SK135394A3 - Hydraulic binder concrete or mortar - Google Patents

Abstract

A hydraulic binder for concrete or mortar contains commercially available cement, such as flying ash cement or slag cement, and possibly additives, as well as fine concrete and/or fine clinker. For preparing concrete or mortar to be formed by a wet-injection process, in particular concrete for tunnels, the binder contains at least 5 % by weight fine cement, and for preparing concrete or mortar to be formed by a dry injection process, in particular concrete for tunnels, it contains at least 5 % by weight fine clinker. The fine cement and the fine clinker have a specific surface area higher than 12,000 cm<2>/g, preferably between 15,000 and 20,000 cm<2>/g.

Description

HYDRAULIC BINDING FOR CONCRETE OR MORTAR

Technical field

The invention relates to a hydraulic binder for concrete or mortar, in particular for the application of dry or wet sprayed concrete or mortar, in particular tunnel concrete, containing conventional cement, such as fly ash, slag cement and optionally aggregates, and fine cement. and / or fine clinker.

BACKGROUND OF THE INVENTION

The binder according to the invention is particularly suitable for concrete or mortar applied by spraying, meeting environmental protection requirements using any (known) spraying process (dry and wet). In general, the binder of the present invention can be used wherever rapid solidification and rapid strength are required. Examples include, in addition to the use of concrete and spray-applied mortar, in the manufacture of prefabricated concrete, in the manufacture of cement-bonded fibreboard and in the production of concrete pipes.

Sprayed concrete is used in so-called. The new Austrian method of construction of tunnels by wet or dry spraying is one of the most important precautionary measures. Until sufficient compressive strength and layer thickness are achieved, the sprayed concrete layer can be used statically for the final tunnel construction. In dry spraying, the dried aggregate is mixed with cement or supplied as a ready-to-use mix for the construction and water is added at the nozzle. The desired rapid solidification can be achieved by adding a (liquid) solidification accelerator at the nozzle, but also by mixing the powder accelerator into the cement-aggregate mixture.

In wet spraying, the cement is premixed with wet aggregates and transported to a spray nozzle by a special pump. A solidification accelerator is mixed at the nozzle to quickly set the concrete.

Commonly used solidification accelerators consist essentially of alkali metal hydroxides, alkali metal aluminates, alkali metal carbonates and / or alkali metal silicates. These solidification accelerators are strongly alkaline and lead to serious health injuries (in particular the burns of persons working as a nozzle operator or working at the front). In addition, these solidification accelerators must not be allowed to enter ground water or sewage systems. Furthermore, the setting accelerators influence the further development of the concrete strength very negatively, as very porous concrete is formed by rapid solidification.

Another problem in the processing (application) of sprayed concrete is the so-called. back reflection. Spraying under pressure reflects concrete partially from the wall and ceilings back. This process, on the one hand, changes the composition of the sprayed concrete mixture, and on the other hand, this reflected portion must be completely removed from the tunnel, for example, into the rubble. Due to the higher alkali content relative to normal concrete due to the composition of the solidification accelerators, this waste should be classified as special waste. Material consumption during spraying as a result of reflection greatly increases. In order to achieve a defined (desired) layer thickness, a markedly prolonged spraying time, and thus a prolonged exposure of sprayers to the health-damaging effects, is necessary.

Sprayed concrete forms the outermost layer of the tunnel in contact with the rock and therefore often comes into contact with water. Depending on the amount and chemical properties of the water, parts of the sprayed concrete may dissolve. This is still strongly supported by the aforementioned porous concrete structure induced by solidification accelerators. In particular, the alkali added to the acceleration results in a high pH of the effluent water. Under no circumstances should this contaminated water enter the ground water (drinking water) and may lead to damages in drains (precipitation, further leaching).

Attempts have also been described to solve these problems. Thus, in Austrian patent application AT-B-382 859 for shotcrete production, shotcrete is devoid of calcium sulphate (i.e., gypsum ground without gypsum) with a specific surface area of 2,000-8,000 cm ² / g according to Blain.

The ground clinker hardens upon the addition and the solidification accelerator is therefore not required. However, a significant disadvantage is that only completely dry aggregates can be used. The solution according to Austrian patent AT-B 382 859 is therefore limited to dry shotcrete. Another disadvantage of instant curing binders is the distinctly poor strength development. In addition, the shotcrete cement according to the Austrian patent specification ΛΤ-Β-382 859 is very little resistant to sulfate attack. Secondary reaction transformations of initially formed calcium aluminum hydrate (C ₄ AH ₆ ) to etringite occur. In this phase transformation, there is a strong increase in volume and thus expansion effects.

DE-B-18 00 103, U.S. Pat. US-A-4,405,372 and other U.S. patents cited in the latter also use clinker ground without gypsum but here with small additives of other solidifying agents such as methylcellulose, aminoformate or aminoacetate in conjunction with lime.

