WO1998035098B1

WO1998035098B1 - Vehicle arresting units and fabrication methods

Info

Publication number: WO1998035098B1
Application number: PCT/US1998/002325
Authority: WO
Filing date: 1998-02-06
Publication date: 1998-09-17

Abstract

Vehicle arresting blocks of cellular concrete (70) are usable to safely slow travel of an object and may be used to construct an aircraft arresting bed at the end of an airport runway. For such purposes, cellular concrete blocks (70) must be fabricated to exhibit compressive gradient strengths of predetermined values to provide sufficient, but not excessive, deceleration forces on an object. Material uniformity characteristics must be met to avoid unacceptable drag force variations, so that arresting blocks desirably exhibit a predetermined compressive gradient strength (e.g., a 60/80 CGS) over a depth of penetration of 10 to 66 percent of block thickness (Fig. 7). A 60/80 CGS will typically represent an average compressive strength of 70 pounds per square inch over such depth of penetration. Prior applications of cellular concrete typically involved meeting minimum strength values and the production methods did not meet uniformity or compressive gradient strength predictability as required for arresting blocks. Described methods include parameter, ingredient and process controls and ranges effective to enable fabrication of arresting blocks having dry densities and compressive gradient strengths which can be specified in order to provide limited deceleration of aircraft and other objects. Limited deceleration can avoid destructive effects inherent in excess rates of deceleration.

Claims

AMENDED CLAIMS[received by the International Bureau on 3 August 1998 (03.08.98); original claims 1-40 replaced by amended claims 1-28 (4 pages)]

1. A vehicle arresting unit, comprising: a three-dimensional block of cellular concrete having a combination of thickness and compressive gradient strength over a depth of penetration effective to provide limited deceleration of a vehicle wheel, said block comprising cellular concrete having a dry density in a range from 12 to 22 pcf.

2. A vehicle arresting unit as in claim 1, wherein said three-dimensional block is formed from a combination including: a slurry of water and cement; a foam prepared from water and a foaming agent; and a curing form arranged to provide three-dimensional support with controlled evaporation for a mixture of said slurry and said foam during a curing period.

3. A vehicle arresting unit as in claim 1 or 2, wherein said three- dimensional block has a 60/80 compressive gradient strength nominally equal to 70 psi, when averaged over a depth of penetration of said block.

4. A vehicle arresting unit as in claim 1 or 2, wherein said three- dimensional block has an 80/100 compressive gradient strength nominally equal to 90 psi, when averaged over a depth of penetration of said block.

5. A vehicle arresting unit as in claim 1, 2, 3 or 4, wherein said three- dimensional block is formed using a slurry which has undergone a hydration related temperature rise in a range of 5 to 12 degrees F, prior to admixture with said foam.

6. A vehicle arresting unit as in claim 1, 2, 3 or 4, wherein said three- dimensional block is formed using a slurry which has undergone a hydration related temperature rise in a range of 6 to 8 degrees F, prior to admixture with said foam.

7. A vehicle arresting unit as in any preceding claim, wherein said three- dimensional block is formed using a slurry which has undergone a hydration related temperature rise to reach a temperature not exceeding 87 degrees F prior to admixture with said foam.

8. A vehicle arresting unit as in any preceding claim, wherein said three- dimensional block is formed using a slurry which has been projected in a stream to produce shearing forces prior to admixture with said foam.

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9. An arresting unit comprising: a deceleration block fabricated to provide non-rebound limited deceleration of an object, said block comprising cellular concrete, having a dry density in a range from 12 to 22 pcf and a strength effective to limit maximum deceleration of said object.

10. An arresting unit as in claim 9, wherein said deceleration block is formed from a combination including: a slurry of water and cement; a foam prepared from water and a foaming agent; and a curing form arranged to provide three-dimensional support with controlled evaporation for a mixture of said slurry and said foam during a curing period.

11. An arresting unit as in claim 9 or 10, wherein said deceleration block has a predetermined compressive gradient strength over a depth of penetration from 10 to 60 percent of block thickness.

12. A vehicle arresting unit as in claim 9 or 10, wherein said deceleration block includes a first layer of cellular concrete having a first compressive gradient strength and a second layer of cellular concrete having a higher compressive gradient strength.

13. An arresting unit as in claim 9, 10, 11 or 12, wherein said deceleration block is formed using a slurry which has undergone a hydration related temperature rise in a range of 5 to 12 degrees F without exceeding a final temperature of 89 degrees F.

14. An arresting unit as in claim 9, 10, 11, 12 or 13, wherein said deceleration block is formed using a slurry projected in a stream to produce shearing forces prior to admixture with said foam.

15. A vehicle arresting unit as in claim 9, 10, 11, 12, 13 or 14, said block additionally including at least two transverse slots to facilitate handling of said block.

16. A vehicle arresting unit as in claim 9, 10, 11, 12, 13, 14 or 15, wherein said arresting unit additionally comprises crushable pieces of a material other than cellular concrete embedded in said block.

17. A vehicle arresting unit as in claim 9, 10, 11, 12, 13, 14, 15 or 16, wherein said arresting unit additionally comprises a layer of higher strength material

28 to increase structural stability of said block.

18. A vehicle arresting unit as in claim 9, 10, 11, 12, 13, 14, 15 or 16, wherein said arresting unit additionally comprises one or more reinforcing members embedded in said block.

19. A method of forming a section of arresting material, characterized by a compressive gradient strength effective to provide limited deceleration of a moving object, comprising the steps of:

(a) forming a slurry of cement and water;

(b) permitting said slurry to undergo a hydration related temperature rise in a range of 5 to 12 degrees F, to reach a slurry temperature not exceeding 89 degrees F;

(c) preparing a foam from water and a foaming agent;

(d) admixing said slurry and said foam to provide cellular concrete; (e) placing a portion of said cellular concrete in a form representative of the shape of said section; and

(f) curing said cellular concrete under controlled evaporative conditions to provide said section of arresting material in a self-supporting three- dimensional shape suitable to provide deceleration of a moving object.

20. A method as in claim 19, wherein step (a) includes projecting said slurry in a stream to induce high-shear mixing.

21. A method as in claim 19 or 20, wherein in step (a) said slurry is formed from water and cement in a ratio range from 0.5: 1 to 0.6:1.

22. A method as in claim 19, 20 or 21, wherein in step (b) said slurry undergoes a hydration related temperature rise in a range of 6 to 8 degrees F.

23. A method as in claim 19, 20, 21 or 22, wherein in step (d) said cellular concrete has a wet density in a range of 14 to 23 pcf.

24. A method as in claim 19, 20, 21, 22 or 23, wherein in step (f) said cellular concrete as cured has a dry density of 12 to 22 pcf.

25. A method of forming a deceleration block, usable to provide limited deceleration of a moving object, comprising the steps of:

(a) forming a slurry of cement and water;

(b) preparing a foam from water and a foaming agent;

29 (c) admixing said slurry and said foam to provide cellular concrete; and

(d) placing a portion of said cellular concrete in a form suitable to provide said deceleration block in a shape and size suitable for use in decelerating a moving object.

26. A method as in claim 25, additionally comprising the step of: including within said form crushable pieces of a material other than cellular concrete.

27. A method as in claim 25 or 26, additionally comprising the step of: including within said form a layer of material of higher strength than said cellular concrete will have after curing.

28. A method as in claim 25, 26 or 27, additionally comprising the step of: including within said form one or more reinforcing members.

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