THIN CEMENTITIOUS DECKING MEMBERS

Abstract

A thin cementitious decking member is described. The thin cementitious decking member can span and be attached to two or more support members. The thin cementitious decking member can include a binder and natural or artificial sands, stones, or other aggregates. The thin cementitious decking member should have a thickness no greater than 1 ¾″. The thin cementitious decking member can include pre-stressed tendons bonded to the thin cementitious member. The pre-stressed tendons can be tensioned to impose a longitudinal compressive force into a cross section of the member. In this manner, the thin cementitious member is capable of supporting weight over a span between the two support members greater than 4 times the width of the thin cementitious member.

Description

RELATED APPLICATION DATA

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/866,359, field Aug. 15, 2013, which is incorporated by reference herein for all purposes.

FIELD OF THE INVENTION

This invention pertains to decking systems, and more particularly to a cementitious decking member that can span long distances.

BACKGROUND OF THE INVENTION

Decking surfaces are made of various materials. Wood products are prevalent in residential and commercial construction. They require maintenance and coatings, and have a limited service life. Ipe or other hard woods are used when more longevity and beauty is desired, but are costly and require frequent maintenance. Increasing scarcity, increasing cost of natural lumber products and growing concern about the environment have led to the introduction of manufactured decking products, consisting of various plastics, aluminum, fiber-cement board, and other materials. These products have mixed results in durability against UV exposure, freeze-thaw cycles, and other natural and artificial elements.

Available concrete pavers are relatively square in plan view and are capable of supporting weight over a relatively short span (10 times their thickness). A substantial width to length ratio in plan view is required to adequately support loading; but spans are currently limited to approximately the width of the member. In addition, concrete pavers are generally at least 2″ thick. Although durable and attractive, the concrete material is heavy and brittle and used in relatively small pieces.

A new decking product that is attractive, long lasting, capable of supporting weight over a relatively long distance requiring fewer supporting members, and easily installed would be desirable and valuable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary isometric view of a horizontal deck surface, according to an embodiment of the invention.

FIG. 2a is a sectional view of one possible configuration of the invention taken across the line 2-2 of FIG. 1.

FIG. 2b is a sectional view of an alternate possible configuration of the invention taken across the line 2-2 of FIG. 1.

FIG. 2c is a sectional view of an alternate possible configuration of the invention taken across the line 2-2 of FIG. 1.

FIG. 3 is a fragmentary isometric view of the configuration of the invention as described in FIG. 2a.

FIG. 4a is a sectional view taken across the line 4-4 of FIG. 1 of a possible attachment of the invention to a supporting member.

FIG. 4b is a sectional view taken across the line 4-4 of FIG. 1 of an alternate possible attachment of the invention to a supporting member.

FIG. 5 is an isometric view of an attachment clip.

FIG. 6a is a sectional view taken along 4-4 of FIG. 1 of an alternate possible attachment of the invention to a supporting member.

FIG. 6b is an isometric view of an edge attachment clip installed on a member as viewed in FIG. 6a.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Considering FIG. 1, a horizontal surface is created with long thin and narrow cementitious plank or board members (10) which span over or between joists support members (11) capable of supporting weight. Support members (11) can be wood, steel, concrete, or other materials. The span between support members (11) can preferably be 30″, but can range to about 60″. The member (10) is capable of relatively long spans between support members (11) as much as 50 times the thickness of the member. The top surface (12) can be decorative and slip resistant. Considering FIGS. 2a and 3, the cementitious plank or board member has two opposite lateral sides (14), a top side (12), and a bottom side (13). The member can be of various sizes. A preferred configuration can have cross sectional dimension of 1⅜″ tall, by 7⅜″ wide. Cementitious members can be made thin (no more than 1¾″ in thickness). Cementitious members can be made in any length, but as lengths get longer, the cementitious members become more fragile to handle and install. Preferred lengths for manufactured boards can be 8′, 10′, and 12′ lengths. The top surface (12) can be flat or slightly convex to shed water. The lateral sides (14) can be perpendicular to the bottom side (13) or slightly beveled.

The thin cementitious member is pre-stressed with non-corrosive tendons (15). The tendons (15) are placed such that there are an equal number of tendons an equal distance above and below, and to the right and left of, the cross sectional center of mass (CM) of the member. Note that the center of mass of the member may or may not be at the same location as the cross sectional center of area of the member, depending on the density of the cementitious material and the casting method. The tendons are textured such that they continuously bond with the cementitious material, allowing the member to be cut without losing the pre-stress.

