DE102008036376A1 - Concrete mixture, useful for producing a concrete, which is useful e.g. in architectural engineering, civil engineering or system building construction, comprises a binding agent and an aggregate - Google Patents

Abstract

Concrete mixture for producing a concrete with increased fire resistance, comprises a binding agent and an aggregate, where the aggregate contains up to at least 50 wt.% of cement clinker with a particle size group of 0/32.

Description

The The present invention relates to concrete having increased fire resistance (Fire resistance) and its use in high and low Civil engineering.

The Use of fire-resistant concrete without clothing is for operational, technical and economic reasons of great interest. In addition to basic economic Advantages in the construction of the building, there are other advantages in operation and maintenance of the plant. So needed for example a single-shell tunnel lining made of fire-resistant Concrete no special entertainment for the fire protection system. In addition, visual checks can be done and inspections of the supporting tunnel construction readily be carried out directly.

The general protection goals in relation to fire-resistant concrete are z. B. in the ZTV-ING Part 5, Section 1 - Closed design - specified by the specification of a maximum critical temperature at the supporting reinforcement of T _max <300 ° C. This requirement aims to reliably prevent permanent stretching of the reinforcement. The protection of the load-bearing reinforcement against excessive heating can only be achieved if there is no or only slight superficial spalling of the concrete cover.

To The current state of the art are tunnels in a single-shell construction in many cases with fire protection clothing in the form of fire protection boards or -putz protected, which is like a thermal insulation act and thus the heating rate and the maximum temperatures reduce the concrete. So far, these systems must be retrofitted and sometimes very complex in a separate operation to be built in. For a traffic and reliable as well as permanent attachment are often special and expensive detail solutions required. Especially against the background of operational safety with regard to dynamic effects (eg pressure and suction forces from traffic) and to moisture high demands on the durability of the clothing system as a fire protection layer and placed on the mounting structure become.

• • Hohe Feuerwiderstandsdauer
• • Keine oder nur geringe Abplatzungen über der Stahlbewehrung
• • Keine toxischen Gase im Brandfall
• • Instandsetzungsmöglichkeit nach dem Brand

Concrete is in itself a refractory building material because it is not flammable. Normal concrete has a thermal conductivity of λ = 2.1 W / mK a poor thermal conductivity, but z. B. leads in tunnel fires to a rapid increase in temperature and thus to a steep temperature gradient in the outer layer of the concrete. For a good and effective fire protection the following parameters are important:

• • High fire resistance time
• • No or little spalling over the steel reinforcement
• • No toxic gases in case of fire
• • Repair option after the fire

however has been shown to turn off buildings and especially tunnels Concrete a fire does not last long. Because of the spatial and fluidic conditions (such. B. the so-called. Fireplace effect) this is especially in tunnels a large Problem.

So arise in a fire in an unclad tunnel the Major damage in the form of progressive, explosive Concrete spalling due to the extremely rapid heating at the beginning of the Brandes. Fire events and experiments have shown that chipping start already in the first minutes and generally after 20 until 30 minutes have passed. Further damage become by the i. d. R. long burning time at very high temperatures up to 1200 ° C caused.

in the Fire occurs due to the enormous temperature stresses the tunnel inner shell to some strong flaking. These in turn obstruct the escape and rescue routes, resulting in a high number of Personal injury may result. Continue to occur Damage to the supporting structure in the worst Case lead to their failure. Cause the damage a complex repair or possibly even a more expensive New building. To avoid this, has already been around for some time Time for firmer concrete for tunnel inner shells and heavily loaded structural components (eg columns, girders, Walls etc.) researched.

The Strength properties and Young's modulus of Normal concrete decreases with increasing temperature. The compressive strength goes to about 1000 ° C to zero. From about 600 ° C occurs already a significant reduction in strength, as well as a clear Decrease in the modulus of elasticity.

