Electrically conducting concrete

• US 3,962,142 A
• Filed: 02/07/1974
• Issued: 06/08/1976
• Est. Priority Date: 02/07/1973
• Status: Expired due to Term

• Current Assignee: Marconi Holdings Company Limited
• Original Assignee: Marconi Holdings Company Limited
• Inventors: Freeman, Alan, Hymers, William
• Primary Examiner(s): Padgett, Benjamin R.
• Assistant Examiner(s): Parr, E. Suzanne
• Application Number:
  US05/440,547
• Time in Patent Office: 852 Days
• Field of Search: 252/503, 252/502, 252/508, 252/509, 106/97, 106/307
• US Class Current: 252/503
• CPC Class Codes: C04B 14/022 Carbon
• CPC Class Codes: H01B 1/18 the conductive material comprising carbon-silicon compounds, carbon or silicon
• CPC Class Codes: H05F 3/025 Floors or floor coverings specially adapted for discharging static charges

Abstract

The invention provides a setable composition consisting of a bonding material (e.g. cement) and an aggregate which aggregate contains a quantity of relatively large electrically conductive particulate material and a quantity of relatively small electrically conductive particulate material. In one form the conductive material is gap-graded. In this form if calcined oil coke and acetylene black is used concretes of resistivities of the order of 25Ω ohm-centimeter may be obtained. In another form, the conductive material includes quantities of conductive material ranging in size between the relatively large and the relatively small conductive material. In this form, where the conductive material is calcined oil coke forming the entire aggregate and the size distribution of the coke is such that the spectrum of size is in accordance with one of the National Standards relating to the spectrum of particle sizes recommended for conventional aggregates in cementitious compositions, concretes having resistivities at least as low as 2Ω centimeter may be obtained, whilst still providing satisfactory mechanical strengths.

Claims

1. A setable composition for use as a structural material comprising a cementitious material and an aggregate, wherein said aggregate contains quantities of carbonaceous material ranging in size between relatively large carbonaceous particulate material and relatively small carbonaceous particulate material, said aggregate constituting at least 20% by weight of the solid contents of the composition, and wherein the aggregate consists of particles of a size distribution such that the spectrum of sizes falls within the extreme limits of the combined specifications of British Standards 882, German Standards DIN 1045 and American Standards ASTMC 33, relating to the spectrum of particle sizes recommended for conventional aggregates in cementitious compositions.

2. A setable composition as claimed in claim 1 and wherein said aggregate consists of carbonaceous particles of a size distribution such that the spectrum of sizes falls wholly within one National Standard relating to the spectrum of particle sizes recommended for conventional aggregates.

3. A setable composition as claimed in claim 1 and wherein said aggregate is composed substantially entirely of carbonaceous material.

4. A setable composition as claimed in claim 3 and wherein said electrically conductive material is calcined oil coke.

5. A setable composition as claimed in claim 1 and including an expanding agent.

6. A composition as claimed in claim 5 and wherein said expanding agent is aluminium powder added at the rate of 8g/Kg of dry cement powder.

30. An anti-static concrete floor comprising a screed formed of a composition as claimed in claim 1.

31. A structure or building having a wall or walls formed at least in part of a composition as claimed in claim 1 in order to afford radio frequency screening.

32. A building or structure comprising at least one section of wall extending the full height of said building or structure and composed of a composition as claimed in claim 1 arranged to act as a lightning conductor.

7. A setable composition for use as a structural material comprising a cementitious material and an aggregate, wherein said aggregate comprises particulate carbonaceous material consisting of at least two fractions, one fraction being relatively large carbonaceous particles and the other fraction being relatively small carbonaceous particles and wherein said relatively large particles consists of particles of a size such that they are all retained on a number 14 British Standards sieve and said relatively small electrically conductive material consists of particles of a size such that they all pass a number 100 British Standards sieve, said aggregate constituting at least 20% by weight of the solid contents of the composition.

8. A setable composition as claimed in claim 7 and wherein the ratio of the quantity by weight of said relatively large particles and the quantity of said relatively small particles is in the range 1:

1 to 50;

1.