The tendons (15) are non-corrosive materials so that the ends do not rust, and they will not corrode under normal atmospheric conditions and cause interior or other degradation of the member. The pre-stress tendon material is selected based on the ability to bond to the cement material, and the ability to hold stress over time with little stress relaxation. ⅛″ type 316 stainless steel type 7×7 RHL wire rope is used in the preferred configuration, but it could be synthetic, carbon fiber, or other materials.

Tendons (15) are tensioned to impose a longitudinal compressive force into the cross section of the member from 400 lbs per square inch to 1300 lbs per square inch, depending on the load carrying requirements of the member.

The tendon mechanically bonds to the cementitious material such that its stress is transmitted to the cementitious material without slippage in a relatively short distance, preferably the thickness of the member or less.

Considering FIG. 3 specifically, reinforcing rods (16) can be placed perpendicular with the longitudinal tendons (15) if required, but is likely not necessary on narrow members with a cross section 1⅜″ tall by 8″ wide or less. The rods can be of any desired material, including pre-stressing or non-stressed tendons.

Considering FIGS. 2a and 4a, a continuous or non-continuous slot or void (23) that is approximately triangular or trapezoidal in cross section (the slot can also be shaped like a dovetail) can be formed in the bottom of the member, which can be used to attach the member to a supporting member with a clip or tab (22).

Considering FIG. 2b, in an alternate configuration, multiple slots (23) that are approximately triangular or trapezoidal in cross section (or shaped like a dovetail) can be used in the member (10) and the pre-stressing tendons (15) can be placed in various configurations as long as they are twice the tendon diameter or more from each other or the nearest edge or opening.

Considering FIG. 2c, in an alternate configuration, members can be constructed with interior longitudinal voids (18) to reduce weight.

Considering FIGS. 4a and 5, members can be fastened to a supporting member with polyurethane or other adhesive (24). One or more slots (23) can receive a tab (22) made of non-corrosive material, nylon, stainless steel, carbon fiber, or other to fasten the member to a supporting member (11). The slot (23) also aids air circulation, allowing the support member (11) to breathe if necessary. The tab (22) is designed such that its bearing points (25) are spaced away from the more fragile edges of the slot in the cementitious member so it will be less likely to fracture or chip, even if the tab is installed in a non-perpendicular fashion. The tab can have guide slots (26) that position a screw or other fastener (27) so that it naturally applies downward pressure against the supporting member as it is tightened, and applies clamping force between the board and its supporting member. The member can attach to the tab by sliding onto the tab: the member does not need to be permanently secured to the supporting member (e.g., by a screw that connects the member to either the tab or the supporting member).

Considering FIG. 4b specifically, grooves on the bottom surface (19) can be formed on the members to allow airflow if used on a wood or other surface that needs air circulation. An alternate attachment method can consist of a mechanical fastener (20), such as a screw, installed through a hole (21) provided in each lateral side of the cementitious member at predetermined longitudinal locations attached to the supporting member (11).

Considering FIGS. 6a and 6b, in an alternate configuration, the member (10) is manufactured with a continuous groove (28) in the sides (14) of the member (10). The lower surface of the groove has an upper surface (29) and lower surface (30) creating a saw-tooth in the lower horizontal surface of the groove. An attachment clip (31) has a lower approximately horizontal leg (32) and a higher and longer opposing approximately horizontal leg (33). The lower leg (32) fits into the lower saw tooth of the groove (30) on the member. The upper leg (33) sits on the upper surface of the saw tooth (29) of the adjacent member. A spacer on the attachment clip (34) maintains a predetermined spacing between the members and holds the attachment clip against the members. The edge attachment clip (31) holds the members to the supporting member (11) with a fastener (35). When multiple members are placed in this manner, the attachment clips hold the members from movement in 3 directions.

Considering FIG. 2a, a decorative slip-resistant texture can be imprinted on the member (10) by the mold surface. A textured and decorative surface can be achieved on the top side (12) and lateral sides (14) of the member after the cementitious material has cured by means of abrasive blasting, high pressure water blasting, or acid etching, exposing the internal aggregate mixture of the cementitious material. The cementitious material can be colored with iron oxide or other pigments.

Material Used

The members are made of a cementitious material, made from natural or artificial sands, stones, and other aggregates, held together with a binder of Portland cement, various pozzolones and chemical admixtures which cures by a chemical hydration process between the cement and water. Aggregates can be from recycled materials, glass, or other. Constituents are properly proportioned to create a strong interlocking matrix.

