DE3115673A1 - Concrete of high compressive strength and tensile strength - Google Patents

Abstract

Concrete mixes of increased compressive strength and tensile strength are produced from cement, fine and coarse aggregates, a setting-regulating material and a concrete plasticiser and water. For processing as bulk concrete having a long retardation time, the concrete mix consists of 1590 to 1600 kg of fine and coarse aggregates having a maximum grain size of 4 to 8 mm, 650 to 680 kg of cement of high standard compressive strength, 180 to 200 l of water per metre cubed of concrete and of an addition of melamine resin as concrete plasticiser in a quantity ratio from 1.5 to 2.2%, relative to the cement, and zinc oxide as setting-regulating material in a quantity ratio from 0.7 to 1.1%, relative to the cement, the additives being mixed into the dry cement.

Description

Concrete with high compressive and tensile strength

The invention relates to a concrete mix for a concrete with increased Compressive and tensile strength from cement, fine and coarse aggregates, a setting regulating Substance as well as a concrete liquefier and water is made.

It has been found that especially with over-sized can be emphasized, as is the case with large foundations, such as aircraft hangar floors or concrete the required properties of the concrete are used during processing the short delay time lead to difficulties or the required properties cannot be fully adhered to.

The simple consideration of using a cement with high standard tensile strength a compression and tensile strength concrete mix has the disadvantage of a high heat of hydration opposite, which is associated with the tendency to crack.

When using aggregates, it is known that this due to their own compressive strength form the basis for a high-strength concrete. A Another criterion when using aggregates depends on the Use of the concrete with regard to the final strength the selection of the largest grain. the end In concrete technology it is known that aggregates with a relatively large maximum grain have a low water requirement. Furthermore, it is known that a reduction the water / cement value is advantageous for achieving a high-strength concrete is. However, it must be taken into account that both the advantage of a large, largest grain as well as the associated reduction in the w / c value against good processability or speak for a long delay.

Admixtures are used throughout to improve the properties of the concrete. When producing high-strength concrete, additives are essential for better workability, Strength increase and setting regulation complement the recipe structure. However, particular difficulties arise in finding the suitable additives especially when combining these resources, each with different tasks on, since the known additives are not among each other, based on the required Properties of the concrete.

Based on the known properties and effects of the for one Concrete with increased tensile and compressive strength required material composition the invention has set itself the task of developing a concrete recipe that it enables such a concrete in terms of good processing than To provide bulk concrete with a long lag time, paying special attention to it it is important to find additives that help regulate the hydration phase and supplement in a particularly beneficial way when increasing the tensile strength.

The concrete mix according to the invention is characterized by 1,590 - 1,600 kg fine and coarse aggregates with a maximum grain of 4 - 8 mm, 650 - 680 kg Cement with high compressive strength, 180 - 200 liters of water per cubic meter of concrete as well by adding melamine resin as a concrete liquefier in a proportion 1.5-2.2% based on the cement and zinc oxide as a setting-regulating substance in a proportion of 0.7-1.1% based on the cement, with the additives added to the dry cement.

The ratio of the W / C value is when determining the basic values the decisive value for compressive strength in the production of high-strength concrete of the concrete.

The one resulting from the specified amounts of water and cement W / C value of 0.27 - 0.3 is far below the values of the known concrete technology, where the value is 0.4%.

Achieving this W / C value is only possible through the use of higher quality Additives possible. Also a high quality cement, for example Portland cement with a standard compressive strength of 73 N / per mm³ could only be more effective after use setting-regulating additives can be used, which was the main criterion to be seen in the compatibility of the additives used.

From the point of view of making a concrete with strength properties, Using the least amount of cement possible is not just economical Side of the production, but also to see the avoidance of side effects, such as B. with excessive cement content per cubic meter of concrete, high shrinkage, creep or tear.

Apart from these consequences, the focus is on the strength of the concrete the stated amount is 650 - 680 kg Portland cement per cubic meter of concrete required, which varies up to 150 kg per cubic meter depending on the area of application and mass can be.

In the case of aggregates for the production of high-strength concretes, a must all things the already mentioned largest grain should be considered as an evaluation criterion. The aggregate quality and purity of the materials are essential for the production of the concretes an important requirement. Both quartzite and limestone aggregates are optional or even more fixed surcharges can be used. Again, it is crucial that the The compressive strength of the concrete increases as the size of the aggregate is reduced. Dependent on In the application, the largest grain should be 4 - 8 mm.

As already mentioned are used as additional means to achieve the concrete with the properties according to the task for better processability, increase in strength and setting regulation melamine resin F 10 and zinc oxide have been proposed, whereby the optimum amount of concentration in relation to the amount of cement is determined through tests has been. The interaction of the two additives is coordinated of particular importance to the amounts added.