9. A setable composition for use as a structural material comprising a cementitious material and an aggregate, wherein said aggregate comprises particulate carbonaceous material consisting of at least two fractions, one fraction being relatively large carbonaceous particles and the other fraction being relatively small carbonaceous particles and wherein said relatively large particles are all of a size such as to be retained on a 3/8 inch mesh sieve and said relatively small particles are all of a size such as to pass a number 300 mesh British Standards sieve, said aggregate constituting a least 20% by weight of the solid contents of the composition.

10. A setable composition as claimed in claim 9 and said relatively large particles having a nominal size of one half inch and said relatively small particles having a nominal diameter ranging from 20 to 50 Angstrom Units.

11. A setable composition as claimed in claim 9 and wherein said relatively large fraction is calcined oil coke and said relatively small fraction is acetylene black.

12. A setable composition as claimed in claim 9 and wherein said cementitious material comprises at least 50% by weight of one or more materials which are capable of forming on reaction with water, stable, substantially insoluble, hydrated calcium silicates and/or calcium aluminates.

13. A setable composition as claimed in claim 9 and wherein said cementitious material includes a Portland cement.

14. A setable composition for use as a structural material comprising a cementitious material and an aggregate and wherein the aggregate consists of carbonaceous particles of a size distribution such that the slope of a plot of the log to the base ten of the percentages of carbonaceous particles passing the various sieves against the log to the base ten of the mesh sizes in microns of said sieves is in the range 0.35 to 0.65, said aggregate constituting at least 20% by weight of the solid content of the composition.

15. A composition capable of setting to produce a structural material having an electrical resistivity of not more than about 25 ohm-centimeter, said composition consisting essentially of:

a. a cementitious component; and

b. an aggregate which comprises particulate electroconductive material consisting of at least two fractions of disparate particle size, one fraction being calcined oil coke having a nominal particle size of 1/2 inch and another fraction being material selected from the group consisting of calcined oil coke and acetylene black and being of a particle size not larger than 1/10 the particle size of said one fraction, said aggregate constituting at least 20% by weight of the solid contents of the composition.

16. A composition as defined in claim 15 wherein said aggregate consists of said two fractions plus a plurality of further fractions, said further fractions being of different particle sizes ranging between the sizes of said two fractions.

17. A composition as defined in claim 16 wherein all of said fractions are calcined oil coke.

18. A composition as defined in claim 16 wherein the smallest size fraction is acetylene black and the remaining fractions are calcined oil coke.

19. A composition as defined in claim 15 wherein said bonding material consists of Portland cement and sand in approximately equal parts by weight.

20. An aggregate for use in forming an electrically conductive setable composition, said aggregate essentially consisting of two portions of different particle size, one portion consisting of particles of a carbonaceous material having a relatively large mean size such that they are all retained on a number 14 British Standards sieve, the other portion consisting of particles of an electrically conductive material having a relatively small mean size such that they all pass a number 100 British Standards sieve, the ratio of the quantity by weight of said one portion and the quantity by weight of said other portion being in the range 1:

1 to 50;

1.

21. An aggregate as recited in claim 20 wherein said one portion is calcined oil coke and said other portion is acetylene black.

22. An aggregate for use in forming an electrically conductive setable composition, said aggregate being gap-graded and essentially consisting of two portions of different particle size, one portion consisting of particles of carbonaceous material having a relatively large mean size such that they are all retained on a 3/8 inch mesh sieve, the other portion consisting of particles of carbonaceous material having a relatively small mean size such that they all pass a number 300 mesh British Standards sieve, whereby said relatively large particles of electrically conductive material have a nominal size of 1/2 inch and said relatively small particles of electrically conductive material have a nominal diameter of at least 20 but not greater than 50 angstrom units.