According to JP-A-50-98 514, Portland cement is mixed with quick-setting cement and cement with high initial strength to achieve certain properties. A fast-setting cement is called a product that contains sodium gluconate and sodium carbonate. These products are harmful to the environment. In Portland JP-A-50-98 514, normal Portland cement 475 (Blain-specific surface area of 5,300 cm ² / g) is used, but not inicrocement.

According to JP-A-60-180 944, normal cement is mixed with up to 40% of very fine cement (Blain specific surface area> 6,000 cm ² / g, preferably 9,000 cm ² / g according to Blain) and mixed with <30% water to produce concrete parts with a large initial strength. In particular, the initial strengths of the cement mix and the fine cement mixes are used. According to JP-A-60-130 944, the high reactivity of microcement to extreme acceleration of solidification, which is much more important than the high strength in the field of application of sprayed concrete or mortar, remains unused.

JP-A-58-223 652 proposes a mixture of normal Portland cement with micronized silica and calcium expandable material. This latter material contains a large proportion of calcium oxide (free lime) and CaF ₂ , as well as the clinker phase (HCaO. 7A1 ₂ O ₃ .CaF ₂ ) typical of some fast setting cements. Microcement is not said here. Also, no particularly fine hydraulic phase is used. The mortar obtained according to Japanese Patent JP-A-58-223 652 is intended to be used for filling joints in concrete components.

DE-A-3 503 385 relates to a Portland cement binder mixture, fused aluminous cement, limestone and lime hydrate, and describes the addition of flowing agents to a concrete mixture and solidification accelerators. This is one of the mixtures that should be avoided for environmental reasons, because the solidification accelerator used (water glass or related substance) is harmful to the environment. In addition, the addition of fused aluminous cement to accelerate the solidification entails known disadvantages of such mixtures (reduced resistance, lower end strengths).

DE-A-2 055 120 mentions that the addition of a powdered accelerator to the cement in the spray nozzle is an unsatisfactory possibility of accelerating solidification. DE-A-2 055 120 discloses the addition of a residual proportion of ground clinker in a nozzle.

DE-AB 341 493 describes the mixing of normal Portland cement with a special calcium aluminate cement. The acceleration of solidification consists in the special properties of C ₁₂ ^A 7r but not in the fineness of grinding of one of the components.

DE-B-1 211 097 again discloses a mixture of Portland cement and fused aluminous cement as well as anhydrite. The particular properties consist in the addition of fused aluminous cement, but not in the high fineness of grinding, and thus the reactivity of part of the binder mixture.

According to DE-A-2 518 799, rapid solidification should be achieved by adding a suspension or a concrete mixture to the molten aluminous cement and / or calcium-halogen-aluminous cement immediately at the nozzle.

SUMMARY OF THE INVENTION It is an object of the invention to provide a binder in which the conventional setting accelerator can be dispensed with completely. In doing so, the retro-reflection when the binder is used for shotcrete (mortar) or mortar should be significantly reduced. At the same time, the high tackiness of the mixed concrete or mortar binder should allow the product to be applied without any technical changes by the two spraying methods used to give the young concrete more time than until now to solidify, thereby achieving better strength development with less pores and up to 5 hours of sufficient initial strength for further engagement in the tunnel construction.

SUMMARY OF THE INVENTION

This object is achieved according to the invention in that the fine cement and / or fine clinker has a specific surface according to Blain &gt;

000 cm ² / g, preferably from 15,000 to 20,000 cm ² / g.

The invention provides a binder, in particular, for gun concrete or mortar, which can be processed both by dry spraying and by wet spraying without damaging the environment. It has been found that this goal is achieved surprisingly and particularly well when the conventional cement, for example in the Austrian tunnel construction, widely used cement containing fly ash Flugaschenzement FAZ 20 or slag cement PZ 275 (II) 20 (tunnel cement) is mixed with 5 to 80 masses. % of specially made cement or clinker of very high fineness of grinding (> 8,000 cm ² / g Blain, preferably > 12,000 cm ² / g Blain). For dry spraying, very fine clinker is used, for wet spraying very fine cement (eg under the name Microcem A or Microcem B from Hcidelberger Zementwerke or Microdur from Dyckerhoff), or as can be obtained in any cement plant without problems by appropriate sorting ). According to the invention, a mixture of two cements of different grinding fineness (wet spraying) or a mixture of conventional cement with a clinker of very fine grinding fineness (> 8,000 cm ² / g by Blain) (dry spraying) is thus used.

In this specification and claims, the terms fine cement clinker ground with the addition of gypsum and fine cement clinker ground without the addition of gypsum.

Preferred binder compositions of the invention are disclosed in the dependent claims.

