FIBER FOR CONCRETE REINFORCEMENT

Abstract

A fiber for concrete reinforcement is provided including 85 wt. % to 98 wt. % of a polypropylene, 2 wt. % to 10 wt. % of a polycarbonate, and up to 5 wt. % of a compatibilizer, wherein the fiber has a tensile strength of at least 600 MPa and a modulus of at least 6 GPa.

Claims

1. A fiber for concrete reinforcement characterized in that the fiber comprises 85 wt. % to 98 wt. % of a polypropylene and 2 wt. % to 10 wt. % of a polycarbonate, wherein the fiber has a tensile strength of at least 600 MPa and a modulus of at least 6 GPa as determined according to EN 14889-2.

2. The fiber for concrete reinforcement according to claim 1 wherein the fiber comprises 85 wt. % to 98 wt. % of a polypropylene, 2 wt. % to 10 wt. % of a polycarbonate, and up to 5 wt. % of a compatibilizer.

3. The fiber for concrete reinforcement according to claim 1 wherein the fiber is spun from a blend comprising 85 wt. % to 98 wt. % of a polypropylene, 2 wt. % to 10 wt. % of a polycarbonate, and up to 5 wt. % of a compatibilizer.

4. The fiber for concrete reinforcement according to claim 1 wherein the fiber comprises 3 wt. % to 8 wt. % of the polycarbonate.

5. The fiber for concrete reinforcement according to claim 1 wherein the fiber comprises 1 wt. % to 5 wt. % of the compatibilizer and wherein the compatibilizer is a styrene-ethylene-butylene-styrene copolymer, or a maleic acid grafted polymer.

6. The fiber for concrete reinforcement according to claim 1 wherein the fiber has an equivalent fiber diameter of at least 300 μm, as determined according to EN 14889-2.

7. The fiber for concrete reinforcement according claim 1 wherein the fiber has a non-circular cross-sectional shape.

8. The fiber for concrete reinforcement according to claim 1 wherein the fiber has a tensile strength of at least 650 MPa as determined according to EN 14889-2.

9. The fiber for concrete reinforcement according to claim 1 wherein the fiber has a modulus of at least 7 GPa as determined according to EN 14889-2.

10. A concrete element comprising fibers according to claim 1.

11. The concrete element according to claim 10 wherein the concrete element comprises the fibers in an amount of 10 kg/m.sup.3 or less.

12. The concrete element according to claim 10 wherein the concrete element has a post-crack residual flexural tensile strength at a crack mouth opening displacement of 3.5 mm (f.sub.R,4) of at least 1.0 MPa.

13. A process for manufacturing a fiber for concrete reinforcement having a tensile strength of at least 600 MPa and a modulus of at least 6 GPa as determined according to EN 14889-2, the process comprising the steps of supplying a blend comprising 85 wt. % to 98 wt. % of a polypropylene, 2 wt. % to 10 wt. % of a polycarbonate, and up to 5 wt. % of a compatibilizer into an extruder, extruding the blend through a spinneret comprising one or more capillaries to form one or more extruded fibers, cooling the extruded fibers, drawing the extruded fiber at a draw ratio of at least 10, and cutting the fibers to a specified length.

14. The process for manufacturing a fiber for concrete reinforcement according to claim 13 wherein the blend comprises 3 wt. % to 8 wt. % of the polycarbonate.

15. The process for manufacturing a fiber for concrete reinforcement according to claim 13 wherein the blend is supplied into a single screw extruder.

Description

COMPARATIVE EXAMPLE 1

[0060] Fibers were spun from a blend of 95.5 wt. % of a polypropylene, 3.5 wt. % of an inorganic filler, and 1 wt. % of nucleating agent.

[0061] The fibers were drawn at a draw ratio of 11.9 and had an equivalent diameter of 0.70 mm.

Comparative Example 2

[0062] Fibers were spun under the same conditions of Comparative Example 1, except that the fibers were spun from a blend of 98 wt. % of a polypropylene, and 2 wt. % of a compatibilizer. The fibers had an equivalent diameter of 0.70 mm.

Example 1

[0063] Fibers were spun under the same conditions of Comparative Example 1, except that the fibers were spun from a blend of 93 wt. % of a polypropylene, 5 wt. % of a polycarbonate and 2 wt. % of a compatibilizer.

[0064] The fibers were drawn at a draw ratio of 20 and had an equivalent diameter of 0.70 mm.

