GB1579798A

GB1579798A - Concrete

Info

Publication number: GB1579798A
Application number: GB1499678A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-11-02
Filing date: 1978-04-17
Publication date: 1980-11-26
Also published as: ATA195378A; AT370709B; DE2749059B1; DE2749059C2

Description

(54) IMPROVEMENTS IN CONCRETE (71) I, JOSEPH COMPERNASS of Nachstenbacher Strasse 27, 6943 Birkenau Nieder-Liebersbach, Federal Republic of Germany, a German citizen do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: It is already known from DE-OS (German Published Applications) 25 12 858 (with additional printed instructions) and 25 16 023 that certain additives e.g. boric trioxide, added to concrete render it radiation-proof, particularly neutron-proof, or put another way, allow a reduction in the wall-thickness required for absorbing radiation and neutrons to an acceptable level. All these additives have, however, the common drawback of considerably reducing the strength values of the finished concrete.

The underlying task of the invention is, therefore, to provide a process for the manufacture of a neutron-proof concrete in the use of which the strength values of the finished concrete are affected by the addition of a neutron-absorbing agent as little as possible.

According to the present invention there is provided a process for manufacturing a neutron-proof concrete comprising immersing a neutron-absorbing agent consisting of granulated boric trioxide in a mixture of an aqueous plastics dispersion and an aqueous cement gel, allowing the mixture of the plastics dispersion and the cement gel in which the neutron absorbing agent is immersed in the hardened mixture of plastics dispersion and cement gel to an unset concrete mixture and allowing the concrete mixture containing the neutron absorbing agent to set to form the neutron proof concrete.

By taking measures according to the invention the neutron-absorbing agent is saturated by the water contained in the mixture of the plastics dispersion and the cement gel and any further water added; yet, due to the effect of the plastics dispersion and the cement gel, the agent is not dissolved. In the course of immersing the neutron absorption agent, its temperature increases to approximately 80"C. Under the effect of heat the dispersion together with the cement hardens and becomes impervious to water within a short time, of the order of magnitude of approximately 10 minutes. Thus the neutron-absorbing agent after having undergone the pretreatment according to the invention exerts its full effect in the finished concrete without being dissolved in the concrete, and without disadvantageously affecting the strength of the concrete.The finished concrete may be evenly loaded in three dimensions.

As regards its individual constituents, a preferred plastics dispersion composition has the following constituents: 20 to 40 parts by weight of polyvinyl prop inionate 0.1 to 5 parts by weight of turpentine oil 0.1 to 5 parts by weight of xylene 0.1 to 5 parts by weight of a fatty acid ester 0.1 to 5 parts by weight of paraffin oil 10 to 40 parts by weight of a chlorine-free aqueous emulsion of bitumen.

A particularly preferred composition has the following constituents: 30 parts by weight of polyvinyl propinion ate 0.75 parts by weight of turpentine oil 0.75 parts by weight of xylene 0.65 parts by weight of a fatty acid ester 0.30 parts by weight of a paraffin oil 18.5 parts by weight of a chlorine-free aqueous emulsion of bitumen.

The above plastics dispersions are known per se and are described in German DAS 22 56 056.

Under certain circumstances, particularly when the plastics dispersion acts very fast, before immersing the neutron-absorbing agent into the mixture of a plastics dispersion and cement gel, it may be necessary to saturate it to the extent that it can take in the residual water required for full saturation from the concrete until the concrete sets. For example, it may be saturated to approximately 80% of full saturation.

Since the neutron-absorbing agent becomes hard as corundum with the exclusion of oxygen, the preferred processes for compacting the concrete are: pressing, vibrating, rolling or centrifuging. In addition, it is possible to apply the concrete by the spraying process whereby a good compaction of the concrete is also ensured. The density should preferably be 2.51 to 2.55 g/cm3.

In the case of sprayed concrete, even gamma rays can be effectively shielded so that the thickness of the concrete used for producing the primary components of reactors can be reduced.

In order to keep the duration of the effect of the initial concrete mixtures on the pretreated neutron-absorbing agent as short as possible the initial concrete mixture is preferably introduced during the spraying process e.g. into the spraying hose, the steel pipe or into the spraying machine (see e.g. German DASi22 15 485). To prevent the mechanical destruction of the neutronabsorbing agent when it hits the substrate during spraying, first a concrete layer is sprayed on which does not contain a neutron-absorbing agent.