An example of a wet cast mix design based on a 100 lb sample:

Type II or Type III white or gray Portland cement 13.5 lbs
Silica fume or Blast Furnace Slag 4.5 lbs
Iron oxide or other color        as required
Water reducing admixtures        as required
Plasticizer                      as required
Air entraining admixture         as required
Water                            6 lbs
Well graded sand less than ⅛″ in size 31 lbs
Coarse aggregate (¼″ to ⅜″ in size) 45 lbs

An example of a dry cast mix design based on a 100 lb sample

Type II or Type III white or gray Portland cement 17.6 lbs
Silica fume or Blast Furnace Slag 5.9 lbs
Iron oxide or other color        as required
Water reducing admixtures        as required
Plasticizer                      as required
Air entraining admixture         as required
Water                            4.5 lbs
Well graded sand less than ⅛″ in size 36 lbs
Additional Fine aggregate ⅛″ in size 36 lbs

Manufacturing Processes

The members can be made in a wet cast process (cementitious material will flow, water to cement ratio of 0.35 to 0.60). In this process, the tendons are stretched in a mold, and the cementitious material cast into and mechanically consolidated into the mold. The cementitious material then cures to an appropriate amount (in the range of 2500 psi compressive strength). The curing (hydration process) can be accelerated with heat while holding the moisture in the freshly cast member (or steam curing). Once the member has cured sufficiently (compressive strength of 2500 psi), the tendons are released from their restraints, transferring stress to the cast member and placing it into compression. For thin members wet cast as described, it is likely that the aggregates will settle in the casting process causing a variation in density of the material with the depth. To account for the variation in density, it is likely that tendons need to be set off-center (not at the center of area) to keep the member from warping. Air entraining and water reducing admixtures can be used that aid in freeze-thaw resistance and strength of the material.

The members can be made with only enough water to hydrate the cement (dry cast). In this case, material will not flow. Water-cement ratio can be limited to 0.18 to 0.28. Since the cementitious material does not flow, dry casting requires compacting the uncured material into a form or mold under substantial force and vibration to consolidate the mix. Dry casting can result in higher strength, lower moisture absorption characteristics, and a durable material. Tendons can be associated closer to the center of area of the member since there is less or no settling of the aggregate in the process, and there is not the concern for warping or distortion that can be associated with pre-stressing a very thin wet cast member. Members constructed with the dry cast process can be finished similar to what was described in the wet cast process, but the aggregate size is smaller.

Having described and illustrated the principles of the invention with reference to illustrated embodiments, it will be recognized that the illustrated embodiments can be modified in arrangement and detail without departing from such principles, and can be combined in any desired manner. And although the foregoing discussion has focused on particular embodiments, other configurations are contemplated. In particular, even though expressions such as “according to an embodiment of the invention” or the like are used herein, these phrases are meant to generally reference embodiment possibilities, and are not intended to limit the invention to particular embodiment configurations. As used herein, these terms can reference the same or different embodiments that are combinable into other embodiments.

Consequently, in view of the wide variety of permutations to the embodiments described herein, this detailed description and accompanying material is intended to be illustrative only, and should not be taken as limiting the scope of the invention. What is claimed as the invention, therefore, is all such modifications as can come within the scope and spirit of the following claims and equivalents thereto.

Claims

1. A decking system, comprising:

two support members; and

a cementitious member spanning and attached to the two support members, the cementitious member including a binder and natural or artificial sands, stones, or other aggregates, the cementitious member have a length, a width, and a thickness, the thickness of the cementitious member no greater than 1¾″,

the cementitious member including pre-stressed tendons bonded to the cementitious member and tensioned to impose a longitudinal compressive force into a cross section of the member, so that the cementitious member is capable of supporting weight over a span between the two support members greater than 4 times the width of the cementitious member.

2. A decking system according to claim 1, wherein the cementitious member is capable of supporting weight over a span between the two support members greater than 10 times the thickness of the cementitious member.

3. A decking system according to claim 2, wherein the cementitious member is capable of supporting weight over a span between the two support members of up to 50 times the thickness of the cementitious member.

4. A decking system according to claim 1, wherein the pre-stressed tendons are made of a non-corrosive material.

5. A decking system according to claim 4, wherein the pre-stressed tendons are made of a material drawn from a set consisting of stainless steel type wire rope, synthetic materials, or carbon fiber.

6. A decking system according to claim 1, wherein the pre-stressed tendons are tensioned to impose a longitudinal compressive force into the cross section of the member of between and including 400 and 1300 pounds per square inch (lb./in2).

