SK282992B6 - Sprayable binder and its application - Google Patents

Abstract

Binder for use in a spraying cement concrete contains a mineral hydraulic binder with a short reaction time for the hydraulic reaction and its particles are (partly) coated with a combination of a hydrophobising agent and an alkali-free accelerator. Binder for use in a spraying cement concrete contains a mineral hydraulic binder, especially a low-sulphate binder, preferably Portland cement, Portland composite cement, blast furnace cement, iron Portland cement or alumina cement and optionally usual additives. The components are such that reaction time for the hydraulic reaction is short. The binder particles are (partly) coated with a combination of a hydrophobising agent and an alkali-free accelerator and also an additive with the water present from 0.5 to 6 wt. %. Independent claims are also included for (a) a method of producing the binder; (b) spraying concrete containing this binder; and (c) a method of producing the concrete.

Description

Technical field

The present invention relates to a process for the production of shotcrete and shotcrete, which is applied to surfaces by, for example, a high impact spraying device and thus seals them. Sprayed concretes are used, for example, in tunnel construction, as a substrate for foil insulation, for filling hollow spaces such as cracks, overprofiles and for reinforcing rocks. It is suitable for use in constructions where safety and support functions are to be considered, as well as for securing slopes and construction pits, for outer layers of building spaces below existing buildings and for small overlapping of tunnel lining, support for slopes and excavation areas as well as walls water tanks.

BACKGROUND OF THE INVENTION

It is generally assumed that sprayed concrete will harden in a short time and be strong enough to suit rock stability, for example in tunnel construction. However, it is necessary to avoid rapid hardening, because instead of the concrete used in some places no longer cracking, it can peel off or start to run off on some sprayed surfaces.

The raw materials for the production of shotcrete are binder, aggregates, additives, additives and water. Mineralogical additives are used as aggregates in the sprayed concrete, for example kýz, stone crush, sand or crushed gravel with round or broken grains. Commonly used additives have a grain size according to DIN 1045 of 0 to 8 mm, with grain sizes B8 or AB8 being preferred (see Abb. 1). It is also possible to add, for example, mineral, glass or even metal and artificial fibers. Other known additional foams can also be used.

Synthetic silicic acid products such as silica smoke or silica dust are used as additives. In particular, silica dust improves the binding properties of sprayed concrete.

Additives are also added to the concrete to accelerate its setting. An additive which retards solidification may also be used and, where used, increased efficacy will be obtained.

Other possible additives are plasticizers, liquid formulations, plasticizer-forming pores and aerators.

For sprayed concrete, the production of dry and wet sprayed concrete differs considerably. The use of different types of cements and / or concretes is critical to the production process.

Conventional dry shotcrete is made of normal cement, which consists of bonding material and natural damp fibers (3-5% moisture), mixed in the transport mixer while driving and transported to the construction site. The material is internally processed in about 1.5 hours, and after mixing with a conventional spray machine, a setting accelerator is added. When using normal cement in a conventional dry spraying process, additional chemicals must be added to adjust the properties of the concrete. For example, it is necessary to take into account longer processing, especially during transport mixing with the addition of a setting retarder. On the construction site it is necessary to increase its efficiency by activators or accelerators.

A disadvantage of conventional dry shotcrete is that its properties are not always optimal to achieve its strength as soon as possible.

Special sprayed fasteners have been developed to make the sprayed concrete meet construction site requirements.

These special spraying agents for use in shotcrete are differentiated according to the shotcrete guidelines of the Austrian Concrete Association in SBM T and SBM FT. These sprayed fasteners have a very short reaction time and therefore it is not necessary to add accelerators. By not adding acceleration allowances, there are no errors on construction sites that would result in poor dosing of the accelerator.

SBM T are sprayed fasteners having a reaction time of less than one minute. Since these binding agents have a very short reaction time, they cannot be used with wet additives. SBM T coupling means are therefore used in so-called " dry mixers. A dry mixer means that dry concrete is premixed in the concrete mixer. The ingredients in this dry mixer must be dried. The maximum permissible humidity is 0.2% by weight. In this way, the machine-made dry mixes can be stored during production or delivered to the site. Machine dry mixes, which are used on construction sites in sprayed concretes, are assessed in particular with respect to dust content in terms of occupational safety and hygiene.

