete, comprising: a geopolymer; a mixture of at least two aqueous alkaline activators, wherein a weight ratio of the geopolymer to the at least two aqueous alkaline activators is 2:1 to 3:1; a fine aggregate comprising a sand and waste iron, wherein a weight ratio of the sand to the waste iron is 1:1 to 3:1; and a coarse aggregate of particles having a particle size of 4.5 millimeters to 8.0 millimeters and comprising hematite ore, dolomite ore, cassiterite ore, or any combination thereof.

2. The anti-radiation concrete according to claim 1, wherein the geopolymer is selected from the group consisting of a fly ash, a kaolin, a pozzolonite, or any combination thereof.

3. The anti-radiation concrete according to claim 1, wherein the at least two aqueous alkaline activators are selected from the group consisting of a hydroxide, a silicate, a sulfate, and a carbonate of an alkali metal.

4. The anti-radiation concrete according to claim 1, further comprising a curing agent selected from the group consisting of an amine, a polyamide resin, an imidazole, a polymercaptan, and an anhydride.

5. The anti-radiation concrete according to claim 1, comprising 10%-20% geopolymer, 4%-8% alkaline activators, 15%-25% fine aggregate, and 50%-70% coarse aggregate.

6. The anti-radiation concrete according to claim 1, wherein the anti-radiation concrete has a linear attenuation coefficient for a .sub.137Cs gamma ray source of 0.2010.002 cm.sup.1 and a linear attenuation coefficient for a .sub.60Co gamma ray source of 0.1620.003 cm.sup.1.

7. A method of producing an anti-radiation concrete, comprising: mixing a geopolymer, a fine aggregate comprising a sand and waste iron, wherein a weight ratio of the sand to the waste iron is 1:1 to 3:1, at least two alkaline activators, and a coarse aggregate of particles having a particle size of 4.5 millimeters to 8.0 millimeters and comprising hematite ore, dolomite ore, cassiterite ore, or any combination thereof, wherein a weight ratio of the geopolymer to the at least two alkaline activators is 2:1 to 3:1; curing the mixture in a mold at 70 C. for 24 hours; aging the cured mixture; and de-molding the aged mixture.

8. The method of claim 7, wherein the geopolymer is selected from the group consisting of a fly ash, a kaolin, a pozzolonite, or any combination thereof.

9. The method of claim 7, wherein the aqueous alkaline activators are selected from the group consisting of a hydroxide, a silicate, a sulfate, and a carbonate of an alkali metal.

10. The method of claim 7, further comprising curing with an agent selected from the group consisting of an amine, a polyamide resin, an imidazole, a polymercaptan, and an anhydride.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a diagram of an example list of anti-radiation concrete components.

(2) FIG. 2 is a flow diagram of an example method of making an anti-radiation concrete.

DETAILED DESCRIPTION

(3) This disclosure describes a geopolymeric cementitious material. More particularly, the present invention relates to a heavy geopolymer-based concrete for shielding radiation which contains no ordinary Portland cement to minimize emission of carbon dioxide.

(4) Hereinafter, the invention shall be described according to the preferred embodiments of the present invention and by referring to the accompanying description and drawings. However, it is to be understood that limiting the description to the preferred embodiments of the invention and to the drawings is merely to facilitate discussion of the present invention and it is envisioned that those skilled in the art may devise various modifications without departing from the scope of the appended claim.

(5) In an implementation shown in FIG. 1, an anti-radiation concrete 100 comprises a geopolymer; a mixture of at least two aqueous alkaline activators; fine aggregate; and coarse aggregate from high density metal containing rocks.

(6) In the preferred embodiment of the invention, the geopolymer-based concrete is formed from geopolymer as a base material and contains no ordinary Portland cement. The geopolymer can be selected from the group, but not limited to, consisting of kaolin, fly ash, pozzolonite, silica sand, or a mixture thereof. Preferably, ASTM Class F fly ash is employed. Class F fly ash is typically from the burning of harder, older anthracite and bituminous coal. Class F fly ash is pozzolanic in which the sum of silicon dioxide (SiO.sub.2), aluminium oxide (Al.sub.2O.sub.3), and iron oxide (Fe.sub.2O.sub.3) is higher than 70%.

(7) The geopolymer is preferably activated with at least two alkaline activators to improve the physical properties of the geopolymer. A mixture of at least two alkaline activators is more preferred. The alkaline activators can be selected from hydroxides, silicates, sulfates, or carbonates of an alkali metal. Preferably, the alkaline activators are sodium silicate (Na.sub.2SiO.sub.3) and sodium hydroxide (NaOH). Preferably, the concentration of the alkaline activators is 10M to 15M. However, a person skilled in the art shall aware that a mixture of two and more alkaline activators or any alkaline activator other than those which contain silicate and hydroxide groups is also feasible. Preferably, the weight ratio of solid geopolymer to liquid alkaline activators is 2.5. Likewise, the weight ratio of silicate activator to hydroxide activator is preferably 2.5. The solid to liquid weight ratio and the liquid to liquid weight ratio depend on the configuration of the final product.