Example 2

[0065] Fibers were spun under the same conditions of Comparative Example 1, except that the fibers were spun from a blend of 89.5 wt. % of a polypropylene, 5 wt. % of a polycarbonate, 2 wt. % of a compatibilizer and 3.5 wt. % of an inorganic filler. The fibers had an equivalent diameter of 0.70 mm.

[0066] A fiber reinforced concrete beam was formed for each type of fibers, the concrete comprising a fiber dosage of 5 kg/m.sup.3. The concrete had a concrete strength class of C25/30, determined according to EN 12390-3 “Testing hardened concrete—compressive strength of test specimens”, and a flexural tensile strength of 4.3±0.3 MPa, determined according to EN 14651.

[0067] The post-crack residual flexural tensile strength of the concrete beam at a crack mouth opening displacement of 3.5 mm (f.sub.R,4) was determined, as shown in Table 1, in accordance with test method EN 14651 “Test method for metallic fibre concrete—Measuring the flexural tensile strength (limit of proportionality (LOP), residual)”.

TABLE-US-00001 TABLE 1 Fiber f.sub.R, 4 Dosage (CMOD = 3.5 mm) Example (kg/m3) (MPa) % Increase Comparative 1 5 1.78 — Comparative 2 5 1.78 — 1 5 2.17 21.9 2 5 2.55 43.3

[0068] Table 1 shows that the performance of synthetic fibers predominantly composed of a polypropylene in fiber reinforced concrete can be improved by approx. 20% by adding 5 wt. % of a polycarbonate and spinning the fibers from a blend comprising polypropylene and polycarbonate.

[0069] Table 1 shows that the performance of the synthetic fibers in fiber reinforced concrete can be further improved by approx. 40-45% by additionally adding an inorganic filler and spinning the fibers from a blend comprising polypropylene, polycarbonate, compatibilizer and inorganic filler.

[0070] In Table 2 the creep of the fiber of example 1 has been compared to the creep of the fiber of comparative example 1. Table 2 and FIG. 1a-b show that the creep of fiber according to example 1 is reduced by 47% as compared to the fiber according to comparative example 1.

TABLE-US-00002 TABLE 2 Average creep at Reduction Example 960 hours (%) in creep (%) Comparative 1 17.6 — 1 9.4 47

Example 3

[0071] The fibers of Example 1 were applied in a spray concrete, also known as shotcrete, with the concrete mixture comprising 440 kg/m.sup.3 of CEM I 42.5 N cement and 5 kg/m.sup.3 of fibers.

[0072] In comparative 3 example 5 kg/m.sup.3 of Barchip 54 fibers, being considered an industry standard, were applied in spray concrete with the concrete mixture of example 3, with the type of fibers being the only difference.

[0073] In Table 3 the amount of energy absorbed by the shotcrete of example 3 has been compared to the amount of energy absorbed by the shotcrete of comparative example 3, determined as an average of 4 samples, in accordance with ASTM C1550-12a:2013 round plate test.

[0074] Table 3 shows that the total energy absorption at 40 mm deflection of the shotcrete of example 3 is increased by 27% as compared to shotcrete comprising the fibers of comparative example 3.

[0075] Table 3 also shows that the energy absorption at 5 mm, 10 mm and 20 mm deflection of the shotcrete of example 3 is increased by 17% to 24% as compared to shotcrete comprising the fibers of comparative example 3.

TABLE-US-00003 TABLE 3 Comparative Increase Example 3 Example 3 (%) Energy absorption at 42 49 17 5 mm deformation (J) Energy absorption at 79 95 20 10 mm deformation (J) Energy absorption at 139 172 24 20 mm deformation (J) Energy absorption at 214 271 27 40 mm deformation (J) Load at break (kN) 24.8 25.0

Example 4

[0076] A fiber reinforced concrete beam was formed with the fibers of example 1, the concrete comprising a fiber dosage of 4 kg/m.sup.3. The concrete had a flexural tensile strength of 4.5±0.3 MPa, determined according to EN 14651.

[0077] The concrete beam had a post-crack residual flexural tensile strength at a crack mouth opening displacement of 3.5 mm (f.sub.R,4) of 3.20 MPa, and a post-crack residual flexural tensile strength at a crack mouth opening displacement of 0.5 mm (f.sub.R,1) of 1.87 MPa determined in accordance with test method EN 14651.