By aggressive, chloride-containing fire gases and flue gas condensation Tunnel components and in flue gas lines cause chloride damage. When burning halogenated plastics, especially PVC-containing substances, chlorides are released. It comes to Formation of hydrogen chloride gas. The chloride ions are after the Fire transported by diffusion into the concrete. The chloride ions cause the destruction of the cement paste, as well as corrosion of reinforcing steel. The corrosion of steel is a long-term one Process and occurs delayed. The process leads not only damage to components in the immediate vicinity the source of the fire, but also damage to components, which are further away from the source of the fire.

Farther damage occurs due to the extremely high temperatures, which to tensions and deformations - with the result of Cracks - lead to the building. This will also be done Parts of the structure affected far from the actual Fire area are located away.

As already mentioned above chipping and the Falling off entire concrete layers is a very big problem These damages already endanger the rescue and extinguishing work and are therefore particularly problematic. For these damages are chemical and physical Processes in the concrete responsible. A major cause existing in the concrete or penetrating during the fire Water, which then evaporates in the concrete structure exerts enormous pressure.

additionally can be due to the high temperatures on the cement stone and at the aggregates also chemical reactions and mineralogical transformations and decompositions take place, which are responsible for the structure and thus also for the, in particular static, Resilience of the concrete and for the stability of the concrete Building are disadvantageous. Among the best known phenomena include the dehydration of cementum, the so-called Quartz crack and decarbonation of limestone.

at about 400 ° C, the dehydration of calcium hydroxide begins to calcium oxide and water. This is a loss of strength of the Cement stone connected, beyond enlarged the split off water the vaporizable amount of water in the concrete and thus reinforces the flaking tendency.

At the Quartz jump becomes the crystal lattice of the quartz at a temperature of 573 ° C transformed. This is associated with an increase in volume, which leads to residual stresses and structural loosening.

at Temperatures of approx. 800 ° C it comes to decarbonation of limestone. It is from the original calcium carbonate Cleaved carbon dioxide, which escape through the pore structure got to. The remaining calcium oxide is less solid than the calcium carbonate. The outer layers of concrete with limestone grains or dissolve aggregates with lime components Therefore, after a fire load when re-cold the less heavily fired core concrete.

For the previously described thermo-mechanical and chemical / mineralogical Processes in concrete comes from the selection of aggregates a central importance too. The strength properties of the concrete During and after a fire are also strong of the Rock type dependent. Causes are the chemical / mineralogical changes and decomposition processes as a result of thermal action.

• – Auftretende Schäden dürfen die Standsicherheit des Tunnels nicht gefährden
• – die Gebrauchstauglichkeit des Tunnels darf durch bleibende Verformungen der Konstruktion nicht eingeschränkt werden
• – die Dichtigkeit muss weitestgehend erhalten bleiben.

In order to ensure sufficient structural fire protection, ZTV-ING places the following requirements on the construction in the event of fire:

• - Occurring damage must not jeopardize the stability of the tunnel
• - The serviceability of the tunnel must not be restricted by permanent deformation of the construction
• - The tightness must be maintained as far as possible.

In Germany, concretes are currently being used for tunnel inner shells, whose production is carried out using conventional aggregates (in accordance with DIN EN 12 620 ), z. As gravel or grit occurs. In addition, additives are used for these concretes, whereby a dense concrete structure (densely supported grain skeleton) is achieved. Fly ash or silica fume, for example, is used as an additive. The addition of additives certain properties of the concrete, z. As consistency, processability or strength, are affected.

• – Verkürzung der Bauzeit und daraus resultierende Kostenersparnis
• – Reduzierung des Ausbauquerschnitts
• – Reduzierung des Betonverbrauchs
• – Bessere Ausnutzung der statischen Höhe
• – Verzicht auf aufwendige Brandschutzbekleidungen der Tunnelinnenschalen.

