SK167898A3 - 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

Sprayed fastener and its use

Technical field

The present invention relates to sprayed bonding agent and its use for the production of sprayed concrete or mortar.

The term shotcrete refers to shotcrete, which is applied to the surfaces, for example by a spraying device with a high impact velocity, and seals it in this process. Sprayed concretes of this kind are used for example in the tunnel construction. According to the Austrian Concrete Association Directive, which is also in force in Germany, the production of shotcrete complies with a certain surface condition (for example as a base for foil insulation), for filling cavities (for example cracks, overprofiles) and for reinforcing rocks. It is also suitable for buildings where safety and support functions need to be kept in mind, for example above the outer layers of hollow building spaces, as well as for securing slopes and ditches, the outer layers of building spaces below existing buildings and small overlapping tunneling, slope support and excavation areas and sprayed concrete walls of water reservoirs.

BACKGROUND OF THE INVENTION

It is generally assumed that sprayed concrete will harden in a short time and be strong enough to suit the stability of rocks, 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.

Starting materials for the production of shotcrete are bonding materials, aggregates, additives, additives and water. Mineralogical additives are used as aggregates for sprayed concrete, for example kýz, stone crumb, sand, or crushed gravel with round or broken grains. Commonly used additives have a grain size according to D1N 1045 of 0 to 8 mm, with grain size lines 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. It is also possible to use an additive which retards solidification and, where used, increased efficacy.

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

For sprayed concrete, the production of dry and wet sprayed concrete varies 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 distinguished according to the shotcrete directive 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 bonding 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 components 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 regard to the occupational safety and hygiene according to the dust content.

SBM FT spray guns have a reaction time of 1 to 3 minutes. In accordance with this reaction time, wet, for example natural, wet additives (as a rule water content of 2 to 4% by weight) can be used for the production of sprayed concrete. 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, with additional 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 construction sites is 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 throughputs and larger continuous application areas can also be achieved. Personnel operating the spray equipment are 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 setting accelerator 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 performance, 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 It is an object of the present invention to provide a sprayable bonding agent which improves the processability of the sprayed mortar or sprayed concrete, in particular the start of hydration and thus the precise controllability of solidification.

It is a further object of the invention to provide a process for manufacturing and processing shotcrete that applies shotcrete with stable properties and reduces manufacturing and processing costs.

These objects are solved by the teachings of both claim 1 and claim 24. Preferred embodiments are indicated in the subclaims.

According to the invention, the bonding agent of the SBM T or SBM FT classification is a sprayed concrete composition having a very short setting and reaction time. According to the invention, these are hydrophobic sprayed concretes with a conventional bonding agent and a subsequent alkali-free accelerator. As the alkaline accelerator, for example, basic aluminum sulfate, for example aluminum hydroxide sulfate, can be used. However, the binding agent described in the invention, hydrophobic and with the alkali-free accelerator, can be mixed in a machine with natural, moist additives. These are ingredients that are added to the mixer without drying. Usually, the wet ingredients have a moisture content of between 2 and 4%. Additives which have a moisture level so low that they are not sufficient to hydrate the bonding agent are simply replenished with more water. The machine pre-mixed concrete can then be conveyed to the structures in the transport mixer as transported concrete. Even though it is a fastener that reacts very quickly, hydrophaging achieves that the transported concrete is processed in an hour and a half without the need for 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 substantial 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 component 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 a mixture 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), 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 used as accelerators for cement, in particular the basic aluminum sulphates of the formula Al (OH) _and (SO ₄ ) _b , wherein b is 0.05 to 4 and a is 3 to 2 x b.

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 milled aid, a hydrophobic agent is metered in from about 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 means can be passed through the fine 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. However, the accelerator may be added during grinding.

In order to produce sprayed concrete with this bonding agent or a mixture of these bonding 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.

This 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, pearl, ceolite, foam glass, micro-glass carbon beads and other known lightweight additives, may be added 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 with a short solidification time of the SBM T or SBM FT classification, it has surprisingly been found that using hydrophobic and basic aluminum sulfate in the bonding agent described 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 only extreme mortar load (accelerator, friction, retarder) will damage one of the hydrophobic agent and alkali-free accelerators that form a protective coating during spraying 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 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 hydrophobization 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. It is believed that this action is that between the accelerator, the cement pre-reaction, the accelerator, the sulfate-free hydrophobic agent, the alkali-free and necessary amount of water produced is dependent upon the dose of alkali-free to produce at 100 km / h, the shell is obviously broken and the rapid reaction of the shotcrete can begin.

which is not a combined cement core.