The SBM FT sprayed fasteners have a reaction time of from 1 to 3 minutes. In accordance with this reaction time, wet, for example natural, wet additives (water content 2-4% by weight) can be used to produce shotcrete. If a wet additive is used, it takes time to process the sprayed fastener and the technique of the process must be combined. Bonding agents which are mixed, for example, with a natural wet additive, other additives and additives directly on site and then processed immediately in a spraying machine, can no longer be stored.

In order to keep this SBM FT with the natural wet additive in the same condition for only a certain period of time, special machines have been invented that divide, dispense and mix sprayed bonding materials as well as natural wet additive. The problem of these machines on the construction site is mainly their large size, maintenance and operation, as well as the desired ratio of cement and additives in their use. Serious disadvantages occur especially in tunnel constructions where the construction space is limited.

The wet sprayed process uses a mixed material (freshly pumped concrete), i.e. running concrete with the necessary water hydration. This wet sprayed concrete is applied by means of a remote-controlled spray arm or spray gun. Since the required amount of fresh concrete is usually heavy, it is not possible to carry out this work manually. In the above spray arms, larger pipe diameters and machines with higher throughputs can be used, and therefore higher application rates and larger continuous application areas can be achieved. Personnel operating the spray equipment move in a dust-free area that is free of kickback. This provides the operator with better occupational hygiene and safety.

In the wet spraying process, solidification accelerators are usually added to wet sprayed concrete. The solidification accelerator is powder or liquid and is metered 3 to 5 meters from the nozzle directly into the transfer hose to achieve sufficient mixing of the solidification accelerator with the pumped concrete. The disadvantage of this procedure is that the instrumentation is too demanding. In addition, the ratio of sprayed concrete to the acceleration setting must also be adapted. In the production of a sprayed concrete top surface, which should be uniform and of equal strength, the nozzle guide, which is very far from the application surface and the large application rate, makes considerable difficulties. The advantage is that machines located in hazardous locations can be operated by personnel from a safe distance.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION The present invention provides a process for the production of shotcrete, wherein at least a portion of the surface of the mineral hydraulic binder is first applied with a hydrophobizing agent followed by a non-alkaline accelerator which is mixed with moist mineral additives or additives and / or modifiers. a predetermined time to increase the initial strength and then sprayed so that the wrapper around the binder has cracks.

The sprayed concrete is stored for 0.5 to 24 hours before spraying.

Crushed gravel and / or sludge and / or crushed stone and / or sand with round or broken grains are used as additives in the sprayed concrete according to the invention, the aggregate used having a grain size of up to 8 mm and a grain size of D8 or AB8 according to DIN 1045 .

According to the invention, metal and / or organic and / or mineral fibers are used as additives, the fibers being steel and / or carbon fibers, and / or glass mineral fibers, organic and / or mineral lightweight materials such as polystyrene foam beads, and / or pumice, and / or perlite, and / or zeolite, and / or foam glass, and / or microsphere hollow spheres.

The additives for influencing the workability of the sprayed concrete according to the invention are silicone dust and / or silicone emulsions, and / or synthetic silicic acid or other known additives, further a plasticizer and / or liquid agents, and / or aerators, and / or sealants, and / or a stabilizer.

According to the invention, the aggregate is used in a natural wet state with a moisture content of from 0.5 to 6 wt. %, preferably with a moisture content of from 2 to 4 wt. %.

In the method according to the invention, the aggregate and / or additives are mixed in a mixer and, after the addition of the binding agent, mixing is continued, whereby the additive can be added and the sprayed concrete is placed in the transport mixer. The rate at which sprayed concrete is applied to the applied surface is> 100 km / h.

The present invention also provides shotcrete which comprises a mineral, hydraulic binder, in particular a low sulphate binder, in particular portland cement, blast furnace cement, ferrous portland cement, or aluminous cement, additives and modifiers in a composition that provides a short hydraulic reaction time. the binder grain coating comprises at least a partial combination of a hydrophobic agent with a non-alkaline accelerator and also a wet additive with water present in an amount of from 0.5 to 6 wt. %, wherein the non-alkaline accelerator is superimposed on the hydrophobic coating.

