Post-tensioned concrete with fibers for slabs on supports

1 . A concrete slab resting on at least two supports, the concrete slab comprising conventional concrete and a combined reinforcement of draped post-tension steel strands and fibers, wherein the draped post-tension steel strands are positioned: in an upper half of the concrete slab above the at least two supports; and in a lower half of the concrete slab in between the at least two supports,

each of said post-tension steel strands

having a diameter ranging from 5 mm to 20 mm, and

having a tensile strength higher than 1700 MPa, and

said fibers being either steel fibers and being present in a dosage ranging from 10 kg/m 3 to 75 kg/m 3 or being macro-synthetic fibers and being present in a dosage ranging from 1.5 kg/m 3 to 9.0 kg/m 3 ,

wherein the concrete slab and the at least two supports are fully connected, partially connected or fully disconnected, and

wherein an amount of steel fibers used is below 1 time an amount of steel recommended as rebar replacement.

2 . The concrete slab according to claim 1 ,

wherein said conventional concrete has a characteristic compressive cube strength of 25 N/mm 2 or higher and/or wherein the concrete slab does not contain any further reinforcement elements and/or wherein the concrete slab is cast in one or multiple steps.

3 . The concrete slab according to claim 1 , wherein said fibers are steel fibers and/or wherein the fibers are glued and/or wherein the macro-synthetic fibers are selected from carbon fibers, glass fibers, basalt fibers or other non-steel based fibers.

4 . The concrete slab according to claim 1 ,

wherein said fibers are steel fibers comprising a straight middle portion that have a tensile strength above 1400 MPa.

5 . The concrete slab according to claim 1 ,

wherein said fibers are steel fibers having two ends and comprising anchorage ends at both of the two ends,

said anchorage ends each comprise three or four bent sections and/or

wherein said steel fibers have an elongation capacity of between 2.5 and 12% and/or

wherein the concrete slab is strain hardening in bending.

6 . The concrete slab according to claim 1 ,

wherein the steel fibers have a length of 10 mm to 100 mm.

7 . The concrete slab according to claim 1 ,

wherein said at least two supports are concrete supports, masonry supports, steel supports or supports combining concrete, masonry and/or steel and/or

wherein the supports are part of a foundation and/or wherein said concrete slab has a uniform average density and/or wherein said concrete slab is cast in one day and/or wherein said concrete slab contains only the fibers and the post-tension steel strands as reinforcement elements and/or wherein conventional concrete has normal shrinkage and/or does not encompass low shrinkage concrete and/or wherein said concrete slab is free of a vapor barrier and/or wherein the concrete slab has a thickness between 4 cm and 75 cm and/or has a width higher than the thickness and/or has a width higher than the thickness and a length higher than the thickness.

8 . The concrete slab according to claim 1 , wherein the at least two supports comprise columns, walls, piles or beams or any combination thereof or any other elements acting as vertical supports, and/or wherein tension is applied to the post-tension steel strands only after the concrete has been cast and the post-tension steel strands remain in place also once the concrete is completely cured/hardened and/or wherein the post-tension steel strands have a tensile strength higher 1800 MPa and/or wherein the post-tension steel strands have a maximum breaking load of higher than 190 KN and/or wherein the post-tension steel strands comprise anchor systems and/or ducts or sheathing.

9 . The concrete slab according to claim 1 ,

wherein the concrete slab further comprises plastic slip-sheets between said concrete slab and the at least two supports.

10 . The concrete slab according to claim 1 ,

wherein the post-tension steel strands are in a banded-banded steel strands configuration or in a banded-distributed steel strands configuration and/or

wherein the post-tension steel strands are used for bonded or unbonded post-tensioning and/or

wherein the anchors for the post-tension steel strands are designed so as to reduce bursting behind the post-tensioning anchors during or after post-tensioning and/or

wherein the fibers are substantially homogenously or homogeneously distributed in the concrete slab.

11 . The concrete slab according to claim 1 ,

wherein the concrete slab and the at least two supports are either permanently fully connected, so that the concrete slab is not free to move from the at least two supports, permanently fully disconnected, so that the concrete slab is free to move, partially connected, so that the concrete slab is partially free to move in certain directions or temporarily disconnected, so that the concrete slab is free to move at least temporarily.