New more fire-resistant concretes should allow a reduced concrete cover while avoiding exceeding of the critical limit of 300 ° C for the reinforcing steel due to spalling. Related benefits include:

• - Shortening the construction time and resulting cost savings
• - Reduction of the expansion cross-section
• - Reduction of concrete consumption
• - Better utilization of the static height
• - Waiver of expensive fire protection clothing of the tunnel inner shells.

It There was therefore a need for safe and simple as well as cost effective solutions.

Surprised has now been found that the fire resistance of concrete can be significantly increased if instead of the usual Aggregates, such as sand, gravel, grit, etc., cement clinker is used in the desired grain size.

The The invention therefore relates to a concrete containing a hydraulic Binder and cement clinker of grain group 0/32 as aggregate, preferably with a largest grain in the range of about 2 to 32 mm, preferably with a largest grain up to 16 mm. The inventively used Cement clinker are characterized by the fact that this already in the manufacturing process temperatures of usually over 1400 ° C were exposed and thus not to a decarbonation which can lead to aggregates, what with the conventional aggregates off Kites and splits can not be excluded.

One Such concrete also shows up over high temperatures long periods extremely stable, d. H. the structure is neither deformed, nor by chemical / mineralogical (Transformation) processes significantly affected. spalling or the falling of concrete parts are largely avoided.

To on the aggregate of cement clinker corresponds to the Composition of the concrete according to the invention of those from usual concretes. The advantages of the invention leave In addition to the tunnel construction also generally in civil engineering.

According to the invention are suitable all known hydraulic binders such as Portland cement, Blast furnace cement, portland composite cement, alumina cement, etc. as a binder. The binder is in a conventional manner according to the selected application selected.

Usually, the grinding fineness of the cements are in the range of 2000 to 6000 cm ² / g (Blaine).

For civil engineering, in particular for tunneling, for example, a CEM I, CEM II or CEM III and a cement with high sulfate resistance (HS) is particularly preferred. In building construction, depending on the application, cements of the main types CEM I, CEM II and CEM III comply with DIN EN 197-1 prefers. For special requirements and cements with special properties such. B. with low heat of hydration (NW), high sulfate resistance (HS) and low alkali content (NA) used.

the Binders or concrete can in the usual way Additives and additives are attached.

Typical admixtures are fluxing agent (FM), concrete plasticizer (BV), retarder (VZ), hardening and hardening accelerator (BE, SBE), stabilizer (ST), air entraining agent (LP), sealant (DM), shrinkage reducer (SRA) and others DIN EN 934 or with general construction supervisory approval. They are used in the usual dosages of 0.1 to 10% by mass, based on the cement weight / binder. Dry, in particular powdery additives are usually added to the binder and / or the concrete mixture; Liquid additives are usually added during mixing (mixing) of the concrete.

typical Additives are ground minerals, (hard coal) fly ash, ground Blastfurnace slag, silica fume, color pigments, plastic and Steel fibers, plastic dispersions and others. These too will, if needed in concrete (available), in the usual Quantities of concrete mix added.

According to the invention as aggregate a cement clinker with appropriate Grain group of 0/32 used. This can be a Portland cement clinker, Alumina cement clinker or mixtures thereof. The cement clinker preferably replaces the coarse aggregate, which formed by the prior art of gravel and / or grit. For the finer proportions, ie z. B. the grain groups 0/2 or 0/4, conventional sand can be used. It But it is also possible that the cement clinker the entire Aggregates, ie fine and coarse aggregates forms.

Of the Cement clinker is usually in Lepol or rotary kiln burned from the raw meal at about 1450 ° C. He exists in Essentially of tricalcium silicate, dicalcium silicate, tricalcium aluminate and calcium aluminate ferrite. The clinker left after leaving the usually connected to the furnace cooling system a grain size of about 0 to 50 mm (Lepolofen up to 20 mm, rotary kiln up to 50 mm).