The sprayed concrete according to the invention contains as a hydrophobic agent stearin and / or a fatty acid, such as stearic acid, wax and / or fatty acid salts, sodium, calcium, ammonium, aluminum or zinc stearate, resin and / or sodium oleate, and / or calcium soaps. , and / or mineral oil emulsions, silanes and / or siloxanes, and / or silicone oils, or sulfate-reduced Portland cement.

The sprayed concrete binder according to the invention contains from 1 to 3 wt. % SO ₃ , preferably from 2 to 2.5 wt.

SO ₃ .

The binder according to the invention contains, as additives, synthetic silicas, silicone dust, silicone emulsions and other substances affecting the workability of the concrete, as an additive a plasticizer and / or a liquid agent, and / or aerators, and / or sealants, and / or stabilizers. The binder components are finely ground and the non-alkaline accelerator is amorphous basic aluminum sulphate of the general formula AI (OH) _a (SO ₄ ) _b , where b = 0.04 to 0.4 aa = 3 to 2 times and this non-alkaline accelerator is present in an amount of 0 2 to 6 wt. %.

According to the invention, the shotcrete is classified as SBM T or SBM FT, i.e. it is a concrete that has a very short setting and reaction time. These are hydrophobic sprayed concretes containing a binder and an alkali-free accelerator. As the alkaline accelerator, for example, basic aluminum sulfate, for example aluminum hydroxide sulfate, can be used. The components of the sprayed concrete can be mixed in the machine with natural moist additives. These are especially additives which are added to the mixer without drying and usually have a moisture content of 2 to 4 wt. %. Additives having a low moisture content that is not sufficient to hydrate the binder are simply supplemented with more water. The machine-mixed concrete can then be conveyed to the structures in the transport mixer as the transported concrete. Although it is sprayed concrete that reacts very quickly, hydrophobization ensures that the transported concrete is processed in an hour and a half without the need to add additional retarders. On construction sites, this bonding agent, or more precisely made with the bonding agent, can be sprayed without further addition of an accelerator or other additives.

Surprisingly, it turned out that the sprayed concrete produced in this way, which was first hydrophobic and then supplemented with an alkali-free accelerator, retained its reactivity for several hours, even days, even though it was mixed and transported for some time either on a slope or in strength, without making any significant changes. Only by hydrophobing alone does such a reaction not be achieved, only a synergistic effect occurs together with the use of alkali-free accelerators, with an increased amount of accelerator showing the beginning of the first visible hydration reactions.

According to the invention, the main constituent of the binder mixture used in the simplest cases for sprayed concrete is Portland cement (CEM 1), which reduces sulphates according to DIN 1164. Alternatively, the binder may contain either manual or latent hydraulic additives such as blast furnace slag or fly ash. Of these, an additional composition of Portland cement (CEM II), blast furnace cement (CEM III), as well as building permissible cements, in which they are either part of mixtures or even a major component, is also possible. For example, electrocement can also be used as an additional hydraulic coupling means. Optionally, it may contain other additives and additives. The setting time of the binder mixture may vary and be determined by the content of the parts used, but also by how finely the milled parts are used as binders.

Suitable hydrophobic agents include, but are not limited to, stearin and oleic acid (fatty acid), waxes, salts of fatty acids (sodium, calcium, ammonium, aluminum and zinc species), resin and sodium oleate. Calcium soaps and mineral oil emulsions are not excluded from this. Silanes, siloxanes and silicone oils may also find application as hydrophobic agents.

Suitable alkali-free accelerators are, for example, the basic aluminum sulphates which are used as cement accelerators, in particular the basic aluminum sulphates of the formula Al (OH) _and (SO ₄ ) _b , where b is 0.05-4a and 3 to 2 xb.

If such hydrophobic agents are used in the production of sprayed concrete, batches of various raw materials, such as Portland cement clinker, dense sand or electrocement, are added together and the necessary amount of sulfate carriers is added. Depending on the type of grinding aid, the hydrophobic agent is metered in from 0.02 to 5 M-%, i.e. i. a. (?). The further course of the process corresponds to the usual cement production. It is also possible to carry out hydrophobization after grinding the mineralogical parts, whereby the finished cement is treated with a so-called " by a known spray mixing process with a hydrophobic composition. Here, the cement is mixed in a special mixer with a hydrophobic agent which is finely ground to a powder binder.