Of another essential importance, time is immediate after concreting. One can assume that the evaporation of what is in the concrete Mixing water due to the evaporation temperature, as already mentioned, in the concrete surfaces leads to tension. The build-up of tension in young concrete results in most Cases of surface cracks because the internal stresses are greater than the increasing ones Tensile strength of the young concrete. But tensions also build up through rapidly developing ones Heat of hydration. To prevent the concrete surface from drying out quickly a water sprinkling is proposed as an aftertreatment, the sprinkling must be continued until it can be seen that the tensile strength of the concrete is higher is than the tensions that can result from evaporation and drying out. The dissipation of the heat of hydration cannot be effectively counteracted by sprinkling alone will.

As a measure against the build-up of internal tensions, a jointless Covering the concrete surfaces with polystyrene is proposed, with the thickness of the polystyrene layer depends on the thickness of the concrete layer. This measure ensures prevention surface evaporation and different cooling.

Here in one embodiment and in the four following Mixtures for the production of high-strength concretes described in the examples can be mixed with various Changes to the individual components modified for very specific areas of application will.

Example 1 Concrete with high compressive strength mm aggregate kg / m3 Grain size and type 0 - 2 sand 115 0 - 2 limestone 480 2 - 4 limestone 680 4 - 8 limestone 320 Subtotal 1,595 Cement PZ 55 Mielke 650 Water Drinking water 195 Concrete liquefier Melamine resin F 10 1.5% setting regulator zinc oxide 0.8% weight of fresh concrete 2,440 flour grain content 694 Consistency Slump over 42 cm Type of post-treatment. Polystyrene edging and cover W / Z 0.30 Example 2 Concrete with increased tensile strength mm aggregate kg / m3 grain size and type 0 - 2 sand 125 0 - 2 clinker 340 0 - 2 Limestone 155 2 - 4 Limestone 390 2 - 4 Slate 170 4 - 8 Limestone 380 Subtotal 1,560 cement PZ 55 Mielke 680 water drinking water 200 concrete liquefier melamine resin F 10 2% setting regulator zinc oxide 1% fresh concrete weight 2,440 flour grain content 875 Consistency Slump 44 cm Type of Machbe polystyrene edging treatment Sprinkling 7 days w / c value 0.29 Example 3 Concrete with increased compressive and tensile strength mm aggregate kg / m3 grain size and type 0 - 2 sand 115 0 - 2 clinker 325 0 - 2 Limestone 195 2 - 4 Limestone 480 2 - 4 Clinker 160 4 - 8 Limestone 325 Subtotal 1,600 cement PZ 55 Mielke 680 water drinking water 180 concrete liquefier melamine resin F 10 2.2% setting regulator zinc oxide 1.1% weight of fresh concrete 2,440 flour grain content 892 Consistency, slump 41 cm Type of post-polystyrene / sprinkling treatment 7 days w / c value 0.29 Example 4 Concrete with increased compressive strength mm aggregate kg / m3 grain size and type 0 - 0.2 fine sand 240 0 - 2 sand 400 2 - 4 Limestone 560 4 - 8 Limestone 390 Subtotal 1,590 Cement PZ 55 Mielke 650 Water drinking water 200 concrete liquefier melamine resin F 10 1.8 8 setting regulator zinc oxide 0.7% weight of fresh concrete 2,440 Flour grain content 910 Consistency, slump 38 cm Type of post-treatment polystyrene edging W / C value 0.30

Claims (5)

Concrete with high compressive and tensile strength Patent claims: Concrete mixture for a concrete with increased compressive and tensile strength made of cement, fine and Coarse aggregates of a setting-regulating substance and a concrete liquefier and water is produced, g e k e n n n z e i c h n e t d u r c h 1,590 - 1,600 kg fine and coarse aggregates with a maximum grain size of 4 - 8 mm, 650 to 680 kg cement high standard compressive strength, 180 - 200 1 water per cubic meter of concrete as well as through the addition of melamine resin as a concrete plasticizer in a proportion of 1.5 - 2.2% based on the cement and zinc oxide as a setting-regulating substance in one Quantity ratio of 0.7 - 1.1% based on the cement, the additives to the dry Cement can be added. 2. Concrete mix according to claim 1, d a d u r c h g e k e n nz e i c Not that a jointless, complete cover is required for post-treatment of the concrete the concrete surfaces are provided with polystyrene. 3. Concrete mix according to claim 1, d a d u r c h g ek e n nz e i c n e t that water sprinkling is provided for the post-treatment of the concrete, The duration of the sprinkling depends on the tensile strength of the concrete. 4. Concrete mix according to claim 1, d a d u r c h g e k e n nz e i c Not that, in coordination with the additives, Portland cement grade 55 with a standard compressive strength of 73 N / mm² is used. 5. Concrete mix according to claim 1, d a d u r c h g e k e n nz e i c Not that the fine and coarse aggregates are quartzitic and / or limestone aggregates are provided.