The solidification of pre-stored shotcrete with a 0.5 M-% alkali accelerator was not only slightly worse than that of immediately shotcrete, but the initial strength of the pre-stored material increased faster compared to the shotcrete and after about 2 hours it 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 slope requirements of the shotcrete. The thick line shows the sprayed concrete according to the invention with 15 minutes pre-loading, the strength pressure during the process, which is shown by the thinner lines, represents the areas of the sprayed concrete according to the Austrian Concrete Union Guideline. The dotted line represents the immediate processing of the shotcrete according to the invention.

The accelerated strength of both sprayed concrete according to the invention is initially the same as that of the known sprayed concrete, but if the sprayed concrete is stored only one hour longer according to the invention, the strength of the sprayed concrete, invented sprayed concrete, strength 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 shotcrete was produced by dry machine mixing, it turned out that the properties of shotcrete using the invented shotcrete 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, the 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 fastener, 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 dustiness, dry the pump to the nozzle. In this manner of use, the inventive bonding concrete was moistened in the hose from the produced shotcrete, with the composition according to diagram II corresponding to the shotcrete line according to the directive within the strength development standard of shotcrete which clearly increases after 3 hours and after approx. 5 hours is stronger than known sprayed concrete. This means that when the sprayed concrete is processed according to the invention in the usual manner in comparison with known concretes, it will show a better reaction to strength. Also in this process, a 0.5 M-alkali-free accelerator was used as the 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 has the advantage that the inventive binding agent does not adhere to either the preparation, the dosing or the mixing, to which other binding agents tend to have a negative tendency. This significantly reduces the cleaning and maintenance costs of the known mixers. 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 the known sprayed concrete, but increases more rapidly in a steeper course, 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 costs are reduced to a large extent by eliminating the existing apparatus and logistics costs.

The inventive bonding agent improves 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 on-site preparation and mixing equipment also eliminates the errors and costs associated with conventional concrete, such as adding additives.

Claims (42)