After the binder becomes hydrophobic, it is a binder with an alkali-free accelerator. However, the further use lies in the composition. The bonding agent can be powdered with a gentle accelerator and then mixed very quickly. It is necessary to achieve the most uniform layering of the accelerator for hydrophobic deposition of the binder, which is adapted to the technique of the process. An amount of accelerator of 0.2 to 6 M-% is suitable for the dry joint compound. The accelerator may be added during grinding.

In order to produce sprayed concrete with this binding agent or the mixture of these binding agents, a natural wet additive with the necessary grain size, for example B8 according to DIN 1045 (according to Abb. 1), is added to the mixing device.

The natural wet additive may have a moisture content of, for example, from 1 to 6%, in particular from 2 to 4%. Metal and / or organic or mineral fibers, for example carbon, glass, or mineral fibers, may be added as additional additives for the production of fibrous shotcrete. Organic and / or mineral lightweight additives, in particular polystyrene foam beads, pumice, perlite, ceolite, foam glass, micro-glass carbon beads and other known lightweight additives may be added as additional additives for the production of lightweight shotcrete.

Only the mixture of coupling agents or coupling agent is dosed to the additive and these are mixed together. As additive, for example, silicone dust, silicone emulsion, synthetic silicic acid and other known additives which affect processability can be used. The finished mixture, i.e. sprayed concrete, is placed in a transport mixer and is thus transported to structures where it is processed by spraying.

Although, according to the invention, the bonding agent corresponds in its composition to a bonding agent having a short solidification time of SBM T or SBM FT classification, it has surprisingly been found that using hydrophobic and basic aluminum sulphate in the disclosed bonding agent can achieve a processing time of more than two hours. that it would be necessary to add retarders. It is believed that the mixing process does not substantially shorten the hydrophobization of the bonding agent, since substantial hydration reaction processes in the finished concrete cannot be demonstrated during the processing time.

It has been shown that a strong hydration reaction occurs first after spraying the concrete. It is believed that the extreme loading of the mortar (accelerator, friction, retarder) during spraying will damage one of the hydrophobic agent and the alkali-free accelerators that form a protective coating so that a hydration reaction can occur. It has been shown that the sprayed concrete protective coating according to the process of the invention, in comparison with the behavior of sprayed concrete with the same bonding agents, does not adversely affect the hydrophobicity and accelerators, but improves their initial catalytic strength.

Surprisingly, the initial strength of the mixed concrete, even after prolonged storage, was out of the question in a pure hydrophobic process. On the other hand, it is also not possible to achieve the necessary solid process with alkali-free accelerators, especially alkaline aluminum sulphates. It is surprising that a synergistic effect is achieved, particularly in this order, by combining hydrophobing with the processing of alkali-free accelerators.

The extended storage time of ready-mixed concrete is not only possible by hydrophobing, but also by the combination of hydrophobing with the alkali-free accelerator. This action is believed to result in a pre-reaction between the hydrophobic agent, the alkali-free accelerator, the cement, and the required amount of water, which is not dose-dependent, and combined to form a reactive sulfate-free cement core. It is only with force and friction when it hits the machining surface at a speed of more than 100 km / h that the casing is obviously broken and the rapid reaction of the sprayed concrete can begin.

The solidification of pre-stored sprayed concrete with a 0.5 M-% alkali accelerator was not only slightly worse than that of immediately sprayed concrete, but the initial strength of the pre-stored material increased faster compared to the immediately sprayed material and after about 2 hours also exceeded the initial strength. "Young shotcrete" according to the following diagram 1.

Diagram 1 shows the course of the compressive strength, so-called. of sprayed concrete. Young shotcrete refers to shotcrete up to 24 hours old. Processes J1, J2 and J3 represent the course of compressive strength according to the requirements of the shotcrete slope. The thick line shows the sprayed concrete according to the invention with 15 minutes pre-storage, the strength pressure during the process, which is shown by the thinner lines, represents the areas of the sprayed concrete according to the guideline of the Austrian Concrete Association. The dotted line represents the instant processing of the shotcrete according to the invention.

The accelerated strength of both sprayed concretes according to the invention is initially the same as the known sprayed concretes, but if the sprayed concretes are stored only one hour longer according to the invention, their strength increases considerably, invented sprayed concretes which are stored for shorter time after approx. 3 hours.