To increase further the strength values and the shielding effect e.g. against electromagnetic impulses, steel or carbon fibres may be added to the concrete mixture.

Example The concrete mixture contains the following constituents; 211.lkg sand with a grain size of 0.0 to 0.2 mm 592.2kg sand with a grain size of 0.25 to 1.00 mm 288.1 keg sand with a grain size of 1.0 to 2.0 mm 326.4kg sand with a grain size of 2.0 to 4.0 mm 499.2kg grit with a grain size of 4.0 to 8.0 mm 350kg blast furnace cement 450L 17.5kg dispersion having the particularly preferred composition described above 0.4kg potassium fluoride 0.6kg carbon fibre 0.008 mm thick and 10 to 30 mm long 150.51 water including the inherent mois ture content of the additives.

This concrete mixtures was applied in the spraying process wherein during the spraying 1 per cent by weight (24kg/m3) of granulated boric trioxide, pretreated according to the invention, was introduced into the spraying hose of the spraying machine.

The radiation protecting concrete thus obtained had a macroscopic absorption cross-section of 2.4 and the following average strength values after 29(90) days: Compressive strength 61.0(82.0) MN/m2 Spall tensile strength 11.2(15.2) MN/m2 Tensile strength 10.5(14.5) MN/m2 The corresponding values of an otherwise identical concrete but without a neutronabsorbing agent amounted to 67.0(91.0), 13.3(17.9), 12.1(16.7) MN/m2 respectively.

By increasing the boric trioxide content up to 5 per cent, by weight, an increase in the macroscopic absorption cross-section of 12 has been achieved. In order to keep the strength values of the concrete constant, the cement, dispersion, potassium fluoride and carbon fibre content of the initial mixtures have also been increased by 5%.

WHAT WE CLAIM IS: 1. A process for manufacturing a neutron-proof concrete comprising immersing a neutron-absorbing agent consisting of granulated boric trioxide in a mixture of an aqueous plastics dispersion and an aqueous cement gel, allowing the mixture of the plastics dispersion and the cement gel in which the neutron absorbing agent is immersed to harden, adding the neutron absorbing agent immersed in the hardened mixture of plastics dispersion and cement gel to an unset concrete mixture and allowing the concrete mixture containing the neutron absorbing agent to set to form the neutron proof concrete.

2. A process according to claim 1 wherein the plastics dispersion consists of the following components: 20 to 40 parts by weight of polyvinyl prop inionate 0.1 to 5 parts by weight of turpentine oil 0.1 to 5 parts by weight of xylene 0.1 to 5 parts by weight of a fatty acid ester 0.1 to 5 parts by weight of paraffin oil 10 to 40 parts by weight of a chlorine-free aqueous emulsion of bitumen.

3. A process according to claim 2 characterised in that the plastics dispersion consists of the following components: 30 parts by weight of polyvinyl propinion ate 0.75 parts by weight of turpentine oil 0.75 parts by weight of xylene 0.65 parts by weight of a fatty acid ester 0.30 parts by weight of paraffin oil 18.5 parts by weight of a chlorine-free aqueous emulsion of bitumen.

4. A process according to any one of claims 1 to 3 wherein before immersion, the neutron-absorbing agent is saturated with water to approximately 80% of full saturation and the agent extracts the rest of the water required for full saturation from the concrete during the time from its addition to the unset concrete to the setting of the con