(8) According to the preferred embodiment of the invention, the anti-radiation concrete comprises both fine and coarse aggregates. Aggregates serve as a reinforcement to add strength to the overall composite concrete. They bind with the geopolymer along with water to form concrete with predictable and uniform properties. For a good concrete mix, aggregates need to be clean, hard, strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete. Fine aggregate includes, but is not limited to, consisting of sand, waste iron, iron slag, or a mixture thereof. Preferably, sand is mainly used as the fine aggregate. However, waste iron which has been crushed, refined, and sieved to about 188 m particle size can be mixed with sand to enhance the concrete density for better radiation shielding. Preferably, the weight ratio of sand to waste iron is 3. Other weight ratio of sand and waste iron such as 3:2 or 1:1 is also possible depending on the desired properties of the concrete.

(9) In accordance to the preferred embodiment of the invention, coarse aggregate is preferably high density natural ore rocks. The ore rocks are crushed and sieved to obtain coarse aggregate of 4.5 mm to 9 mm particle size. Fine ore rocks that are able to pass through the sieve can be mixed with the fine aggregate. Preferably, the ore rocks are selected from, but not limited to, consisting of hematite, dolomite, cassiterite, or a combination thereof. A person skilled in the art shall aware that any other ore rocks that contain nonradioactive heavy weight metals can also be used.

(10) One shall note that the particle size of the aggregates is subjected to variation depending on the desired concrete structure and density. Careful selection of different aggregate sizes enhances the close packing of the concrete structure and consequently improves densification.

(11) As described by the preferred embodiment of the invention, the anti-radiation concrete comprises geopolymer, alkaline activators, fine aggregate, and coarse aggregate. Preferably, the antiradiation concrete comprises fly ash, NaOH, NaSi.sub.2O.sub.3, sand, waste iron, and crushed ore rocks. Advantageously, the composition of the anti-radiation concrete is 10%-20% geopolymer, 4%-8% alkaline activators, 15%-25% fine aggregate, and 50%-70% coarse aggregate.

(12) As shown in FIG. 2, a further embodiment of the invention is a method 200 of producing an anti-radiation concrete as described in any of the preceding descriptions comprising the steps of mixing alkaline activators, geopolymer, fine aggregate, and coarse aggregate; curing the mixture in a mold at 70 C. for 24 hours; aging the cured mixture; and de-molding the aged mixture.

(13) Prior to mixing the required composition, a mixture of at least two alkaline activators is mixed at a predetermined ratio. The alkaline activators can be hydroxides, silicates, sulfates, or carbonates of an alkali metal. Preferably, the alkaline activators are sodium hydroxide and sodium silicate which are mixed at a weight ratio of 2.5. The geopolymer is then activator by the alkaline activators. The geopolymer can be kaolin, fly ash, pozzolonite, silica sand, or a mixture thereof. The alkaline activators mixture is gradually added to the geopolymer with agitation for a sufficient duration until a homogenours mixture is obtained. Preferably, the geopolymer is fly ash and the weight ratio of alkaline activators to geopolymer is 2.5.

(14) In the further embodiment of the invention, the activated geopolymer is mixed homogeneously with fine and coarse aggregates with stirring. The fine and coarse aggregates are crushed and sieved to a desired particle size prior to mixing with the activated geopolymer. Fine aggregate may include sand, waste iron, iron slag, or a mixture thereof. Preferably, the fine aggregate is a mixture of sand and waste iron in a preferred weight ratio of 3:1. Other weight ratio of sand and waste iron such as 3:2 or 1:1 is also possible depending on the desired properties of the concrete.

(15) Advantageously, the coarse aggregate is any heavy weight natural ore rock that is nonradioactive. Preferably, the ore rocks can be hematite, dolomite, cassiterite, or a combination thereof.

(16) According to the further embodiment of the invention, the activated geopolymer/aggregates mixture comprises 10%-20% geopolymer, 4%-8% alkaline activators, 15%-25% fine aggregate, and 50%-70% coarse aggregate. The homogenous activated geopolymer/aggregates mixture is then inserted into a mold covered by a thin plastics layer to prevent water evaporation, following by curing at a temperature of 60 C.-80 C. for at least 24 hours. Preferably, the curing temperature and curing time is 70 C. and 24 hours respectively, in a low temperature electrical furnace.

(17) Subsequently, the mold is left cool to room temperature and aged for at least 7 days at room temperature. The mold is kept covered by the thin plastics layer during aging. The anti-radiation concrete is obtained after de-molding for at least 28 days.

(18) Although the invention has been described and illustrated in detail, it is to be understood that the same is by the way of illustration and example, and is not to be taken by way of limitation. The spirit and scope of the present invention are to be limited only by the terms of the appended claims.

EXAMPLE

(19) The composition of the anti-radiation concrete according to one of the preferred embodiment of the invention is as shown in Table 1.

(20) TABLE-US-00001 TABLE 1 Fine Aggregate Fly Alkaline Activators (g) (Sand + Waste Hematite Coarse Ash (g) NaOH NaSi.sub.2O.sub.3 Iron) (g) Aggregate (g) 625.77 71.52 178.79 800 2400
The compressive strength of the concrete produced with the composition as shown in Table 1 is determined using a mechanical testing machine as according to ASTM C 109/C 109 M standards. The compressive strength, density, porosity, water absorption, linear attenuation coefficient for both .sub.137Cs and .sub.60Co gamma ray sources of the produced concrete is as shown in Table 2.

(21) TABLE-US-00002 TABLE 2 Linear Attenuation Compressive Water Coefficient for two Strengh Porosity Absorption Density Gamma sources (cm.sup.1) (MPa) (%) (%) (kg/m.sup.3) .sup.137Cs .sup.60Co 87.112 8.73 3.39 4189 0.201 0.162 0.002 0.003