Depending on the application, the aggregates should preferably have a particle size distribution (grading curve) in the range 2, 3, 4 according to DIN 1045-2 exhibit. The largest grain should be in the range of 8 to 32 mm, preferably about 16 mm. The fine fraction, ie particle sizes which pass through the sieve with a mesh size of 0.125 mm, is generally below 10% by volume, preferably below 5% by volume, in particular below 2% by volume. The clinker is therefore broken and / or screened to obtain the desired grain groups. These methods and the grain groups are known to those skilled in the art, for. 0/1, 0/2, 0/4, 2/4, 2/5, 2/8, 4/8, 5/8, 8/11, 8/16, 11/16, 16/22 or 16/32 mm.

Of the as a hydraulic binder used cement is in contrast to the invention as an aggregate cement clinker obtained by grinding the clinker, usually the grain size of fine and coarse cements between 1 to 40 microns (fine) and 1 to 200 microns (roughly) lies. Such cement is for use as Aggregate unsuitable while cement clinker in the grain groups used according to the invention not acting as a hydraulic binder. It is true that When breaking the clinker and fines are obtained, the Amount should be low. Preferably, the fines are sieved.

It is preferred if the clinker as aggregate ago wetting the concrete with water.

The Processing of the concrete according to the invention is possible in any known way. He can work in both the precast plant as well as on site as in-situ concrete, ready-mix concrete, shotcrete etc. are used, with binders, additives and additives adapted to the intended application.

to Further improvement of the fire resistance is preferred in which concrete creates a system of air pores. This may be the concrete an air entraining agent (LP) can be added. One more way consists in the addition of hollow microspheres (MIC). A third variant is the incorporation of plastic fibers, eg. As polypropylene (PP), which melt in a fire (typically at about 160 ° C) and only in case of fire, a system of finest Kapillarporen and / or Create cracks. These measures can in case of fire in the concrete formed water vapor escape more easily and thus become damage caused by water vapor (pressure) (eg chipping or blasting) avoided.

A preferred shotcrete according to the invention consists z. B. from 270 to 450 kg / m ³ cement (wet spraying) or 300 to 500 kg / m ³ cement (dry spraying), with a w / c 0.38 to 0.50 (NS) or 0.45 to 0.60 (TS), 1800 to 2100 kg / m ³ cement clinker with a grading curve in the range 2-4, preferably 3-4 and a maximum grain size of 8 to 16 mm, and optionally with liquefying additives (eg FM, BV). A conventional hardening accelerator is added to the concrete directly at the spray nozzle.

A preferred ready-mixed concrete according to the invention or in-situ concrete consists z. B. from 240 to 450 kg / m ^{3 of} cement, a w / c value of 0.40 to 0.65, 1700 to 2100 kg / m ³ cement clinker with a grading curve in the range 3-4 and a maximum grain size of 8, 16 , 22 or 32 mm, and possibly liquefying, retarding, stabilizing, air-entraining and other additives

Out The concrete according to the invention can also Precast concrete elements such as segments, beams, columns, Binder, wall elements, ceiling elements, garages and other manufactured become.

The concrete according to the invention, ie buildings or components produced therefrom, have an increased fire resistance. In this regard, in the ZTV-ING and in the EBA guideline (Eisenbahn Bundesamt), corresponding protection goals are formulated together with the specification of combustion chamber or combustion gas temperature-time curves, see 8th ,

at A tunnel fire must be within a very short initial phase from only 5 minutes of temperatures up to 1200 ° C become. This means increased for tunneling Requirements for structural fire protection.

According to the ZTV-ING Part 5, Section 1 - Closed construction - is used for the supporting reinforcement a critical temperature at Tmax. <300 ° C.

fire tests have shown that flaking starts in the first few minutes and i. d. R. are completed after 20 to 30 minutes. In the trials was also proved by the long fire duration at very high temperatures up to 1200 ° C further damage occur on the building / component.

Of the concrete according to the invention has an increased Fire resistance, d. H. compared to concrete, the one contains conventional aggregate, the temperature of the concrete rises at the reinforcement with the same concrete cover slower or a lower concrete cover is for a Limitation of the temperature at the reinforcement to <300 ° C necessary.