23. An aggregate for use in forming an electrically conductive setable composition having an electrical resistivity of not more than about 25 ohm-centimeters, said aggregate essentially consisting of more than two portions of carbonaceous material, each portion having a given size, each given size corresponding to the mesh size of a distinct sieve which would retain particles larger than said given size and pass particles smaller in size than said given size, each portion constituting a given percentage by weight of said aggregate so that the slope of a plot of the log to the base 10 of the percentage of particles which would pass each of said distinct sieves against the log to the base 10 of the mesh sizes in microns of said distinct sieves is at least 0.35 but not greater than 0.65.

24. An aggregate for use in forming an electrically conductive setable composition having an electrical resistivity of not more than about 25 ohm-centimeters, said aggregate consisting essentially of a plurality of portions of carbonaceous material, wherein said portions are made up of the following proportions by weight of particle sizes:

approximately 0 to 20% of a size such as to be retained by a BS410 sieve size 3/16 of an inch, approximately 0 to 30% of a size such as to be retained by a BS410 sieve size 7, approximately 0 to 25% of a size such as to be retained by a BS410 sieve size 14, approximately 0 to 10% of a size such as to be retained by a SB410 sieve size 25, approximately 50 to 8% of a size such as to be retained by a BS410 sieve size 52, approximately 30 to 7% of a size such as to be retained by a BS410 sieve size 100, and approximately 20 to % of a size such as to pass through a BS 410 sieve size 100.

25. An aggregate as recited in claim 24 wherein said aggregate consists entirely of calcined oil coke.

26. An aggregate for use in forming an electrically conductive setable composition having an electrical resistivity of not more than about 25 ohm-centimeters, said aggregate consisting essentially of a plurality of portions of carbonaceous material, wherein said portions are made up of the following proportions by weight of particle sizes:

approximately 0 to 10% of a size such as to be retained by a BS882 sieve size 3/16 of an inch, approximately 0 to 30% of a size such as to be retained by a BS882 sieve size 7, approximately 0 to 20% of a size such as to be retained by a BS882 sieve size 14, approximately 0 to 25% of a size such as to be retained by a BS882 sieve size 25, approximately 50 to 10% of a size such as to be retained by a BS882 sieve size 52, approximately 35 to 5% of a size such as to be retained by a BS882 sieve size 100, and approximately 15 to 0% of a size such as to pass through a BS882 size 100.

27. An aggregate for use in forming an electrically conductive setable composition having an elecrical resistivity of not more than about 25 ohm-centimeters, said aggregate consisting essentially of a plurality of portions of carbonaceous material, wherein said portions are made up of the following proportions by weight of particle sizes:

approximately 5 to 20% of a size such as to be retained by a DIN1045 sieve size 3/16 of an inch, approximately 10 to 30% of a size such as to be retained by a DIN1045 sieve size 7, approximately 10 to 25% of a size such as to be retained by a DIN1045 sieve size 14, approximately 20 to 10% of a size such as to be retained by a DIN1045 sieve size 25, approximately 25 to 8% of a size such as to be retained by a DIN1045 sieve size 52, approximately 20 to 7% of a size as to be retained by a DIN1045 sieve size 100, and approximately 10 to 0% of a size such as to pass through a DIN1045 sieve size 100.

28. An aggregate for use in forming an electrically conductive setable composition having an electrical resistivity of not more than about 25 ohm-centimeters, said aggregate consisting essentially of a plurality of portions of carbonaceous material, wherein said portions are made up of the following proportions by weight of particle sizes:

approximately 0 to 10% of a size such as to be retained by a ASTM C33 sieve size 3/16 of an inch, approximately 0 to 20% of a size such as to be retained by a ASTM C33 sieve size 7, approximately 20 to 30% of a size such as to be retained by a ASTM C33 sieve size 14, approximately 20% of a size such as to be retained by a ASTM C33 sieve size 25, approximately 20 to 15% of a size such as to be retained by a ASTM C33 sieve size 52, approximately 20 to 5% of a size such as to be retained by a ASTM C33 sieve size 100, and approximately 20 to 0% of a size such as to pass through a ASTM C33 sieve size 100.

29. An earth connection comprising an electrode set into the earth by a composition as claimed in claim 28.