12 . The concrete slab according to claim 1 ,

said at least two supports being arranged to form a regular rectangular pattern or quadrilateral shape, said concrete slab comprising straight zones connecting the at least two supports via a shortest distance in two directions post-tension steel strand bundles being present only in said straight zones in a closely-spaced arrangement, where a maximum distance between bundles does not exceed 1.5 m and/or

said concrete supports being arranged to form a regular rectangular pattern or quadrilateral shape, said concrete slab comprising straight zones connecting the supports via the shortest distance in two directions post-tension steel strand bundles in one direction being present outside said straight zones in a largely-spaced arrangement, where the maximum distance between bundles exceed 1.5 m.

13 . The concrete slab according to claim 1 ,

wherein a span of the concrete slab between two of the at least two supports for a thickness is increased by between 5 and 50% over the concrete slab with a same slab thickness but without fibers and post-tension steel strands and/or

wherein a thickness of the concrete slab for a span between two of the at least two supports is reduced by between 5 and 50% over a concrete slab with a same span but without fibers and post-tension steel strands.

14 . The concrete slab according to claim 1 ,

wherein an amount of concrete is reduced for a slab thickness or a span over a concrete slab but without fibers and post-tension steel strands by between 5 and 50%.

15 . The concrete slab according to claim 1 , wherein a combination of post-tensioned steel strands and fibers increases a structural capacity for flexure, deflection, shear, punching shear, structural integrity, temperature resistance and/or shrinkage resistance over a concrete slab without steel fibers and/or steel strands.

16 . The concrete slab according to claim 1 ,

wherein said conventional concrete has a characteristic compressive cube strength of 28 N/mm 2 or higher.

17 . The concrete slab according to claim 1 ,

wherein the macro-synthetic fibers are polyolefin fibers, or

wherein an amount of steel fibers used is below or equal to 1.0 time an amount of steel recommended and used for the steel bars or rebars to be replaced.

18 . The concrete slab according to claim 1 ,

wherein said fibers are steel fibers comprising a straight middle portion that have a tensile strength above 1500 MPa.

19 . The concrete slab according to claim 1 ,

wherein said steel fibers have an elongation capacity of between at least 3.5% and 12%.

20 . The concrete slab according to claim 1 ,

wherein the steel fibers are present in the concrete slab in a dosage ranging from 20 kg/m 3 to 30 kg/m 3 , and/or

wherein the fibers have a length of between >10 mm and 70 mm.

21 . The concrete slab according to claim 1 ,

wherein the supports are not part of a foundation, and/or

wherein the concrete slab has a thickness between 5 cm and 65 cm.

22 . The concrete slab according to claim 1 ,

wherein the at least two supports are point supports, linear supports or area supports, and/or

wherein the post-tension steel strands have a tensile strength higher 1900 MPa, and/or

wherein the post-tension steel strands have a maximum breaking load of higher than 195 kN.

23 . The concrete slab according to claim 1 ,

wherein the concrete slab further comprises plastic slip-sheets between said concrete slab and the at least two supports at points of contact between the slab and the supports, or

wherein the plastic slip-sheets are not present between the slab and the supports.

24 . The concrete slab according to claim 1 , wherein the post tension steel strands are arranged in a configuration without maximum and/or minimum spacing requirements.

25 . The concrete slab according to claim 1 ,

wherein a span of the concrete slab between two of the at least two supports for a thickness is increased by between 10 and 40% over the concrete slab with a same slab thickness but without fibers and post-tension steel strands, and/or

wherein a thickness of the concrete slab for a span between two of the at least two supports is reduced by between 10 and 40% over a concrete slab with a same span but without fibers and post-tension steel strands.

26 . The concrete slab according to claim 1 ,

wherein an amount of concrete is reduced for a slab thickness or a span over a concrete slab but without fibers and post-tension steel strands by between 10 and 40%.

27 . The concrete slab according to claim 1 , wherein the concrete slab does not contain rebars or steel nets or steel mesh.

28 . The concrete slab according to claim 1 , wherein the concrete slab is fully casted.

29 . A concrete slab resting on at least two supports, the concrete slab comprising conventional concrete and a combined reinforcement of draped post-tension steel strands and fibers, wherein the draped post-tension steel strands are positioned: in an upper half of the concrete slab above the at least two supports; and in a lower half of the concrete slab in between the at least two supports,

each of said post-tension steel strands

having a diameter ranging from 5 mm to 20 mm, and

having a tensile strength higher than 1700 MPa, and

said fibers being either steel fibers and being present in a dosage ranging from 10 kg/m 3 to 75 kg/m 3 or being macro-synthetic fibers and being present in a dosage ranging from 1.5 kg/m 3 to 9.0 kg/m 3 ,

wherein the concrete slab and the at least two supports are fully connected, partially connected or fully disconnected, and

wherein the concrete slab is free of a vapor barrier.