About that In addition, there is a directive in Austria "Increased Fire protection with concrete for underground traffic structures ". Again, the protection goals are defined and the impacts (Austrian Temperature-time curves for railway and road tunnels) shown. Furthermore, the design and dimensioning as well treated the concrete composition, production and processing.

The The following examples are intended to further illustrate the invention, without, however, to the specific embodiments described to restrict. Unless otherwise stated, refer Information of parts and% on the weight or mass

Examples

For all mixtures, a Portland cement DIN EN 197-1 - OEM 142.5 N-HS was used by HeidelbergCement AG from the Schelklingen plant. Properties:
Density [g / cm ³ ] 3.27
spec. Surface [cm ² / g] 3367
Compressive strength after 2 days [N / mm ² ] 22.2
Compressive strength after 28 days [N / mm ² ] 50.3

aggregates

Various aggregates were used. In all mixtures, washed Rhine sand from Upper Rhine material was used by the company Krieger from the Rheinhausen plant with the following properties:
Grain density [kg / dm ³ ] 2.66
Resistance to fragmentation (Los Angeles method) Cat. LA ₃₀
Content of fines f 1.5

1. Cement clinker from the company HeidelbergCement AG from the factory Leimen with the following characteristics:

• Grain density [kg / dm ³ ] 3.1
• Grain number 3.68

For some attempts were unscreened cement clinker with oversize used. For others, the cement clinker became the grain groups 2/8 and 8/16 sieved. He is concreting to water saturation been wetted.

2. gravel from the company Krieger from the Rheinhausen plant with the following characteristics:

• Grain density [kg / dm ³ ] 2,62
• Resistance to fragmentation (Los Angeles method) Cat. LA ₃₀
• Content of fines cat. F _1,5
• Plating index Cat. Fl ₁₅
• Grain number 4.14

3. Granite from the company Röhrig from the Heppenheim plant with the following characteristics:

• Grain density [kg / dm ³ ] 2,72
• Resistance to fragmentation (Schlagzertrümmerung) cat. SZ ₁₈
• Content of fines cat. F _1,5
• Grain shape Cat. Sl ₁₅
• Frost-thaw resistance Cat. F ₁
• Grain number 4,11

4. Gravel high-grade chippings from Krieger from the Rheinmünster-Stollhofen plant.

• Kornrohdichte [kg/dm³] 2,7
• Widerstand gegen Zertrümmerung (Schlagzertrümmerung) Kat. SZ₁₈
• Widerstand gegen Polieren Kat. PSV₅₄
• Gehalt an Feinanteilen Kat. f₁
• Kornform Kat. Sl₂₀
• Widerstand gegen Hitze VSZ 2,1 (Angabe des Herstellers, keine Normprüfung)
• Körnungsziffer 4,09

The gravel chippings consists of the main components quartz / quartzite and limestone, small amounts of lime sandstone, gneiss / amphibolite, granite / aplite, fine and medium sandstone, volcanic / porphyry and silica shale. It has the following properties:

• Grain density [kg / dm ³ ] 2.7
• Resistance to fragmentation (Schlagzertrümmerung) cat. SZ ₁₈
• Resistance to polishing Cat. PSV ₅₄
• Content of fines Cat. F ₁
• Grain shape Cat. Sl ₂₀
• Resistance to heat VSZ 2.1 (specified by the manufacturer, no standard test)
• Grain number 4.09

So far the aggregates became available in different Grain groups used.

When The additive was fly ash from Safa, Baden-Baden the product name Safament HKV used.

