DD264420A1 - STEEL FIBER CONCRETE INJECTION MIXTURE - Google Patents

Abstract

The invention relates to a Stahlfaserspritzbetongemisch for performing work of lining buildings, such as tunnels, tunnels and caverns and for repair of engineering structures both dry and wet spraying. The steel fiber sprayed concrete mixture is intended to improve the strength of the linings and surfaces; It should be applied with conventional machines and equipment, without hedgehog formation of the steel fiber. According to the invention, the steel fiber sprayed concrete mixture is made of the known aggregates with the proportions of 350-420 kg cement PZ 4/25, 1 350-1 610 kg BKS 0.4, 277-281 kg BK 4/8, 180-210 kg water and 80-420 kg. 150 kg of machined steel fibers having the characteristics of a length of 1.5-2.5 times the maximum grain diameter of the aggregates, with an average thickness of 0.4-0.7 mm; based on 1 m3 volume. The proportion of steel fibers in the steel fiber sprayed concrete mixture is 0.9-5.0 vol.%.

Description

Characteristic of the known solutions

There are known concrete mixtures, in addition to the usual additives also plastic dispersions and / or plastic or steel wire fibers (DE-OS 1571395, OE-OS 2221373, DE-PS 336479, DE-OS 28533/8).

The concrete mixtures with synthetic fibers are only of limited suitability for the aforementioned field of application, since they have only a slight reinforcing effect because of the relatively low Ε-modulus. But especially in the lining of shafts and tunnels, there is a great firmness and insensitivity to the subsidence of the present mountains.

Although concrete blends with steel wire fibers largely meet this requirement, they have the disadvantage that the bond between the bare steel wire and the cement matrix is low and therefore relatively long steel wire fibers are required.

Steel wire fibers also have the disadvantage that they cause a strong hedgehog formation both during their storage as well as in the mixing process with the concrete mass, which also has a very adverse effect on the strength. In order to be able to incorporate this type of fiber, it is also necessary to experience special fiber-singulation measures, which in turn greatly reduce the efficiency of the mixing process. Furthermore, it can be seen that with the use of steel wire fibers with their increasing length, the rebound increases significantly.

It is also known to improve the bonding of Stahldrahtfa ^ ern by their profiling or to provide them with a coating. But here, too, a tendency to lock was found especially at a higher fiber content.

Also cut from sheet smooth or corrugated metal strips are known (DE-OS 2824777) and the addition of plastic dispersions to the chips (DE-OS 2221373). All shavings made of steel wire or sheet steel are relatively expensive, since they consist of both high-quality steel grades and by the drawing and rolling processes large amounts of energy and many workflows are objectified.

With extraction fibers a similar strength of the steel fibers obtained from the steel melt can not be achieved, whereby no definable strength of such a Botons can be achieved.

Object of the invention

The aim of the invention is to avoid the above mentioned objective and economic shortcomings and to facilitate and improve the production of steel fiber shotcrete and its use and to find a mixture which can be mixed with simple and conventional mixing, conveying and spraying equipment and technologies using an economical steel fiber.

Explanation of the essence of the invention

The invention has for its object, based on conventional aggregates of shotcrete mixtures such as grit, gravel, sand, cement, water and possibly known additives for quick hardening, with further addition of steel fibers a Stahlfaserspritzbetongemisch specify which with simple and conventional mixing -, conveying and spraying equipment and technologies can be manufactured and processed and no hedgehog formation ^! n all technological processes and no high fiber recoil arises as well as no additional equipment for fiber separation are needed. According to the invention the object is achieved in that, starting from the intended use and the expected load, a Stahlfaserspritzbetongemisch using machined steel fibers in about the following composition, based on 1m ³ , is used:

350-42OkQ cement PZ

1350-1610kg concrete boat sand% or sand "h and ² U 270-280 kg concrete gravel Ve 70-160 kg steel fibers 180-210kg water.