PATENT CLAIMS A bonding agent for use in sprayed concrete, wherein the bonding agent is a mineral, hydraulic bonding agent, in particular a low-sulfate bonding agent, in particular Portland cement, blast furnace cement, ferrous Portland cement, or aluminum (oxide-alumina) cement are conventional additives. additives and additives with the binder components in accordance with each other in such a way that a short reaction time is achieved in the hydraulic reaction, wherein the binder bead coating is at least initially a combination of the hydrophobic agent with the alkali-free accelerator. Coupling means according to claim 1, characterized in that the alkali-free accelerator is superimposed on a hydrophobic casing. Coupling agent according to claim 1 and / or 2, characterized in that the coupling agent has stearin and / or oleic acid (fatty acid) as the hydrophobic agent. Bonding agent according to one or more of the preceding claims, characterized in that the bonding agent has water and / or fatty acid salts as the hydrophobic agent. Bonding agent according to claim 4, characterized in that the bonding agent has sodium, calcium, ammonium, aluminum or zinc species as the hydrophobic agent. Bonding agent according to one or more of the preceding claims, characterized in that the bonding agent has as hydrophobic agent resin and / or sodium oleate and / or calcium soaps and / or mineral oil emulsions. Bonding agent according to one or more of the preceding claims, characterized in that the bonding agent has silanes and / or siloxanes and / or silicone oils as the hydrophobic agent. Bonding agent according to one or more of the preceding claims, characterized in that the bonding agent has a substantially hydrophobic, sulfate-reduced Portland cement. Coupling means according to claim 8, characterized in that the coupling means has an SO ₃ content of from 1 to 3%. Coupling means according to claim 8 and / or 9, characterized in that the coupling means has an SO ₃ content of from 2 to 2.5%. Bonding agent according to one or more of the preceding claims, characterized in that the bonding agent has, as additives, synthetic silicas, silicone dust, silicone emulsions and other additives which affect the workability of the concrete. Bonding means according to one or more of the preceding claims, characterized in that the bonding means has, as an additive, a plasticizer and / or a liquid agent and / or aerators and / or sealants and / or stabilizers. Coupling means according to one or the preceding claims, characterized in that the coupling material is finely ground. more that ingredients Coupling means according to one or more of the preceding claims, characterized in that the alkali-free accelerator is an amorphous basic aluminum sulfate. 15th 16th Coupling agent according to one or more of the preceding claims, characterized in that the amorphous basic line sulfate is a basic aluminum sulfate of the general formula Al (OH) - (SO 2) -, wherein b is 0.04 to 0.4 and a is 3 to 2 times Coupling means according to one or more of the preceding claims, characterized in that the alkali-free accelerators are present in an amount of from 0.2 to 6 M-%. 17th The method of more) wherein the components a 18th Method p of the component is 19th Method of>. during mli at least < 20th The method of grinding and pc is combined 21st Method pc characterized up to 6%. 22nd Process according to one or more of claims 1 to 16, characterized in that the mineral grinding time is ground and a hydrophobic agent is added. and claim 17, characterized in that the mineral elute is finely or finer. and claim 17 and / or 18, characterized in that an accelerator is added after addition of the hydrophobic agents. A method as claimed in claim 17 and / or 18, characterized in that after the hydrophobic agent has been adjusted, it is added and mixed. at least one accelerator. and one or more of claims 17 to 20, by adding an accelerator in an amount of from 0.2 and one or more of claims 17 to 21, by adding hydrophobic agents 1 0.02 to 5 M-%. A spray tone comprising a bonding agent according to one or more of claims 1 to 16, 23rd the concrete contains at least one additive in the usual amount as well as water in an amount of 0.5 to 6 M-%. 24. In the method for producing shotcrete according to claim 23, the bonding material is mixed according to the method of one or more of claims 1 to 16 with mineral additives in conventional amounts with additives as well as with additives and water to form the shotcrete. Method according to claim 24, 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 claim 25, characterized in that an aggregate having a grain size of 0 to 8 mm is used. Method according to claim 25 and / or 26, characterized in that an aggregate having a grain size line D8 or AB8 according to DIN 1045 is used. Method according to one or more of claims 24 to 27, characterized in that metallic and / or organic and / or mineral fibers are added as additives. Binder according to claim 28, characterized in that steel and / or carbon and / or glass mineral fibers are added. Method according to one or more of claims 24 to 29, characterized in that organic and / or mineral additives (lightweight substances) are added as additives. Method according to claim 30, characterized in that polystyrene foam spheres and / or pumice and / or perlite and / or zeolite and / or foam glass and / or micro-glass hollow spheres are added as additives. Method according to one or more of claims 24 to 31, characterized in that substances such as silicone dust and / or silicone emulsions and / or synthetic silicic acid and / or other known additives are added to influence the processability. Method according to one or more of Claims 24 to 32, characterized in that a plasticizer and / or liquid means and / or aerators and / or sealants and / or stabilizers are added as admixture means. Method according to one or more of claims 24 to 33, characterized in that the aggregate is used in a natural wet state. Method according to one or more of claims 24 to 34, characterized in that aggregates with a moisture content of from 0.5 to 6 M-% are used. Method according to one or more of claims 24 to 35, characterized in that aggregates with a moisture content of from 2 to 4 M-% are added. Method according to one or more of Claims 24 to 36, characterized in that the aggregate and / or the additives are mixed in a mixing device and, after addition of the binder mixer, further mixed or an admixing agent can be added. Method according to one or characterized in that the transport mixer. A plurality of sprayed claims 24 to 37, the concrete is placed in Method according to one characterized in that, for some time, or several claims 24 to 38, the sprayed concrete is sprayed prior to spraying in order to increase the necessary initial strength. Method according to claim 39, characterized in that the sprayed concrete is stored for 0.5 to 24 hours before spraying. Use of a hydrophobic, mineral bonding agent, in particular a bonding agent according to one or more of claims 1 to 16, in a dry mix intended for the machine production of shotcrete. Use of a binder according to one or more of claims 1 to 16 in sprayed concrete to be transported. Use of a binder according to one or more of claims 1 to 16 in wet sprayed concrete. Use of a binder according to one or more of claims 1 to 16 in dry shotcrete. Pressure strength of young shotcrete