The mixtures were z. T. polypropylene fibers type Duomix Fire (M6) Bekaert added. The polypropylene fibers have a length of 6.0 mm with a nominal diameter of 18.0 μm. Their elongation at break is 15.0%, their density is 0.91 kg / dm ³ .

additive

1. Plasticizer (FM)

When Plasticizer was used for the preliminary tests in the Blends with gravel and granite the flux ViscoCrete-1051 used by Sika. The solvent ViscoCrete-1051 acts based on polycarboxylate ether (PCE). The recommended dosage range is between 0.2 and 2.5% of the cement weight. It is recommended that Flux, with the addition of water to add. For the blends with gravel chippings and cement clinker became the flow agent Addiment FM 6 used by Sika. The highly effective superplasticizer, based on melamine / naphthalenesulfonate, is without delaying Effect for high quality concrete in precast plants and usable on construction sites. The recommended dosing range is between 0.2 and 2.3% of cement weight. The eluant can either be added with the addition water or separately.

2. Air entrainment agent

For an attempt was made using the air entraining agent LPS A-94 from Sika. The air entraining agent acts on the basis of synthetic surfactants. The recommended dosage range is between 0.2 and 0.8% of the cement weight. To achieve the required amount of air pores in fresh concrete a precise dosage of the air entraining agent is desirable. However, the air entraining agent has different with each mixture Effects on fresh and hardened concrete properties, so that the exact amount to be added has been adjusted.

3. Micro hollow spheres (MIC)

For a main experiment, a mixture with MIC was made. The MICs consist of a white paste and act on a polyvinylidene chloride-acrylonitrile polymer base. The MICs have a density of 0.2 kg / dm ³ and a size of 6.0 microns. The MICs have the same effect in the concrete matrix as the air entraining agent. With MIC can be made very accurately an air-entrained concrete. The MIC does not reduce the concrete compressive strength. The MICs are added to the concrete mix during concrete mixing during the mixing process.

On the concretes both fresh concrete properties and hardened concrete properties were determined. The slump was according to DIN EN 12350-5 and the degree of compaction according to DIN EN 12350-4 certainly. The fresh concrete density was reduced DIN EN 12350-6 and the air content after DIN EN 12350-7 he averages.

The mixtures summarize Tables 1 and 2: TABLE 1 Examples with cement clinker Constituents [kg / m3] Example 1: Cement clinker Example 2: Cement clinker Example 3: Cement clinker water 180 238 238 cement 338 419 419 fly ash 112 138 138 superplasticizer 8th 7 7 PP fibers 2 2 2 Sand 0/2 332 491 546 grain group (2/16) 1599 (2/8) 769 (8/16) 501 (2/8) 571 (8/16) 360 Air-entraining agents 1.4 MHK 3.5 Table 2 Comparative Examples Constituents [kg / m3] Comparative Example Gravel Comparative Example 2 granite Comparative Example 3 Gravel chippings water 170 170 170 cement 320 320 320 fly ash 106 106 106 superplasticizer 6 6 5 PP fibers 2 2 2 Sand 0/2 551 546 375 grain group (2/8) 644 (8/16) 512 (2/5) 571 (5/11) 360 (11/16) 289 (2/5) 884 (5/11) 227 (11/16) 264

The tested fresh concrete properties are summarized in Table 3 and the hardened concrete properties in Table 4. Table 3: Fresh concrete properties of Examples B1-B4 and Comparative Examples VB1-VB3 property B1 B2 B3 VB1 VB2 VB3 Slump dimension a [mm] 430 450 460 480 440 440 Density c 1.04 - - 1.05 1.06 1.14 Bulk density D [kg / m3] 2240 2140 2270 2310 2295 2350 Air pore content [Vol%] 6.0 11.9 6.6 3.4 6.5 2.0

The Measurements prove that the use of cement clinker as aggregate in the context of the usual concrete mixtures possible is and does not affect the fresh concrete properties.

In 1 the surface of a fresh concrete mixture according to the invention is shown based on cement clinker. Table 4: hardened concrete properties of Examples B1-B4 and Comparative Examples VB1-VB3 property B1 B2 B3 VB1 VB2 VB3 Compressive strength f _{c, cube} [N / mm2] 28 d 38.0 45.7 59.4 47.2 50.6 49.6 Micro air pore content A ₃₀₀ [% by volume] 1.87 3.03 1.60 0.84 1.73 0.88 Distance factor [mm] 0.26 0.16 0.24 0.33 0.27 0.32

The Measurements confirm that also the hardened concrete properties still to a reasonable extent. The use of air entraining agents or hollow microspheres allows the somewhat lower compressive strengths when using cement clinker as aggregate compensate.