It has been shown that the use of the inventive hydrophobic spray binder in current processes, such as machine dry blending or suburban dry concrete production using natural wet additives, offers considerable advantages over known conventional spray binders.

In experiments in which sprayed concrete was produced by dry machine mixing, it turned out that the properties of sprayed concrete using the invented sprayed bonding agent improved slightly compared to known concrete. Sprayed concrete with the inventive bonding agent reacts better than conventional concrete, for example the material reflects less from the sprayed area.

In addition to unexpectedly large differences during the initial strength, differences in hydration and drying behavior of the shotcrete were also found. While sprayed concrete according to standard techniques typically exhibits light gray, cured and substantially dried sprayed concrete after a few hours, sprayed concrete according to the invention has both a dark gray color before and after it as still wet concrete. It is believed that the protective layer will allow the thickening to be achieved over a slightly longer period of time.

When using the inventive bonding agent, it is not necessary that dry (hardened) additives are used in dry machine mixing or machine premixing. Additives with a moisture content in which the sprayed bonding material is relatively water resistant can be used. For example, additives with a mine moisture content of 0.8 to 1%.

In this case, the advantage is that the relatively high drying of the additive substances is eliminated if machine mixing is used. This humidification achieves minimal dustiness, which must be assessed positively in terms of occupational hygiene and occupational safety. In addition to these advantages, the more favorable strength development must also be forgotten.

In further experiments, shotcrete was made by machine, as a dry mortar using the inventive bonding agent. To reduce dust, dry concrete was moistened in the hose from the pump to the nozzle. The sprayed concrete produced in this way, using the inventive bonding agent, according to diagram II corresponds to the sprayed concrete line according to the directive within the standard of development of the strength of the sprayed concrete, which clearly increases after 3 hours and is stronger after approx. This means that when sprayed concrete is processed according to the invention in a conventional manner in comparison with known concretes, it will have a better reaction to strength. Also in this process, an alkali-free accelerator of 0.5 M-% was used as coupling agent.

J1, J2 and J3 show the course of the compressive strength according to the requirements of the shotcrete guidelines. The thicker line shows the sprayed concrete according to the invention. In another experiment, the sprayed concrete of the invention was sprayed as a machine-made dry mortar using an admixture of relatively high humidity, for example 0.5%, and stored for 36 hours before processing.

It could be stated that the inventive binder was not relatively sensitive to moisture variations in the additive. This results in the advantage that the inventive bonding agent does not adhere either during preparation, dosing or mixing, to which other bonding agents tend to have a negative tendency. This significantly reduces the cleaning and maintenance costs of known mixing devices. A further advantage of using the inventive bonding agent in this process is that during the first hours the solidification process corresponds to the solidification of known sprayed concretes, but in the subsequent course it increases faster, so that after 24 hours approximately strengths are achieved which are above the required compressive strengths. in the shotcrete directive.

The invented spray-on coupling means allows the technical processes used hitherto to be greatly simplified and the costs are reduced to a large extent by eliminating the existing apparatus and logistics costs.

The inventive bonding agent improves the processing properties, has a lighter, dust-free, solidifying reaction, and a higher cured strength.

The inventive bonding agent can also be processed by known methods, in which case improved processability and setting properties and concrete strength can be achieved.

Thus, an essential advantage of the inventive bonding agent is that sprayed concrete using a highly reactive sprayed bonding agent, such as conventional, normal cement, containing dry shotcrete, can even be processed as conventional transported concrete, making it unnecessary to use more costly large equipment for site preparation and mixing, eliminating the defects and costs associated with conventional concrete, such as adding additives.

Claims (33)