7. A decking system according to claim 1, wherein the pre-stressed tendons are spaced equally above and below a center of mass of the cementitious member.

8. A decking system according to claim 1, wherein the pre-stressed tendons are spaced equally to the right and left of a center of mass of the cementitious member.

9. A decking system according to claim 1, wherein the cementitious member further includes perpendicular rods running perpendicular to the longitudinal tendons.

10. A decking system according to claim 1, wherein the cementitious member further includes a slot for attaching the cementitious member to each of the two support members using tabs, the tabs including an upper portion shaped to fit into the slot in the cementitious member.

11. A decking system according to claim 10, wherein a shape of a cross section of the slot is drawn from a set consisting of a triangle, a trapezoid, and a dovetail.

12. A decking system according to claim 10, wherein the tabs include bearing points that extend to contact edges of the slot.

13. A decking system according to claim 10, wherein the pre-stressed tendons are positioned within the cementitious member at least two times the diameter of the pre-stressed tendons from the slot.

14. A decking system according to claim 10, wherein the slot is positioned approximately in the center of the cementitious member.

15. A decking system according to claim 10, wherein:

the slot is a longitudinal groove on at least one side of the cementitious member; and

the cementitious member further includes a second longitudinal groove on the at least one side of the cementitious member, the second longitudinal slot located at the bottom of the cementitious member.

16. A decking system according to claim 15, wherein the tab includes a spacer to maintain a predetermined spacing between the cementitious member and an adjacent cementitious member.

17. A decking system according to claim 1, wherein the cementitious member includes a longitudinal void.

18. A decking system according to claim 1, wherein the cementitious member includes longitudinal grooves to facilitate airflow between the cementitious member and the two support members.

19. A decking system according to claim 1, wherein the cementitious member is attached to the two support members using a fastener drawn from a set consisting of glue and screws.

20. A decking system according to claim 1, wherein the cementitious member is made using a wet cast process.

21. A decking system according to claim 1, wherein the cementitious member is made using a dry cast process.

22. A cementitious member having a length, width, and thickness, comprising:

a binder and natural or artificial sands, stones, or other aggregates; and

pre-stressed tendons bonded to the cementitious member and tensioned to impose a longitudinal compressive force into a cross section of the member, so that the cementitious member is capable of supporting weight over a span between the two support members greater than 4 times the width of the cementitious member, the thickness of the cementitious member no greater than 1¾″,

wherein the cementitious member is designed to span and be attached to two support members.

23. A cementitious member according to claim 22, wherein the cementitious member is capable of supporting weight over a span between the two support members greater than 10 times the thickness of the cementitious member.

24. A cementitious member according to claim 23, wherein the cementitious member is capable of supporting weight over a span between the two support members of up to 50 times the thickness of the cementitious member.

25. A cementitious member according to claim 22, wherein the pre-stressed tendons are tensioned to impose a longitudinal compressive force into the cross section of the member of between and including 400 and 1300 pounds per square inch (lb./in2).

26. A cementitious member according to claim 22, further comprising a slot for attaching the cementitious member to each of the two support members using tabs.

27. A cementitious member according to claim 26, wherein a shape of a cross section of the slot is drawn from a set consisting of a triangle, a trapezoid, and a dovetail.

28. A cementitious member according to claim 26, wherein the slot is positioned approximately in the center of the cementitious member.

29. A cementitious member according to claim 26, wherein:

the slot is a longitudinal groove on at least one side of the cementitious member; and

the cementitious member further includes a second longitudinal groove on the at least one side of the cementitious member, the second longitudinal slot located at the bottom of the cementitious member.

30. A cementitious member according to claim 22, wherein the cementitious member includes longitudinal grooves to facilitate airflow between the cementitious member and the two support members.

31. A tab for connecting a cementitious member and a support member, comprising:

means for attaching the tab to a support member; and

a top portion with an approximately triangular shape, the top portion designed to fit in a slot in the cementitious member.

32. A tab according to claim 31, further comprising bearing points on the top portion of the tab that extend to contact edges of the slot in the cementitious member.

33. A tab for connecting a cementitious member and a support member, comprising:

means for attaching the tab to a support member; and

a top portion including two approximately horizontal legs, the two approximately horizontal legs designed to fit in a longitudinal groove in the cementitious member and a second longitudinal groove in an adjacent cementitious member.

34. A tab according to claim 33, wherein the tab includes a spacer to maintain a predetermined spacing between the cementitious member and the adjacent cementitious member.