Fire tests were carried out on specimens of a concrete according to the invention (with cement clinker) and a prior art concrete (normal concrete, gravel), exposing the specimens to direct flame exposure with a standard torch flame (set at maximum temperature) for 45 min. The distance of the nozzle to the sample surface was 14 cm, so that the flame tip reached the concrete surface. The burner was attached to a fixture so that both samples were lit at the same distance and with the same flame setting. The mentioned experimental setup for the flame is in the 2 and 3 shown.

The results of the fire are in the 4 - 6 shown. It can be seen clearly that the conventional concrete is severely damaged after 45 minutes of flame treatment ( 4 . 5 ). The decay occurred already after a few minutes.

In the case of the concrete according to the invention, on the other hand, only a few cracks, which do not significantly affect the integrity ( 6 . 7 ).

In In another experiment, specimens were made from a reference concrete with conventional gravel as aggregate and a concrete of the invention referred to as cement clinker concrete or clinker concrete produced. The two specimens with the dimensions 500 mm × 500 mm × 105 mm was about 2 months ago Carried out the small fire test.

• – Bewehrung: 2 × Q 188 (Stabdurchmesser: 6 mm, Abstand längs/quer: 100 mm)
• – Betondeckung: 30 mm
• – Anordnung von im Innern liegenden Thermoelementen beim Zementklinkerbeton: 1 × mittig direkt auf der Schalung, 1 × mittig zwischen der Bewehrung
• – Lagerung nach der Herstellung im Klimaraum 20/65

The specimens were formed from the following concretes: Cement clinker concrete reference concrete cement CEM 142.5 R-HS rasp blades, 340 kg / m ³ CEM 142.5 R-HS rasp blades, 340 kg / m ³ Mixing water 181 kg / m ³ 181 kg / m ³ w / (z + 0.4f) value 0.53 0.53 Air pore content (target) 3.5% by volume 3.5% by volume additive PP fibers Duomix Fire PP fibers Duomix Fire M6, 2 kg / m ³ M6, 2 kg / m ³ additive LPS A94; 0.68 kg / m ³ LPS A94; 0.68 kg / m ³ surcharge 0/2 sand EuA, 437 kg / m ³ 2/8 clinker, 478 kg / m ³ 8/16 clinker, 711 kg / m ³ 0/2 sand EuA, 524 kg / m ³ 2/8 gravel, 619 kg / m ³ 8/16 gravel, 619 kg / m ³ Calculated fresh concrete density 2060 kg / m ³ 2214 kg / m ³ 28d-Festbetonrohdichte 2186 kg / m ³ 2206 kg / m ³ 28d compressive strength 36.2 N / mm ² 39.8 N / mm ²

• - Reinforcement: 2 × Q 188 (bar diameter: 6 mm, longitudinal / transverse distance: 100 mm)
• - Concrete cover: 30 mm
• - Arrangement of internal thermocouples in the cement clinker concrete: 1 × in the middle directly on the formwork, 1 × in the middle between the reinforcement
• - Storage after production in the climatic chamber 20/65

a Day before the fire test were on the fire Side (corresponds to the non-shuttering side) of the specimens glued two Oberflächenthermoelelemente. These each were exactly in the middle and on the perpendicular bisector, respectively 7.5 cm from the top.