Method for producing shotcrete, characterized in that at least a part of the surface of the mineral hydraulic binder is first applied with a hydrophobicizing agent, followed by a non-alkaline accelerator, which is mixed with wet mineral additives or additives and / or modifiers, and stand for a predetermined time to increase the initial strength and then spray so that the wrapper around the binder has cracks. Method according to claim 1, characterized in that the sprayed concrete is pre-stored for 0.5 to 24 hours before spraying. Method according to claim 1 or 2, characterized in that crushed gravel and / or calf, and / or crushed stone and / or sand with round or broken grains are used as additives. Method according to claims 1 to 3, characterized in that the aggregate used has a grain size of up to 8 mm. Method according to claim 3 or 4, characterized in that the aggregate used has a grain line D8 or AB8 according to DIN 1045. Method according to claims 1 to 5, characterized in that metallic and / or organic and / or mineral fibers are used as additives. Method according to claim 6, characterized in that the fibers are steel and / or carbon and / or glass mineral fibers. Method according to one or more of Claims 1 to 7, characterized in that the additives are organic and / or mineral lightweight materials. Method according to claim 8, characterized in that the additives are polystyrene foam beads, and / or pumice, and / or perlite, and / or zeolite, and / or foam glass, and / or micro-glass hollow beads. Method according to claims 1 to 9, characterized in that the additives for influencing the processability are silicone dust and / or silicone emulsions, and / or synthetic silicic acid or other known additives. Method according to claims 1 to 10, characterized in that the additives are a plasticizer and / or liquid means, and / or aerators, and / or sealants, and / or a stabilizer. Method according to one or more of Claims 1 to 11, characterized in that the aggregate is used in a natural wet state. Method according to claims 1 to 12, characterized in that aggregates with a moisture content of from 0.5 to 6 wt. %. Method according to claims 1 to 12, characterized in that aggregates with a moisture content of from 2 to 4% by weight are used. %. SK 282992 Β6 Method according to one of Claims 1 to 14, characterized in that the aggregates and / or additives are mixed in a mixer and, after the addition of the binder, stirring is continued, and an additional agent can be added. Method according to claims 1 to 15, characterized in that the sprayed concrete is placed in a transport mixer. Method according to one or more of the preceding claims 1 to 16, characterized in that the speed at which the sprayed concrete is applied to the applied surface is> 100 km / h. Sprayed concrete produced by the method according to one or more of claims 1 to 17, characterized in that it comprises a mineral, hydraulic binder, in particular a low-bond binder, in particular Portland cement, blast furnace cement, ferrous Portland cement or aluminous cement, additives and modifiers. a composition which provides a short reaction time for the hydraulic reaction, wherein the binder grain coating comprises at least a partial combination of a hydrophobic agent with a non-alkaline accelerator and also a wet additive with water present in an amount of 0.5 to 6 wt. %. The sprayed concrete of claim 18, wherein the non-alkaline accelerator is superimposed on a hydrophobic casing. A shotcrete according to claim 19, characterized in that it contains stearin and / or a fatty acid such as stearic acid as the hydrophobic composition. Sprayed concrete according to claims 19 and 20, characterized in that it contains wax and / or fatty acid salts as the hydrophobic agent. A shotcrete according to claim 21, wherein the hydrophobic agent is sodium, calcium, ammonium, aluminum or zinc stearate. Sprayed concrete according to claims 19 to 22, characterized in that the hydrophobic agent is a resin and / or sodium oleate, and / or calcium soaps, and / or mineral oil emulsions. A shotcrete according to claims 19 to 23, characterized in that the hydrophobic agent is silanes and / or siloxanes and / or silicone oils. A shotcrete according to claims 19 to 24, wherein the hydrophobic agent is sulfate-reduced Portland cement. 26. The shotcrete of claim 25, wherein the binder comprises from 1 to 3 wt. SO ₃ . A shotcrete according to claim 26, wherein the binder comprises from 2 to 2.5 wt. SO ₃ . A shotcrete according to claims 19 to 27, characterized in that the binder contains as synthetic substances synthetic silicas, silicone dust, silicone emulsions and other substances affecting the workability of the concrete. Sprayed concrete according to claims 19 to 28, characterized in that the binder comprises, as an additive, a plasticizer and / or a liquid agent, and / or aerators, and / or a sealing material, and / or stabilizers. A shotcrete according to claims 19 to 29, characterized in that the binder components are finely ground. A shotcrete according to claims 19 to 30, characterized in that the non-alkaline accelerator is amorphous basic aluminum sulfate. A shotcrete according to claims 19 to 31, characterized in that the amorphous basic aluminum sulfate has the general formula Al (OH) _a (SO ₄ ) _b , where b = 0.04 to 0.4 and a = 3 to 2 x b. A shotcrete according to claims 19 to 32, wherein the non-alkaline accelerator is present in an amount of from 0.2 to 6 wt. %.