If the sprayed concrete or mortar is to be sprayed with the binder according to the invention by wet spraying, the method according to the invention is advantageous in which the concrete or mortar containing water and aggregate as well as the fine clinker binder is sprayed onto the surface to be applied. a layer of concrete or mortar and characterized in that the fine clinker is mixed only immediately before the concrete or mortar leaves the spraying equipment,

Ί especially at the nozzle. This prevents premature solidification of the concrete or mortar.

DETAILED DESCRIPTION OF THE INVENTION

Fine cements of the abovementioned denominations have the following parameters:

Microcem A:

Blain fineness: grain size:

about 11,000 cnr / g 95% <16 pm,

Microcem B:

Blain grinding fineness: grain size:

about 15,000 cm ² / g 100% <10 µm, <8 µm.

Furthermore, the O-sample of GK4 (pre-mixed dry ready mix concrete cement Wietersdorfer + Peggauer Zementwerke) with BE-2) is compared on an alkaline basis with a cement replacement of PZ 275% conventional accelerator (Addiment with samples without accelerator but (H) 20 microcement In addition, work was carried out with and without a flowing additive (Liquiment from Chemie Linz), as well as various microcements (Wietersdorfer Mikrozement, Heidelberger Mikrozement Microcem B), and Wietersdorfer Mikrozement with a reduced SO ₃ content. Aliva 242 by dry spraying The water coefficient (water to binder ratio) was about 0.55 for liquids without liquefaction and about 0.50 for liquids with liquefaction.

The spraying formula GK4 has the following parameters (the formulation corresponds to the following mortar mixture):

largest grain: bulk density: start of solidification: end of solidification:

4 mm around 1 600 kg / m around 30 seconds around 60 seconds

Addiment BE-2 is an alkaline solidification accelerator (manufactured by Hoidelberger Baustofftechnik) based on sodium aluminate.

Liquiment is a naphthalinsulfonate based resin.

- The results are shown in Tables 1 to 3. Table 1 gives the characteristic binder additives of the individual samples of the mixtures. Table 2 shows the compressive strengths measured after each time period with a 3 mm needle penetrometer for each of the mixtures of Table 1. Table 3 gives the compressive strengths after additional time periods, measured on drilled cores, again for each of the mixtures of Table 1. 1 (Tables 1 to 3 correspond to Table 1 of the PCT application).

Table 1

mixture accelerator 5% BE-2 Mikrocement fluidizing additive 0 5% BE-2 - 1 - 20% w & p - 2 - 30% w & p - 3 - 30% w & p 0.53% 4 - 30% w & p 0.53% (-so ₃ ) 5 - 50% w & p 0.53% 6 - 75% w & p 0.53% 7 - 100% w & p 0.53% 8 - 30% Micro B -

notes:

The liquid additive liquid w & p is a microcement of the following parameters: Blaine: about 18,000 cm ² / g, grain size: 100% <10 μιη, 95% <μπι

BE-2 is a sodium aluminate accelerator (Trade Mark Addiment BE-2) w & p (-SO ₃ ) is a microcement with the above parameters, with a SO ₃ content reduced by 3% compared to normal micronized cement w & p

Dust and reflection at 10 - 30% lowest, then up to 75% microcement only dust, higher for 100% micronised cement dust and reflection as for mixture 0.

Table 2

mixture 5 min. 15 min. Compressive strengths (N / mm ² ) 6 h. 30 min. 1 h 2 h. 3 h. 0 0.4 0.6 0.7 0.9 1.0 > 1.0 nz 1 < 0.1 <0.1 00:12 0.2 0.3 0.4 0.7 2 < 0.1 0.2 0.3 0.4 0.5 0.7> 1.2 3 < 0.1 0.2 0.3 0.45 0.55 0.75> 1.2 4 0.1 0.3 00:45 0.6 0.75 0.95> 1.2 5 0.1 0.2 0.3 0.45 0.6 > 1.2 nz 6 00:15 0.3 0.4 0.5 0.8 > 1.2 nz 7 00:15 00:25 0.4 0.6 0.9 > 1.2 nz 8 < 0.1 0.2 0.3 0.45 0.6 1.1> 1.2 remark nz - Not Identified ľabulka 3 mixture Compressive strengths (N / mm ² ) dL D3 D7 D28 0 12.5 16.5 22.0 31.0 1 11.0 31.5 38.0 53.5 2 21.0 27.0 32.8 49.0 3 23.0 29.0 35.0 53.0 4 33.0 39.0 44.5 59.0 5 38.2 43.0 62.0 61.0 6 41.0 44.0 53.0 58.0 7 37.0 40.0 46.0 54.0 8 29.0 38.5 40.5 49.0

With all variations, layer thicknesses> 30 cm can be sprayed in one working area without any problems. Mixtures 3 and 4 were also sprayed overhead. The minimum requirements for shotcrete according to the January 1989 directive (D1> 5 N / mm ² ) can be achieved without problems in all recipe variants. Initial strengths of up to 1 hour are lower than those of the prior art accelerated shotcrete. This is compensated by high tack. From 1 hour on shotcrete according to the invention there is a very rapid development of strength, which substantially exceeds the achieved strength values after 24 hours on shotcrete made according to the prior art.