• – 01: Brandraumtemperatur, ca. 10 cm von Probe „Zementklinkerbeton" entfernt
• – 02: Brandraumtemperatur, ca. 10 cm von Probe „Referenzbeton" entfernt
• – 03: einbetoniertes Thermoelement („Zementklinkerbeton", mittig auf Schalung)
• – 04: einbetoniertes Thermoelement („Zementklinkerbeton", mittig zwischen Bewehrung)
• – 05: Oberflächentemperatur Kaltseite „Zementklinkerbeton", mittig
• – 06: Oberflächentemperatur Kaltseite „Zementklinkerbeton", auf Mittelsenkrechte, 7,5 cm vom oberen Rand entfernt
• – 07: Oberflächentemperatur Kaltseite „Referenzbeton", mittig
• – 08: Oberflächentemperatur Kaltseite „Referenzbeton", auf Mittelsenkrechte, 7,5 cm vom oberen Rand entfernt

For the small fire test there were altogether the following 8 temperature measuring points:

• - 01: Combustion chamber temperature, approx. 10 cm away from sample "Cement Clinker Concrete"
• - 02: Combustion chamber temperature, approx. 10 cm away from sample "reference concrete"
• - 03: embedded thermocouple ("cement clinker concrete", centered on formwork)
• - 04: embedded thermocouple ("cement clinker concrete", centered between reinforcement)
• - 05: Surface temperature cold side "cement clinker concrete", in the middle
• - 06: Surface temperature cold side "Cement clinker concrete", on perpendicular bisector, 7.5 cm from the upper edge
• - 07: Surface temperature cold side "reference concrete", in the middle
• - 08: Surface temperature cold side "reference concrete", on perpendicular bisector, 7.5 cm from the upper edge

The The concrete specimens described above were used before the two opposite openings of the small fire tester in accordance with DIN 4102 Part 8, all around with mineral fiber board strips sealed and held with a clamping device.

The boiler room was lit with fuel oil EL according to DIN 51603 part 1. It was driven with maximum burner power. The obtained measuring curves of the measuring points 01 and 02 are the 9 refer to.

The oven temperature at the beginning of the test was 18 ° C. The maximum temperature of 1200 ° C was only after approx. 2.5 hours trial period achieved. The fire room overpressure was not specifically regulated, but only registered. Throughout the duration of the experiment it was between 0 Pa and 22 Pa, measured at half specimen height. The measured surface temperature is the 10 refer to.

The measured surface temperature increases the side facing away from the fire were clearly visible in cement clinker concrete lower than the reference concrete; towards the end of the experiment when cement clinker concrete 96 or 83 K achieved while 235 or 244 K were measured for the reference concrete.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited non-patent literature

• - DIN EN 12 620 [0019]
• - DIN EN 197-1 [0028]
• - DIN EN 934 [0030]
• - DIN 1045-2 [0034]
• - DIN EN 12350-5 [0059]
• - DIN EN 12350-4 [0059]
• - DIN EN 12350-6 [0059]
• - DIN EN 12350-7 [0059]

Claims (10)

Concrete mixture for producing a concrete with increased fire resistance comprising a binder and an aggregate, characterized in that the aggregate consists of at least 50 wt .-% of cement clinker with a grain group 0/32. Concrete mixture according to claim 1, characterized in that the coarse aggregate with a grain size in the range of 2 mm to 32 mm consists of cement clinker. Concrete mixture according to claim 1 or 2, characterized in that additives are included. Concrete mixture according to claim 1, 2 or 3, characterized in that additives are included. Concrete mixture according to one of the preceding Claims, characterized in that air entraining agents or hollow microspheres are contained. Concrete mixture according to one of the preceding Claims, characterized in that polypropylene fibers are included. Use of a concrete mixture according to a of claims 1 to 6 for producing a concrete for high-low or precast construction. Use according to claim 7, characterized characterized in that the concrete obtained from the concrete mixture as Shotcrete is used for tunneling. Use according to claim 7, characterized characterized in that the concrete obtained from the concrete mixture as In-situ concrete is used for tunneling. Use according to claim 7, characterized characterized in that the concrete obtained from the concrete mixture to a precast concrete element such as segments, beams, columns, Binder, wall elements, ceiling elements, garages, is processed.