The strained steel fibers have a length of ι -3.5 times the value of the largest grain diameter of the aggregates, since

shorter fibers will cause less rebound and severely restrict the formation of certain voids due to bridging by the fibers. The average thickness of the fibers is 0.4-0.7 mm and the width to average thickness ratio of the steel fibers 3 ... 7. The proportion of steel fibers in the mixture is 0.9 to 5% by volume, preferably 0.9 to 3% by volume.

In the substance calculation of the mixture, the proportion of steel fibers according to the invention is to be used, the Steel fibers are to be regarded as a fraction of chippings.

^r: e View line of the aggregates is a deviation from the usual rules to B or between B and C of the Regelsieblinien, the

Fine grain content (grain size 0 to 2 mm) must be present according to Sieblinie ß, since the proportion of fine mortar a significant Condition for the cladding of steel fibers and the strength and tightness of the concrete is. In addition, it will be the Cement content reduced to the necessary feet and thus reduces the tendency to shrink in the hardening process. The addition of fiber has the effect of increasing the early strengths and strengths, as well as improving the internal gearing of the fibers Building material already during spraying, so that can be taken away from er3tarrungsbeschleunigern in the rule. Ausfuhrungsbuisplel The invention will be explained in more detail in the following examples. Mixtures with different grading curves and fiber contents were produced, of which the following are examples Recipients of the starting mixture should be mentioned:

Mixture 1:

420kg / m ³ cement PZ 4/45 1373kg / m ³ concrete gravel 0 / 4rnm 281kg / m ³ concrete gravel 4/8 mm 2i0kg / m ³ water 80kg / m ³ machined steel fiber, 30mm long

Mixture 2:

420 kg / m ³ cement PZ 4/45 1654 kg / m ³ concrete sand 0/8 mm 210kfl / m ³ water 117kg / m ³ machined steel fiber, 26mm long

Mixture 3:

400 kg / m ³ cement PZ 7/35 1317 kg / m ³ concrete sand 0/8 329 kg / m ³ concrete sand 0/2 200 kg / m ³ water 152 kg / m ³ machined steel fiber, 28mm long

The metering and mixing was done in a conventional manner according to the known concrete technologies. The fibers were portioned in accordance with the mixer contents in the feed elevator or on the feed belt and fed with the other additives to the mixer. The advantage of the mixture is that it can be mixed in a conventional freefall or gsm mixer, transportable in the transport and loading wagon without hedgehog formation of the steel fibers like a normal concrete mixture, and also in the spraying machines, conveying pipes and hoses for no clogging leads. From measurements it was found that the hardened Stahlfaserspritzbetongemisch, depending on the Fas irgehaltgehalt in the mixture, both a significant increase in compressive strength and a significant increase in shear, Spaltzug- or bending tensile strength compared to the shotcrete mixture without steel fibers, which in the table below 1 is shown.

Table 1: Average strength values from the examples given

example Pressure / splitting tensile / bending tensile strength / N / mm ² 6.43 t) 6.37 ²¹ 1 2 3 45.2 3.47 49.06 5.09 ¹¹ bending tensile strength not determined ²¹ at the compressed bending balcony

Claims (1)

Stahlfaserspritzbetongemisch, for lining buildings and for the repair of engineering structures, based on conventional shotcrete mixtures with aggregates grit, gravel, sand, cement and water and with or without other additives for faster concrete hardening, characterized in that it has such a high proportion of fine mortar that the grading curve of aggregates with 0 to 2 mm grain diameter corresponds to the sieving line B of the control sieve line and the steel fiber spraying concrete mixture is around or just above the sieving curve B and that it further comprises sawn steel fibers of a mass structural steel with a proportion of 0.9 to 5, 0VoI .-% having a length of 1.5 to 3.5 times the largest grain diameter of the aggregates, an average thickness of 0.4 to 0.7 mm with a ratio of the width to the average thickness equal to 3 to 7. Field of application of the invention The invention relates to a Stahlfaserspritzbetongemisch for use in lining of structures such as shafts, tunnels, caverns and for repair of engineering structures of industrial, transport and hydraulic engineering or civil engineering, both dry and wet spraying. Furthermore, the Stahlfaserspritzbetongemisch is applicable for stabilizing embankments.