Addiment ST2, used in the mortar formulation for spraying, is chemically a cellulose ether.

* The following mortar formulation was used for the experiments:

PC 275 (H) 20

170 kg <- replacement of part by fine cement

stone crumb 0 / 0,3 90 kg 0.3 / 0.8 310 kg 0.8 / 0.2 171 kg 2.0 / 4.0 250 kg Addiment ST 2 0 , 25 kg As binder advantages by of the invention

concrete technology and its processing can be mentioned:

- smaller outflows

- higher initial strengths,

- greater stability to environmental and weathering effects,

- higher tightness,

- better corrosion protection of steel reinforcement,

- less mechanical abrasion,

faster hardening, and

- higher reactivity to concrete additives.

A preferred feature of the invention is, when using cement to gunite cement or clinker, ground and classified to a specific surface according to Blaine> 8000 ^cm2 / g, preferably> 12,000 cm @ ² / g according to Blaine, and in particular 15000-20 000 cm ² / g by Blain, with the usual phase composition as well as HS-clinker as an admixture of alkaline alkaline compositions in proportions of 5% to conventional cements. This shotgun. the cement furthermore enables the production of environmentally friendly sprayed concrete without an alkali-containing accelerator and with minimum back-reflection in both dry and wet spraying.

As a further peculiarity of the cement and micronized cement mixtures according to the invention, it has been found that they react surprisingly strongly to a conventional concrete additive such as an accelerator. If a particularly rapid initial strength development is desired, any commercially available accelerator (e.g., alkali metal hydroxides, alkali metal aluminates, metal carbonates and / or water-soluble metal silicates) can be used to accelerate solidification. However, in contrast to the dosage required for normal cements (often 5-7%), the dosage can be reduced by at least 75% due to the high reactivity of the microcement used in the mixture. Thus, in laboratory experiments, by direct comparison of shotcrete of strength class J3, the requirements of the guideline for shotcrete with normal shotcrete could only be achieved with a 6% accelerator (sodium aluminate) dosing, while corresponding 30% binder could be achieved by only 0.8% of the same accelerator.

The invention may be summarized as follows. It is a hydraulic binder for concrete or mortar, containing conventional cement, such as fly ash, slag cement and possibly aggregates, as well as fine cement and / or fine clinker. The binder contains at least 5% by weight for the production of concrete or mortar intended for use by wet spraying, in particular tunnel concrete. % of fine cement, and for the manufacture of concrete or mortar intended for dry spraying, in particular tunnel concrete, of at least 5 wt. % fine clinker. Fine cement and fine clinker have a specific surface area of> 12,000 cm ² / g, preferably 15,000 to 20,000 cm ² / g. The binder can be combined with concrete additives. Due to the high reactivity of the microcement component, the dosage of this additive in concrete can be reduced by at least 75% compared to conventional cements. If the binder according to the invention is mixed with conventional concrete additives, dosing of up to 20% of the dosing amounts of known binders is sufficient to achieve the desired properties changes.

Claims (7)

PATENT CLAIMS A hydraulic binder for concrete or mortar, in particular dry or wet sprayed concrete, preferably tunnel concrete, containing conventional cement, such as fly ash containing cement, slag cement and optionally aggregates, and fine cement and / or fine clinker, characterized in that the fine cement and / or fine clinker has a specific surface area of> 12,000 cm ² / g according to Blain, preferably 15,000 to 20,000 cm ² / g. Binder according to claim 1, characterized in that it contains at least 5 wt. % fine cement and / or fine clinker. Binder according to claim 2, characterized in that it contains 5 to 80 wt. %, preferably 10 to 50 wt. %, in particular 20 to 30 wt. % fine cement and / or fine clinker. Binder according to any one of claims 1 to 3, for the production of concrete or mortar for wet-spraying, characterized in that it comprises fine cement. A binder according to any one of claims 1 to 3 for the production of concrete or mortar for dry spraying, characterized in that it comprises fine clinker. A binder according to any one of claims 1 to 5, characterized in that it is mixed with conventional concrete additives. Method of applying sprayed concrete or mortar by wet spraying, in which the concrete or mortar, water and optionally aggregates, as well as the fine clinker-containing binder according to one of claims 1 to 3, 5 or 6 are sprayed onto the surface to be coated concrete or mortar, characterized in that the fine clinker is added to the mixture only immediately before N ** • ó ó - 14 at the outlet of concrete or mortar from the spraying device, in particular immediately at the spray nozzle.