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. before immersing the neutron-absorbing agent into the mixture of a plastics dispersion and cement gel, it may be necessary to saturate it to the extent that it can take in the residual water required for full saturation from the concrete until the concrete sets. For example, it may be saturated to approximately 80% of full saturation. Since the neutron-absorbing agent becomes hard as corundum with the exclusion of oxygen, the preferred processes for compacting the concrete are: pressing, vibrating, rolling or centrifuging. In addition, it is possible to apply the concrete by the spraying process whereby a good compaction of the concrete is also ensured. The density should preferably be 2.51 to 2.55 g/cm3. In the case of sprayed concrete, even gamma rays can be effectively shielded so that the thickness of the concrete used for producing the primary components of reactors can be reduced. In order to keep the duration of the effect of the initial concrete mixtures on the pretreated neutron-absorbing agent as short as possible the initial concrete mixture is preferably introduced during the spraying process e.g. into the spraying hose, the steel pipe or into the spraying machine (see e.g. German DASi22 15 485). To prevent the mechanical destruction of the neutronabsorbing agent when it hits the substrate during spraying, first a concrete layer is sprayed on which does not contain a neutron-absorbing agent. To increase further the strength values and the shielding effect e.g. against electromagnetic impulses, steel or carbon fibres may be added to the concrete mixture. Example The concrete mixture contains the following constituents; 211.lkg sand with a grain size of 0.0 to 0.2 mm 592.2kg sand with a grain size of 0.25 to 1.00 mm 288.1 keg sand with a grain size of 1.0 to 2.0 mm 326.4kg sand with a grain size of 2.0 to 4.0 mm 499.2kg grit with a grain size of 4.0 to 8.0 mm 350kg blast furnace cement 450L 17.5kg dispersion having the particularly preferred composition described above 0.4kg potassium fluoride 0.6kg carbon fibre 0.008 mm thick and 10 to 30 mm long 150.51 water including the inherent mois ture content of the additives. This concrete mixtures was applied in the spraying process wherein during the spraying 1 per cent by weight (24kg/m3) of granulated boric trioxide, pretreated according to the invention, was introduced into the spraying hose of the spraying machine. The radiation protecting concrete thus obtained had a macroscopic absorption cross-section of 2.4 and the following average strength values after 29(90) days: Compressive strength 61.0(82.0) MN/m2 Spall tensile strength 11.2(15.2) MN/m2 Tensile strength 10.5(14.5) MN/m2 The corresponding values of an otherwise identical concrete but without a neutronabsorbing agent amounted to 67.0(91.0), 13.3(17.9), 12.1(16.7) MN/m2 respectively. By increasing the boric trioxide content up to 5 per cent, by weight, an increase in the macroscopic absorption cross-section of 12 has been achieved. In order to keep the strength values of the concrete constant, the cement, dispersion, potassium fluoride and carbon fibre content of the initial mixtures have also been increased by 5%. WHAT WE CLAIM IS:

1. A process for manufacturing a neutron-proof concrete comprising immersing a neutron-absorbing agent consisting of granulated boric trioxide in a mixture of an aqueous plastics dispersion and an aqueous cement gel, allowing the mixture of the plastics dispersion and the cement gel in which the neutron absorbing agent is immersed to harden, adding the neutron absorbing agent immersed in the hardened mixture of plastics dispersion and cement gel to an unset concrete mixture and allowing the concrete mixture containing the neutron absorbing agent to set to form the neutron proof concrete.

3. A process according to claim 2 characterised in that the plastics dispersion consists of the following components: 30 parts by weight of polyvinyl propinion ate 0.75 parts by weight of turpentine oil 0.75 parts by weight of xylene 0.65 parts by weight of a fatty acid ester 0.30 parts by weight of paraffin oil

18.5 parts by weight of a chlorine-free aqueous emulsion of bitumen.

crete.

5. A process according to any one of claims 1 to 4 wherein the unset concrete containing the neutron absorbing agent is compacted by a pressing, rolling, vibrating or centrifuging process.

6. A process according to any one of claims 1 to 4 wherein the unset concrete containing the neutron absorbing agent is compacted by being applied onto a substrate using a spraying process.

7. A process according to claim 6 wherein the neutron-absorbing agent immersed in the hardened mixture of aqueous plastics dispersion and aqueous cement gel is introduced into the unset concrete during spraying, e.g. into the spray hose, the steel pipe or to the spraying machine.

8. A process according to any one of claims 5 to 7 wherein the concrete is compacted to a density of 2.51 to 2.55 g/cm3.

9. A process according to claim 6 or 7 wherein before the application of the neutron-proof concrete spray, a layer of concrete not containing a neutron-absorbing agent is applied onto the substrate.

10. Aprocess according to any one of the preceding claims wherein steel, synthetic or carbon fibres are added to the concrete mixture.

11. A process for the manufacture of neutron-proof concrete as claimed in claim 1 substantially as hereinbefore described in the Example.

12. Neutron-proof concrete when produced by a process as claimed in any one of the preceding claims.