MICROFIBROUS SHOTCRETE MIXTURE

Abstract

A microfibrous shotcrete mixture which is used in mining applications, in highway, railway, subway tunnels, as excavation support element slope applications. The microfibrous shotcrete mixture provides a decreased amount of rebound. The objective of the present invention is to increase cohesion significantly and reduce the rebound amount in shotcrete up to four times by establishing a bridge between concrete particles by means of the special structure of the developed microfiber.

Claims

1. A shotcrete mixture, which reduces an amount of rebound in shotcrete and significantly increases cohesion by forming a bridge between concrete particles, comprising: microfibers having a diameter between 10-35 microns, tensile stress between 700-1200 MPa, dtex value between 150-25000 dtex, finish oil max. between 0.02%-2%, elongation amount between 1%-75%, melting temperature of 65-705° C., and a length between 0.4 mm and 70 mm.

2. A microfibrous shotcrete mixture according to claim 1, wherein the microfibers are present in concrete in a range of 0.001%-4% by volume.

3. A microfibrous shotcrete mixture according to claim 1, wherein at least one microfiber which of the microfibers is selected from the group consisting of PET, PP, PA, PEN, carbon, glass, cotton, other natural and synthetic fibers, and combinations thereof.

4. A microfibrous shotcrete mixture according to claim 3, wherein the at least one microfiber is PET.

5. A microfibrous shotcrete mixture according to claim 2, wherein an amount of PET microfiber used in 1 m.sup.3 concrete is in range of 0.0138 kg to 55.2 kg.

6. A microfibrous shotcrete mixture according to claim 2, wherein at least one microfiber of the microfibers is selected from the group consisting of PET, PP, PA, PEN, carbon, glass, cotton, other natural and synthetic fibers, and combinations thereof.

7. A microfibrous shotcrete mixture according to claim 6, wherein the at least one microfiber is PET.

8. A microfibrous shotcrete mixture according to claim 4, wherein an amount of PET microfiber used in 1 m.sup.3 concrete is in range of 0.0138 kg to 55.2 kg.

9. A microfibrous shotcrete mixture according to claim 7, wherein an amount of PET microfiber used in 1 m.sup.3 concrete is in range of 0.0138 kg to 55.2 kg.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] “Microfibrous shotcrete mixture” developed to fulfill the objectives of the present invention is illustrated in the accompanying figures, in which:

[0019] FIG. 1 is a graphical illustration of the comparison of the rebound amount in conventional shotcrete application without fiber content and the rebound amount in the microfibrous shotcrete mixture according to the invention in kilograms.

[0020] FIG. 2 is a graphical illustration of the comparison of the rebound amount in conventional shotcrete application without fiber content and the rebound amount in the microfibrous shotcrete mixture according to the invention as percentage (%).

DETAILED DESCRIPTION OF THE INVENTION

[0021] The amount of rebound in the shotcrete is decreased by means of the microfiber developed within the scope of the invention, and it significantly increases cohesion by forming a bridge between concrete particles. The microfibrous shotcrete mixture according to the present invention has a diameter between 10-35 microns, tensile stress between 700-1200 MPa, dtex value between 150-25000 dtex, finish oil max. between 0.02%-2%, elongation amount between 1%-75%, melting temperature of 65-705° C., and a length between 0.4 mm and 70 mm. Within the scope of the invention, PET (polyethylene terephthalate) is preferably used as microfibers, at least one microfiber selected from a group consisting of PP, PA, PEN, Carbon, Glass, Cotton and other natural fibers and other synthetic fibers and various combinations thereof, including PET fibers is also used. The content of microfiber in concrete is in range of 0.001%-4% within the scope of the invention.

[0022] Within the scope of the invention, microfibers are homogeneously distributed in the concrete so that they can take an active role within the concrete. Addition of fibers into the concrete can be performed with concrete transmixer or by adding into the aggregate band in concrete plants. Cohesion is provided by means of forming a bridge between concrete particles thanks to homogenously distributing microfibers within the concrete. Its use can be specified as fiber use of 0.001%-4% by volume in concrete, which is amount range of PET fiber to be used in 1 m.sup.3 of concrete depending on specific weight of 1380 kg/m.sup.3, it can be specified as 0.001% fiber amount.fwdarw.13.8 g/m.sup.3 and 0.1% fiber amount.fwdarw.1.38 kg/m.sup.3. The density of PET fibers is 1.38 gr/cm.sup.3, that is it corresponds to 1380 kg/m.sup.3 0.1% 1380*1/1000=1.38 kg/m.sup.3. It is used in range of 0.001%-4% (13.8 g/cm.sup.3-55.2 kg/m.sup.3) within the concrete. Accordingly, within the scope of the invention, preferably the amount of PET fiber used in 1 m.sup.3 of concrete ranges from 0.0138 kg to 55.2 kg (0.0138 kg/m.sup.3 to 55.2 kg/m.sup.3).

[0023] The microfibers used within the scope of the invention increase the fire resistance in concrete, reduce the occurrence of rupture/spalling and reduce the amount of rebound in shotcrete in range of 10-90% according to the objectives of the invention.

EXPERIMENTAL RESULTS

Experiment 1

[0024]

TABLE-US-00001 TABLE 1 Illustration of concrete content which does not comprise fiber providing rebound. Amount used in Product 1 m.sup.3 concrete Cement (Cem 1 42.5N) 460 kg 0-4 mm aggregate 1600 gr Water 200 kg Amount of Plasticiser 3 kg

[0025] 1 m.sup.3 concrete is 2263 kg. In the experiment, 5 m.sup.3 non-fibrous concrete was used and 2380 kg of rebound was obtained in 5 m.sup.3 of concrete.

Experiment 2

[0026]

TABLE-US-00002 TABLE 2 Illustration of concrete content which is developed within the scope of the invention and has fiber content providing rebound. Amount used in 1 Product m.sup.3 concrete Cement (Cem 1 42.5N) 460 kg 0-4 mm Aggregate 1600 gr Water 200 kg Amount of Plasticiser 3 kg Amount of Water 300 g

[0027] 1 m.sup.3 fibrous concrete is 2263.3 kg. In the experiment, total 5 m.sup.3 of concrete was tested and 600 kg of rebound was obtained in 5 m.sup.3 of concrete.

[0028] In the microfibrous shotcrete mixture developed within the scope of the invention, addition of 300 g/m.sup.3 fiber has reduced the rebound amount by 75%. This advantage in cost means that it will benefit from both concrete and microfiber to be used in it. By means of the fiber that has been developed, the projects can be sustainable and equity capital can be maintained since the production of waste concrete is reduced. With the invention, rebound in shotcrete is reduced up to four times, less shotcrete is used in shotcrete productions carried in this manner, and labor and time advantage is achieved in processes such as waste removal and scraping of spilled materials after excavation support.